ALBERT

Notes: A new detection scheme for Fourier transform-ion cyclotron resonance (FT-ICR) studies is proposed and initial experimental results are presented. While in conventional FT-ICR, the difference of the transient signals from two opposite electrodes is recorded and Fourier transformed, it is also possible to use the sum of these signals. In this way resonances are observed at the harmonic of the reduced cyclotron frequency 2 ν+ as well as ν+−ν− and ν++ν−, the later being important for accurate mass measurements. The experiments were performed with a Penning trap in an electromagnet.

Notes: An in situ cell suitable for transmission EXAFS measurements on catalytic samples is described. The cell can be used for catalyst pretreatments in various atmospheres (including H2, H2S, O2 and CO) in a temperature range upto 700 K. The sample is heated by conducting heat from an external heater to the sample. During measurement the samples can be cooled down to 77 K by conducting heat from the sample to an external liquid nitrogen container. During the pretreatment and the measurement a waterflow through the body of the cell keeps certain crucial parts from overheating or icing up. To avoid radiation leaks in powdery samples these samples are pressed in a selfsupporting wafer and held in a disk-shaped sampleholder. Tests by various catalytic groups have proven the suitability of the design.

Notes: The dedicated VUV radiation source Super-ACO is part of the Orsay synchrotron radiation complex. The construction of this 800-MeV positron storage ring was started in 1982, and the first beam was stored on March 18, 1987. Super-ACO is expected to accommodate up to six undulators. The first, a 3.2-m-long optical klystron has already been operated between 500 and 800 MeV. A 1.3-m-long undulator has been recently installed. The experience gained during the three periods of operation is presented. From March to October 1987 measurements were taken of the machine properties in the low emittance regime, as well as performances in single and multibunch operation. In March 1988 the optical klystron was tested together with the commissioning of two beamlines out of a bending magnet. Starting from May 1988 two undulators and six beamlines progressively operated.

Notes: Since the first operation of the Photon Factory ring in the beginning of 1982, we have constructed seven insertion devices of various types: a superconducting wavelength shifter; two undulators, including a multiundulator; two multipole wigglers; and two multipole wigglers for circularly polarized synchrotron radiation sources. The performances of those devices are summarized, and the possibilities of the use of the TRISTAN main ring as an advanced synchrotron radiation source are presented.

Notes: A 2-m undulator magnet and associated beamline have been installed on the electron-positron storage ring PEP. The undulator is designed to produce photons at 12 keV with high intensity when the storage ring is operated at its nominal energy of 14.5 GeV. We report measurements of the spectral and angular properties of the radiation when PEP is operated in a low-emittance (ε∼6×10−9 m rad) configuration. The spectral properties are in good agreement with theoretical predictions.

Notes: A 3.3-cm period Nd-Fe-B hybrid undulator has been designed and successfully operated in the Cornell Electron Storage Ring (CESR). This 2-m-long, 123-pole insertion device is a prototype of one of the undulators planned for the Advanced Photon Source. In dedicated operation, the undulator produced the expected brightness at 5.437 GeV with the fundamental x-ray energy ranging from 4.3 to 7.9 keV corresponding to a change in gap from 1.5 to 2.8 cm.

Notes: A few electron storage rings exist (and possibly could be available in the future), with energy 〉10 GeV and with straight sections of the order of 100 m on which very long undulators could be installed. The exceptionally low emittance that these machines can reach when run at relatively low energies would allow highly degenerate radiation to be produced in the soft and medium x-ray range, with applications to biological imaging near the C and N K edges, holography, and nonlinear optics down to a few angstroms, pumping of soft x-ray ion lasers, picosecond or femtosecond resolution spectroscopy, etc.

Notes: This paper consists of a general presentation of the Storage Ring FEL activities at LURE (Orsay). We first summarize the results obtained previously with an optical klystron installed on the ACO storage ring, and then make a presentation of the different projects that have begun on the new storage ring Super-ACO. The ACO storage ring experiments were of two kinds: the Free Electron Laser oscillator (FEL), and the coherent harmonic generation (CHG). The first allowed us to reach the visible spectral range, between 6500 and 4600 A(ring). In the second, we were able to produce coherent emission in the VUV: it was the shortest wavelengths (1773 and 1064 A(ring)) ever obtained with an optical klystron or an undulator acting as a nonlinear medium. In this last configuration, the fundamental wave was an external pulsed and doubled Nd-Yag laser, focused in the optical klystron. The new Super-ACO storage ring has been equipped with a new optical klystron. The first "spontaneous emission'' spectra have been observed and they show that the performance is in good agreement with theoretical predictions. FEL oscillator experiments in the visible range are planned for the end of the year. In parallel, CHG experiments in the VUV will begin.

Notes: Since 1979, experiments on the storage ring VEPP-3 with an optical klystron (OK) have been performed at the INP Academy of Sciences of the USSR. In 1979, 1981, and 1983, three different OK magnetic systems based on SmCo permanent magnets undulators were installed at the VEPP-3 straight section at 6300-A wavelength. The following gains per pass have been obtained: 0.5% in 1980, 1% in 1982, and 2%–2.5% in 1984. In late 1985, we decided to improve the storage ring VEPP-3 and develop a dc bypass, a special straight section dedicated for OK operation. The bypass allowed us to install an OK magnetic system of 7.8 m length and significantly increase the gain per pass in March of 1988. The bypass was installed at the storage ring VEPP-3 on 3 June 1988. We obtained lasing in the red and yellow light spectral range from 5800 to 6900 A with 5%–10% gain per pass. After changing mirrors for new ones with minimum losses at 4150 A, lasing in the violet and near UV spectral range with 3%–6% gain per pass from 4500 to 3750 A was obtained on 8 July. All work is being carried out at an energy of 350 MeV. Threshold currents for lasing are 1–10 mA depending on the optical cavity mirror conditions. The maximum current is 80 mA at present. A set of measurements on studying lasing in various conditions is underway.

Notes: We describe the recent, intensive construction program of new beamlines at the Wisconsin Synchrotron Radiation Center. In particular, we discuss technical features of new TGM lines, and the development of the advanced photoemission spectromicroscope MAXIMUM, based on undulator radiation.

Notes: Micropole undulators (wigglers) are undulators (wigglers) with submillimeter periods and are referred to, generically, as micropole insertion devices. Compared to ordinary insertion devices, whose period λu is typically ≥l cm, micropole devices have periods smaller by a factor f≤10. Therefore, the first-harmonic radiation emitted by a micropole undulator will have its photon energy Eγ increased by f and its spectral purity Δλ/λ by f, provided the total length of the undulator lu stays unchanged, and magnetic field errors, as well as the electron-beam emittance, are sufficiently small. Furthermore, to generate photons of the same Eγ as from the conventional device, the electron-beam energy Ee can be reduced by f 1/2 , resulting in significantly lower construction and operating costs. Radiative energy losses can be correspondingly diminished for the associated storage rings. In this paper we report on results recently obtained by us in the practical implementation and design of micropole undulators at the Stanford Synchrotron Radiation Laboratory (SSRL) and the Lawrence Livermore National Laboratory (LLNL). Based on our work, micropole undulators with f≤104 appear feasible at the present time.

Notes: In actual performance, the 35 pole wiggler/undulator (W/U) at BESSY has been shown to deliver 50 to 250 times more flux than a TGM with 10 mrad of dipole radiation under otherwise comparable conditions. The beamline, laid out for photon energies from 15 to 400 eV, has been calibrated and the resolution measured at several energies. Interactions of the W/U with the storage ring have been studied and, in part, corrected for: the working point does not change in either direction (〈10%) as the gap is varied and the electron beam position in the ring remains constant to within 10 μm and the angle of emission of the SR from the ring to within 5 μrad for K≤2.7. The reduction of the lifetime of the electron beam in the ring and the change in the vertical size of the beam as a function of the gap are typical of the problems associated with the interaction of such a device on a high brightness ring. The beamline has been in normal user operation for over a year.

Notes: The construction of the wiggler W2 at DORIS is described together with the major components of the beamline. Details are given on the assembly and performance of the magnet structure. Three different monochromators are used in the beamline alternatively. One of them, a Laue–Bragg-type monochromator is described in more detail.

Notes: Using undulator radiation from 2 to 8 keV, quantum efficiencies [QE(E)] of gold photocathodes, microchannel plates (MCP), and silicon surface barrier (SSB) detectors have been investigated. For the gold photocathodes, the detailed structure of QE(E) near the M absorption edges has been presented. Also, the secondary electron conversion efficiency of gold has been calculated using the mass absorption coefficient given by a relativistic Hartree–Slater model and by the semiempirical values of Henke et al., respectively. Extended x-ray absorption fine structure (EXAFS) has been observed in the secondary electron current of the gold photocathode as well as in the detection current responses of an MCP and of an SSB detector. Furthermore, the new findings adding to our recent paper1 have been summarized as follows: (i) EXAFS above the Si-K edge in the MCP response depends on photon incident angles, and (ii) a little upshift of the starting point energy of EXAFS in the MCP response is observed. These detailed characteristics and their interpretation are described in the following: (i) The current responses of the MCP are obtained as a function of the incident x-ray energy for θ=13° (the bias angle of the MCP), and 40° by using a gold-monitor current. Here, θ denotes the incident angle of the photons to the channel. The data for θ=40° show a smaller jump near the Si-K edge as compared with the data for θ=13°.This is explained as follows: The incident photons for θ=13° are irradiated to and absorbed in the MCP ingredient of SiO2, while photons for θ=40° are incident to the electrode region. (The depth of the electrode coating is more than 10 μm from the MCP surface, while the photons are absorbed at less than 8 μm from the surface for θ=40°.) Thus, the data for θ=40° strongly reflect the characteristics of the electrode, but not of SiO2. The data for several values of θ consistently indicate that the height of this jump becomes smaller with increasing θ. (ii) The observed upshift of the starting point energy of EXAFS in the MCP response presents a contrast to EXAFS in the SSB detector response, in which upshift is not observed. This upshift is ascribed to the molecular structure of SiO2 (the chemical shift); that is, some valence electrons are removed from the Si atoms due to the oxidation (i.e., SiO2). Thus, the screening effects of the valence electrons on the core electron-nucleus attraction are reduced. This results in the shift of binding energy towards the higher-energy side. On the other hand, EXAFS in the SSB detector response reflects the characteristics of Si.

Notes: This article describes the outline of a time-resolved x-ray measurement system developed at the Photon Factory to study the pulsed laser annealing of silicon crystals. This system consists of a triple-crystal diffractometer, Q-switched Nd:YAG laser, and two fast detector electronics using a plastic scintillation counter, and enables us to examine the time-change behavior of nearly intrinsic rocking curves under laser irradiation with a time resolution of about 50 ns. The difference in the recovery from lattice deformation between 1.06-μm laser annealing and 0.53-μm laser annealing is clarified.

Notes: This article is devoted to investigations of the mechanism of muscle contraction based on high time-resolution studies of meridional and equatorial diffraction patterns from frog sartorius muscle with the use of synchrotron radiation. Paired stimulation has been used for studying nonfatigued and fatigued muscles. The results obtained are discussed on the assumption of a noncontact mechanism of force development. Original viewpoints are presented on the role of repeated pulses in activation of fatigued muscles.

Notes: A new x-ray beamline has recently been built, and is now operational, on dipole magnet 2 of the Synchrotron Radiation Source (SRS) at Daresbury. This beamline takes 32 mrad of horizontal aperture from a central tangent point. The time-resolved x-ray diffraction (TRXD) Station 2.1, takes 17 mrad of horizontal aperture and is the central point of this paper. Beamline 2 has been realized as part of a SERC–MRC agreement.

Notes: A parallel-beam geometry with analyzer crystal is used for x-ray diffraction experiments on fast-moving machine parts. With this method in rotating samples, like turbine blades, strain can be measured in different directions with respect to the acting force by appropriate choice of the diffraction plane. Stroboscopic gating of the counter allows position-resolved strain examination. Further applications are diffraction experiments on fluids and melts.

Notes: A stopped-flow apparatus was constructed for x-ray scattering study at subzero temperature. It can be operated over a wide temperature range down to −20 °C with highly viscous solution (20 cP) successfully. We have applied the stopped-flow x-ray scattering method to many biological reactions. In particular, the association of E. coli ribosomal subunits was detected at −10 °C which was too fast to be detected at room temperature. Dissociation of E. foetida hemoglobin was measured by the stopped-flow x-ray scattering method combined with a time-resolved imaging plate as a detector.

Notes: Luminescence excitation spectra in barium fluorohalides have been studied using synchrotron radiation of the SIBERIA-I electron storage ring in the energy range from 4 to 35 eV. The energy position of edge and core exciton formation as well as that of the electronic excitation multiplication threshold have been established. These luminophors find their practical application in the novel image-plate technique.

Notes: In expressions of film stress, the term containing the film elastic modulus is negligibly small (with respect to other terms) when the ratio of substrate-to-film thickness is large, thus allowing the calculation of stress in films of unknown modulus. However, the consequent large radii of curvature require large-field-of-view interferometers. A Michelson interferometer capable of producing interferograms from 25-mm-diam samples was constructed using standard large precision optics. The large field of view compared to the usual 1-mm diameter allows determination of very large radii of curvature.

Notes: The kinetics of the pressure-induced phase transformations in minerals are of considerable importance in affecting the dynamics of convection in the Earth. Because of the long exposure time of the high pressure in situ x-ray observations, however, it was very difficult to study the kinetics of such transformations. Combination of the synchrotron radiation and a large-volume high-pressure and high-temperature apparatus made it possible to perform such a study. The kinetics of the olivine-spinel transformation in Ni2SiO4 have been studied at conditions of 3.6–4.8 GPa and 765–980 °C. X-ray diffraction experiments were carried out using the MAX-80 high-pressure, high-temperature cubic-anvil apparatus at the National Laboratory for High Energy Physics, Japan. Synchrotron radiation was supplied by an accumulator ring operating at 6.5 GeV and between 15 and 5 mA. Ni2SiO4 olivine powder was hot pressed in the olivine stability field and then the pressure-temperature conditions were changed to initiate the transformation to spinel. Reaction progress was monitored by collecting x-ray diffraction patterns at intervals of either 30 or 100 s. The extent of transformation was estimated as a function of time and the data were analyzed on the basis of a nucleation and growth model. Pressure and temperature dependence of the transformation rate were determined from the present study.

Notes: A molecular beam epitaxy (MBE) apparatus furnished with two E-gun evaporators, two Knudsen cells and RHEED, was built for in situ grazing incidence x-ray diffraction studies. By adopting horizontal sample setting geometry, the entire ultrahigh vacuum chamber was rotated simply with the aid of a spring, and a large sample area was irradiated by the x-rays. Using this apparatus, we observed the 7×7 superstructure on a Si(111) surface and at a SiO2/Si(111) interface.

Notes: In order to study the process of reaction in crystals, it is necessary to observe decomposition of precursor and formation of the product during the transformation. Since such change is related to the structures of both the phases, x-ray diffraction is the most powerful method for this purpose. However, not only Bragg reflections but diffuse scattering or satellite reflections are observed occasionally in the early stage of the process and intensities of those scattering are extremely weak although they are important to analyze the process. Therefore, use of synchrotron radiation is desirable to study those problems. There are many compounds which show topotaxy during phase transformation. Since the product of such transformation is formed in an oriented manner under the influence of the structure of the precursor, diffraction patterns of the product are similar to those of a single crystal and anomaly of the diffraction can be easily detected. We have consequently studied the process of dehydration in α-AlOOH which indicates topotaxy in the process of dehydration. α-AlOOH transforms to α-Al2O3 at about 500 °C when it is heated in air. Lima-de-Faria (1963) found that the products revealed distinct satellite reflections along c* direction on x-ray diffraction patterns when the samples are quenched to room temperature in the early stage of reaction. Similar phenomena are also known in dehydration of α-FeOOH to α-Fe2O3 (both of them are isostructural to α-AlOOH and α-Al2O3, respectively). No interpretation has yet been established to the origin of the satellites. We have analyzed the averaged structure, interpreted the satellite reflections and change of profile of the satellites, and have elucidated the process of the reaction. The results indicate that the origin of the satellites is ascribed to the modulation of Al content along c direction and the change of the profile to the change in the mode of the modulation.

Notes: X-ray intensity versus energy (I-E) curves were measured in order to obtain the rod profiles. The three-dimensional surface structures of Si(111) 7/8 × 7/8 -Bi and -Ag were analyzed. The adsorption sites with respect to the crystal were derived from the intensity changes along the integral-order rods especially near the Bragg points by utilizing the interference effect between the x rays diffracted from the adsorbed layer and the bulk crystal. The positions of the surface Si atoms were studied by using the interference effect between the x rays diffracted from the adsorbed layer and the surface Si layer.

Notes: An ultrahigh-vacuum compatible four-circle diffractometer coupled to a molecular-beam epitaxy growth chamber has been designed to collect grazing-incidence x-ray diffraction (GIXD) spectra on in situ grown III-V semiconductor surfaces and interfaces. The unit is on line at the D25 bending magnet beam port of the LURE-DCI hard x-ray synchrotron-radiation facility (Orsay, France). Epilayer growth, surface processing, and diffraction data collection are performed without interruption of the ultrahigh-vacuum environment (in the low 10−10-mbar range) around the sample. The setup has been first applied to the determination of the atomic structures of GaAs(001) reconstructed surfaces. Results concerning the As-saturated c(4×4) phase are presented together with preliminary information on the As-stabilized 2×4 reconstruction.

Notes: Synchrotron radiation obtained from the 6-T vertical-wiggler source at the Photon Factory has been used to study dynamical x-ray diffraction in a nearly perfect germanium crystal under total external reflection conditions. A specially designed goniometer has allowed independent control of the glancing angle and the deviation angle from exact Bragg incidence. The rocking-curve profiles observed from slightly asymmetric Bragg planes as a function of glancing angle were found to be quite different for both the diffracted and specular beams. These profiles show unusual features arising from the excitation or de-excitation of the wave fields in shallow surface layers of the bulk crystal. Furthermore, GeK fluorescence signals measured during the Bragg reflection showed characteristic modulations, demonstrating the feasibility of new standing-wave experiments for determination of interface structures.

Notes: X-ray powder diffraction measurements using synchrotron radiation are currently being carried out on three experimental stations on the SRS at Daresbury Laboratory. Station 9.1 contains a general purpose powder diffractometer for angular dispersive measurements. The instrument is sited on the wiggler beamline, which provides radiation with a critical energy of 12 keV. A Si(111) water-cooled, channel-cut monochromator gives useful flux over an energy range from 6 to 30 keV. A cryostat and furnace are available for experiments requiring special environments, while a curved position sensitive detector can be used for time-resolved measurements. The wiggler white beam is employed on Station 9.7 for energy dispersive powder diffraction experiments. Various sample stages for kinetic experiments are in use on this station, and examples are shown of recent high-pressure work. A new high resolution powder diffractometer has been built and commissioned on Station 8.3, using bending magnet radiation. The diffractometer is based on the Parrish and Hart design, in which long, parallel foils are used to define the angular divergence accepted by the detector. In this way, large synchrotron beam cross sections can be employed while maintaining high angular resolution.

Notes: The new powder diffractometer installed on the beamline B2 at HASYLAB/DESY is described. It features a new design with a blocked double circle plus a third single circle which can be translated towards one another. The wide space between the two circle units conveniently holds complicated and spacious attachments and makes the instrument especially suitable for measurements under controlled environment conditions.

Notes: A new powder diffractometer for the Photon Factory was designed and constructed in 1986. Its performance has been confirmed as follows: (1) it is capable of determining the wavelength of the Cu K edge as 1.380619±0.000012 A using NBS standard Si powder 640b, while the reported one is 1.38059 A; (2) the accuracy of monitoring the incident beam intensity was ±0.2%, which was estimated by the normalized integrated intensity; (3) the angle resolution of diffraction lines was comparable with that of SSRL; and (4) the sum of three Gaussians was the best profile function fitted for lines from NBS standard Si powder 640b.

Notes: X-ray diffraction and absorption spectroscopy provide complementary structural tools for the in situ characterization of electrode surfaces. To optimize surface sensitivity, techniques such as glancing angle scattering geometries and spectrum differencing can be employed while the application of synchrotron radiation allows the real-time collection of data. This paper outlines recent developments in in situ electrochemistry on the Daresbury SRS and describes an electrochemical cell for in situ x-ray studies, associated glancing angle instrumentation, together with computer hardware and software optimized for data acquisition using potential modulation techniques. Important fundamental and industrial applications are highlighted.

Notes: A beamline (BL 6A) for x-ray crystallography mainly utilizing photographic methods was designed and constructed at the Photon Factory. A focusing mirror was installed at the beamline in order to obtain a beam with high photon flux while eliminating higher energy x rays in the beam. The mirror chamber located at 11.8 m from the source point is maintained in a high vacuum so as to keep the mirror surface clean. It accommodates a 1.3-m-long steel holder on which a mirror block is mounted. Two types of mirror blocks, plane and cylindrical ones of fused quartz, are prepared for alternative use. A radiation shielding hutch placed at around 15 m from the source is sufficiently large for installing a monochromator and various types of cameras. When the plane mirror was bent vertically, the size of the focused beam at 15.3 m was reduced to about 0.18 mm in the vertical direction. By the use of focused x rays, preliminary Laue diffraction experiments were carried out on protein crystals. Good quality diffraction patterns recorded on imaging plates were obtained by exposure of several milliseconds.

Notes: Heat loading tests were conducted with up to 360 W of undulator radiation incident on liquid-gallium-cooled silicon monochromators. Rocking curve measurements and temperature profiles (infrared camera) were obtained as a function of beam current. With large heat loads, the width of the rocking curves were observed to broaden and the gain in output flux per mA of beam current was significantly less at high beam currents than during low-current operation. The best performance was obtained using a slotted crystal with cooling channels located 0.76 mm below the surface. This crystal showed strong heating effects only above 40 mA and continued to produce an increase in output flux with beam current at the highest current tested of 76 mA.

Notes: Monochromator crystal heating and radiation damage may be reduced significantly by reflecting much of the incident radiated power from the surface of the crystal. This requires strong Bragg diffraction of the monochromatized beam at grazing incidence angles. Examples of such cases are described, such as extremely asymmetric diffraction and grazing angle diffraction, which would permit continuously tunable x-ray energy. Additional benefits such as increased angular acceptance, variable beam cross section, adjustable bandpass, and increased flux for self-filtering monochromators are presented, and various considerations in implementation are discussed. Finally, the possibilities for exploiting the unused reflected x rays will be explored.

Notes: There are two well-known methods to generate coherent x-ray photons: bound state x-ray lasers (BXL) and free electron x-ray lasers (FEXL). Both rely on induced photon emission. Because of the short lifetime of inverted states and high required energy densities for BXLs on the one hand, and strict tolerance specifications for FEXLs on the other, serious technological obstacles have yet to be overcome before a working device will be available for research purposes, particularly in the hard x-ray range. Coherence saturation is proposed here as an alternative method to generate coherent energetic photon beams. It does not make use of stimulated emission, therefore, it is not subject to the same technological and cost restrictions which have so far limited the effectiveness of BXLs and FEXLs in the short wavelength range. In fact, the method does not affect the process of photon emission at all: instead it rearranges the photon after they have been emitted, to achieve an increase in (transverse) coherence. The rearrangement is to be accomplished by dynamical optical means, i.e., by a collection of optical elements at least one of which is nonstationary. The speeds required are well within the range of present day technology. The method was devised primarily to facilitate certain interference experiments (e.g., holography) in the x-ray range. Correspondingly, its aim is to increase (first-order) transverse coherence. The special case will be discussed when only one optical element is nonstationary, and that is a rotating mirror. The transversely coherent intensity, I⊥, is defined as the number of photons crossing the (transverse) coherence area per unit time. Denoting by I the total photon intensity, define the (degree of) transverse coherence as C⊥=I⊥/I. Thus, C⊥≤1, and is saturated when C⊥=1.For given I, the time required to record a certain interference experiment is smallest when C⊥ is saturated. A device will be described which accomplishes coherence saturation by first decomposing an original beam into components, each of which has C⊥≈1, and then reconstitutes a resultant beam without significantly altering C⊥. In this manner device is able to increase C⊥ by the transverse coherence enhancement factor fc. For photons emitted from the PEP storage ring at Stanford, fc is calculated to be 102–103, depending on a variety of parameters, including wavelength and emittance. The method proposed here can be used in conjunction with any noncoherent photon source, but it should prove most advantageous when (a) the photons are expensive to generate, (b) the photon duty cycle is low, and (c) the photon intensity is one of the principal limiting factors in the experiment.For high-energy electron synchrotron radiation sources (a) and (b) both hold, while for interference experiments (c) does as well. It appears that the method just described will allow the construction of a novel type of x-ray source, for transversely coherent photon beam generation. There seems to be no fundamental reason why it should not be effective over a wide spectral range, including the hard x-ray region.

Notes: The term "dynamical optics'' is defined as a set of optical elements at least one of which is nonstationary as seen from the laboratory. Present technology allows the construction of fast rotating mirrors as components in dynamical optical systems. Calculations show that such systems can be used to achieve subpicosecond x-ray pulses and extremely high instantaneous intensities, and, alternatively they can be utilized to saturate the transverse coherence of x-ray beams thereby making possible to perform certain interference experiments. Some properties and additional applications of fast rotating mirrors are discussed: (1) The focusing properties of rotating mirrors can differ significantly from those of stationary reflectors, even though the mirrors are, of course, nonrelativistic. A small (diameter 〈1 mm) plane mirror when rotating can have a focal length fm down to a few meters. By changing the speed of rotation, the focal length can be altered continuously from its minimum value, fm, through infinity (when the mirror is at rest) to −fm (when it's rotation is reversed). Thus, mirrors can be constructed which can be made to both focus and defocus with continuously and accurately variable focal length. (2) Rotating mirrors will induce a frequency change Δω in the reflected beam, allowing one in principle to tune across resonance lines, and also "active monochromatization'' of x-rays, i.e., increasing the spectral intensity in a selected range, while decreasing it outside that range, all this without any change in the total photon beam intensity. This option is of interest when the total photon intensity cannot be increased beyond a certain limit, high resolution monochromatization is available, and large spectral density is called for in a chosen frequency range.(3) The maximum speed whch a rotor can tolerate is determined by its shape as well as its mechanical properties, such as density, elasticity, and tensile strength. Because of their high intrinsic symmetry, spherical rotors are of interest both theoretically and experimentally, but higher speeds can be achieved by rotors specifically shaped for that purpose. A variety of examples will be given to illustrate the relationship between rotor speed and selected parameters.

Notes: The power-filtering capabilities of multilayer bandpass x-ray mirrors relative to total reflection low-pass mirrors are presented. Results are based on calculations assuming proposed wiggler sources on the upcoming generation of low-energy (1.5 GeV) and high-energy (7.0 GeV) synchrotron radiation sources. Results show that multilayers outperform total reflection mirrors in terms of reduction in reflected power by roughly an order of magnitude, with relatively small increases in total absorbed power and power density over total reflection mirrors, and with comparable reflected flux values. Various aspects of this potential application of multilayer x-ray optics are discussed.

Notes: The use of multilayer reflectors under intense synchroton x-ray beams requires to develop a new generation of multilayered materials that can withstand a high-power load in excess of 100 W/mm2. Multilayers with the high-Z layer consisting either of a pure element or of compounds such as carbides, nitrides, or silicides have been produced. Because the fabrication conditions are not yet optimized, thin films with satisfactory layer were not obtained leading to poor reflectivities. Such multilayers have been both thermally annealed in a furnace and exposed to a synchrotron beam with a power density of about 1 W/mm2. The resulting damage ranges from the total destruction of the layering to a reduction of the reflectivity by typically 40%–60%. In some cases an only 1%–15% loss in reflectivity has been observed.

Notes: Multilayer mirrors have been designed, fabricated and tested for use as a wavelength-selective filter of ∼100 eV for photo-CVD experiments at the beamline 12C of Photon Factory, KEK. Mo/Si and Rh/Si multilayers were selected in accordance with new simple optical criteria and fabricated on super-polished CVD-SiC substrates by means of ion-beam sputtering. Both mirrors showed a reflectance of over 40% at around the designed angle of incidence of 45°.

Notes: A curved Bragg reflector for focusing synchrotron radiation has been fabricated using a recently developed magnetron sputtering equipment. The Bragg reflector consists of alternate thin-film layers of W and C deposited on a cylindrical substrate of 46 mm in radius of curvature, covering a 50×50-mm2 area. The focusing properties of the Bragg reflector were examined at beamline 15B of the Photon Factory. The focused beam intensity per unit area was six times higher than the unfocused beam, and the observed variations in beam size and shape with optical distances showed qualitative agreement with ray-tracing calculations.

Notes: We report on a new coarse tip distance adjustment and positioner for a scanning tunneling microscope, which was designed with ease of sample manipulation and UHV compatibility in mind. It has no mechanical connections in UHV and has been successfully used for measurements of microfaceted platinum surfaces in air and cleaved Si(111) surfaces under liquids.

Notes: This note describes the surface treatment of a mirror furnace, made from a block of aluminum. The method offers an inexpensive way to obtain temperatures up to 2100 °C.

Notes: An accurate method of measuring the temperature dependence of the scintillation efficiency in NaI(Tl) crystals is described that uses the single-electron technique. The optical intensity of scintillations is determined from the measured time spectrum that represents the temporal dependence of scintillation intensity, and hence the result is not affected by the temperature effect on the scintillation decay time. Typical experimental data obtained by the proposed method are also presented.

Notes: We have measured by interferometry the diameter of a fused-quartz hemispherical rotor to 200 nm, or an accuracy of 4 parts-per-million (ppm), at both room temperature and at liquid helium temperature. We placed the rotor in an optically contacted fused-quartz etalon, and used a continuous-wave dye laser to measure the lengths of the optical cavities. The laser frequency was referenced to Doppler-free absorption lines in molecular tellurium and molecular iodine. These measurements were done in order to determine the area of a superconducting ring used in a precision determination of h/me. Our results confirm earlier length measurements at room temperature performed by the National Bureau of Standards (NBS).

Notes: A new inelastic electron tunneling spectrometer with an absolute peak intensity is described. A smoothed second differential calculation is directly applied to high precision (7.5 digits) tunneling current-voltage data measured with Al/AlOx/Benzoic Acid/Pb tunnel junctions at 4.2 K. Interpolation and accumulation in addition to the above calculation permit high resolution and high signal-to-noise ratio inelastic electron tunneling (IET) spectra with absolute intensities. The half width at half maximum is 22 cm−1 and signal-to-noise ratio is more than 26 at 1598 cm−1 at the smoothing parameter M=19. The absolute peak intensities of tunnel junctions doped with solutions of different concentrations are measured easily and simply with this new method. The absolute peak intensities increase with an increase in both the solution concentration and dipping time. This method shows promise as a quantitative surface analytic system.

Notes: The design of the control system for a scanning tunneling microscope is described. The control system was optimized for a tube scanner instrument and for constant-current-mode operation. The optimization process included measurement of the transient and frequency responses of the instrument, design of the appropriate control electronics, and development of software consistent with the characteristics of the instrument and electronics. The limiting factor for tube scanner performance was found to be the transient settling time rather than the lowest mechanical resonant frequency of the tube. The settling time for the mechanical resonances of the tube scanner was reduced from 100 to 1 ms by potting the device with silicone rubber. After the potting procedure, the sensitivity of the tube scanner was essentially unchanged.

Notes: The microtron accelerator at Bell Laboratories presently produces 16-μs-long, 40-mA pulses of 18.5-MeV electrons at a repetition rate of 30 Hz. Energetic positron-electron pairs are produced at a 4-mm-thick W beam dump. The positrons are moderated to a few electron volts energy by a 9-mm-diam W(110) single crystal and bunched by a parabolic potential accelerator to 14-ns full width at half maximum bursts containing (7±1)×104 positrons. The collection efficiency of the buncher is 63%. With the buncher turned off, the positron production efficiency is 4×10−8 positrons per electron.

Notes: A polarimeter has been designed and built to completely analyze the state of polarization of VUV radiation. It is based on the changes in amplitude and phase occurring upon reflection from a metal surface. The first experimental experience indicates the usefulness of this device provided the alignment problem can be solved satisfactorily.

Notes: A cross correlator for measurements of ultrashort UV pulses is described. The optical system is based on down-conversion of the UV pulses. The system can also be used to measure the second- and third-order autocorrelation function of pulses in the visible. The system is experimentally tested with UV pulses of 23-ps duration, that appear to be symmetric.

Notes: The electronic drive circuitry employed in the operation of a synchroscan Photochron IV streak camera is described. The experimental performance of two synchronization systems, a passive configuration (whereby the deflection signal is derived directly from a mode-locked pulse source) and an active system (incorporating a tunnel-diode oscillator phase locked to the laser), have been compared. A semiquantitative assessment of phase noise in the deflection signal and its effects on achievable temporal resolution is detailed and tested experimentally. On the basis of this analysis it has been possible to optimize the streak circuitry and thereby demonstrate a limiting instrumental resolution of 930 fs.

Notes: A new fiber-optic light-scattering spectrometer, which uses fiber-optic detector probes each comprising of an optical fiber and a graded index microlens is described. The fiber-optic detectors form an integral part of the scattering cell, which no longer requires transparent windows for the exit (or entrance) light beam. This feature eliminates the need for a goniometer which is one of the most bulky and expensive components of a conventional light-scattering spectrometer. Thus, the spectrometer, unlike all of its predecessors, has no moving parts. Our fiber-optic light-scattering spectrometer can utilize a reaction vessel of whichever shape or composition as the scattering cell for light-scattering measurements because the fiber-optic detector probes are directly immersed in the scattering medium. Furthermore, with the miniaturization using the optical fiber/microlens combination, the light-scattering spectrometer can be held in the palm of one hand and the signals processed by standard optical fiber remote sensing techniques.

Notes: A photoelectron-counting system has been constructed for all kinds of quasielastic light-scattering studies. The system consists of two parts, a data-acquisition unit, based upon a 16-bit microprocessor with additional hardware and software, and an evaluation unit, which can be any minicomputer, provided it has a parallel input port. The sample time resolution of the data-acquisition system is 500 ns at a data width of 4 bits, 1 μs at 8 bits, and 50 μs at 16 bits. The storage size is 2 Mbyte or more. The system also controls and remotes the measurement, as it is necessary for electrophoretic experiments or for time-resolved investigations. It is possible to store the raw data on a file. The evaluation either leads to a power spectrum or performs an autocorrelation function, with the time-critical parts written in assembly language.

Notes: In the photon energy range from 40 to 1000 eV, we have measured reflectances and transmittances of polyimide foils as well as reflectances and total photoelectron yields of Cu and Pt films. We compare sets of optical constants derived by the different methods applied to the same sample. The degree of agreement gives an indication of the present status of determining optical properties in the XUV. This is relevant for the planning of advanced instrumentation.

Notes: We present optical constants for Ti, V, and Ni in the 2–4.5 nm wavelength region. The reflected synchrotron radiation intensity was measured at more than 30 incident angles for each wavelength. A protective layer of carbon was sputtered onto each sample to prevent surface oxidization. A three-phase model was used to analyze the data. Instead of replacing some of the parameters by values determined by other experimental methods, eight parameters were simultaneously used in the least squares fitting. A 5-nm layer of carbon was found to be thin enough not to cause significant errors in the derived optical constants of the test materials.

Notes: Two-dimensional x-ray photoelectron diffraction (XPED) patterns of Ga3d and As3d photoelectrons from GaAs(001) were rapidly measured by using a retarding field-type electron energy analyzer and a synchrotron radiation x-ray source. In the raw images of photoelectrons obtained with this analyzer, clear XPED patterns were not observed, for most of the contrast was caused by moiré patterns of the four-grid electrodes. In order to obtain net XPED contrast, it is necessary to remove such instrumental functions. For this purpose, three techniques were applied: First, to perform pixel-by-pixel division between an image from a single-crystal sample and one from a polycrystalline sample. Second, to restore the XPED pattern by arithmetic treatments from two images measured before and after sample rotation. Third, to perform pixel-by-pixel division between an image from the crystal-state sample and one from the amorphous state, where the samples of two different states were obtained from the same sample before and after annealing without changing its position. In the case of GaAs, clear XPED patterns of Ga3d and As3d were obtained only by the third technique. The resultant patterns agreed well with calculated XPED patterns.

Notes: In this paper an electronic simulation system for laser Doppler velocimetry (LDV) is presented. This simulation system provides a light beam with an intensity that varies with time, as the scattered intensity does in a differential LDV experiment, where a laser whose Gaussian profile intensity has been turned into a uniform intensity profile is used. Several experiments with the simulation system are presented to illustrate its applications.

Notes: The construction of a prototype system capable of directly detecting and digitizing secondary-ion images using a charge-coupled device (CCD) is described. The CCD, alone, replaces the microchannel plate, fluorescent screen, and optical recording medium currently in use as the detection system on a CAMECA IMS-3f ion microanalyzer. Using the CCD as the image detector ensures that the secondary-ion signal is digitized in the most direct manner possible. A description of the hardware and image-acquisition process is given. Some of the first secondary-ion images to be detected using a CCD are presented, and the performance of the CCD as a detector of keV ions is evaluated. While preliminary trials appear promising, results indicate that the optimum efficiency is limited by the design of CCDs commercially available.

Notes: This paper describes the realization of a new electrostatic electron spectrometer, called MAPDESS, for the parallel measurement of angular distributions in gas-phase electron scattering experiments. The electron beam originates from a filament and a standard 127° cylindrical monochromator, and the beam is carried to the collision center at the desired energy by three successive cylindrical electron lenses that partly compensate for the high dissymmetry of the beam. The electrons scattered off the gaseous target are filtered by a 19-aperture angle selector (from 18° to 162°) and injected into the energy analyzer by means of an annular zoom lens. This lens allows one to keep control of the beam in the retarding or accelerating process, which is necessary to get a good resolution and/or intensity. The analyzer is a novel truncated spherical mirror symmetric about the scattering center and whose ring-shaped exit is coupled to 19 channel electron multipliers, thereby allowing parallel multiangle detection. This spectrometer thus directly gives the angular distribution of an energy-resolved scattering event in a plane. The angular resolution is shown to be ±3°. Some measurements in rare gases are presented, showing an energy resolution of 25 meV at a pass energy of 7 eV.

Notes: An algorithm is presented for fitting histogram data which may be considered the sum of several different Poisson sources (compound Poisson distribution). The average values and the fractions of the population associated with each average value are calculated from the moments of the experimental histogram. It is believed that the algorithm obtains the maximum possible information from the data.

Notes: A digital low-frequency-pass filter is tested and applied to the data pretreatment of exponentially decaying signals. If the high-frequency cutoff of the low-frequency-pass filter is chosen properly, the filtration process can improve the signal-to-noise ratio of the data. Furthermore, correct characteristic parameters which would otherwise be buried by high-frequency noises can now be retrieved from the filtered signal. The technique is simple to implement using a personal computer and may find use in measurements of slowly decaying functions and kinetic studies.

Notes: A multichannel vacuum Bragg-crystal spectrometer has been developed for high-resolution measurements of the line emission from tokamak plasmas in the wavelength region between 4 and 25 A(ring). The spectrometer employs a bent crystal in Johann geometry and a microchannel-plate-intensified photodiode diode array. The instrument is capable of measuring high-resolution spectra (λ/Δλ≈3000) with fast time resolution (4 ms per spectrum) and good spatial resolution (3 cm). The spectral bandwidth is Δλ/λ0=15% at λ0=8 A(ring). A simple tilt mechanism allows access to different wavelength intervals. In order to illustrate the utility of the new spectrometer, time- and space-resolved measurements of the n=3–2 spectrum of selenium from the Princeton Large Torus tokamak plasmas are presented. The data are used to determine the plasma transport parameters and to infer the radial distribution of fluorinelike, neonlike, and sodiumlike ions of selenium in the plasma. The new ultrasoft x-ray spectrometer has thus enabled us to demonstrate the utility of high-resolution L-shell spectroscopy of neonlike ions as a fusion diagnostic.

Notes: Since the real part of the refractive index of silica glass is smaller than unity in the soft x-ray region, it has been shown1–3 that silica-glass hollow-core fibers can transmit soft x rays. However, the transmittance for the silica fibers bent over a 90° were found to be lower than 0.1%. On the other hand, the multilayer metal coating technique has been developed in fabrication of flat mirrors for soft x-ray optics. If suitable multilayers can be deposited on the inner surface of a flexible hollow glass fiber, the transmittance for soft x rays of the fiber is expected to be considerably higher than that of noncoated hollow fibers. It is important to study the transmission characteristics of the hollow-core fiber whose inner surface is coated with metal. In the present study, we report the soft x-ray transmission characteristics of a Au-coated silica hollow-core fiber. The experimental setup is similar to that previously reported.4 The inner diameter of the Au-coated silica fiber used is about 2 mm and its length is 230 mm. The Au coating on the inner surface of the fiber was achieved by chemical plating. We measured the transmittances of the Au-coated silica fiber and a noncoated silica fiber with the same size. We measured the transmittance only for the bend angles smaller than 20°, because these relatively thick silica fibers were broken at about 25°. For a large bend angle (20°), the transmittances of the Au-coated fiber were one order of magnitude lower than that of the noncoated fiber in the short wavelength region below 45 A(ring). In the long wavelength region (longer than 60 A(ring)), the transmittance of the Au-coated fiber was higher than that of the noncoated fiber. At the oxygen K-shell absorption wavelength (23 A(ring)), the strong dip in transmission was observed in the noncoated silica fiber. However, there was not seen a strong dip in the Au-coated fiber. These results, the better transmittance for the long wavelengths, and no dip at 23 A(ring), show that the Au coating is effective in improving the soft x-ray reflectance in the inner surface of fibers.

Notes: Ultrasoft x rays are a useful probe for mechanistic studies of radiation damage in living cells. The highly localized energy deposition from a low energy x-ray occurs in a volume comparable to the sensitive biological targets within a cell, so that these low-energy x rays can be used as a tool to investigate radiation effects on the subcellular level. In the ultrasoft x-ray energy region the bright intensity and tunable energy selection of synchrotron radiation is unmatched by conventional sources. A beamline and irradiation chamber for dosimetry and radiation biology studies has been set up at the ES-0 exposure station of the Center for X-ray Lithography at Aladdin. The beamline includes a 10-μm-thick Be entrance window and a combination filter and single synthetically fabricated multilayer mirror for energy selection. The irradiation chamber contains another Mylar window for isolation, a two-dimensional scanning system allowing a 400-cm2 exposure area with scanning rates up to 3.5 cm/s, a rotating feedthrough system that enables motion in the third dimension, several viewports and a specially designed cell sample holder which can be filled with gases at various pressures and holds up to 18 cell culture dishes. The system has been characterized with a gas flow proportional counter to determine energy bandpass and spectral purity and a calorimeter and ionization chamber to assess photon intensity at various energies within the range 500–2000 eV.

Notes: Photoemission spectroscopy using synchrotron radiation is a powerful tool to investigate electronic states of solid surfaces. In the present study, the oxidation process of the Si(100) surface has been extensively examined. Experiments were carried out with soft x-rays monochromatized by the grazing incidence monochromator,1 at beamline 8A at the Photon Factory. The energy resolution, including both the electron energy analyzer (a double-pass type CMA) and the monochromator, was estimated from the Au Fermi edge. The Au foil was sputter cleaned by Ar ions. For the photon energy between 40 and 200 eV, the resolution is about 0.3 eV with electron pass energy of 10 eV and monochromator exit slit width of 10 μm. The oxidation process of a Si(100) surface has been examined in situ at the base pressure of 5×10−8 Pa. The Si(100) clean surface is obtained by repeating Ar ion sputtering and annealing. We have measured the Si 2p photoelectron spectra of the Si(100) surface exposed to oxygen. At the early stage of 20–1000 l oxygen exposure at room temperature, outermost Si atoms are partially oxidized and an energy shift of 1–2 eV is observed. The oxidation proceeds much faster when the surface is heated at 300–400 °C during oxygen exposure. In this case, three intermediary components (SiOx x〈2) and SiO2 are detected. By further oxidation (104 l oxygen exposure) at 700 °C, a thin SiO2 layer is formed. In addition, valence band and Si L2,3 XANES spectra have been taken for the surface. The results support the oxidation process clarified by the present method.

Notes: Recent progress in photochemical processing involving photochemical etching and photochemical vapor deposition are really remarkable and such processes become the most promising candidates as a next-generation VLSI fabrication technology. Thus the study to elucidate the reaction mechanism of the photochemical processing is of both fundamental and technological importance. In order to promote this study, we have designed and constructed a new beamline at Photon Factory (BL 12C). It consists of three major parts; a prefocusing mirror, a multilayer mirror monochromator, and a differential pumping system. A Pt-coated SiC toroidal mirror (Rh:0.539 m, Rv:490 m) is installed in a prefocusing mirror chamber (18.3 m from the source), accepts 5.0-mrad horizontal and 1.0-mrad vertical divergence of the synchrotron radiation, reflects it 3.8° upward, and focuses it onto the middle of the exit arm of the monochromator (32.3 m from the source). A multilayer mirror, which was designed and fabricated by Yamamoto et al., so as to get high reflectance around 100 eV of photon energy (see the preceding paper), is installed in the monochromator, steers SR beam downward, and selects photon energy by changing an incident angle. With this arrangement, a quasimonochromatic and bright beam is obtained in the energy region 80–100 eV. The output flux is expected to be ∼1015 photons/s⋅10% bw with 200-mA ring current.

Notes: Since stratospheric particles have a possibility to make a large effect on the climate in a global scale, a number of observations have been carried out using different techniques.1 Those particles were found to consist of mainly sulfuric acid and to be 0.1–1.0 μm in size. Turco and co-workers proposed a model that the particles are formed through chemical and physical processes initiated by photodissociation of OCS (λ〈2600 A).2 In order to examine this model, a simulation experiment in a laboratory system has been planned, in which ultraviolet components of SR are utilized. An optical system including a Seya-Namioka monochromator has been designed, constructed, and tuned precisely.3 In this system, the first prefocusing mirror (sphere) deflects the SR beam horizontally by 30°, and the second and the third ones (sphere) focus the beam vertically onto the entrance slit of the monochromator. The grating radius is 0.5 m. The monochromatized photon beam is reflected into the horizontal direction by the postfocusing mirror (toroid). A ray-tracing calculation was performed, and the obtained spot diagrams showed that the widths of the rays are about 100 μm at the two slits, and the spot size is 1.5×0.8 mm2 at the experimental point.These calculated results were confirmed experimentally by using visible and ultraviolet components of SR. From an estimation on the rate of the particle formation using the data available in the literature, the rate determining step was found to be the photodissociation of OCS in the ultraviolet region. At first, the photoabsorption spectra (cross section) were measured at room temperature and at −80 °C (near to the stratospheric temperature). The spectrum is composed of a broad band centered at 2250 A(ring) and of a number of small peaks. Photodissociation rates of OCS at several altitudes have been calculated using the present cross-section values, which indicated that the life of OCS is about 15 years at 20 km and two months at 30 km. It is known that CO and S are formed through the photodissociation of OCS. A computer-controlled mass spectrometer was made for pursuit of the time variation of CO density in the reaction cell, in which the sample gas, a few percent OCS in He, is introduced and irradiated by the photon beam. A chamber has been designed and constructed, in which a pseudostratospheric air is being irradiated by the ultraviolet radiation. A particle counter of laser-scattering type is being connected to this chamber in order to observe the particle number in it. The present study is the first examination applying SR to problems in the stratosphere as a simulated solar radiation. The obtained results have shown opening a new scientific opportunity in the utilization of SR.

Notes: A simple computer-controlled digital lock-in amplifier is presented. It has been designed as an interface for a personal computer with a minimum number of components. Its simplicity and the fact that all parameters are computer controlled makes the amplifier well suited for multichannel phase-sensitive detection. A comparison with a commercial analog lock-in amplifier is presented.

Notes: The aim of this study is to visualize the coronary artery with the intravenus injection of contrast media. We propose a method of rapid and successive acquisition of two-dimensional images in a digital processing system which uses a pair of video cameras, a shutter operation, and a beam-splitting apparatus. A prototype of the high-speed acquisition system was constructed. The two-monochromatic video-camera method was very suitable for quick acquisition. Electro-optical shutters (PLZT) were found practical with respect to the dynamic range and response time. The field blanking method was essential for the data acquisition.

Notes: A fortran program is described that runs on a 16-bit minicomputer under a single-user real-time operating system. This program combines interrupt-driven data collection, beamline positioning, and data analysis in a way that allows analysis of previously collected data while the program is collecting new data. It has been successfully used for several years on beamline X-24A at the National Synchrotron Light Source for fluorescence spectroscopy studies, surface extended x-ray absorption fine structure, and back-reflection standing-wave measurements.

Notes: A one-coordinate x-ray detector for digital subtraction angiography using synchrotron radiation is described. It comprises two x-ray-sensitive lines, each having 128 independent channels of scintillation counters. The detector is designed to simultaneously measure the intensities of two linear monochromatic beams being 8–10 mm distant from each other. The spatial resolution of each line ranges from 0.2 to 2 mm. The maximum counting rate is 6 MHz for each channel, and the detection efficiency of the 33.2-keV quanta is close to 100%. Preliminary results of the testing of the detector channels on synchrotron radiation beam are given.

Notes: A cine k-edge subtraction imaging system has been constructed for less invasive transvenous angiography research. It utilizes synchrotron radiation and consists of a monochromator, an x-ray television camera with a high-speed shutter, and a data-acquisition and control unit. A 50×60-mm2 monochromatic x ray of about 400 mR/s intensity is produced. The x-ray photon energy is changed by using an oscillating cam mechanism which changes the angle of the crystal with respect to the beam. 16 ms is required to change the photon energy across the k edge for a change up to 800 eV. K-edge subtraction angiography of rats is performed following intravenous injection of materials containing iodine. Dual-energy images are acquired using 17-ms exposures with the same interval. Repetition of this sequence gives a series of k-edge subtraction images. Arteries of 0.3–0.4 mm diam are clearly seen.

Notes: A two-dimensional charge-coupled device (CCD) detector, based on the Texas Instruments "virtual phase'' CCD, has been developed at the University of Michigan for synchrotron radiation applications. A series of performance tests were carried out at the LURE synchrotron facility, and the results show that the detector is ideally suited to measurements in dispersive absorption spectroscopy, high-resolution diffuse scattering, and small-angle scattering. The characteristics of the detector also show great promise for time-resolved experiments.

Notes: An experimental station with a four-circle diffractometer combined with tunable and focusing optics was designed and constructed for x-ray crystallography using synchrotron radiation from the vertical wiggler at the Photon Factory. The optics implemented into beamline 14A comprises a double-crystal monochromator and a double-focusing mirror so as to yield high photon flux x rays tunable over wide wavelength regions. The diffractometer with its equatorial plane in the horizontal was specially fabricated for rapid and accurate measurements of x-ray diffraction intensities from macromolecular crystals, and was provided with an alignment carriage as well as computer control and measuring systems. The station has proved to be particularly useful for such applications as anomalous scattering studies of protein crystals and also EXAFS studies at high photon energies.

Notes: A triple-axis spectrometer for high-energy ((approximately-greater-than)150 keV) synchrotron radiation has been constructed and characterized. The reciprocal space resolution function of this instrument has been measured using perfect silicon crystals as monochromator, sample, and analyzer. It was found to have dimensions of 1.0×10−5 A(ring)−1 and 2.3×10−4 A(ring)−1 in the directions perpendicular and parallel to the momentum transfer Q, respectively, comparable to those achievable using standard 8-keV triple-axis instruments. The large penetration depths of high-energy x-ray photons, combined with the high instrumental resolution, opens new possibilities in the study of truly bulk condensed matter systems.

Notes: A high-resolution Compton spectrometer has been installed for 29.5-keV incident x rays from a vertical wiggler inserted in the 2.5-GeV storage ring of the Photon Factory at Tsukuba. This spectrometer consists of bent-crystal monochromator, a Cauchois-type bent-crystal analyzer, and an imaging plate as a position sensitive detector. The overall momentum resolution is 0.084 a.u. for the incident x-ray energy of 29.5 keV. High-resolution Compton profile measurements on Al, a quasicrystal Al-Li-Cu, and solid and liquid phase of Li are shown to demonstrate the performance of this spectrometer.

Notes: A system for a very high precision absolute lattice spacing measurement has been developed. It employs, in principle, a bond method using a highly collimated and a very narrow bandwidth beam available from a monolithic (+, +) monochromator. Owing to the temperature stabilization of the hutch, where the equipment is installed, it has routinely achieved a precision of 2 parts in 106 in lattice spacing measurements.

Notes: A vertical axis goniometer has been constructed for precision diffractometry on a multipole wiggler beamline at the Photon Factory. The goniometer permits angular increments of 0.02 arcsec in ±15° range by a stepping motor and 0.001 arcsec increments in ±10 arcsec range by a piezoelectric transducer. The goniometer is mounted on an antivibration system with horizontal resonant frequency of 0.6 Hz.

Notes: A four-circle diffractometer mounted on an alignment carriage has been installed at the branch beamline BL-10A for use with the synchrotron x rays at the Photon Factory. The optical design and diffractometry are described. This system was used for x-ray anomalous scattering studies on the ordering effect in a ternary system and the atomic distribution in superlattice films. A technique developed that can extract the x-ray intensity by anomalous scattering from total intensity was applied to studies on K-shell electrons in (Co, Ni, Zn)SiO3 and SrTiO3.

Notes: This paper describes the performance of a four-circle diffractometer installed at the Photon Factory for extensive use with synchrotron radiation for various investigations in the field of solid state physics. Its main part is based on a Huber 5020.4 type diffractometer with a crystal analyzer designed for vertical diffraction plane attitude. The diffractometer is mounted on a carriage table, which can precisely adjust the position of the diffractometer with respect to the incident beam monochromatized by successive reflection from a pair of Si(111) crystals. With a perfect crystal used as the analyzer the large size of the ω and 2θ circles enables us to make high resolution (ΔQ/Q∼10−4) measurements of x-ray scattering intensity distribution from a single crystal. The large space in the center of the diffractometer permits us to put a pressurizing cell or a cryostat on the φ table for scattering measurements at controlled pressures and temperatures. Selected examples of the application are presented.

Notes: By using synchrotron radiation with high brightness, high energy, and continuous spectrum in energy, x-ray diffraction for liquid metals has been measured at pressures to 9 GPa and temperatures to 800 °C by a transmitting and energy-dispersive method. A cubic-type apparatus for high-pressure and high-temperature experiments was used. A thick specimen could be used as the absorption coefficient was small for high energy x rays (40–120 keV). A sharp slit system eliminated the background intensity from the pressure-transmitting medium and the sample container. This method has been applied to the investigation of pressure-induced structural changes in liquid selenium, gallium, and bismuth.

Notes: The carbon-fiber-reinforced plastic (CFRP) that can be used for window material in place of beryllium is a composite-type material comprising twisted carbon fibers and bisphenol-A plastic. Since the constituent elements of hydrogen, carbon, and nitrogen are thoroughly dispersed as a compound, the mass absorption coefficient of CFRP is somewhat larger than that of beryllium. The diffraction pattern of CFRP shows only a single halo pattern without a Bragg-like peak which is found in Mylar. Through x-ray diffraction, CFRP was confirmed to be practical for use as a non-Bragg window material with a moderately low mass-absorption coefficient and could be substituted for crystalline beryllium.

Notes: A station for studying the solid-state chemical reactions by the in situ Laue method using synchrotron radiation is described. A two-dimensional position sensitive x-ray detector is used as the registration device. In the reaction chamber the sample is kept at the controlled temperature and under the pressure of air atmosphere (or vacuum). The possibility of investigating the kinetic and space regularities during the solid-state chemical reactions are shown on the example of crystalhydrate dehydration in vacuum.

Notes: A diffractometer has been constructed for structural studies of high-temperature melt with synchrotron radiation. It was designed to measure diffracted intensities from the free surface of a molten sample by scanning a scintillation counter with a fixed glancing angle of the incident beam. In order to heat samples up to 1500 °C, a small electric furnace is attached to the diffractometer. It carries a hemicircular (100 mm in diameter) cover, which has a window for the passage of x rays. The window is covered with a Kapton film. The sample container made of 30 Rh-Pt is mounted at the center of the furnace. A test measurement was performed on GeO2. Monochromatic beams with λ=1.32 A and its second harmonics were taken out of synchrotron radiation by a β-alumina crystal (d002=11.3 A) and used as incident beams. To partial scattering curves obtained with λ and λ/2 were combined to a single curve after correction for absorption. The radial distribution function obtained from these data is in good agreement with that previously reported which was derived from diffraction data collected on a conventional diffractometer.

Notes: Synchrotron radiation (SR) has been proved to be a powerful tool for x-ray study under pressure. So far, an energy dispersive method has been used because the intensity of the monochromatized beam is not strong enough for the very small sample under pressure, even if SR is used. In order to perform an angle-dispersive method under pressure, we need to use one- or two-dimensional detectors. Recently, a photostimulable fluorescence plate, named an imaging plate (IP), has been successfully used as an x-ray detector at the Photon Factory. We tried to combine a diamond anvil cell with SR and IP. Exposure time on IP for the diffraction from Ag in a diamond anvil cell at 22 keV is shorter than that on an x-ray film by a factor of 50. Resolution of IP (180 μm) is not a severe problem where IP is apart from the sample by 150 mm. Data on IP are digitally treated, so that it is easy to integrate the intensity along the Debye ring. Then, the reliability becomes more than 10 times better than a one-dimensional scan. Accuracy in determination of lattice constants and integrated intensity will be presented.

Notes: Structural studies of interfaces with synchrotron x-radiation (SXR) are presently carried out with several different methods which were developed in connection with SXR over the past decade: dynamical x-ray diffraction using standing wavefields (XSW), kinematical surface diffraction (KSD), Fresnel reflection (FR), and absorption spectroscopy (SEXAFS, SXANES). These methods can determine different, and often complementary parameters of a system such as short-/long-range order, relaxation relative to bulk, structure normal/parallel to surface, valence state of surface atoms, roughness of a buried interface, etc. Accordingly, these different principles have also been combined to form new methods such as diffraction of evanescent x rays during total external reflection (DEXTER) and reflection EXAFS (REFLEXAFS). It is, therefore, highly desirable to have the opportunity to study the same interface system with different methods. On the other hand, preparation of a system in ultrahigh vacuum requires in most cases expensive bulky equipment and time consuming techniques. These considerations call for a setup which provides different experimental options. We have, therefore, installed at the beamline ROEMO I at HASYLAB a versatile UHV system for interface studies. A sample can either be prepared inside a chamber with three Knudsen cells for MBE growth and standard equipment for cleaning, heating and surface characterization by RHEED, or inside a chamber for aggressive gases. The first one is installed outside the interlock area providing access also when the ROEMO beam is on and the second one inside the interlock area.From either chamber the sample can be transferred into an analysis chamber at the ROEMO I station or into a transportable baby chamber. The analysis chamber can be used for measurements with standing waves, absorption spectroscopy and reflectivity measurements. Electrons are detected with a spherical analyzer and photons outside the vacuum through Be windows with a NaI detector for reflectivity and with a Si(Li) for scattered radiation. The baby chamber can be transported to other stations at HASYLAB which are equipped for kinematical surface diffraction and measure with high angular precision the intensity/angle correlation of many (often several hundred) different reflections. The baby chamber approach is used to avoid heavy and expensive diffractometer designs or sophisticated UHV angular feedthroughs. The baby chamber can also be used to measure with XSW, FR, and DEXTER. The performance of the system will be illustrated together with first results on different detection schemes.

Notes: The A1 station on the CHESS wiggler beamline has been the workhorse for most macromolecular crystallographic experiments. This station is equipped with a fixed energy focusing germanium (111) monochromator and a focusing total reflection mirror. Our macromolecular crystallographers made full use of the high flux of more than 1012 photons/s/mm2 and the stable beam conditions, both in position and energy resolution. As a result, the A1 station was heavily oversubscribed. CHESS is presently expanding its capabilities and a new diffraction station for macromolecular crystallography is under construction. This beamline will be powered by a 24-pole hybrid permanent magnet wiggler with a critical energy of 25 keV. A focusing monochromator, which handles a specific heat load of 10 W/mm2, will have a range of tunability which covers all relevant absorption edges from 7 to 15 keV using a Ge(111) crystal. The energy resolution and the focusing properties remain constant within a factor of 2 over the entire tunability range. We expect a brilliance of about 1013 photons/s/mm2/mrad2/0.1% bandpass. The diffraction station will be equipped with an oscillation camera which can be used with x-ray film of 5×5 or 8×10 in. size or alternatively with Kodak storage phosphors. A wide variety of clamp-on accessories, like crystal coolers, fast shutters, helium pathways, polarimeter, etc. are available. The station will contain a beampipe system, which can also be used for small angle scattering experiments with sample-to-detector distances of up to 3000 mm. The entire diffraction station, its control area, a biological preparation area, and a darkroom are to be embedded in a biological safety containment of the level BL3. This will allow diffraction studies of virulent strains of viruses and other biohazards, which could not previously be studied at synchrotron radiation sources before without causing major disruption to the normal laboratory procedure.

Notes: In the field of material sciences, it has long been desired to develope the equipment to obtain crystallographic information of micrometer-size crystalline substances. Synchrotron radiation (SR) could be a candidate to deal with such a small specimen other than electron microscope. It seems more advantageous to utilize SR from the viewpoint that the processing of the diffraction data that has already been established for identification of the materials, structure analysis, and refinement. Even in the case of SR, special care should be taken for the measurement of very weak diffracted intensities. In the case not using SR, the size of 50 μm might be the limit for the specimen to be examined by the diffraction method. The diffracted intensity is proportional to the volume of the specimen, and that of micrometer-size crystal is estimated as 10−5 times of that of the limit mentioned above. The noise level of the experiment, therefore, should be as low as possible. If the noise level becomes negligibly small, the signal could be accumulated continually to the desired intensity level by adjusting measuring time. The experiment, for the purpose, should be carried out in vacuum with the stational crystal method and with very narrow collimated x-ray beams.The Laue method is employed by the above reason, as well as the fact that the intensity of each Bragg reflection on a reciprocal row passing through the origin of the reciprocal space is superposed with each other, which also intensifies a diffraction spot on the photographic plate. The Laue camera is set up at BL-4B of Photon Factory, sealed in vacuum and installed with a very narrow collimater. The development of the system has been performed to the level which several Bragg reflections of molybdenum single crystal with 0.8 μm in its diameter can be taken on the imaging plate for 50-min exposure with ring current from 128 to 125 mA. The origin of diamonds in meteorites has been a controversy as to whether they are formed from carbonaceous materials by impact shock or directly formed from vapor. Recent discovery of vapor-growth diamonds in carbonaceous chondrites has generated a renewed interest in the origin of ureilite diamonds. Two types of micrometer-size diamonds were prepared. One of them was grown under low pressure by chemical vapor deposition (CVD) from gaseous mixtures of H2 and CH4, and another was synthesized by shock effect (kindly offered by Nippon Oil & Fats Co., Ltd.) The micro-Laue method was applied to them in order to get information about their microstructures. Two characteristics are recognized in profiles of reflections themselves and in whole patterns of the Laue photographs. The reflections of CVD diamonds are elongated but symmetric in their profiles and are distributed regularly as they are indexed by the diamond lattice, while those of shock effect are also elongated and asymmetric, and are distributed at random as they cannot be indexed. The characteristics observed by the method may be useful to ascribe the origin to CVD or shock effect.

Notes: The station designed to speed up the collection of integral intensity data from protein and virus crystals is constructed on the SR beam of the VEPP-3 storage ring. A flat triangular Si crystal cut at 8° relative to the (111) plane is used to monochromatize the radiation. The monochromator is placed on the automatic goniometer which allows us to obtain the necessary energy of radiation, to make the adjusting turns and displacements, and to bend the crystal in order to achieve focusing in the horizontal plane. All the mechanical drive units are supplied with position sensors based on multiturn potentiometers.A conventional Arndt-Wonacott rotation camera is used to collect structure information. The station also includes an optical bench which can turn about the axis coinciding with that of the monochromator, and a set of slits to cut the background and to form the beam. The ionization camera serves to adjust the monochromator and to monitor the beam.

Notes: The beamline 14B at Photon Factory is one of three branches of the 5T vertical superconducting wiggler beamline (BL14) at Photon Factory. This branch is used mainly for precision x-ray optics experiments and partly for commissioning a low-angle double-crystal spectrometer and a gas-phase scattering apparatus. A double-crystal fixed-exit monochromator was installed on this beamline; it has two offset positions, 200 and 500 mm. In order to avoid the leak of high-energy x rays from the monochromator chamber, the first crystal is shielded by lead with a rotatable 2θ window inside the vacuum chamber. A precision x-ray optics experiment facility consists of two vertical axis goniometers designed for the use of vertical polarization. Rough rotation (360° with the finest step of 3.24 arcsec) and fine rotation (within 6°, the finest step of 0.01 arcsec) are changed with a clutch. A rotary encoder with precision of 1.0 arcsec is equipped. A double-crystal aligner mounted on one of the precision goniometers is constructed to make another double-crystal arrangement. Combining the beamline double-crystal monochromator with this aligner, we can make a fixed-exit four-crystal monochromator of (+n,−n,−m,+m) setting, known as the high resolution x-ray optics in energy as well as momentum. Two independent microcomputer control systems are used for beamline monochromator and experimental facility. These two systems are connected by a serial communication (RS-232C) line via a software controlled line selector. This makes it quite easy for user-made equipment to control the beamline monochromator synchronously by its own control system. A low-angle double-crystal spectrometer was further constructed to characterize synthetic multilayers. This spectrometer consists of two ω-2θ goniometers mounted on x- (used for vertical axis) or xz- (used for horizontal axis) translation stage. These goniometers are mounted on independent carriers of a y-translation stage along the x-ray beam.

Notes: We have developed a fast measuring system of energy dispersive x-ray diffraction intensity. A solid state detector (SSD) has been used to measure the energy dispersive x-ray diffraction intensities. The energy resolution of SSD is almost ten times higher than that of a scintillation counter or proportional counter. For full use of SSD, a fast processing system of the signal is needed, especially when x rays from synchrotron radiation (SR) are used. When SSD is used for x rays from SR, however, we have two problems. One is that the dead time of conventional signal processing system is long, which prevents the efficient use of synchrotron radiation source. The other is that a fast data recording system is needed, because the number of data of a single diffraction spectrum is large. To solve these two problems, we have designed a new measuring system. The system consists of a personal computer and an interface board of multichannel analyzer function. The interface consists of peak hold, fast ADC, memory, add one, and DMA. (1) Improvement of the dead time. We adopted a successive approximation ADC to shorten the conversion time. The dead time is then 2 μs in the present system, which is much shorter than that of the Wilkinson ADC (about 40 μs). (2) Fast data recording. In most conventional MCA, the memory of MCA is separated from that of computer and the data are transferred between MCA and computer. In this case, the data are transferred by GP-IB or RS232C, and the data transfer time is several ten seconds. In the present system, the same memory is accessed by MCA and computer and the data transfer time is zero. This fast measuring system has already been installed at Photon Factory, KEK and utilized to measure the energy dispersive diffraction intensities. We have observed Pendellösung fringe induced by x-ray resonant scattering to make use of this system.

Notes: In the summer of 1988, the National Synchrotron Light Source installed a 35 period soft-x-ray undulator. We are using this device as a radiation source for a beamline designed for soft-x-ray imaging experiments that require high brightness for practical operation. We present the design philosophy and implementation of this beamline. Preliminary characterization of the beamline and undulator indicate that the central intensity of the undulator is within a factor of 2 of design. We have measured an intensity of more than 1015 photons/s/0.1% BW/mrad2 at 36 A(ring). The monochromator has achieved its design resolving power of 2000.

Notes: It has been an earnest desire of protein crystallographers to collect fast, accurate, high resolution diffraction data from protein crystals, preferably with exposure time as short as possible. In order to meet this challenge, a new type of Weissenberg camera has been developed for the recording of diffraction intensity from protein crystals using synchrotron radiation. The BL6A2 line has a plane-bending mirror designed by Y. Sato. The optical bench with triangular tilt-cut Si crystal monochromator was designed by N. Kamiya and was installed in the BL6A2 hutch. The Weissenberg camera was set on the 2θ arm of the optical bench. This camera can be used with Fuji Imaging Plate (IP) as an x-ray detector, and the reading out of the image from the IP is carried out by using BA100. The characterization of this system was carried out using the native crystal of chicken gizzard G-actin DNase I complex and its Yb3+, PCMB, indium, and FMA derivatives. Since these crystals are very sensitive for x rays, the resolution limit of the diffraction was 5 A(ring) with a 4-circle diffractometer on a rotating anode x-ray generator (N. Sakabe et al., J. Biochem. 95, 887. This complex was crystallized in space group P2,2,2, with a=42.0, b=225.3, and c=77.4 A(ring). The data were collected with this system with the 430-mm radius cassette when Photon Factory was operated at 2.5 GeV and 270 mA and the wavelength λ=1.004 A(ring) was chosen. In order to avoid overlapping of diffraction spots, oscillation angle range and coupling constant (degree/mm) were settled on the basis of simulation patterns of diffraction spots up to the maximum resolution to be measured considering the direction of the crystal axes, wavelength, radius of the camera, and mosaicness of the crystal. When the oscillation axis was a axis, the oscillation angle range was selected at either 10° (1°/mm) or 5° (0.5°/mm) depending on the density of reciprocal lattice points along the incident beam, and typical exposure time in each IP was 50 and 25 s, respectively. The exposure was stopped after 10 times oscillation. The total range of 117.5° was recorded on 16 sheets of IP with an overlapping range 0.5°.The data processing was carried out using program weis coded by T. Higashi. Two complete data sets along the a and c axes were collected using two crystals, independently, and the merge R(F2) for native crystal was 0.068. In order to know the feasibility of the data (F+−F−), Patterson maps were calculated with data of each derivative, and heavy atom vectors clearly appeared as prominent peaks in the Harker sections of the Patterson maps of both Yb3+ and PCMB derivatives. The heavy atom positions were obtained from the combinations of different Patterson and different Fourier maps, and were refined by using least-squares techniques. The final figure of merit up to 2.5 A(ring) resolution was 0.61 with 22 700 reflections. The assignment of DNase I part on the electron density maps is progressing using the Nicholson molecular model referring to its structure reported by C. Oefner and D. Suck [J. Mol. Biol. 192, 605 (1986)]. In addition to promising results of ω-aminoacid pyruvate aminotransferase [N. Watanabe et al., Book of abstracts of second Japan-China Bilateral Symposium on Biophysics, p. 83 (1988)], these results support that this data collection system consisting of a new type of Weissenberg camera using SR, Fuji Imaging Plate, BA100, and program weis is one of the fastest and most accurate systems for protein crystallography in use today. We thank the Education Ministry and the Foundations of Yamada, Naito and Toray for the financial support of this project. We are grateful to Dr. K. Namba of ERATO for our use of BA100.

Notes: A cathode constructed of a thin, directly heated strip of LaB6 is described. The cathode is simple to construct, requires modest heating power, has high current emission capability and is quite rugged. Construction details will be given and cathode performance data presented. The cathode has been used in tokamak dc current injection experiments.

Notes: We describe the use of a simple spherical aluminum-coated mirror to image the radiation of a distant XUV-emitting plasma in the slit of a vacuum spectrograph. Calculations to determine the optimum position and curvature radius of the mirror as a function of the divergence of the emitted plasma radiation are described. Efficient light collection by the grazing incidence mirror allows calibration of an intensified diode array used as a detector with a low-pressure (10−4 Torr) dc capillary discharge that does not require a complex differential pumping system.

Notes: The β spectrum of Tl obtained using a 200-μm detector is distorted with a prominent peak centered around 97 keV. The features of this spectrum can be reproduced by a Monte Carlo procedure. The minimum ionizing nature of the electrons with energy higher than about 300 keV is responsible for the prominent peak. This combined with the energy deposited by the lower-energy electrons leads to the observed experimental spectrum.

Notes: An oxide cathode assembly has been designed for long life and serviceability in a duoplasmatron ion source using deuterium gas; with cathode lifetimes on the order of 250 h with an arc discharge power of 5 kW.

Notes: Regarding the section on conversion efficiency on p. 1474 [Sec. II, part (5)], the reference to Eq. (2) in the text is in error and should in fact read, "Equation (1) provides...'' Also, in Fig. 3 the reference to Eq. (2) should be a reference to Eq. (1). Finally, in Fig. 3, the reference to Eq. (3) in fact refers to the unnumbered expression for PDCE' in the text on p. 1474, column 2.

Notes: Injection of test impurities into the edge plasma of tokamak discharges by erosion probes containing these impurities is described. By applying a short bias pulse to the probe inserted into the sol-plasma, the plasma density and temperature at the probe location can be deduced and the time of injection during the discharge can be controlled. By locating the probe at an appropriate position it is possible to release defined quantities of the material and to influence the fraction which penetrates into the core plasma. The injection of Li into hydrogen discharges of the small-sized tokamaks Castor and MT-1 is demonstrated. The nature of the main erosion process (ion sputtering or arcing) has been found to depend on the radial position of the probe and the probe potential. The lithium amount released by sputtering is determined, while in the case of arcing only an estimate can be given. The temporal evolution and the radial penetration of the Li influx into the plasma have been observed by monitoring the neutral emission line using a grating spectrometer and a CCD camera. In addition, Li transported through the plasma was collected on solid samples. An estimate is given on the fraction of the impurity efflux from the core plasma which is collected on the samples.