ALBERT

Notes: A multichannel far-infrared interferometer used on the Joint European Torus (JET) is described. The light source is a 195-μm DCN laser. The instrument is of the Mach–Zehnder type, with a heterodyne detection system. The modulation frequency (100 kHz) is produced by diffraction from a rotating grating. There are six vertical and two oblique channels. The latter rely on retroreflection from mirrors mounted on the vessel wall. Their vibration is compensated by a second wavelength interferometer at 118.8 μm. The various subsystems are described, with emphasis on features necessitated by (a) large path lengths, (b) remote handling requirements, (c) fluctuations in atmospheric humidity, and (d) unmanned automatic operation. Typical measurements, along with real-time and off-line data analysis, are presented. The phase-shift measurement is made with an accuracy of (1)/(20) of a fringe, corresponding to a line-integrated electron density of 5×1017 m−2. Comparison with other electron density diagnostics are shown. The introduction of additional optics allows measurements of the Faraday effect and a determination of the poloidal magnetic field distribution. The signal processing and data analysis are described. Errors introduced by the calibration procedure, birefringence of the probing beams, toroidal field pickup, the flux geometry, and the density profile are considered. The Faraday angle is measured with an accuracy of 5% and a time resolution of 1–10 ms. The poloidal magnetic field is deduced with an accuracy of ±15%.

Notes: A pulse-height-analysis (PHA) technique of soft x rays is applied to Heliotron E experiments. The primary interest of this measurement is the determination of the electron temperature. Since the number of photons measured in a PHA system is extremely restricted owing to a finite processing rate of the system, it is most important to use the full amount of information involved in the spectral data. The statistical estimator from the maximum-likelihood method is efficiently used for this purpose. The estimated temperature is in good coincidence with the temperature by the electron-cyclotron-emission measurement, which is calibrated by the laser Thomson scattering. A check of reliability of the estimated electron temperature is developed from a statistical test of goodness of fit. The identification of impurity lines buried in a thermal spectrum is also discussed in the spectra accumulated through several or several tens of plasma discharges. The line emissions from Si, Cl, Ca, and Ti are identified. A systematic error in the estimated temperature due to the impurity lines is evaluated. The contributions from Cl and Ti cannot be neglected in the temperature estimation from a spectrum accumulated through several currentless ECH plasmas in Heliotron E. A removal of those contributions to the temperature estimation is successfully demonstrated. The electron temperature with several percent uncertainty is obtained by PHA every 10 ms during a Heliotron E discharge.

Notes: An absorption method of soft x ray is applied to Heliotron E plasmas for measurement of the electron temperature. Nitrogen gas is used as an absorber for convenience, owing to its accurate, uniform, and easily controllable density. The general feature of the absorption method for measurement of the electron temperature is discussed using a model with two parameters: the generalized thickness of the absorber and the electron temperature. The energy resolution of this method is not sufficient as a general method for spectral analysis. Hence, it is necessary to assume in advance such a model spectrum as consists of bremsstrahlung, recombination radiation, and impurity line radiation. Since the spectrum is always assumed before the analysis, we should try to find the origins of deformation of the energy spectrum and to correct the contribution. The effect of line emission from impurity ions to the estimated electron temperature is evaluated as a function of the electron temperature and the energy of the line relative to the generalized absorber thickness used in the measurement. An actual spectrum is measured by a pulse-height analysis (PHA) of the soft x ray. The one clear line, from chlorine, is not significant in the present determination of the electron temperature by the absorption method. Another possible line from iron at energy less than 1 keV is included in the analysis. Using a convenient method for determination of local emissivity from a chord-integrated emissivity, the electron temperature is determined from the local emissivity. The observed broad electron-temperature profile might be an artifact due to recombination radiation of the highly ionized ion diffused out of the hot core of the plasma. It is confirmed that the absorption method gives absolute measurement of the electron temperature at the plasma center, when additional information on impurity lines are given by PHA. The estimated temperature is consistent with the PHA measurement. The absorption method combined with PHA provides an easy and inexpensive measurement of the electron temperature compared with a system fully constructed by PHA.

Notes: The brief note describes diverse aspects of the technique used for rhenium plating the hot plate used for contact ionization of barium in a Q plasma source. The rhenium plating optimizes the probability of barium ionization. Special care has to be taken in order to deposit a uniform layer of rhenium, for this purpose a slow rotation is given to the plate during deposition.

Notes: The simultaneous photon-counting and wavelength scanning by IBM compatible computers is described. Real-time photon counting is accomplished using the EG&G Ortec ACE-MCS interface board while the monochromator scan is simultaneously driven by a DCC5 multifunction counter-timer interface board. Count rates of up to 100 MHz are achieved.

Notes: We have developed new types of ion-optical systems having larger solid angles (i.e., collecting power) and flexibility than many existing designs. They use relatively simple axially symmetric elements, namely solenoids, axial magnetic dipoles, and radial electric field lenses. The systems can focus, with good optical properties, energetic ions in the range of tens of keV up to tens of MeV kinetic energy and are capable of operating in nondispersive, achromatic modes. The key elements for the latter are new types of defocusing magnetic and electrostatic correction lenses. The lens systems have applications in any existing devices used to collect and focus energetic ions (including electrons). Typical devices are: mass spectrometers, leak detectors and gas analyzers, ion sources, accelerators and ion implantation systems, nuclear particle spectrometers, electron microscopes, ion microprobes, and ion-beam lenses for cancer therapy.

Notes: An electron spectrograph is described that covers electron energies from 400 eV to 200 keV with an energy resolution of 10%. This overlaps the range of electrostatic deflection devices at low energy and solid state detectors at high energy. The spectrograph uses magnetic deflection of the electrons to achieve energy separation and images the full range of energies on a single plane. The magnetic circuit uses the fringing field of two axially located magnets to attain the large energy range. Six separate electron beams can be dispersed in the field, each entering the circuit from a different angle. This is a particular advantage when measuring plasma electron three-dimensional velocity distributions. The angular response of the instrument is particularly favorable and the stray magnetic field is sufficiently low to meet spacecraft requirements. Compared with electrostatic deflection devices, the spectrograph is particularly advantageous for measuring high energy electron plasma velocity distribution functions with fast time resolution at modest energy resolution.

Notes: A simple source chamber is described which enables the introduction of laser-generated, vacuum ultraviolet (VUV) radiation below 102 nm into most existing photoelectron and photoion spectrometers. A long capillary light guide provides a conductance barrier between the VUV source and experimental chambers, and also provides a small, well-collimated VUV beam at the interaction region. A platinum photodiode is found to provide a useful measure of the VUV intensity with minimal interference from the unconverted UV light. The performance and capabilities of the source are demonstrated by several applications using photoelectron spectroscopy.

Notes: A parallel-plate refractometer has been developed which can be used to measure the refractive index of liquid and solid films with an accuracy of 0.4%. The refractometer, which is a modification of the Pfund single-plate refractometer, provides the ability to measure film thicknesses which range between 0.1 and several millimeters.

Notes: A device for rapid-tuning cw, Q-switched lasers for a CO2 heterodyne detection lidar is presented. It is shown that it is possible to utilize galvanometer-driven mirrors to rapidly switch wavelengths over randomly selected lasing transitions in the 9–11 μm portion of the spectrum. Both a transmitter and a local oscillator are simultaneously switched between transitions while still achieving the frequency stability typically required for a coherent lidar system.

Notes: A gating circuit is described which provides a cutoff efficiency of approximately 99% by pulsing the first dynode of an RCA C31034 type linear-focused photomultiplier by only 18 V. This is accomplished by utilizing a local minimum in the photomultiplier gain which occurs immediately before the sharp turn-on point. The circuit achieves the requirements of fast turn-on, variable gating duration, and minimal switching transients. The technique is especially suited to photon-counting applications in which stability of the anode baseline voltage is critical.

Notes: A new optical method using a Pockels device is developed to simultaneously measure two directional components of an electric field. In this method, an output light beam from a Pockels device is split into two beams and then each of the beams is transmitted through a polarizing plate whose polarization direction is different, depending on the measured field component. The relation between two measured field components and the required polarization direction of the polarizing plate is theoretically derived for representative materials of the Pockels device and is also examined experimentally. A field sensor is made on the basis of this new idea and is used to investigate a nonuniform electric field. An electric field changing spatially by 20% per centimeter can be measured with an accuracy of 5% using the Pockels sensor. The sensor is successfully applied to measure an impulse electric field between a sphere-to-sphere gap.

Notes: Using two commercially available hot-wire X probes, a conventional measurement technique, and the evaluation method described here, the magnitude of the time-averaged velocity vector and the magnitudes of the Reynolds normal stress components as well as the magnitudes and signs of the Reynolds shear stress components can be determined. The evaluation method employs as a basis the spatial directional sensitivity of hot-wire probes and involves the squaring of the anemometer's output signal. Furthermore, the region of applicability of this method is discussed.

Notes: The TEXTDB data base organizes the analyzed experimental data from the TEXT experiment so as to aid in understanding the physics of a complete discharge. The data base was constructed using a commercial relational data base. The relational model provided a flexible structure for organizing data from many different diagnostics into a unified description of the plasma discharge.

Notes: This article deals with the determination of the magnitude and sign of the three components of the instantaneous velocity vector from the output signals of a triple-sensor hot-wire probe. All three sensors lie in the same plane with a given angular orientation. Measurements with this triple probe are performed with the wire plane inclined at an angle of about 45° to the main transport direction of the fluid, thus ensuring high sensitivity of the probe and the determination of the three components of the instantaneous velocity of the flow in magnitude and sense. Furthermore, the region of applicability and the accuracy of the values of the flow parameters of the method are discussed.

Notes: A microprocessor-controlled system has been developed to automatically scan tissue culture dishes in order to detect and locate fluorescently labeled cell colonies for subsequent cloning. An X-Y recorder mechanism moves an 80-mm-diam dish in a raster scan through a stationary laser beam adjacent to a photomultiplier tube equipped with an emission filter. Front-end electronics processes the PMT signal to screen out small-scale fluorescent artifacts of selectable size (e.g., 〈0.2 mm). Appropriate signals are input to the computer which then interrupts the raster scan to perform a limited fine scan of the dish to accurately localize the fluorescent spot position. An additional artifact test using a different filter is then performed. The underside of the dish is scribed at the location of spots that pass this test. Using fluorescein as a label, fluorescence as low as 25% above intrinsic cell background fluorescence can be detected. The fluorescence signal level threshhold can be set (e.g., 70% above intrinsic cell background) to within an accuracy of approximately 15% of intrinsic cell background fluorescence, and the system will reliably find colonies with a signal exceeding that level. With the above typical values, the number of false positives is typically less than five per dish and the time to completely scan an 80-mm-diam tissue culture dish is 2–4 min.

Notes: This paper describes an x-ray K-edge subtraction television system for noninvasive angiography utilizing synchrotron radiation. The phantom, including contrast material (iodine), is irradiated by monochromatized dual-energy x-ray flux, alternately, using a high speed monochromator. The monochromator consists of a silicon crystal plate vibrating at 15 Hz so that the phantom is irradiated by the x-ray flux of 150 eV above and below the K-edge photon energy of iodine, 15 times per second. As an x-ray detector, TV cameras optically coupled to an x-ray image intensifier are used and the video signal is processed to display the subtraction image of pairs of successive images in real time. This system was fully implemented and moving phantoms were examined. Both the time interval between the energy change and the exposure time of each image has been shortened to 2 ms.

Notes: The possible integration of a recently fabricated high-purity silicon radiation-sensor array into experimental-instrumentation systems currently being developed for digital-subtraction angiography (DSA) procedures conducted with synchrotron radiation is discussed. In order to motivate the intended application of the sensor, the medical-imaging techniques of conventional coronary angiography and DSA are briefly reviewed followed by a summary of the different system and detector designs currently in use.

Notes: A linear x-ray gas position sensitive detector with delay line readout has been constructed. The detector is described, characterized, and used for detecting x-ray diffraction patterns from polycrystals.

Notes: Transient heat generation by absorption of x-ray and far-infrared beams was successfully detected by a photoacoustic detection method. The photoacoustic detectors of solid and gas phase for x rays and of solid materials for far-infrared light are shown together with its instrumentation. The x-ray photoacoustic signal showed a linear dependence on the ring current and ionization chamber current, both of which are the measure of the photon flux. Typical examples of photoacoustic signals were shown, and their characteristics were briefly discussed in relation to the physicochemical properties of the samples. The potential use of this detection method is discussed.

Notes: We have developed a current-to-frequency converter which is designed to be used with electron multipliers whose anodes are raised to high voltages. It has three sensitivity scales: 10 fC/Hz, 100 fC/Hz, and 1 pC/Hz, with 6.7 decades of dynamic range in each scale. We show that this technique has the high signal-to-noise ratio required for use with electron detectors such as channel plate multipliers and channel electron multipliers.

Notes: The photon counting method is proposed for the field of A(ring) x-ray diffraction. For this purpose, a new memory device was developed. The photon distribution and the photon autocorrelation were measured, and high-intensity sources such as the rotating anode generator and the Photon Factory were characterized. It has been shown that the method is useful to investigate time-dependent phenomena on the time scale down to 10 μs.

Notes: To assess the ability of the high-speed K-edge energy subtraction system which was made at beamline 8C of Photon Factory, Tsukuba, we performed an animal experiment. Rabbits were used for the intravenous K-edge subtraction angiography. In this paper, the actual images of the artery obtained by this system, are demonstrated. The high-speed K-edge subtraction system consisted of movable silicon (111) monocrystals, II–ITV, and digital memory system. Image processing was performed by 68000-IP computer. The monochromatic x-ray beam size was 50×60 mm. Photon energy above and below iodine K edge was changed within 16 ms and 32 frames of images were obtained sequentially. The rabbits were anaesthetized by phenobarbital and a 5F catheter was inserted into inferior vena cava via the femoral vein. 1.5 ml/kg of contrast material (Conlaxin H) was injected at the rate of 0.5 ml/kg/s. TV images were obtained 3 s after the starting point of injection. By using this system, the clear K-edge subtracted images were obtained sequentially as a conventional DSA system. The quality of the images were better than that obtained by DSA. The dynamical blood flow was analyzed, and the best arterial image could be selected from the sequential images. The structures of aortic arch, common carotid arteries, right subclavian artery, and internal thoracic artery were obtained at the chest. Both common carotid arteries and vertebral arteries were recorded at the neck. The diameter of about 0.3–0.4 mm artery could be clearly revealed. The high-speed K-edge subtraction system demonstrates the very sharp arterial images clearly and dynamically.

Notes: During the last years attempts have been underway at several synchrotron radiation laboratories1–4 to employ the abrupt change of absorption at the iodine K edge (33.17 keV) to the imaging of coronary arteries. The subtraction of two images taken with photon energies just above and below the edge strongly surpresses background contrast like bone and soft tissue and allows for amplification of iodinated structure contrast. At HASYLAB, for these studies, a beamline at a bending magnet was only available until 1987. At this beamline the system NIKOS I was tested to obtain information on its essential components like monochromator and detector by in-vivo investigations of dogs.The basic feature which differs from the approaches in other laboratoriesis simultaneous registration of two stationary beams in a two-line detector without any beam switching. Based on the experience with this system during the last year all its components have been improved and changed to dimensions capable of taking a 12-cm-wide image of the human heart. At present the new system NIKOS II is under testing at the new wiggler beamline HARWI. The new monochromator comprises two pairs of a thin Si Laue case crystal and a Ge Bragg crystal, each, with inherent focussing of the beam to a horizontal line focus of about 0.5 mm height and 12 cm width. The advantage of the Laue crystals which are optimized in thickness (30 μm) for maximum reflectivity, is the low heat absorption and the full use of the white beam in the production of two monochromatic beams. The crystals are cooled in a stream of helium. Compared to the NIKOS I version5 the detector was changed in the following points: The two detection lines are enlarged to 125 mm width and the phosphor at the entrance is exchangeable to be either made of powderlike Gd2O2S:Tb or of single crystals like CdWO4 or CaF2:Eu separated by thin walls for optimum spatial resolution. The numerical aperture of the glass fiber optics guiding the light via image intensifiers to the photodiode arrays is higher. The gain of the intensifiers is raised to 1000.Now two photodiode arrays are needed for the simultaneous readout of the two entrance lines. The readout time is halved by reading the odd and even number diodes by two ADCs per array. All these measures will increase the detective quantum efficiency from 0.2 to 0.6. The performance of the new system will be tested again by investigations of dogs before moving to investigations on humans, expected at the end of this year.

Notes: When detecting x-ray images by solid-state semiconductor imagers (charge-coupled devices, photodiode arrays) there arise specific distortions caused by the diffusion of minority photogenerated carriers in the semiconductor substrate. The mode and scale of the diffusion and, accordingly, of distortions which arise are determined by properties of both the detector and the image. In this paper, some aspects of the diffusion are experimentally studied and the results obtained are interpreted on the basis of a theoretical model obtained in definite approximations. The result of the theoretical model is presented as the Fourier transfer function of the time and spatial frequencies, normalized over the quantum efficiency. This function incorporates the following parameters: the diffusion length and diffusion factor for minority carriers, the depth of the depletion regions of sensitive cells, the thickness of the epitaxial layer (or the single-crystal substrate), the linear absorption coefficient of radiation for a semiconductor material, and the angle of incidence of the radiation on the device surface. For the corresponding point-spread function, among the properties illustrated experimentally are the peculiarity providing a good geometrical resolution, the formation of a "stepped'' profile at the grazing incidence, the formation of the "halo'' of the scattered charge. The results of the x-ray and optic measurements have also shown that diffusion from the passive (peripheral) regions, which determines, to a considerable extent, the applicability of linear imagers (lines) in high-resolution systems, contributes appreciably to the distortions. The authors have considered some ways of diminishing the distortions which are accessible to experimenters: diaphragming and oblique incidence of the radiation, and an increase of the depths of the depletion regions of the cells. In addition, the authors dwell briefly upon the influence of the diffusion on the quantum noise and the effect of spectra superimposition, the contribution of x-ray fluorescence and the photoelectron range to the distortions. As an illustration, the possibility of utilizing solid-state imaging detectors to x-ray tomography systems has been evaluated.

Notes: Since the early 1980s a tandem system consisting of an electrostatically focused image intensifier and an image vidicon has found extensive applications to visualization of the images formed by weak fluxes of x radiation. We present the result of measurements of some parameters of this complex linear video signal shaper (LVSS). The test x-ray image—x-ray lines dispersed in space by a single-crystal diffraction scheme (the projections of the linear focus of an x-ray tube) is directed onto a commercial one-stage image intensifier with electrostatic image focusing whose fiber-optics input window is covered by a luminophor to convert x radiation to light. The outlet of the image intensifier is fiber-optically coupled to the input fiber glass window of the commercial image vidicon (silicon intensifier target tube with intensifier section). The measurements performed on the device for absolute calibration of x-ray imaging detectors and x-ray counters (see the report at this Conference) have shown that the use of this LVSS permits one to record threshold flux densities of monoenergetic photons which are more than one order of magnitude lower than with the use of the image vidicon alone. Measurements of the dependence of the threshold flux density on the photon energy have been made. For example, for 8 keV (Cukα), when using gadolinium oxysulphide as the luminophor the threshold flux density is 20 times lower than for the image vidicon alone, and achieves 105 cm−2 s−1. At such a high sensitivity, detection of small-scale details of images with low brightness and contrast requires taking account of the noise of the radiation being detected, which is caused by the fluctuations of the photon flux. This LVSS visualizes light flashes caused by single hard x-ray photons and β particles which are incident upon the luminophor settled on the inlet window of the image intensifier. Both the x-ray images of the test objects and the luminescent flashes caused by photons and fast electrons are represented in digital form (see the report on multiframe digitization x-ray images at this Conference).

Notes: Using monochromatic synchrotron radiation and a high resolution x-ray sensing pickup tube as a two-dimensional detector, we have improved the spatial resolution of x-ray computed tomographic (CT) images. A quantitative elemental analysis was made based on the difference between two CT images measured just above and below an element's absorption edge energy. The developed CT imaging system has been used to observe nondestructive fine structures, such as cracks, in a ceramic material. High resolution of 10 μm was obtained. The differential CT value, which was seen as the shading intensity in the differential CT image, was proportional to the concentration of the specific element.

Notes: The performance of a system for quantitave microtomography with synchrotron radiation is described with regard to the spatial resolving power. The experimental setup consists of a double-crystal monochromator, a monitor in front of a sample stage and a line scan detector which is built up of two photodiode arrays (Reticon RL1024SF), which are cooled by Peltier elements to increase the dynamic range. We present the modulation transfer function of the detector and several monitor configurations. So far a spatial resolution of 100 μm has been achieved.

Notes: Recent developments of a high-precision diffractometer for multiple crystal arrangement at the Photon Factory is described. New x-ray optics for topography using this diffractometer are shown, including plane-wave topography, ultraplane wave topography and equilattice-spacing mapping topography.

Notes: A versatile environmental facility for in situ x-ray topographic (white radiation) investigations of the perfection of nearly perfect single crystals is described. The system is built to UHV standards and can be optimized to investigate the defect structure in many materials at variable pressure and temperature. High quality data have been obtained with this facility during the decomposition of nickel sulphate hexahydrate and calcite. In the former case, in contradiction to what has previously been believed, the results clearly show that dislocations are not involved in the nucleation of the reaction process.

Notes: In many cases the fluorescence EXAFS signal is contaminated with fluorescence from nearby elements. If this fluorescence is of lower energy than the element of interest, x-ray filters are not effective. One method for dealing with this problem is the double fluorescence method described by Wong and Rao. This paper describes an improved version of this double fluorescence scheme that greatly improves its efficiency. Data are presented for a sample of 1/2% Hf in Ni3 Al, and 1.6% CuO in NiO. When standard fluorescence is used, both signals are almost completely obscured by the (approximately-equal-to)100× larger Ni K fluorescence signal. With the double fluorescence detector the Hf L3 and Cu K-edge signals are clearly observed, and good spectra can be obtained in about an hour.

Notes: An improved method for light scattering from acoustic phonons in small, low-symmetry solids is described. This instrumentation greatly facilitates the determination of elastic constants in highly anisotropic materials. Elastic scattering can be greatly reduced so that weaker phonon modes can be observed. Errors associated with the determination of the polarization directions of an anisotropic material are minimized by considering crystal optics.

Notes: A double beam laser interferometer is built up to study high-frequency piezoelectric and electrostrictive strains. The system is capable of resolving a displacement of 10−2 A(ring) using lock-in detection and measuring the strain all the way to the piezoelectric resonance frequencies using a digital oscilloscope for detection. The interference of sample bending to the detected signal is effectively avoided.

Notes: We describe a method for measuring the internal friction of solids at low temperatures. Our design uses a composite oscillator vibrating in torsion at 100 kHz. The oscillator makes good thermal contact to the cryostat while maintaining a low background loss of Q−1(approximately-equal-to)2×10−6 at 2 K. The usefulness of the design is demonstrated by data for BaF2 and a-SiO2 from 2 to 300 K.

Notes: A pneumatic-based, hydrogen isotope pellet injector that was developed at the Oak Ridge National Laboratory (ORNL) has been used in recent plasma fueling experiments on the Joint European Torus (JET). The injector consists of three independent machine-gun-like mechanisms (nominal pellet sizes of 2.7, 4.0, and 6.0 mm in diameter) and features repetitive operation (1–5 Hz) for quasi-steady-state conditions (〉10 s). An extensive set of injector diagnostics permits evaluation of parameters for each pellet shot, including speed, mass, and integrity. Pellet speeds range from 1.0 to 1.5 km/s. Over 3700 pellets have been fired with the equipment at JET, with about 1500 pellets shot for plasma fueling experiments. In recent experiments, the system performance has been outstanding, including excellent reproducibility in pellet speed and mass, and a reliability of 〉98% in delivery of pellets to the plasma.

Notes: The magnetic susceptibility, χ, at 295 K of a wide variety of common laboratory construction materials has been carefully measured. Only materials with well-characterized compositions are included in the final data. Materials such as Cu alloys and filled epoxies showing ferromagneticlike saturation behavior are listed with the recognition that workers will probably want to use these with great caution in precision experiments where magnetic effects may be a source of error. Susceptibility values are given for over 30 materials for which χ values are not available in the literature and which exhibit χ independent of H.

Notes: Single photon avalanche diodes (SPADs) are avalanche photodiodes specifically designed for reverse bias operation above the breakdown voltage and used for detecting single optical photons. A new silicon epitaxial device structure was designed to give improved timing performance with respect to previous SPADs. Extensive tests were carried out in order to establish the timing resolution of the device in time correlated photon counting (TCPC). The timing resolution of the SPAD in terms of its full-width at half-maximum (FWHM) contribution to the overall instrumental response width is 20 ps with the detector cooled to −65 °C, and 28 ps at room temperature. This is the highest resolution so far reported for solid-state single-photon detectors. In vacuum tubes, comparable results are obtained only with special microchannel-plate photomultipliers (MCP-PMT). Results from time-resolved photoluminescence measurements in GaAs demonstrate the power of the TCPC technique when used with the new SPAD detector. With the excellent timing resolution of the SPAD and the well-known advantages of TCPC systems (high sensitivity, linearity, etc.), various applications are foreseen in areas so far dominated by streak cameras.

Notes: A high-sensitivity high-spatial-resolution eddy-current apparatus has been set up for contactless conductivity measurements on Si and HgCdTe. The inductive sensitivity limit has been demonstrated, on Si slices, to a very low σt (product of conductivity and thickness) of 0.0004 Ω−1 and the spatial resolution was shown to be about 4 mm, both a threefold improvement over past published results. HgCdTe bulk slices and epitaxial films have been measured over a wide range of σt from 0.001 to 1 Ω−1 at 77 K. The conductivity mapping measurements on HgCdTe material were also demonstrated for the first time. The sensitivity of eddy-current probes consisting of miniature commercial rf coils were shown to be not only temperature independent, but also very stable after repeated thermal cyclings between 300 and 77 K. This feature makes the eddy-current method an ideal technique for routine contactless conductivity measurements on HgCdTe material at 77 K. We also show that both the sensitivity and the spatial resolution of eddy-current probes can be explained quantitatively by a simple theory which treats coils as magnetic dipoles.

Notes: A new high-resolution ac calorimetric technique is described for measuring the absolute heat capacity of extremely small samples. The method uses a thermocouple as the weak link to the bath and modulates the temperature of the bath sinusoidally in time. This eliminates the need for a separate thermometer and heater on the sample while retaining the ability to make absolute measurements with minimal addenda. Results for a 2.9 μg sample of the superconductor Ba0.6K0.4BiO3 in a magnetic field of 60 kOe show a jump at Tc=21 K, which is above the noise level of ∼2 parts in 104.

Notes: The speed of torsional stress waves transmitted in solid waveguides submerged in a liquid depends, among other things, on the liquid's density and viscosity and the waveguides' cross-sectional geometry. By measuring the speed of torsional stress waves in two waveguides of different cross-sectional geometries, one can obtain both the liquid's density and viscosity. An on-line, real-time sensor for the simultaneous measurement of density and viscosity is described. The article details the sensor's principles of operation and reports experimental results conducted using viscosity standard calibration liquids with well-known thermophysical properties. For fluids with density ρf 〉1×103 kg/m3, it is estimated that the instrument can measure density with a precision better than 0.5%. For fluids with the product shear viscosity (μ) and density, ρfμ〉100 kg2/(m4 s), it can measure the shear viscosity with a precision better than 1%.

Notes: The 200-MeV linac injector was completed in October 1987 and commissioned to the designed targets. The 800-MeV storage ring is expected to complete the installation by the end of 1988. Five beamlines and experimental stations, which are under construction, are described.

Notes: X-ray resonance magnetic scattering (XRMS) is a combined effect of a spin-dependent electromagnetic interaction and a spin polarization of the intermediate state in resonance. The first observation of XRMS, which was performed by the present author and his co-workers, was concerned with Ni K-shell electrons. Information derived from that experiment was therefore restricted to the polarization of the p-type density of states above the Fermi level. In the present work, however, XRMS from Gd has been observed near the L absorption edge. The spin polarization spectrum relevant to the unoccupied d-type density of states has also been investigated. Owing to a high value of d-band density of states and its high polarization and also to large value of atomic scattering factor, the asymmetrical ratio of XRMS, (I↑−I↓)/(I↑+I↓), amounts to several percent at the maximum by contrast with the value of 1×10−3 for the case of Ni. The majority spin of Gd d band is found to be in excess at approximately 2 eV above the Fermi level and the minority spin in excess at approximately 8 eV above the Fermi level. The results derived from XRMS are compared with the results of a band theory calculation. Both temperature and magnetic field dependencies of the asymmetrical ratio are also discussed.

Notes: A small synchrotron radiation source in the hard-x-ray region was conceptually designed and its injection scheme, dynamic aperture, and beam instabilities were studied. Synchrotron radiation with the critical wavelength of 0.1 nm is emitted from a pair of superconducting bending magnets. The storage ring has only one pair of quadrupole magnets to save its drift space. The decay time of the kicker magnet and the angle between the central orbit and the orbit of the injected beam were optimized by computer simulation. The reduction of the dynamic aperture due to the errors of the bending field is less than 20%. Considerations of possible instabilities showed that there is no critical instability up to the beam current of 200 mA when the beam is injected with higher energy than 650 MeV.

Notes: We have designed a 1.5-GeV storage-ring system for a new synchrotron-radiation project at Hiroshima. The storage ring has an achromatic structure with six dispersion-free straight sections for insertion devices. Superconducting horizontal wigglers are used to generate hard x ray. The multipole field of the wiggler causes no problem on beam dynamics. In spite of its small size, 100 m in circumference, the ring can generate excellent synchrotron radiation in a wide wavelength region from VUV up to hard x rays.

Notes: This paper outlines the status of a 6-GeV synchrotron radiation designed at RIKEN. This facility consists of a main storage ring, a booster synchrotron, a 1.5-GeV preinjector linac, positron injection linacs, and others. The electronan GeV. The storage ring has a circumference of 1069.2 m and 7-m-long straight sections for insertion devices. The lattice of the main ring is a Chasman–Green-type one and has 36 periodicity. The low emittance (εx=8.2 nm rad) and large dynamic aperture are expected even with field errors and misalignments of magnetic elements. Three years of a preconstruction research and development period and 5 years of construction period are scheduled.

Notes: Electrons or positrons were stored in the electron storage ring of the Photon Factory (PF). The vacuum of the PF was so good that differences in the instantaneous beam lifetimes between electron and positron storage modes were very slight. Abnormal decrements of the stored beam current observed in the electron storage mode did not appear in the positron storage mode. Thus, the decay curves of the beam current in the positron storage mode were smoother than those in the electron storage mode. Though the instantaneous beam lifetime was nearly the same in storage modes, the practical beam lifetime of a positron was about 10% longer than that of an electron.

Notes: A requirement for electron storage rings for the synchrotron radiation experiments is that circulating beam is very stable. In particular, for small emittance machines, obtaining a high-quality beam is the most important subject. Though the rf-accelerating cavities are essential for the storage rings, sometimes they cause serious beam instabilities, and lead to a current limit and an emittance growth. The Photon Factory storage ring (KEK) is a dedicated synchrotron radiation source. There are four single-cell cavities in the ring. Beam instabilities arising from the cavities have been investigated. The resonant frequencies of these cavities were trimmed by choosing the proper length of blank-flanges attached to the cavity ports, to avoid the conditions unstable for all existing coupled-bunch instabilities. Reduction of the instabilities was remarkable.

Notes: A new finite element code, resonance analysis system for Maxwell's equation (RAMAX), has been developed for the numerical analysis of electromagnetic fields of multidimensional resonance frequency (rf) cavities. The penalty function method is used to deal with both the divergence-free condition and the boundary condition. The present code is able to analyze 2D (x-y,r-z) waveguide problems, 2.5D [x-y-(z), r-z-(r)] and 3D cavity resonator problems. In this article, the formulation and the features of the code are described. Several numerical examples of 2D, 2.5D, and 3D problems are also presented to demonstrate the accuracy and efficiency of the code.

Notes: The bunch length was measured by using a highly sensitive streak camera with a time resolution of 2 ps. It was found that fine structures appeared in the electron bunch shape and that the shapes of electron bunches were described by a Gaussian distribution on the average. The dependence of bunch length on beam current was measured for an electron beam of 607 MeV. The bunch length was well represented by a power function of beam current with an exponent of 0.197 at currents lower than 35 mA or 0.30 at high currents. The experimental results suggest that the longitudinal coupled-bunch beam instability takes place at low beam currents and the turbulent instability dominates at high currents. It was also found from the three-dimensional bunch shape measurements that the bunch shape tended to blow up at high currents.

Notes: It is shown that multicycle injection in an electron storage ring with a superconducting bending magnet can, in principle, be possible at low energy because of short radiation damping time and long Touschek life time due to beam enlargement. We estimated possible beam current by multicycle injection for a circular ring: radius=0.5 m; field index=0.5; injection energy=15 MeV; injector current=50 mA, and found that beam current of about 1 A can be injected in 5 min if injected beam is stable. However, it should be noticed that threshold stored current due to beam instabilities go down with energy. We should further study beam instability in order to check the feasibility of low-energy multicycle injection.

Notes: The Aurora is a compact SR-light system optimized for x-ray lithography. The system includes a superconducting electron storage ring, a 150-MeV race track microtron as an injector, and light beamlines. The SR-ring features a single magnet body, in which the 650-MeV electron beam orbits a true circular trajectory of 1 m diameter. The computer control system developed for Aurora has a three-level hierarchical architecture. The top level is the Central Intelligence System, and the second an Autonomic Control System (ACS). The bottom is an assembly of distributed local controllers linked to the ACS level through optical fibers. This system provides fully automatic and remote operation, and a powerful machine study capability through the associated man–machine console and the interpretive operation language.

Notes: Bending deformations of small storage ring vacuum chambers under atmospheric pressure are described. Results from a finite element model are presented which show that bending deformations due to pressure forces on metal bellows and arc chambers can cause severe misalignments at the exit ports. The deformations are shown to be larger in arc chambers of small radii. The effect of using bellows load compensators and flexible supports to reduce the deformations in an existing storage ring by an order of magnitude is evaluated by analysis and compared to actual measurements.

Notes: The design of an electron beam scanning system for compact storage ring synchrotron light sources is described. The main features are a scan frequency of 100 Hz and an angular amplitude of ±5 mrad. Different configurations of scan dipoles permit confining the scan to one cell using four dipoles or to repeat the scan periodically along the whole circumference by means of two scan dipoles per cell. Combinations of these basic configurations are possible. The location of the nodes of the pivoting electron beam can be optimized with respect to the maximum scan angle by slightly unbalancing the field strength in different scan dipoles. The scan dipoles are H-shaped magnets made from laminated iron. Their gap width is 68 mm. They are powered by fast transistor-bridge supplies which are controlled by freely programmable function generators capable of realizing a triangular current waveform with a deviation of less than 0.1% except for a 1% neighborhood of the apex. Estimates of the influence of the scanning on both quantum and Coulomb lifetime indicate acceptable lifetime reductions provided the minimum distance between distorted closed orbit and aperture exceeds about six standard deviations of the spatial electron distribution.

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: We describe the spectrometer and experimental stations on the infrared beamline (IR4) at the National Synchrotron Light Source, Brookhaven. We also report measurements of the source characteristics in the range 30–400 μm (25–350 cm−1), including both flux and brightness and compare them with corresponding measurements from a 1000-K blackbody source.

Notes: A new apparatus for the study of photoionization processes has been designed and constructed. The main capabilities of the apparatus include measurements of angle-resolved photoelectrons, as well as time-of-flight measurements of photoions in coincidence with total, energy selected, or threshold electrons.

Notes: The design of a photoemission microprobe beamline at the MAX laboratory is presented. The beamline will utilize the radiation from a 26 period undulator on the 550-MeV MAX storage ring. The beamline will be capable of providing about 1010 photons/s of monochromatized radiation (bandwidth better than 0.25 eV) in the energy range of 20 to 150 eV focused into a submicrometer focal spot. It will be used for scanning photoemission experiments with a lateral resolution better than 1 μm. The optical system is comprised of a plane-grating monochromator with a Kirkpatrick–Baez objective and a specially designed ellipsoidal focusing mirror.

Notes: New experimental developments for high-resolution spectroscopy and dynamics studies of complex multi-ionized molecules are presented. Using photoion-photoion coincidence measurements in the doubly ionized C6F6 (hexafluorobenzene) molecule obtained with a conventional time-of-flight spectrometer and the ACO storage ring as an example, we demonstrate the importance of improving (i) the light source by using the new storage ring Super-ACO, (ii) the detection mode by using the photoelectron-photoion-photoion coincidence method, and (iii) the mass resolution of the spectrometer by constructing a reflectron time-of-flight mass spectrometer.

Notes: For the study of state selected ion–molecule reactions using synchrotron radiation, an apparatus incorporating a dodecapole collision chamber has been constructed. Its performance has been examined utilizing the Ne+ ions produced by photoionization of Ne at the 2P3/2 threshold. It has been confirmed that both the transmission of the primary ions and the collection efficiency for the secondary ions remain unchanged when the ion kinetic energy is varied over a wide range of interest. The ion–molecule reaction Ne++OCS has been studied using this apparatus, selecting the spin-orbit states of the reactant ion by the time-of-flight coincidence technique.

Notes: Optical characteristics of a new beamline consisting of a premirror, a Grasshopper monochromator, and a refocusing mirror have been investigated. The intensity of the monochromatic soft x-ray was estimated to be about 108 photons/(s 100 mA) at 500 eV with the storage electron energy of 600 MeV and the minimum slit width. This slit width provides a resolution of about 500. Angular distributions of fragment ions from an inner-shell excited nitrogen molecule have been measured with a rotatable time-of-flight mass spectrometer by using this beamline.

Notes: In this article, we report the layout of our VUV beamline including a VUV monochromator and a molecular-beam photoionization apparatus. This experimental system has recently been completed at a UVSOR Facility of this Institute for studying van der Waals complexes produced by supersonic expansion. Several experimental results are also presented to show the characteristics of the apparatus.

Notes: Ionic fragmentation following 3d core photoexcitation of trimethylgallium has been studied in the vapor phase using synchrotron radiation. The threshold electron spectrum and photoionization efficiency curves are presented and discussed. The Ga+ and GaMe+ ions are predominantly produced following 3d photoexcitation. The fragmentation patterns following the 3d core excitation of trimethylgallium can be explained in terms of the hybrid orbitals constructed from the 3d, 4s, and 4p atomic orbitals.

Notes: This article discusses pulse radiolysis using synchrotron radiation from the TRISTAN accelerators, the accumulation ring (AR) and the main ring (MR). They provide intense radiation, the energy of which goes up to the γ-ray region, and a pulse length below 50 ps, which could be below 10 ps. The time separation between neighboring bunches is 1.25 μs at the AR and 5 μs at the MR. These features should make it possible to detect reactive intermediates in radiation-induced reactions in the time span from picoseconds to microseconds. Possible applications of the picosecond synchrotron radiation pulse radiolysis are introduced. They include studies of radiation effect on resist materials, on radiation sensitive materials, biological systems, and reaction from selected states such as Rydberg state, inner-shell excited states, and multi-ionized states.

Notes: Combining a nanosecond ruby laser with a detection system (a polychromator, an image intensifier and a linear position-sensitive detector) controlled by a microcomputer, a convenient laser photolysis system has been constructed. Operating the image intensifier in gated or continuous mode, the time-resolved absorption and emission spectra from the nanosecond to millisecond time regime can be recorded very easily by one or two excitation laser shots. The spectral resolution is 2.5 nm, while the shortest temporal resolution is 10 ns. Also, by simply turning a mirror in the polychromator, the multiple-component decays of transient absorptions, fluorescences, and phosphorescences can be analyzed by means of a combination of a photomultiplier with an oscilloscope controlled by a microcomputer.

Notes: Correlators based on the measurement of the time of arrival of photoelectron pulses are subject to a start-pulse bias related to the method according to which the pulse that triggers the count sequence is selected. For the bias to be negligible, the count rate must be low or the coherence time of the fluctuating signal must be short. In this work we point out a new start-pulse selection method that considerably broadens the useful range of time-of-arrival correlators. Results of tests conducted on laser light scattered by a ground-glass disk are reported.

Notes: This article describes the design and operation of a second-generation combined CARS-LDV instrument capable of measuring temperature and two velocity components in a turbulent combusting flowfield. Improvements to the instrument over the first-generation system include multiple acquisition modes ranging from independent to 4-μs time coincidence, more extensive automation of the data acquisition and burner controls, and improved procedures for analysis and display of raw data. Measurements made on a propane–air diffusion flame are discussed.

Notes: A device has been developed for generating well-defined, one-dimensional streams of small (200–1000 μm), mono-sized droplets of a variety of fuels. The droplets produced are well separated (〉30 droplet diameters), making this technique well suited to experimental combustion studies of unsupported, isolated droplets. This method has been used successfully to generate droplets of light and mid-distillate petroleum fuels, heavy oils, boron/JP-10 slurries, and coke/oil slurries, for a range of combustion studies. The principle of operation of the device is the aerodynamic stripping of incompletely formed droplets emerging from the tip of a capillary/fine wire which resides in the throat of a venturi or convergent nozzle. By varying the fuel flow rate through the capillary, the gas flow rate through the nozzle, and the diameter of the capillary, precise control of the initial droplet size, spacing, frequency, and velocity can be achieved. Design criteria, exemplary results, and a brief survey of other droplet generating schemes are presented, along with a description of the integration of this device into a laboratory combustion apparatus.

Notes: Photothermal deflection spectroscopy (PDS) at 77 K is described. The sample is immersed in liquid nitrogen with the liquid nitrogen acting as both the cooling and the deflecting medium. The experimentally obtained thermal diffusion length and relative change of refractive index of liquid nitrogen are compared with those of carbon tetrachloride. The construction of the liquid-nitrogen cryostat is the key factor in reducing the noise. A sensitivity of αd=10−4 is obtained for the present system. This technique enables the sensitive measurement of PDS at low temperatures.

Notes: The implementation of a 16-channel, low-temperature bolometer linear detector array is described. The detectors are silicon samples, whose surfaces are doped with phosphorus by the technique of ionic implantation. A single digital processor implemented on a common PC both provides the scanning of the array and performs synchronous signal detection from the different bolometers. The actual system has been tested with a broad infrared source, and some possible improvements are indicated.

Notes: The problem of measuring the average velocity of exhaust particles coming from vacuum-burning flares is solved by mounting two narrow-field-of-view photometers at two different positions downstream from the burning flare. The naturally occurring, high-frequency fluctuations in the flare's unstable burning rate send hot, luminous particles down the exhaust plume in clumps rather than a smooth distribution; by cross-correlating fluctuations in the two photometer signals, we can measure the exhaust particles' time of flight and thus their average velocity. These measurements are confirmed using an approximate formula connecting the particle velocity to the infrared radiance emitted by the flare's exhaust plume.

Notes: We have employed x-ray absorption spectroscopy, including surface EXAFS (extended x-ray absorption fine structure) and x-ray standing waves (XSW) in the in-situ structural study of electrochemical interfaces. The SEXAFS technique was used to study the structure of half a monolayer of copper underpotentially deposited on a Pt(111) electrode. From analysis of the data a Cu–Cu distance of 2.85 A(ring) and a coordination number of six were determined, strongly suggesting that the deposit is largely composed of clustered sites. The electrosorption isotherm of iodide on a Pt(111) electrode surface was measured in situ using x-ray absorption spectroscopy, and it exhibited two plateaus which we ascribe to changes in packing density and surface structure. Using x-ray standing waves, we have studied the potential dependence of the adsorption of iodide onto a Pt/C LSM and have interpreted the results in terms of distributional changes in the vicinity of the electrode surface.

Notes: Design features of a proposed high-resolution, high-speed powder diffractometer for operation at a synchrotron source are described. A key feature of the design is the use of imaging plates to record an almost complete range of data including both the high-angle and the small-angle scattering regime. The x-ray optics involve the use of a condensing-collimating channel-cut monochromator (CCCC) to achieve narrow parallel beams with cross sections of the order of 50 μm in the plane of diffraction, so that geometrical aberrations are very low and the beam cross section is well matched to the spatial resolution of the imaging plate detector. Angular resolution in 2θ of the diffractometer is easily variable, and designed to range from 0.01° upwards. Optional translation of the detector perpendicular to the incident-beam direction makes it possible to obtain time-resolved data. Applications of the instrument include high-resolution powder data collection for Rietveld analysis, studies of dynamic phenomena such as chemical reactions and phase transformations, particle-size determination, texture analysis, residual-stress measurements, single-crystal studies of the truncation-rod effect and surface scattering, microdiffraction, combined high-angle and small-angle scattering measurements, and studies of multilayer structures. As an illustration of the sort of results attainable with the proposed system, we present an oscillation photograph of the crystal-truncation rod effect for a Si wafer which was recorded at a synchrotron source using an imaging plate as the detector.

Notes: An erbium laser (λ=1.5 μm) with a pulse energy of 2 J delivered in 2 ms was used for rapid heating to investigate the kinetics and structural mechanism of the thermotropic phase transitions of a phospholipid/water system by fast x-ray small-angle powder diffraction. The phase transitions were induced by a single laser pulse, leading to a T jump of about 10 °C and the structural relaxations following the T jump were detected in 1-ms resolution. The results show that the transition at 29 °C (Lβ-Lα) is at least as fast as the heating time (2 ms) and that the lamellar/hexagonal transition around 57 °C (Lα-HII) is considerably slower with a half-time of the order of 100 ms.

Notes: A method for calibrating high-resolution laser spectra in the visible is described. The system is based on an evacuated Fabry–Perot étalon whose cavity length is servolocked to a stabilized HeNe laser; the absolute order number of the fringe at the HeNe frequency is known and the free spectral range can be determined with high accuracy. For absolute-frequency measurements the order number of a transmission fringe is obtained from a commercial wavemeter (whose accuracy is sufficient to identify the fringe); the absolute frequency is then the HeNe frequency multiplied by the ratio of the "unknown'' order number to the "lock-point'' order number. The long-term frequency reproducibility of the system is better than 25 MHz. Small-frequency splittings such as molecular hyperfine intervals can be measured to ±1 MHz, while large-frequency intervals (of the order of 500 GHz) are consistent to better than 10 MHz.

Notes: Fluorescence detection is often used to obtain the extended x-ray absorption fine structure (EXAFS) of dilute samples and thin films. As the samples become concentrated and the films become thick, significant errors can be introduced in the EXAFS amplitudes. With detailed calculations we determine the reduction in the coordination numbers (N) and the deviation in the mean-squared relative displacements (σ2) as determined by fluorescence detection. Experimental results on Cu, Ni, Fe, and Nb samples support the predictions of the calculation. We suggest corrections to obtain the correct coordination numbers and σ2 values for studies of concentrated samples by fluorescence EXAFS detection when other methods are not feasible.

Notes: A new method is described for the measurement of soft x-ray (SXR) and ultrasoft x-ray (USXR) radiation of fusion plasmas. The system applies the microchannel plate (MCP) detector and can be used to measure the emitted radiation along 12 chords in different energy ranges. The operation of the MCP in the measurement is discussed in detail. Some results are included which demonstrate the capabilities of the device.

Notes: An elliptical spectrograph and a scintillator/fiber-array detection system have been developed to provide time-resolved measurements of the x-ray spectra from a Z-pinch plasma. The elliptical spectrograph (1.2-m focal distance, eccentricity=0.9586) observes the 1-keV region, covering a range of λ/2d=0.5–0.9. The detector consists of a thin scintillator butt-coupled to a fiber optic array which transmits the signal to a streak camera in a remote location. This system provides continuous time history with temporal resolution of ∼3 ns, and a spectral resolving power of ∼165. The detection scheme is limited to spectral lines with intensities greater than ∼106 W/sr-eV.

Notes: A time-of-flight type neutral particle energy analyzer can discriminate between neutral particle loss and radiation loss from a plasma by use of the difference between their times of flight. The energy distribution of hydrogen atoms which are emitted from the plasma can be estimated from the time evolution of the detector signal. The energy distribution of radiated photons can be obtained by using several filters which transmit different ranges of the photon energy. With this method the ratio of the particle and radiation losses emitted from the same plasma volume and within the same detector solid angle can be obtained.

Notes: This article reports work in progress on laser diagnostics of negative-ion transport velocity in H−-ion volume sources. The plasma dynamics after the laser shot is discussed in detail, and the effect of the potential perturbation on the H− velocities is evaluated. A method of evaluation of the H− transport velocity from single-laser-beam photodetachment experiments is proposed. To substantiate this method, two-laser-beam photodetachment experiments have been effected. The velocities thus determined are pressure dependent; they correspond to H− energies in the range 0.23–0.08 eV.

Notes: The perveance law for ion sources is modified based on experimental data gained during the conditioning phase of three multiaperture ion sources for neutral-beam injection into TEXTOR. The ion sources are modified JET PINIs with a three-grid accel-decel extraction system designed for 55 kV, 88 A, 4.8 MW, operated in hydrogen. Results show that best agreement of the perveance law with the experimental data is achieved when the measured ion species mixture is used and, additionally, when the total width of the first acceleration gap, usually determined by the geometrical distance d1 between grid 1 and grid 2 and thickness D1 of grid 1, is enlarged by a third distance term r2, taking the effect of distortion of the electrical field lines at the decel grid into account. At perveance matched conditions, i.e., minimum beam divergence, the optimum value is found to be r'2 =0.8r2, where r2 is the aperture radius of the decel grid. The species fractions were measured by optical and magnetic spectrometry.

Notes: Magnetic field perturbations with specific spatial geometry can be detected in the presence of a large magnetic field "background'' using printed circuit pickup coils which have the advantages of large effective area, near dc frequency response, precise geometry, thin profile, and low cost. The design and construction techniques to produce these coils are presented. A printed circuit coil has been used to detect the magnetic field from the perturbed plasma current distribution in the TEXT tokamak due to current in an external helical (m=7,n=3) winding. The measured sensitivity of this coil, ΔBcoil/Btotal, is ∼3×10−6.

Notes: An ultrahigh-brightness laser system has been developed to study the spectroscopy and dynamics of molecules and clusters in the vacuum ultraviolet (VUV) extreme ultraviolet (XUV) spectral region. The laser utilizes pulse amplification of a single-mode ring dye laser, frequency doubling, and four-wave mixing in a pulsed jet. Pulse energies of 〉100 mJ in the visible and 〉1011 photons/pulse in the VUV-XUV have been obtained. The bandwidth of the laser has been measured to be 91 MHz in the visible and 210 MHz in the XUV.

Notes: It is found that the appearance of high reverse-voltage spikes on the thyratron anode in the discharge of metal vapor lasers due to high laser impedances can easily be monitored by a dc current meter in series with the bypass inductor of the discharge circuit. Experiments are demonstrated using a copper vapor laser. Results show that the proposed impedance monitor is effective, reliable, and economical. The meter deflection corresponding to acceptable, well-behaved thyratron operation can be obtained easily by the residual ionization-control method using a clean laser tube. By keeping the deflection within a specified limit, the lifetime of thyratron can greatly be extended.

Notes: A high-stability, high-level (1.3-A) current source circuit of modest cost is described, suitable for powering lead-salt laser diodes or other semiconductor devices, especially expensive, delicate, or rare experimental samples requiring the protection features this current supply offers. The supply features circuits to shut off current to the laser or other device smoothly and quickly (in less than 90 μs) if there is an overvoltage, overcurrent, main battery supply failure, or elevated temperature condition, to protect the laser or device from any of these potentially damaging conditions. Spectral data of a lead-salt laser emitting in the 1840-cm−1 region are presented to demonstrate the use of the current supply.

Notes: Results of a new experiment investigating fiber-coupled, astronomical CCD cameras as imaging systems for electro-optic devices are described. These results indicate that single-electron detection is achievable at 10-kV energy and that the resolution can exceed 35-μm FWHM. A system using such a camera to read a matched, high-resolution phosphor is described, and characterizations of the various component efficiencies are given. It is concluded that this system offers formidable competition to microchannel plate intensified systems with respect to dynamic range, absolute sensitivity, and cost.

Notes: A description is presented of a laser system that can be used for two concurrent and independent types of picosecond spectroscopic measurements. Two data-collection sybsystems, (1) a picosecond pump-probe transient absorption/emission spectrometer and (2) a streak camera system for time-dependent measurements of absorption and emission, have been developed as independent work stations within an integrated system based on a single mode-locked Nd:YAG laser oscillator which concurrently supplies each subsystem with picosecond pulses. The electronic links among the two work stations and the laser are discussed. In addition to applications involving pump-probe absorption and pulsed laser-induced emission measurements, this system can be used for picosecond-pulsed preparation-pump-probe absorption and preparation-pump emission experiments. Examples of data collected with each subsystem are presented to illustrate the complementary nature of the information that can be obtained with this versatile laser system.

Notes: A broadband detection scheme for a time-resolved infrared absorption spectrometer, based on a multielement mercury-cadmium-telluride (MCT) array, has been successfully implemented. The spectrometer achieves a resolution on the 10-ns time scale despite the much larger time constant characteristic of the MCT elements. Our signal-collection circuitry takes advantage of the slow decay by integrating the detector response to pulsed IR radiation. The dynamic range is 100–1 and the resultant noise level is near the detector limit. Data acquisition for the 120 elements is fast enough to allow scan rates of 30–40 Hz. The completed electronics are sufficiently compact to be situated local to the array detector, and the design is relatively inexpensive to construct using commonly found electronic components.

Notes: A high-speed, normally on, gating circuit has been developed for linear-focused photomultipliers such as the EMI 9816. The gate is capable of attenuating photomultiplier response by 〉5000:1 with a turn-off and turn-on time of 60 and 40 ns, respectively. The circuit is compact enough to fit in a standard photomultiplier housing and has low enough power consumption to run off the photomultiplier high-voltage supply. The high speed and high extinction efficiency make this gate suitable for pulse rejection in low-light level, submicrosecond, time-resolved luminescence measurements.

Notes: The analog electronics commonly found in frequency domain fluorometers are limited to collecting only a single frequency at a time, and can be a source of systematic errors. We have developed an instrument in which most of the analog electronics are replaced with a computer-controlled digital-acquisition system. The computer is used for the direct collection of multifrequency data; filtering and calculation of the phase and modulation ratio are done by the software. From these values, fluorescence lifetimes can be determined. This new approach reduces most of the systematic errors due to the analog electronics' hardware and allows for reconfiguration of the instrument with only minor changes of the software. This digital-acquisition system is not a simple substitution of an analog element, but it provides a new function and new capabilities for frequency domain fluorometers. We have used this digital approach to build a "parallel'' phase fluorometer which simultaneously collects and processes several modulation frequencies.

Notes: A circuit for photon count spectroscopy and its interface to a digital signal processor (DSP) are described. The complete circuit is housed in a standard IBM-PC board and, as it contains its own processor and memory, has a background mode of operation that releases the host system for being used in other tasks while the correlator is running. The basic autocorrelation routine executed by the DSP on data collected by the count circuit is also discussed. The use of the DSP lends the system great flexibility allowing for a high degree of customization while keeping performance to a level comparable to that of large dedicated units.

Notes: A RHEED system, consisting of a high-resolution (75-μm FWHM) and high-brightness (10-μA) electron gun, and a phosphor screen with high resolution and good linearity, was developed. The system is based on concepts from projection television. The results show that this setup is particularly useful for obtaining quantitative RHEED patterns.

Notes: A high-resolution LEED system with optimum operating parameters for use below 100 eV has been designed and tested. A field-emission-based electron gun with an angular divergence of 2 mrad, and a large sample detector distance of 150 mm provide the major improvements in resolution. Measured beam widths (Δk/2π FWHM) for both specular and nonspecular beams are approximately 0.002 A(ring)−1 in the energy range of 50–100 eV.

Notes: A moving-sample susceptometer based on a Hartshorn inductance bridge is described. This instrument makes it possible to measure magnetic susceptibility as a function of temperature. The lower limit of detection is approximately 50 parts per million of powdered YBa2Cu3Ox superconductor contained in a 5-mg sample, corresponding to approximately 10−6 emu/g. Measurements can be conducted in the 4.2–300 K temperature range. The apparatus can be built inexpensively of commonly available parts. Construction, operation, and possible applications are discussed.

Notes: In high-accuracy work, electron-spin-resonance (ESR) g values are generally determined by calibrating against the accurately known proton nuclear magnetic resonance (NMR). For that method—based on leakage of microwave energy out of the ESR cavity—a convenient technique is presented to obtain accurate g values without needing conscientious precalibration procedures or cumbersome constructions. As main advantages, the method allows the easy monitoring of the positioning of the ESR and NMR samples while they are mounted as close as physically realizable at all time during their simultaneous resonances. Relative accuracies on g of ≈2×10−6 are easily achieved for ESR signals of peak-to-peak width ΔBpp(approximately-less-than)0.3 G. The method has been applied to calibrate the g value of conduction electrons of small Li particles embedded in LiF—a frequently used g marker—resulting in gLiF@B:Li=2.002 293±0.000 002.

Notes: The design of a computer system which directly controls tunnel barrier width in a scanning tunneling microscope (STM) is described. This capability allows STM scans to be performed at a speed which is automatically determined by the roughness of the surface under study. The computer system is inexpensive and designed with readily available components for the VME bus.

Notes: Equipment has been designed for the study of the energy distribution and mass composition of particles, particularly positive ions, emitted from solids upon irradiation with laser pulses from a TEA CO2 laser (power densities in the order of 108 W/cm2). The equipment for the mass/energy analysis consists of a quadrupole mass spectrometer (QMS) and a modified cylindrical mirror analyzer (CMA) which can measure parallel ion beams. This paper describes the equipment, the basic construction, and the operation principles of the experimental setup. The system performance and experimental procedures are described on the basis of some preliminary experimental results. The results indicate that the analyzer described in this paper is capable of measuring the mass composition and the energy distribution of particles, particularly positive ions, supplied either in a pulsed or in a continuous manner. It is useful in studying charged particles in processes involving multispecies plasmas, like those occurring in thin film deposition through evaporation of targets by means of a pulsed laser.

Notes: Field distortions in the vicinity of wire meshes can change the direction of passing ions. Small deflection angles of ions passing through wire meshes in the reflector can reduce the mass resolution of time-of-flight mass spectrometers. We calculate these effects.