ALBERT

Notes: Two magnetically insulated gas-puff diodes were tested. In one design the plasma source was a fast inductive coil; in the other a coaxial gun created the plasma. The plasma current density from both sources, as well as the accelerated beam from each, was comparable to the Child–Langmuir limit of ∼10 A/cm2.

Notes: Addition of cesium vapor to H−/D− multicusp volume sources has been shown to result in significantly increased extracted ion current density. However, using a cesium oven, the initial introduction of Cs vapor causes high-voltage breakdowns that persist for extended periods. In the extreme case, source operation may no longer be possible without shutting down and thoroughly cleaning source components. If operation can be recovered, the increase in extracted ion current density persists for many days, usually until filament burn-out or other failure unrelated directly to Cs introduction. We have refined the procedure for Cs introduction to produce less catastrophic initial source operation and shorter recovery times to consistent operation. The new procedure has produced consistent H− currents of 35–42 mA at 30 keV. Higher currents, up to 64 mA, have been achieved for short periods soon after recovery. These data were obtained for a 6.4-mm-diam emission aperture using a modified Pierce geometry. In this paper, the new procedure for introduction of Cs will be described with the associated recovery characteristics. This paper will compare the emittance changes as a function of H− current, equivalent current, and plasma electrode bias. The behavior of the output over many days and shutdown-operation-shutdown cycles also will be described.

Notes: Production processes of vibrationally excited hydrogen molecules and their effects on H− production are studied theoretically by using a set of particle balance equations in a steady-state hydrogen plasma. For vibrational excitation, three processes, i.e., fast-electron collisional excitation, neutralization of moleculer ions, and atom-surface recombination, are taken into account. Enhancement of vibrational excitation including vibrational distribution and H− production is obtained as a function of three different excitation processes.

Notes: Although optimizing the magnetic filter position and the plasma grid potential is one of the most effective factors to enhance H− yield, details concerning their roles are not now clarified well. In this article, spatially resolved measurements of the electron energy distribution function, plasma fluctuations, and plasma parameters are presented. On the basis of these experimental results, we will discuss the roles of both the magnetic filter and the plasma grid biasing voltage Vb on enhancement of H− production and extraction of H− ions.

Notes: A large semicylindrical negative ion source, whose dimensions are 34 cm in diameter and 104 cm in length, has been developed. By optimizing a chamber depth and a filter strength, a H− current of 650 mA (7.7 mA/cm2) was obtained at an arc condition of 1.3 Pa, 70 V, and 1200 A. In order to increase the H− current and to reduce an operating pressure, a small amount of Cs was injected. As a result, the H− current was increased from 550 mA (6.5 mA/cm2) to 850 mA (10 mA/cm2) under an arc power of 70 V×800 A. The most significant feature of the cesium effect was the reduction of the operating pressure. With maintaining the sufficient current of 670 mA (8 mA/cm2), the operating pressure could be lowered to 0.03 Pa. At this pressure, the highest gas efficiency of 20% was achieved.

Notes: The principal electron excitation cross sections for vibrational excitation in a hydrogen discharge are reported. In the first chamber of a two-chamber hydrogen negative-ion-source system subject to the beam-line constraint of a maximum gas pressure, the density of vibrationally excited molecules reaches an asymptote for increasing discharge current or the equivalent fast electron density. Operating near this first-chamber asymptote, there exists a spatially dependent maximum negative-ion density in the second chamber. With the extraction grid placed at this maximum the optimum performance of a hydrogen-based system is determined. This optimum performance provides a criterion for the selection of differing source types for fusion applications.

Notes: It is demonstrated that a cesium-seeded volume H− ion source can be operated very stably for long pulse durations of up to 24 h. The source consists of a 20 cm cylindrical multicusp plasma generator and a 9 cm × 10 cm multiaperture extractor. By seeding a small amount of cesium, the source has produced 50 keV, 0.5 A, 1000 s H− ion beams with a current density of 14 mA/cm2. The cesium effect lasted for more than 24 h once 100 mg cesium was seeded before operation. Power flow measurement revealed that the heat loading of the ion source was low enough to operate the source in the dc mode.

Notes: A D− surface-conversion source using a solid barium converter is designed for steady-state operation to produce 200 mA of D−. A similar ion source of twice the size as the one discussed here will meet the requirements set by the present US-ITER neutral beam injector design. Among the possible types of ion sources being considered for the US-ITER neutral beam design, the barium converter surface-conversion source is the only kind that does not use cesium in the discharge. This absence of cesium will minimize the number of accelerator breakdowns.

Notes: The cesium catalysis effect of H− ion production in a volume production type of H− ion source has been investigated by the authors. These investigations suggest that the beam current enhancement is caused by a surface H− ion production process at the cesium covered plasma electrode. In order to examine this process in detail, measurement of the H− ion production probability by scattering thermal hydrogen atoms from a cesium covered molybdenum surface has been made. The measured H− ion production probability agrees reasonably well with the quantum mechanical calculation.

Notes: As part of an on-going effort to develop diagnostics for energetic charged particles from laboratory and space experiments, we examined the possibility that particle identification could be expedited by varying the applied bias voltage on silicon surface barrier detectors (SBDs). Using MeV protons, tritons, and alphas, we performed spectroscopy experiments whereby we observed changes of the energy spectrum as a function of the bias voltage. These particles were either generated via a Cockcroft–Walton linac as fusion products, or emitted from radioisotopes. The results indicate that, contrary to commonly held belief, the detector sensitive depth is not generally the depletion depth. Indeed for partially depleted SBDs the performance is not greatly degraded even for zero bias.

Notes: The gamma to charged particle branching ratios for the radiative capture reactions of deuterons by 2H, 6Li, and 10B have been measured between center of mass energies of 20 and 40 keV, 80 and 110 keV, and 150 and 170 keV, respectively. The branching ratios for these very high-energy gamma rays, having values of 23.8, 22.3, and 25.2 MeV for the targets 2H, 6Li, and 10B, respectively, constitutes the data base for the gamma ray diagnostics of the corresponding fusion plasmas. For the fusion gamma ray detector on TFTR, counting rates for these gamma rays as a function of the total fusion reaction rate will be presented.

Notes: An in situ measurement of the absolute detection efficiency of the fusion gamma ray detector on TFTR has been completed. The efficiency was determined by measuring the yield of the 4.44 MeV gamma ray from a plutonium-berrylium source situated within the vacuum vessel. The absolute detection efficiency at 4.44 MeV is extended to higher energies using the known energy dependence of the gamma ray attenuation coefficients in the vessel port cover, the detector neutron moderator, and the scintillator. The absolute detection efficiency (full energy peak detected gamma rays per source gamma ray) varies from 8.6E−9 at 4.44 MeV to 1.1E−8 at 17 MeV and is insensitive at the few percent level to relatively large variations in the radial profile of the gamma ray source distribution in the plasma. The absolute detection efficiency is used to determine the total d-3He reaction rate during recent deuterium neutral beam heated 3He plasmas on TFTR.

Notes: A camera with a 3 ns time resolution and a continuous ((approximately-greater-than)100 ns) record length has been developed to image a 1012–1013 W/cm2 ion beam for inertial-confinement-fusion experiments. A thin gold Rutherford-scattering foil placed in the path of the beam scatters ions into the camera. The foil is in a near-optimized scattering geometry and reduces the beam intensity∼seven orders of magnitude. The scattered ions are pinhole imaged onto a 2D array of 39 p-i-n diode detectors; outputs are recorded on LeCroy 6880 transient-waveform digitizers. The waveforms are analyzed and combined to produce a 39-pixel movie which can be displayed on an image processor to provide time-resolved horizontal- and vertical-focusing information.

Notes: Probe tips for scanning tunneling microscopy have been sharpened using focused ion beam milling. Reproducible tips were formed on polycrystalline W and Pt-Ir shanks, but this technique is not limited to these materials. The tips were found to have cone angles of 12±3° and radii of curvature as sharp as 4 nm. Focused ion beam machining allows precise control of the final shape of the tips which is important in metrology measurements of various nanostructure devices.

Notes: Commercial carbon composition resistors have been used as gauges to make dynamic stress measurements in homogeneous and heterogeneous reactive and inert materials. Initial loading was provided by plane wave lenses or shaped charge jets. A series of gas gun and aquarium experiments has been conducted to characterize the behavior of the gauges. Calibrations up to about 14 GPa for nominal 470 Ω resistors and 17 GPa for nominal 4700 Ω resistors are presented. The accuracy of the carbon resistor gauges is limited by response time considerations when submicrosecond rise times are encountered, and there is hysteresis during release. The gauge-to-gauge reproducibility appears to be adequate, and they survive in situations where no other stress transducer has been successfully used, such as in reacting beds of large-particle gun propellants.

Notes: A theoretical analysis of standing waves in a pipe with flow was conducted aimed toward the development of a flowmeter based on a measurement of phase difference between two points on the circumference of a pipe separated axially by an integral multiple of half sound wavelength. Effects of nonzero Mach number, variable ratios of upstream and downstream running waves, choice of location of the sensing pressure taps, and the incorrect spacings were examined numerically. Calculations were also made for steam flow where the maximum Mach number is much smaller than in cold air flows. For an industrial application where steam flow velocities are below 50 m/s, a very accurate sensor is shown to be possible. Experimental data were obtained by using an active aeroacoustic source over the range of 50 m/s to zero in an air flow. Experimental phase plots obtained from several coast-down tests have been compared with analytical results. The agreement with theory is excellent when the spacings are near Nλ/2 and the sensing locations are near the pressure antinodes. Otherwise, some zero shifts are introduced. Theory predicts that for steam flow much better results can be expected because the maximum Mach number is much smaller. Effects due to the (1−M2) factor would be imperceptible for steam flow.

Notes: A flowing solvent reactor for coal liquefaction has been developed, which uses direct electrical resistance heating of the reactor tube wall to achieve rapid, controllable heating. A computerized control system previously developed for a wire-mesh pyrolysis apparatus is used for temperature control; heating rates between 0.1 and 10 K/s, peak temperatures up to 450 °C, and isothermal holding times from 5 to 1600 s have been obtained. Alternating current is used for heating, allowing a simple thyristor bridge to be used for power control. Solvent is fed from a pressurized reservoir at up to 100 bars, obviating the need for a supply pump. Using this apparatus the effects of a variety of parameters on primary coal liquefaction processes can be examined; the design of the system and typical results are presented.

Notes: The hardware and software designs for fast measurement of dielectric properties of different substances over a wide range of characteristic times (10−5–10−10 s) by means of time domain dielectric spectroscopy (TDS) are presented. The characteristic feature of the described installation is the nonuniform time sampling of measured signals, which enables one to cover a wide range of characteristic times with a single measurement. Comparative results for an aqueous solution of lysozyme obtained on the traditional apparatus and on the described one are presented.

Notes: In this article we describe a simple SQUID magnetometer system useful for the magnetic characterization of high temperature superconductors. The system employs a commercial rf SQUID probe with associated electronics located in a 4He gas exchange cryostat. The system is equipped with a copper coil dc magnet for fields up to 50 Gauss. The cryostat is surrounded by a μ-metal shield that keeps the remanent field to less than 20 mGauss. The apparatus has been used extensively to measure both the superconducting transition temperature and width as well as the relative quantities of magnetic flux expulsion and exclusion. It has therefore served as an important first step in the evaluation of sample quality.

Notes: We describe two novel devices for optical beam alignment. One allows for a variable angle, fixed position of incidence upon a target. The other allows for a variable position, fixed angle of incidence upon a target. Cascaded together, these devices allow placement of a laser beam upon a sample with arbitrary angle and arbitrary position of incidence. These devices are particularly useful for experiments and applications involving ultrashort pulses since the time of flight through either of these devices is a constant independent of the angle of incidence and position of incidence.

Notes: The populations of ground electronic state atomic hydrogen and ground electronic state, vibrationally–rotationally excited hydrogen molecule in a negative hydrogen ion source discharge have been measured using vacuum ultraviolet (VUV) laser absorption spectroscopy. These populations have been measured under a variety of discharge conditions in two different regions of a tandem chamber ion source. Preliminary results of the measurements in the driver region and filter region are given. It is observed that the atomic hydrogen density decreases as one goes from the driver to the filter region. This indicates that the surfaces directly adjacent to the filter region are net sinks for hydrogen atoms. In contrast, the molecular vibrational population distribution shows only a small difference between the two regions, indicating that these surfaces are not net sinks for the excited molecules.

Notes: The use of electron injection into rf plasma of the radial extraction rf ion source improves the beam brightness due to the decrease of electron temperature of the plasma. Also, an emphasis was given to other factors that affect beam brightness such as aberration in the extraction cathode lens and effect of perveance.

Notes: The influence of electrons interaction with ion beams extracted from rf source on the behavior of ion beam optics has been studied. Both theoretical and experimental studies show decrease of beam emittance and beam radius due to decrease of space-charge effect produced by partial neutralization of ion beams. Decrease of neutralization percentage and increase of the beam angular divergence occur with increasing the plasma intensity of the source.

Notes: igun is a program for the simulation of positive ion extraction from plasmas. It is based on the well known program egun for the calculation of electron and ion trajectories in electron guns and lenses. The mathematical treatment of the plasma sheath is based on a simple analytical model, which provides a numerically stable calculation of the sheath potentials. In contrast to other ion extraction programs, igun is able to determine the extracted ion current in succeeding cycles of iteration by itself. However, it is also possible to set values of current, plasma density, or ion current density. Either axisymmetric or rectangular coordinates can be used, including axisymmetric or transverse magnetic fields.

Notes: Progress in Z-pinch experiments at Sandia's Saturn facility have underscored a need for an absolute yield measurement for DD fusion neutrons. The technique chosen for making this absolute yield measurement was neutron activation of indium metal samples. To calibrate the technique, a 175-keV deuteron beam was allowed to impinge on a 3.0-μm-thick erbium deuteride target, producing neutrons through the 2H(d,n)3He fusion reaction. The neutron flux produced at 0° and incident on nominal 5-g indium samples was determined by the associated particle method. This method employed protons measured from the 2H(d,p)3H reaction to infer the neutron flux produced. After neutron irradiation, the activity of the indium samples was measured with a Ge gamma-ray detector. The total activity of the metastable state 115mIn (336.23 keV) was measured, compared with the total incident flux, and a calibration factor (indium counts/neutron/gram of indium) determined. For completeness, a calibration factor for DT neutrons from the 3H(d,n)4He fusion reaction was also obtained through the measured activity of the metastable state 114mIn(190.29 keV). The experiment and the measured calibration factors for both reactions are described in the paper.

Notes: An innovative design for an ion source extractor has been carefully investigated, aimed at transporting a beam that is as parallel as possible between the plasma hole and the puller. The known ideal solution in radially unbounded electrodes is used for part of the plasma electrode, while a reentrant puller is designed and proposed, in place of a sharp or a flat one, in order to best shield the beam from the close beam pipes (as confirmed by electrostatic simulations). Beam tracking shows accordingly a substantially better current density uniformity for the reentrant puller case, when no magnetic field is present. A significant B (∼7.4 kG at the plasma hole in our case) tends to smooth out the differences in performance and improve the beam uniformity.

Notes: Ion sources with electrostatic containment of the primary electrons are very attractive since they possess an upgraded ionization efficiency and are simple to realize. However, their plasma potential is quite different from the potential of the plasma electrode, which supports extraction apertures, resulting in a non-negligible space-charge sheath between the plasma and the extraction plane. An experimental comparative study of the extraction of an ion beam with and without electrostatic containment shows the influence of the space-charge sheath on the extracted ion beam characteristics. For the same extraction potential condition, the ion beam current is lowered when the ion source uses the electrostatic containment. For monoaperture applications, an improvement of the ERIS structure in which the anode is the extraction aperture itself has been tested. In this case, space-charge sheath effects in the extraction area are negligible and the matching conditions are much better than with a standard reflex structure. For multiaperture applications, space-charge sheath effects in the extraction area are reduced when the plasma grid is positively biased with respect to the cathode potential. Experimental results prove that this polarization permits to upgrade transmission of beamlets.

Notes: Beam transportation evokes various secondary effects caused by beam-internal surfaces interaction. A number of effects connected with secondary emission of ion-electron type is considered. The cylindrical device is described which neutralizes beam spatial charge by the secondary electrons captured in the potential well of an ion beam. The conditions are discovered which lead to the following effect: secondary emitted electrons after drifting to the ion source form a virtual source of ions created due to the residual gas molecules ionization. These secondary low-energy ions drift together with the primary ions. The output part of the optical system where virtual ion source is localized works as a diverging lens, so at some distance the increased image of the local surface is formed and easily observed.

Notes: This paper describes the design and operation of a 40 spatial channel Thomson scattering system that uses multiple 20-Hz Nd:YAG lasers to measure the electron temperature and density profiles periodically throughout an entire plasma discharge. As many as eight lasers may be fired alternately for an average measurement frequency of 160 Hz, or they may be fired in rapid succession (〈10 kHz), producing a burst of pulses for measuring transient events. The high spatial resolution (1.3 cm) and wide dynamic range (10 eV–20 keV) enable this system to resolve large electron density and temperature gradients formed at the plasma edge and in the scrape-off layer during H-mode operation. These features provide a formidable tool for studying L–H transitions, edge localized modes (ELMs), beta limits, transport, and disruptions in an efficient manner suitable for large tokamak operation where shot-to-shot scans are impractical. The scattered light is dispersed by interference filter polychromators and detected by silicon avalanche photodiodes. Laser control and data acquisition are performed in real time by a VME-based microcomputer. Data analysis is performed by a MicroVAX 3400. Additional features of this system include real-time analysis capability, full statistical treatment of error bars based on the measured background light, and laser beam quality and alignment monitoring during plasma operation. Results of component testing, calibration, plasma operation, and error analysis are presented.

Notes: In plasma physics, laser diagnostics were first developed to probe the core region of magnetically confined high-temperature plasmas, but the advent of various new lasers has turned out to be useful for edge plasma studies. The recent developments of various arc and glow discharges for industrial plasma applications have required measurement of the same quantities as in the edge plasma studies and expertise in the latter has been fully exploited for the former. The experience thus gained has then been used for the advantage in the studies of edge plasma behavior in high-temperature plasmas. The interplay of these two fields of plasma studies, where laser diagnostics of plasmas (which we call "laser-aided plasma diagnostics'') is extensively used, is discussed.

Notes: A 400-fiber optic bundle has been installed as part of the beam emission spectroscopy diagnostic for measuring density fluctuations in Tokamak Fusion Test Reactor. One hundred bundles, each composed of four 1-mm-diam fibers, transmit Hα light 50 m away to 20 detectors located outside the radiation area. To shorten the time spent manually switching the bundles among the 20 detectors, a mechanized fiber selector was installed. The fiber bundles were separated into radial and poloidal groups of 220 and 180 fibers and coupled by a computer-controlled, motorized precision translation stage. The fibers were fastened to a plate and placed less than 0.003 in. from an identical plate that holds a similar array of fibers which transmits the light to the detectors. Holding the fiber spacing tolerance to 0.001 in., and using refractive index matching fluid, the highest measured loss was less than 0.5 dB, and generally was very small compared to the fiber's insertion loss. The stages are actuated with precision encoded micrometers and controlled by the beam emission spectroscopy VAX-resident software via a RS-232/CAMAC interface allowing arbitrary selections of fibers between plasma discharges with a 5 min repetition rate.

Notes: High-density plasmas are being used in the manufacture of electronic devices and systems because they provide high throughput at low pressure and low ion energy. Low pressure is desirable for maximizing process uniformity over large substrates while low ion energy is desirable for minimizing process-induced damage. However, the optimal design for a high density plasma reactor is unclear and the technology has largely developed empirically: many alternatives for magnetic and geometric design are offered for the same processing applications. In this talk we discuss diagnostic measurements of high density plasma reactors and how they can be used in developing improved reactor designs and in providing insight into materials processing. Laser-induced fluorescence measurements of metastable ion velocity distributions are made in both Ar and Cl2 electron cyclotron resonance and helicon plasmas. The effects of magnetic field configuration, power, and pressure on the energy and angular distributions of the ions will be described along with electron density measurements made by microwave interferometry. Where appropriate, comparisons will be made with the recent theoretical results of Graves and Porteous [D. B. Graves and R. K. Porteous, American Vacuum Society National Symposium, Seattle, WA, November (1991)].

Notes: The beam emission spectroscopy optical fluctuation diagnostic requires the highest possible quantum efficiency detector at 656 nm to minimize the photon statistical baseline limit to the detectable fluctuation level. A photoconductive photodiode detector with an extremely low-noise preamplifier and a reactive feedback circuit provides quantum efficiencies up to 70%–80% for a useful frequency range of at least 0–150 kHz with incident powers of ∼10 nW. The diodes are chosen for negligible leakage current and hence do not require active cooling. These detectors have provided increase in the sensitivity to plasma fluctuation amplitude by a factor of ∼14 over photomultipliers and a factor of 4 over large area avalanche photodiodes.

Notes: A comparison of fluctuation spectra from both microwave scattering and beam emission spectroscopy (BES) on TFTR has been done at similar values of k and in a plasma in which the toroidal rotation and density profile have been well characterized. The two systems measure somewhat different values of k (k〈1.5 cm−1 for BES and k(approximately-greater-than)2.5 cm−1 for microwave scattering) and average over somewhat different regions of space (2–3 cm for BES and 30–40 cm for microwave scattering). As a result, the observed spectra can be different because of intrinsic differences in ||〈δne(k)〉||2 and because the spectra are affected differently by plasma rotation. Nevertheless, when beam induced toroidal plasma rotation is known or is minimized and the two systems are looking at similar spatial locations, the results from the two systems are similar and respond in the expected way to changes in toroidal rotation. A detailed discussion of several model cases will be presented.

Notes: The further progress in the employment of ion beams in technology depends on the improvement of the ion beam formation and transport systems. The range of the devices constructed now includes both weak current devices focusing the beam to less than 0.01 μm for the purpose of microelectronics, and powerful high current multibeam plants to modify metals and alloys. Among the wide range of such equipment are the universal devices able to generate the ion beams of different species without constructive changes. For these devices the laser plasma ion source is particularly helpful. This report presents a review of the 20-year study of the laser plasma, the parameters of laser plasma ion components, the means of the ion beam formation from laser plasma, as well as the results concerning the employment of laser plasma ion sources in analytical and technological equipment.

Notes: There are now approximately 40 electron cyclotron resonance ion sources (ECRIS) for highly charged positive ions, either operating or under construction, worldwide. In recent years, the number of operating sources has been doubling about every three years. The present working level for high performance is now a compact, CW 14-GHz source with high magnetic confinement, simplified microwave injection, and a somewhat suppressed first stage. It has become clear that electron injection into the main stage plasma, from electron guns, biased cathodes, or high secondary electron emission surfaces close to the plasma, raises ion extracted currents, and several efforts are under way to understand this phenomena. Much effort has also been devoted to the production of ions from nongaseous materials, with positive ion beams from approximately half the periodic table now having been produced in ECRIS. The afterglow mode may permit intense short pulse beams of highly charged ions for injection into synchrotrons. Present development efforts are centered on understanding the performance scaling with microwave frequency and magnetic confinement, as well as continued development of intense highly charged ions in existing sources and the development of new metallic species.

Notes: We make a review of the very first observations of a sharp current peak of multicharged ions observed at the turnoff of the rf power in ECR ion sources called the afterglow pulsed current. An elementary model is presented in order to explain the charge dependence of this phenomenon. Preliminary transmission measurement shows that this kind of current seems useful for accelerator applications.

Notes: The most popular methods of producing ions of solid elements are recalled: (a) utilization of gaseous compounds; (b) oven techniques; (c) insertion techniques, which thanks to the ECRIS plasma confinement enable heating the metallic sample up to unparalleled temperatures (yielding enough vapor even for the most refractory elements); and (d) wall recycling techniques which play an important role in the ECRIS behavior. Typical ion yields for various elements are shown, comparisons are done, and a few practical hints are given.

Notes: Several key features of the electron-beam ion trap (EBIT) enable it to provide superior ion-source performance for many applications requiring ultra-high-charged ions. This paper briefly reviews these features and the operating conditions in the existing EBITs. The present performance of the EBIT as an ion source is demonstrated by producing and extracting ions up to Th80+ and U70+ at microsecond-wide ion beam pulses of about 104 ions per second. Using as examples the production of U92+, U90+, and Dy66+, modeling results are presented to show how the fundamental processes limit the quality and quantity of ions that can be obtained from an upscaled EBIT.

Notes: The SATURNE synchrotron facility is equipped with an EBIS source for heavy ion nuclear-physics experiments. SATURNE is accelerating either conventional heavy ions as Kr30+ or polarized 6Li3+ produced in two external ion sources, injected and stripped inside DIONÉ. In this paper, the DIONÉ last performances will be given and recent developments as well: evaporative cooling experiments and the main options for a new EBIS project: RHÉA.

Notes: The electron beam ion source (EBIS) is an intense source of bare nuclei of light elements (C,N,O,Ne) for short pulses. A fast extraction time of 4 μs allows advantageous single turn injection into a medically dedicated synchrotron. Since the EBIS can provide bare nuclei of all light ions, it combines favorably with a 1.8 m long radio-frequency-quadrupole accelerator (RFQ) as the only LINAC needed for an injection energy of 1 MeV/u. The required intensity of 108 ions per pulse in 1 s is easily exceeded by a factor of 10 to compensate for beam losses. The technology of an EBIS with an electron current of 165 mA at 3 keV and 50 A/cm2 is well established and has proven to be very reliable for synchrotron injection over many years in Dubna, Saclay, and Stockholm. The low duty factor (10−4) of the RFQ, where 250 kW pulses of rf power will be applied for 25 μs, eliminates the need for cooling. Therefore a four-rod structure may be put on ceramic stands, biased with a negative high voltage to avoid high voltage on the source. The combination of an EBIS with a short RFQ may be considered as the least complex and most reliable injector solution for filling a cancer therapy synchrotron with fully stripped light ions.

Notes: A multipassage magnetic spectrometer has been constructed which allows selection of a specific high charge state from the extracted ion pulse of our electron beam ion source (EBIS) and to reinject it in the emptied source, now using the electron beam of meanwhile changed energy as a target of free electrons for the study of ionization, dielectronic recombination (DR), or radiative electron capture (REC). The spectrometer consists of a H-magnet with round pole pieces and 4 identical arrangements of achromatic lenses and mirrors under 90° forming a versatile ion switchyard with the possibility of recirculation. The chromaticity of the recirculating transport system and the dispersion of this spectrometer are adjustable by electric potentials on suitably placed electrostatic deflectors inside of the magnetic field. For the injection of ions from an external ion source into the EBIS and to the beam lines, the mirror potentials are pulsed accordingly.

Notes: The article is devoted to the problems of heating and cooling of highly charged ions in EBIS. The loss rates for ions with the Boltzmann distribution function of energies for different ionic species are determined. The results suggest the use of the lightest possible ions for ion cooling. Continuous flow of light ions is proposed for cooling. The necessary parameters of light ion flow are defined in the article.

Notes: The CRYogenic electron beam ion source at Kansas State University has been in operation since spring 1989. It produces up to Ar18+, Kr34+, and Xe44+ on a regular basis. Acceleration tubes and a beamline system were added during 1990. The ion source is mounted on a high voltage platform, which can be used to vary the ion energies between 2 and 200 kV per charge. The extraction-, analyzing-, and beamline systems were designed to accept a wide range of ion masses and charge states with the mass energy product (M⋅E/q2) stretching over four orders of magnitude. The system is used to study the low-energy highly charged ions interacting with electrons, atoms, thin foils, and surfaces.

Notes: An experimental system composed of a standard negative ion source and an Nd:YAG laser is used to study the formation of negative ions by laser impact and the interaction of the laser with the negative ion beam. Using a Q-switched Nd:YAG laser (about 107 W/cm2) impinging on the solid FeS sample of a Cs-sputter source, pulses of negative ions of sulphur with a peak intensity of 3 mA and a width of 150 ns were observed. The time structure of the pulses is measured and shows a complex behavior, not yet fully understood. The same experimental system is used to analyze the production of rare negative ions in the lanthanide and actinide regions and to study their interaction with a laser beam. Cross sections for photodetachment in La− and Th− are measured.

Notes: We have developed a high-speed method to compress the two-dimensional angular distribution of space particles gathered by space plasma instrumentation into the pitch angle distribution, where the pitch angle is polar angle with respect to the ambient magnetic field. The pitch angle sorter can handle rates of up to 2 MHz and it is designed to accommodate high angular resolution plasma analyzers that are placed on a rotating spacecraft. This compression is achieved by relying on digitally encoded lookup tables to eliminate all arithmetic operations while applying the high symmetry of this compression to reduce the amount of digital memory.

Notes: A novel manometric technique that can be used to measure the inside diameter of otherwise inaccessible vertically aligned bores of known geometry is described. The technique was developed to measure the inside diameter of a long (1.5 m), relatively thin tapered tube with an uncertainty of ±0.5% (±0.2 mm in 40 mm). A substantial reduction in this uncertainty is shown to be achievable. The technique is potentially applicable to a wide variety of bore measurement situations where the desired measurement site is completely inaccessible and/or must be measured in situ.

Notes: Electrical resistance measurements at 4.2 K on an electron-beam welded Cu-Ag joint and a simple screw-fastened Cu-Ag joint are reported. It was found that the welded joint, when annealed, gives a contact resistance that is about three times smaller than the resistances for the best screw-fastened joints.

Notes: A novel "point-diffraction'' interferometer has been implemented on the Los Alamos solid fiber Z-pinch experiment. The laser beam is split into two legs after passing through the plasma. The reference leg is filtered with a pin-hole aperture and recombined with the other leg to form an interferogram. This allows compact mounting of the optics and relative ease of alignment. The Z-pinch experiment employs a pulsed-power generator that delivers up to 700 kA with a 100 ns rise time through a fiber of deuterium or deuterated polyethylene (CD2) that is 5-cm long and initially solid with radius r≈15 μm. The interferometer, using a Δt≈200 ps pulse from a Nd:YAG laser frequency doubled to λ=532 nm, measures the electron line density and, assuming azimuthal symmetry, the density as a function of radial and axial position. Calculations predict Faraday rotations of order π/2 for plasma and current densities that this experiment was designed to produce. The resulting periodic loss of fringes would provide the current density distribution.

Notes: A code for calculating the actual spectral line shapes in magnetically confined plasmas of the tokamak type is described. The code determines the resulting line shape averaged along the line-of-sight of the spectrometer, starting from prescribed thermal temperature, ion emissivity, and flow profiles, for a plasma immersed in a magnetic field. In addition, the influence on the impurity linewidths of nonthermal fluctuating velocities due to fluctuating electric fields and to possible magnetic fluctuations is also included. Typical applications of the code to spectral data analysis in the TJ-I tokamak are given.

Notes: In materials testing it is well known that material strengths depend on: loading rate, whether loading is compressive or tensile and, in some cases, previous loading history; a widely useful loading technique should provide adjustable loading rate and reproducible compressive or tensile loading. Further, real-time microscopic studies require localized loading in a predetermined region−the microscope field of view. Symmetrical axial loading of cylindrical specimens can provide predetermined loading localization. Symmetrical loading may also facilitate analysis by localizing loading within a region of specimen material far from interfaces with other material or fixed or free ends. We describe a symmetrical impulse loading technique for compressive or tensile microscopic response studies. The technique is based on the use of magnetically induced stress waves and is capable of microsecond pressure pulse widths, (approximately-greater-than)10 000 psi pressure peaks and nanosecond synchronization of the symmetrical loading pulses. Our goal is to observe in real time the response of structural materials at the micron level with a scanning electron microscope.

Notes: Use is made of the fast response capability of the hot film shear gauge to perform unique shock tube and field test blast wave surface shear measurements. Mean flow turbulent calibration data are presented from three different test facilities: a low speed wind tunnel, a high pressure pipe facility, and a laboratory scale shock tube. Favorable agreement in calibration data between the three facilities is demonstrated. The good correlation in calibration results validates the "established'' formulation procedure and provides a unique verification of available shock tube shear data. Measurements of ground shear under clean wall, i.e., nondusty, flow conditions are reported for blast waves created by high explosive detonations under large scale field test conditions. Satisfactory scaling of results in terms of event yield and overpressure location is demonstrated.

Notes: An alternative form of application of an electric field to semiconductors so as to provide electroreflectance modulation is presented. Two metallic contacts, a large ring-shaped one enclosing a small transparent one, are deposited on the specimen surface and connected to the two leads of a signal generator. Results from a highly doped n-type silicon bulk and from an undoped 4000 nm silicon film on sapphire demonstrate that this technique yields spectra equivalent to traditionally performed electroreflectance or photoreflectance. We also show that electroreflectance response can be obtained with a current generator connected across a single metal contact.

Notes: A new white beam single-crystal Laue diffraction (LD) and energy-dispersive powder diffraction (EDPD) facility has been constructed on station 9.7 of the SRS. This station receives radiation from a 5-T superconducting wiggler magnet with useful photon flux from 5 to 60 keV and a peak flux on the sample of 7×1011 photons/s/mm2 in a 0.1% bandwidth at 10 keV. The novel design of this facility allows rapid changeover between the two experiments without compromising either. Components have been built in a modular manner for ease of optimization for a particular set of data capture conditions.

Notes: The high brilliance of the new generation of synchrotron radiation sources improves the grazing incidence x-ray diffraction techniques and leads to great advances in the determination of crystal surface structures. The evaluation of the diffraction pattern intensity can be obtained in the distorted-wave approximation introduced by Vineyard. In conditions of total reflection, typical penetration depths are about 50 A(ring) and only the atoms in the near-surface layers interact with the electric field and produce the diffraction pattern. This model is the ground for a simulation code developed in order to calculate the diffracted peaks intensity of reconstructed and/or relaxed surfaces. An example of application, the Au (110) (1×2) reconstructed surface, is given. The intensity and the position of the diffraction peaks are determined for different values of the azimuthal angle and for different diffraction orders. The program takes into account the parameters of the beamline Advanced Line for Overlayer Interface and Surface Analysis (ALOISA) which will be available at the storage ring ELETTRA in Trieste.

Notes: The two-circle powder diffractometer on Station 8.3 at the SRS has recently been relocated to station 2.3, some half the distance from a dipole radiation source with the same nominal 1.2T field. The purpose of this paper is to detail the changes and modifications to the diffractometer operation.

Notes: A versatile precision diffractometer for nuclear Bragg scattering was designed and constructed at the Photon Factory. Standardized component goniometers can be arranged to address various requirements of incident beam conditioning for nuclear Bragg scattering, including a high-energy resolution monochromator with wide angular acceptance as well as a circularly polarized incident beam.

Notes: Results of measurements of the reflected beam intensity and photoelectron yield under conditions of dynamical 111/220 diffraction of synchrotron x-ray radiation are presented. The experiments were carried out on beam lines 15C and 14B at the Photon Factory. Two possible multicrystal arrangements were used for the preprocessing of the incident beam. In the first one, a double-crystal Si (111) monochromator was used for monochromation and collimation of the x-ray beam in the vertical plane and a Si (220) channel-cut crystal was used for collimation in the horizontal plane. The second crystal arrangement is based on a (111)-oriented Si crystal adjusted for a six-beam Laue diffraction condition. The anomalously transmitted (μt/γ0 ≈ 40) beam was used as an incident beam in the x-ray standing wave measurements. The angular dependence of the total photoelectron yield was measured using a gas flow proportional counter.

Notes: The high-precision x-ray optics station is to be installed on one of the five branches of the wiggler beamline at the new dedicated synchrotron radiation source "Zelenograd.'' It is intended for the precision x-ray diffraction measurements using different methods which have been developed in the last decade for the structure studies of nearly perfect crystals and interfaces. The station consists of the double-crystal monochromator unit, the main goniometer with the crystal analyzer, the slit system with ion chambers, and the control and data acquisition system. The design of principal units and modules of the station is treated. The x-ray optics schemes which can be implemented on the station are described. The control and measuring system for x-ray experiments is presented.

Notes: A triple-axis/four-circle diffractometer was newly designed and installed in the experimental station BL-3A of the Photon Factory. The station is currently used for multipurpose works such as diffraction, scattering, and absorption in the x-ray region both for basic and applied research. The diffractometer consists of three different types of goniometers: (1) a four-circle goniometer having a high-precision ω axis and a large, off-centered χ circle to mount various apparatuses such as an electric furnace and a helium cryostat; (2) a two-circle goniometer for crystal analyzers; and (3) a two-circle goniometer for collimators. "Dynamic'' studies at high temperatures and microarea diffraction studies are possible by using a highly focused x-ray beam provided by a mirror-monochromator system in BL-3A. Furthermore, the combination of the high precision diffractometer and the well-collimated beam makes possible such experiments as high energy and/or momentum resolution measurements, ultrasmall angle scattering, and diffuse scattering.

Notes: In order to achieve the ultimate time resolution of a synchrotron source we propose a new experimental technique by which time-dependent structural changes can be monitored on the time scale of synchrotron pulse widths. Samples will be studied by a rotating crystal Laue diffraction technique where we rapidly spin the sample and observe the diffraction pattern from a broadband of incident x rays. A computer simulation is presented of the diffraction pattern time evolution using the parameters for an APS undulator of a phase change in the YBa2Cu3O7−x superconductor. We will discuss the application of this and closely related techniques at other synchrotron sources including bending magnets and insertion devices at NSLS and CHESS.

Notes: The station is intended for x-ray analysis of single crystals, primarily that of proteins with the beam of synchrotron radiation from the superconducting wiggler of a special storage ring E=2.0 GeV, I=0.3 A in the town of Zelenograd (TNK).1 The dimensions of the radiation source are 2.352 σx⋅σz=1.5×0.05 mm2, the brightness for λ=1.5 A(ring) is 1015 photon/(s mm2 mrad.2 0.1% (Δλ/λ)). The station comprises the device forming the monochromatized primary beam (λ=0.5–2.2 A(ring), Δλ/λ−3∼10−4) that consists of an asymmetric focusing monochromator with triangular-shaped Si or Ge crystal curved as a round cylinder,2 a segmented mirror of total external reflection placed behind the monochromator on a rotating bench consisting of 8 flat glass 200×50×25 mm2 segments that form a surface imitating an elliptical cylinder, three pairs of horizontal and vertical slits, monitor–ionization chamber, four-circle diffractometer with scintillation counter and horizontal main axis placed on the adjustable carriage that can turn about the monochromator axis; position-sensitive proportional chamber with spherical drift space, 512×512 elements of space resolution and time resolution of 106 photons per second that can be vertically shifted and bent around the holder horizontal axis. The monochromator goniometer as well as the crystal bend and the mirror segments are driven by the multiple-turn potientiometers by the computer and CAMAC interface.The automatic four-circle goniometer device is controlled by stepping drives, the angles being controlled by means of 16 register absolute optoelectronic detectors and the same computer. The data from the position-sensitive detector are read through the increment channel to annex memory of 256 K word (16 registered) capacity in the CAMAC block and then to the computer to be followed by visualization on the coloured display. All the station units are to be manufactured in 1991. The working out and manufacturing of the instrumentation is being fulfilled by the Institute of Crystallography of the USSR Academy of Sciences, the Department of nonfilm chambers of the High Energy Laboratory of the Joint Institute for Nuclear Research (Dubna) and the Special Design Bureau at the Institute of Crystallography.

Notes: An imaging-plate system designed for the full Rietveld refinement of crystal structures at high pressure is described. Emphasis is given to techniques that have been developed to obtain data free from contaminating diffraction peaks. Initial results from studies of III–V semiconductors and La2CuO4 are given.

Notes: Elastic and thermal properties of Au/Ni superlattices have been investigated by x-ray diffraction on a synchrotron radiation source at the Photon Factory. An elastic response of [Au(10 A(ring))/Ni(10 A(ring))]50 to hydrostatic pressure generated by a diamond anvil cell has been measured in the layer-stacking direction. Its compressibility obtained from the pressure dependence of its superlattice period (Λ vs P) shows an anomalously small value compared with either bulk Au or Ni metal. Linear thermal expansions has also been measured by a similar method (Λ vs T). A significant anisotropic behavior between the layer-stacking and in-plane direction was found in both [Au(10 A(ring))/Ni(10 A(ring))]50 and [Au(4 A(ring))/Ni(4 A(ring))]210.

Notes: High intensity for diffraction experiments with high-energy resolution on an intense x-ray beam, like the bending magnet beam lines at the ESRF, requires a strict control of the curvature of the optical elements placed in the beam for geometrical focusing and for wavelength monochromatization. Unwanted curvatures can come from nonuniform and variable heating of the optical elements produced by the absorption of x rays. To design the CRG/D2AM beam line described in the accompanying paper, some new techniques were developed to control these effects based on geometrical, i.e., topological, considerations. (1) Cooling of the entrance mirror: longitudinal curvature can be strongly reduced by cooling the mirror from the sides (and not from the rear) and only near the reflecting surface (i.e., not over the whole lateral surface). The cooling can be achieved for instance with an isothermal liquid Ga eutectic bath. (2) Cooling of the first single-crystal Si monochromator: because of the size of the crystal, only cooling from the rear is conceivable in this case. It can be shown by calculation that the curvature due to the front-to-rear gradient can be exactly compensated by the thermal expansion of a metallic layer at the rear of the crystal, having a larger expansion coefficient than Si.

Notes: An x-ray beam line BL-3A at the Photon Factory has been designed and constructed to have optical components of a collimating paraboloidal mirror, a sagittal-focusing double-crystal monochromator, and a focusing paraboloidal mirror. The evaluation at the (+,−,−) setting of Si (111) showed that the vertical angular divergence was reduced from 13.4 to 9.5 (arcsec) by the collimating mirror. The vertical focusing with two mirrors gave the beam size of 0.2 mm (1/50). The horizontal beam size was reduced to 1/60 by sagittal focusing.

Notes: A new low-energy electron diffraction (LEED) system has been constructed with a pulse counting position sensitive detector using channel plates and a wedge and strip anode. The detector accepts diffracted electrons over a 120° angle and the LEED pattern is recorded as a 256×256 pixel image. Individual LEED spot intensities can be measured up to a maximum linear count rate of ∼5 kHz while the dark count rate is ∼0.02 Hz, yielding a dynamic range greater than 105. Incident beam currents for LEED measurements are ∼1 pA. Diffuse LEED intensities from disordered systems can be measured using the large dynamic range of this instrument. Examples of diffuse LEED measurements are presented. The low incident beam currents also allow for LEED intensity-voltage measurements on surfaces sensitive to electron beam damage and on nonconducting surfaces.

Notes: The multiwavelength anomalous diffraction and diffuse scattering (D2AM) beam line project is designed for a 0.8-T bending magnet at the ESRF for scattering experiments with multiwavelength anomalous techniques in the fields of (1) Materials Science (small angle and diffuse scattering) and (2) Crystallography of Biological Macromolecules (in particular MAD diffraction). Symmetric optics (a horizontally focusing double monochromator placed between two long, pseudoparabolic, vertically focusing mirrors) are planned. The optics, tested using the program shadow, should achieve a focus of 0.3×0.3 mm2 with an estimated flux of 1011 photons/s in a relative bandwidth of 2×10−4. Details of the beam line design are described in this note.

Notes: Using a gamma-ray detector and a television camera system for synchrotron light, high-energy bremsstrahlung and horizontal growth of the synchrotron light source were observed when sudden decrease in the electron-beam lifetime occurred due to dust trapping in the electron beam. Two types of beam current losses were found; one was a continuous beam current loss, and the other was a short-term beam current loss. High-energy bremsstrahlung at a location was observed in a short time and after that, the bremsstrahlung was not detected in spite of the occurrence of dust trapping phenomena. The fact suggests motions of the trapped dust particles in the longitudinal directions. Materials collected in the beam chamber are dust particles from ion pumps and dust particles made during the beam chamber processing for welding. Most of the collected dust particles were less than 2 mm in size and surfaces of some dust particles were melted with the electron beam. Simple analysis was carried out for the conditions necessary for a dust particle to be trapped, for motions of the trapped dust particle, and for interactions between the trapped dust particle and the electron beam. The analysis showed that a dust particle less than 3 mm in size, made of Al, can be trapped and that the trapped dust particle can move in the vertical and longitudinal directions.The analysis also suggested that a dust particle in size of about 2 mm can be continuously trapped around the electron beam without being destroyed by the electron beam. Furthermore, the analysis explained the difference between the two types of beam current losses observed in the ring. Experiments which simulate the electron beam using a Cu wire in an evacuated beam chamber show that a dust particle (less than 70 μm) is trapped sufficiently. The experiments also coincide with theory for an attractive force acting to a conducting small particle. The calculated electric field of the electron beam and the calculated electric charge of dust particles given through the photoelectric effect in the TRISTAN accumulation ring are 100 times and 104–106 times higher than those of the simulated experiments, respectively. In the ring, the attractive force caused with the average electric field and with the expected charge is 10–103 times larger than that of the simulated experiments. Therefore, a dust particle (less than 2 mm) can be trapped sufficiently. An electrostatic dust collector using an electron beam and an electrostatic force are effective in removing all of the sample dust particles in the test chamber for the simulated experiments. A method to remove trapped dust particles using electrostatic electrodes is also discussed. It is expected that such electrodes can be useful for trapped dust particles moving in a longitudinal direction.

Notes: An easy to build, high intensity monochromator for helium II radiation is presented. The design includes a double focusing, nonblazed, toroidal grating with a groove density of 800 l/mm. The adjustment and focusing properties of the design have been studied using an optical simulation program. It is found that all necessary adjustments of the grating may be performed by using only two degrees of freedom; rotation and sidewise shifting. Inner and outer valence photoelectron spectra of N2 and CO have been recorded using monochromatized HeIIα radiation. The study reveals extensive vibrational structures in the inner valence region of both molecules. A new state has been identified in the CO molecule.

Notes: A versatile small-angle x-ray diffraction/scattering system has been developed at Stanford Synchrotron Radiation Laboratory for studies of biological and other materials. The system includes two sets of collimation slits separated by an ionization chamber, a sample holder cooled by a circulation bath, a vacuum/He scattering path after the sample holder and a detector, either a linear one-dimensional position-sensitive proportional counter or a position-sensitive quadrant detector. Data aquisition is controlled by a VAXstation through a CAMAC interface. Menu-driven data acquisition and on-line analysis software has been developed. The system can be used to collect small- to intermediate-angle x-ray scattering and diffraction data. Monochromatic, anomalous, and time-resolved diffraction/scattering experiments are possible. A time-resolved spectrophotometer using photodiode arrays has also been developed for simultaneous measurements of optical absorption spectra and x-ray scattering/diffraction.

Notes: Outlined are design features of a versatile high-resolution two-axis diffractometer that is being constructed for operation at the Photon Factory as an Australian national facility. The instrument features optional use of multiple-imaging plates on a translating cassette to allow rapid recording of an almost complete range of data covering both the high-angle and small-angle scattering regime or alternatively the use of electronic detectors. The instrument will be capable of operation in various modes including the following: (i) high-resolution powder diffraction with single-channel counter and crystal analyzer, (ii) high-resolution, high-speed powder diffraction in the Debye–Scherrer mode with imaging plates as recording medium, either stationary or translating (for time-dependent studies), (iii) small-angle x-ray scattering with imaging plates as recording medium, (iv) protein crystallography in screenless Weissenberg mode, and (v) two- or three-axis single-crystal diffractometry. The salient features of the instrument are the use of a double-crystal sagittal focusing monochromator as primary monochromator together with the optional use of a condensing–collimating channel-cut (CCCC) monochromator or other channel-cut monochromator as secondary monochromator. The use of a CCCC monochromator enables fine tuning of beam position on sample, harmonic suppression, beam-condensation, and variation of wavelength bandpass. Further features include the use of high-precision incremental encoders on both axes, together with the capability of operating the whole diffractometer, including secondary monochromator and detectors, in vacuum of order 10−3 Torr in order to reduce absorption and parasitic scattering, and the use of a large camera radius (approximately 0.57 m) for the imaging plate cassette in order to increase angular resolution and signal to noise.

Notes: This article presents the design of two diffraction beamlines, BL2 and BL3, at the European Synchrotron Radiation Facility. The materials science beamline will produce a monochromatic beam tunable in the energy range 5〈E〈60 keV and provide an energy resolution of 10−4 〈 ΔE/E 〈 3 × 10−4 below ∼40 keV. The radiation is generated by a 24 pole wiggler with critical energy εc = 28.8 keV and K=14.0. It produces 4.9 kW of power over a horizontal fan of 1.5 mrad. The heat load on the first monochromator crystal is controlled by an adaptive premirror set to reflect an energy band exceeding the desired monochromator energy by 20% or by low energy absorbing filters. The first monochromator crystal will be cryogenically cooled. The premirror and a symmetric postmirror will collimate and refocus in the vertical plane. Horizontal focusing will be done by sagittal bending of a rib enforced second monochromator crystal. The white beam station BL3 is optimized for Laue diffraction in the energy range 5〈E 〈60 keV. The source is a 44 pole wiggler with εc = 17.2 keV and K=4.7. It produces a power of 1.8 kW and an integrated flux ∼ 6 × 1017 ph/s. over a horizontal fan of 0.5 mrad. The radiation is focused by a toroidal mirror with fixed sagittal radius.

Notes: The design and test of the focused x-ray beam line 4W1C for general purpose diffraction study at the Synchrotron Radiation Laboratory of the Institute of High Energy Physics is reported.

Notes: The first x-ray diffraction experimental station at Beijing Synchrotron Radiation Laboratory has been available for synchrotron radiation users in research. The station is located on the back-end of 4B9A, a beamline from a bending magnet. When the storage ring of BEPC operates in a dedicated mode (2.2 GeV), 4B9A provides a focused monochromatic x ray in between 4 and 12 keV. A four-circle diffractometer with a crystal analyzer is installed. Experimental processes such as apparatus alignment, monitoring of incident radiation, acquisition of diffracted intensities, and running of the monochromator, are controlled with a computer through CAMAC modules. In this article, instrumentation and performances of the station are outlined.

Notes: A new energy dispersive diffractometer has been developed. It consists of a solid tungsten carbide conical collimator and a large area annular detector. Diffracted intensities are increased by at least one order of magnitude. Developed for high-pressure studies and their microsamples, the instrument will improve the accuracy of intensity measurements by reducing crystallite statistics effects and the collection of a complete cone of diffraction will greatly facilitate high-pressure single-crystal studies. The results of the first test of the instrument are reported.

Notes: Focusing optics have been installed on the 5.0 T Wiggler beam line of the SRS at Daresbury Laboratory for use with x-ray diffraction measurements of surfaces and interfaces. A significant increase in the flux has been achieved without excessive degradation of the resolution in the vertical plane. The full width at half-maximum of the focused image compares well with the predictions of ray tracing analysis.

Notes: A purpose-designed x-ray fiber diffraction camera has been constructed in the Keele University Physics Department to be used at the SERC Daresbury Laboratory Synchrotron Radiation Source. The camera allows time-resolved studies of the change in both the high- and low-angle diffraction patterns during drawing and annealing of polymer films to be recorded. Drawing of the films is achieved by two opposed stepper motors which allow films to be drawn uniaxially in both directions. The temperature of the sample environment can be controlled to within 1 °C by a radio spares proportional, integral, and derivative (PID) controller. Diffraction patterns can be recorded on the Enraf-Nonius TV FAST detector or on photographic film. Exposure times using the FAST detector are typically 5 s, representing a gain of approximately a factor of 5 over photographic film. The FAST detector has a further advantage over photographic film in that essentially an unlimited number of diffraction patterns can be recorded end-to-end while a structural transition is being followed. A video camera is incorporated to allow the variation in the gross appearance of the specimen to be recorded during drawing and annealing and to be related to the variation in the diffraction pattern. The application of the camera in the study of drawing and annealing of poly (aryl-ether-ether-ketone) (PEEK) is described.

Notes: The resolution function of a powder diffractometer at a synchrotron radiation source increases with increasing Bragg angle of the monochromator. Consequently, a monochromator close to backscattering has been designed and built. Two mosaic crystals of beryllium in nondispersive setting serve as optical elements. They are mounted on goniometer heads inside a tube-like housing which may be evacuated. Fine adjustment of one of the crystals is done with a micro-goniometer driven by a magnetostrictive actuator. The fact that the housing is a tube allows the use of the assembly as part of a multi-purpose monochromator system for powder diffraction.

Notes: A new instrument (Station 9.5) has been established on the wiggler line at the Daresbury Synchrotron Radiation Source (SRS). It extends the experimental capability at Daresbury for macromolecular crystallography beyond what is provided for with Stations 7.2 (Ref. 1), 9.6 (Ref. 2), and 9.7 by providing a point focused white beam (from a Pt-coated toroid mirror) and/or a rapidly tunable monochromatic beam (using a water-cooled double-crystal monochromator (Ref. 3). The design principles of the new Station 9.5 have been published (Ref. 4). A CCD detector for the station is being developed (preliminary work is described in Ref. 5, or see the additional poster at this meeting) to allow time slices of part of a diffraction pattern to be measured. Laue patterns are currently recorded on film, but access to an image plate detector will shortly become available. Shutter speeds down to 50 μs are routinely available using a rotating disk shutter (Ref. 6). Fluorescence detectors are available for optimized anomalous dispersion data collection. The experimental bench is long enough to accommodate a camera system, and downstream from it an "on-line'' image plate scanner. Data collected on the instrument in various modes of operation will be described for a variety of macro and small molecule crystal systems.

Notes: Very-high-energy resolution measurements using x rays can be achieved by extreme backreflection (Bragg angle close to 90°) from perfect crystals. This technique, combined with the high intensity of x rays emitted by the HARWI wiggler at DORIS, DESY Hamburg, allowed the development of the instrument INELAX for inelastic scattering experiments. Recently, the high-energy resolution of 9 meV could be achieved and the instrument proved to be an excellent tool to investigate collective excitations in condensed matter. Energy transfers from 10 meV to 5 eV and wavevectors over the whole reciprocal space are accessible.

Notes: A multiple crystal diffractometer for polarization optical experiments in x-ray region was constructed at the Photon Factory. Using an x-ray phase retarder of transmission type in Bragg geometry, tunable-wavelength circular polarized x rays of both helicities were produced with high degree of circular polarization. A method of complete determination of the polarization states in x-ray region was developed with the reverse use of the phase retarder. Polarization switching with a frequency of 0.3 Hz was performed by flipping the phase retarder in a bistable mode. An optical scheme of producing highly intense circular polarizations using the phase retarder and an x-ray undulator is discussed.

Notes: There have been various ideas for generation of circularly polarized synchrotron radiation. Among them, this paper is concentrated on the novel multipole wiggler, elliptical multipole wiggler (EMPW), developed as an intense circularly polarized x-ray source at the National Laboratory for High Energy Physics. The EMPW has two jaws of magnet arrays. One jaw is coupled vertically and located along an electron beam axis to the other coupled horizontally with a phase difference of 1/4 magnetic period. In this article, spectral and technical performances of EMPW's are described as compared with those of asymmetric wiggler.

Notes: We describe pump-probe experiments in the x-ray region using synchrotron radiation to supply both the pump and probe beams. The time between pump and probe is adjustable on the nanosecond time scale by means of an optical delay line operating in the x-ray region. With the "third generation'' sources presently under construction around the world it should be practicable to study optical excitations using similar techniques to those described here. The initial studies we describe were carried out at the National Synchrotron Light Source. A 30-μm-thick silicon [110] crystal was irradiated by white light from a bending magnet. The radiation passing through this sample was monochromated by two silicon [660] reflections in such a way that the monochromatic beam was directed onto the first surface of the thin crystal sample. The surface of this thin crystal was probed by recording the symmetric (220) reflexion 2.78 ns after illumination by the white beam. Techniques for overcoming the background problem resulting from scattering of the white beam by the sample crystal are discussed.

Notes: Taking advantage of the high brightness of synchrotron radiation, changes in the microstructure of silicon steel sheets in the secondary recrystallization process at 1233 K were measured by consecutive recording of the pole figure using a newly developed system consisting of the x-ray diffractometer and the translating imaging plate and by real-time observation of Laue topographic pattern using two kinds of TV camera. It was shown that {110} 〈001〉 oriented grains grew, after a certain incubation period of time, at a burst and occupied most of the sample volume. There was an appreciable anisotropy in the migration of the recrystallization front. When tensile strain was applied to the sample, growth of the {110} 〈001〉 oriented grains was appreciably delayed.

Notes: A high-resolution fluorescence spectrometer using a Johann geometry in a backscattering arrangement was developed. The spectrometer, with a resolution of 0.3 eV at 6.5 keV, combined with an incident beam, with a resolution of 0.7 eV, form the basis of a high-resolution instrument for measuring x-ray absorption spectra. The advantages of the instrument are illustrated with the near-edge absorption spectrum of dysprosium nitrate.

Notes: In the past γ-ray Compton scattering experiments proved their value for the investigation of many-body effects in the electronic structure of solids by measuring the projection of the electron momentum density onto the scattering vector, the so-called Compton profile. Due to the availability of modern synchrotron radiation facilities the momentum resolution of the technique was improved substantially and, by using circular polarized photons, "magnetic'' Compton profiles could be determined in ferromagnetic materials. A new approach, where the Compton scattered photon is measured in coincidence with the recoiling electron, allows for a direct determination of electron momentum densities in solids. This (γ,eγ) scattering technique will reach its full potential once synchrotron radiation from undulators in electron storage rings operating at energies above 10 GeV will be available.

Notes: Application of high resolution instrumentation to the study of the near-threshold behavior of fluorescent and scattered radiation along with such properties as polarization and angular distribution has proven fertile. This article reviews some alternative strategies for improving the efficiency with which such secondary spectra can be registered.

Notes: Backreflection x-ray standing waves (BRXSW) and crystal truncation rod (CTR) scatterings have been used to probe the structure of heteroepitaxial CaSrF2 crystals on GaAs(111)B substrate. Coupled with the film-thickness information obtained from x-ray Fresnel reflectivity data, the combined x-ray standing wave and BRXSW data suggest one or both of the F and As layers missing from the heteroepitaxial interface. The CTR data support a missing F layer and interface (Ca, Sr) atoms occupying the T sites on GaAs(111) surface.

Notes: A versatile experimental setup is presented for both x-ray standing waves (XSW) and x-ray photoemission spectroscopy (XPS) studies in an energy range up to 7 keV. The compact apparatus operates under ultrahigh vacuum and includes in situ sample preparation and characterization techniques. For the XSW scans the incident photon energy is tuned through the Bragg reflection from the sample for aitch-thetaB ≈ 90° while measuring the intensity and energy distributions of both the emitted electrons and fluorescence radiation simultaneously. Alternatively, desorbing positive ions can be analyzed as a function of the standing wave phase shift using a time-of-flight spectrometer. In addition, energy dependent high-energy XPS measurements with medium overall energy resolution (ΔE=1.5 eV at 3 keV) can be performed. Selected results obtained at the focused EXAFS II beamline of HASYLAB are shown.

Notes: An x-ray beam incident on a liquid surface at glancing angles may be specularly reflected (XR), diffracted (GID), or yield fluorescent radiation (GIF). The three mechanisms, encompassing liquid surface x-ray spectrometry, give complementary information about the liquid surface structure. In common is the incident monochromatic beam: It has the shape of a downward sloping thin sheet with the sheet normal and the propagation direction ideally spanning a vertical plane. Methods to produce such a beam from a horizontal, polychromatic synchrotron radiation beam are discussed. For a high brilliance undulator source the simplest solution turns out to be Bragg reflection from a single tilted monochromator crystal in Laue geometry.

Notes: Ion sources can be damaged by arcs between metallic components of the source if these arcs are permitted to last. The negative-biased low-work-function converter in a surface conversion negative ion source is especially susceptible to metal-arc breakdown damage. Here an electronic circuit for minimizing the damage caused by such an arc is described. The circuit uses a transistor switch and an inductor in series with the converter bias power supply to limit the damage during the metal-arc breakdown.

Notes: As with most similar equipment, the method consists in applying a sinusoidal voltage to an unknown impedance and measuring the current through it. The advantage of the developed equipment is that it allows independent and simultaneous measurement of the resistive and reactive components of the current through the sample impedance, thus making possible the determination of impedances in magnitude and phase. The measurements can be controlled with a computer using a digital interface. The instrument may also be controlled with a computer using a digital interface. The instrument may also be controlled manually from a front panel. The apparatus was designed to operate in the audio range 1 Hz–100 kHz for currents even below 1 μA. The analog outputs may either be connected to an X-Y recorder or the data can be acquired with a computer through an analog-to-digital converter. The laboratory tests have shown a good performance according to the design specifications. These tests have been carried out using discrete circuits made of calibrated components.

Notes: A new amplifier, designed to operate with fast semiconducting bolometers, is presented. Based on current detection of the bolometer signal, it allows one to obtain good sensitivity with response times of about 10 ns without using cryogenic electrical components. The amplifier was used to detect heat pulses propagating in a Si crystal.

Notes: A fraction marker-timer controller has been designed that partially automates peak collection and provides event marking during high-performance liquid chromatography of partially purified samples having complex chromatograms. The device is activated via a pushbutton switch when a peak of interest elutes. The apparatus places an event mark on the detector's chart recording, provides a time delay to account for detector-to-fraction-collector dead volume, and then advances a fraction collector to capture the peak in a test tube. If more than one peak elutes in the dead volume window, up to three independent time delays may be triggered.

Notes: A design for a heater stage capable of operating in a high oxygen partial pressure is presented. Substrates attached to the stage may be heated up to 900 °C in oxygen partial pressures from 10−3 to 760 Torr. The design of the heater allows easy replacement of all parts.

Notes: A simple yet reliable laboratory laser microrefractometer is described. A detailed theoretical analysis of the errors is made. The construction permits the utilization of various lasers as light sources. Preliminary investigations on some liquids with a He-Ne laser are carried out. The results confirm the applicability of the configuration, and the practical accuracy is in good agreement with the theoretical one. The possibilities for further improvement of the device in terms of range and accuracy are discussed.

Notes: The distortion of the cylindrical Langmuir probe I-V characteristic, connected with the ohmic resistance of its operating element, is investigated. The relations given in the paper enable one to reconstruct the shape of the undistorted I-V characteristic from the experimental data.