bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitive depth of semiconductor radiation detectors in current and pulse mode operations (abstract)
Authors: Chen Xing , Petrasso Richard D.
Published: July 2002

The sensitive depth of semiconductor radiation detectors is widely believed to be the depletion depth. Recent experiments, however, showed that the x-ray response of surface-barrier detectors is independent of the depletion depth when operated in dc current mode [K. W. Wenzel and R. D. Petrasso, Rev. Sci. Instrum. 59, 1380 (1988)]. We report experimental observation of such detectors in both current mode and pulse mode operations to alpha particles and to short-pulsed x rays (0.1–1 μs). It demonstrates that the difference in sensitivity between the detector’s dc response and pulsed-signal response is caused by the different charge collection time in depleted and undepleted regions. Therefore, the sensitive depth depends on how the detector is operated, and is not always the depletion depth. The construction and operation of the short-pulsed x-ray source is also described. This work was supported by the U.S. Department of Energy contract No. DE-AC02-78ET51013.
Studies of K- and L-shell x-ray emission from laser plasmas for use as a high-energy backlighter (abstract)
Authors: Molitoris J. D. , Shimkaveg G. M. , Keane C. J. , Fry A. R. , Fields D. J. , daSilva L. B. , MacGowan B. J. , Rupert V. C.
Published: July 2002

We are developing a backlighter in the 4–10 keV energy range using K-shell spectra from elements with Z≤30 and the L-shell spectra from elements with Z≥58. Using one beam of the Nova laser yielded about 3.0 kJ of 0.53 μm wavelengths light in a 1.0 ns square pulse which was focused to a spot of less than 100 μm in diameter on 12.5 and 25.0-μm-thick foil targets. Our initial results include time-resolved spectra from slab (2 mm×2 mm) and disk (100 μm diameter) targets of Ce (Z=58), Zn (Z=30), and Ti (Z=22). The Zn and Ti exhibit strong emission from the cold Kα line and satellite states, while the Ce spectra show prominent L-band structure. By exploring the differences between disks matched to the beam focus and extended slabs we hope to obtain information on plasma cooling mechanisms.
Triple Langmuir probe measurements in the Phaedrus-T tokamak
Authors: Diebold D. , Wang E. Y. , Pew J. , Winz G. , Breun R. , Li W. , Che H. Y. , Hershkowitz N.
Published: July 2002

Triple Langmuir probe data have been obtained in the initial phase of Phaedrus-T operation. The data were obtained during ohmic discharges of roughly 60 kA, 〈n〉=5×1018 m−3, Te(0)=0.5 keV, BT=0.7 T, q(a)=4 and 80 ms duration. Measurements of Te, φF, and n were made in a radial scan in the scrape-off layer of the plasma. The toroidal and poloidal positions were fixed throughout the scan. The spectra of Te, φF, and n fluctuations up to 100 kHz were also measured. One of the interesting features of these data is that m=2 oscillations detected by Mirnov coils were very pronounced in the φF and Te fluctuation spectra, but are not as evident in the n fluctuations. These data are presented and the techniques employed to get these data are discussed. Future plans to extend the maximum frequency resolution of the fluctuation measurements up to and beyond the frequency range of the ICRF power (13–18 MHz) that will be injected into Phaedrus-T are also discussed.
Recent x-ray backlight source development at KMS
Authors: Failor B. H. , Gabl E. F. , Busch G. E. , Bosch R. A. , Gerber G. L. , Armentrout C. J.
Published: July 2002

The development of intense x-ray sources and sensitive gated detectors is needed for the diagnosis of ICF implosions. A laser plasma x-ray source, with an instantaneous power of 200–500 MW in the range 2.7–3 keV, was used to evaluate a specific detector configuration. The detector, consisting of a PET crystal and a MCP framing camera, was used to obtain radiographs of NaCl-doped targets. Applications are currently signal limited, indicating the need for brighter x-ray sources and/or more sensitive detection systems.
Optimization and performance of a saddle field ion source
Authors: Godechot Xavier , Bernardet Henry , Lejeune Claude
Published: July 2002

The saddle field ion source operates at low gas pressure and requires neither magnetic field nor filament. We have designed a cold cathode saddle field ion source and characterized the discharge with hydrogen in the oscillating (‘‘low pressure’’) mode and in the transition mode. The anode design was optimized for maximum electrostatic confinement of the electrons and thus also maximum discharge current. A discharge current of 100 mA was obtained at a pressure of 0.5 Pa (3.8 mTorr) and a voltage of 10 kV. The discharge anisotropy was investigated and the discharge was found to be mainly an axial one in which the electrons oscillate near the axis. A highly peaked radial profile of current was measured at the end cathodes in the low pressure mode, and was dependent upon the operating pressure. A phenomenological explanation of these results is presented.
A model of charge collection in a silicon surface barrier detector
Authors: Kanno Ikuo
Published: July 2002

Charge collection process in a silicon surface barrier detector (SSB) was investigated as a following phenomenon of the formation and erosion of a plasma column the author reported elsewhere [Rev. Sci. Instrum. 58, 1926 (1986)]. As an application of Ramo’s theory, a model of charge collection process was presented. With this model, the top and bottom position and disappearance time of a plasma column were determined analytically. The induced currents and charges were calculated for alpha particle and 40Ar ion whose plasma delays were determined as a function of field strength by other authors’ experiments. The contributions of electrons and holes to the induced currents and charges were determined separately. The times of the plasma column disappearance and the last hole arrival to the negative electrode, and the maximum induced currents were tabulated. The peak time of the induced currents became slightly longer as the bias voltage of the SSB increased from 50 to 200 V.
Computer automation of the Pulse Reactor, a pulse operated low-pressure metal organic vapor phase epitaxy machine
Authors: van Sark W. G. J. H. M. , Hogenkamp J. E. M. , van Suchtelen J. , Giling L. J.
Published: July 2002

A modular and thereby flexible software package has been developed to control and operate a recently designed Pulse Reactor, a new type of low-pressure metal organic vapor phase epitaxy (MOVPE) machine. The user-friendly software package allows the operator to grow complicated layer structures automatically, whereby the composition of the growth mixture for each growth pulse can be varied. The hardware consists of a VMEbus based microcomputer system in combination with a UNIFIVE [derived from UNIX■ system V (UNIX■ is a trademark of AT&T Bell Laboratories)] operating system. Interfacing with the reactor system is performed through the use of a Philips MIOS subsystem. The UNIFIVE operating system is modified so as to establish good real-time behavior. Multilayer structures consisting of several GaAs and AlGaAs layers have been grown with good results, demonstrating not only the reliability, the real time behavior, and the correctness of the software package, but also the quality of the Pulse Reactor itself.
Factors affecting emittance measurements of ion beams (abstract)
Authors: Tsai C. C. , Akerman M. A. , Becraft W. R. , Dagenhart W. K. , Haselton H. H. , Schechter D. E. , Stirling W. L. , Whealton J. H. , Donaghy J. J.
Published: July 2002

The emittances of hydrogen and deuterium negative ion beams produced by volume ion sources have been measured in a transverse plane normal to the beam trajectory. The extraction voltage was varied from 10 to 40 kV, and the transverse magnetic field in the Penning discharges was varied from 0.1 to 0.2 T. Measurements were made on beams with current densities up to 60 mA/cm2 at Oak Ridge National Laboratory with an emittance scanner originally developed at Los Alamos National Laboratory. The beam profile at the scanner can be used to improve the accuracy of the emittance measurements. Other factors affecting emittance measurements are discussed. This analysis may be applicable to other ion sources.
An instrument for measuring high-power laser beam profiles and beam attenuation
Authors: Fetherolf B. L. , Litzinger T. A. , Kuo K. K.
Published: July 2002

An instrument has been developed for measuring high-power laser beam profiles and the amount of beam attenuation during radiative ignition of solid propellants. The detector houses a 1.0 mm square PZT (lead-zirconate-titanate) sensing element that responds to changes in incident laser beam intensity. A chopper wheel with three slots was employed to produce the changes in beam intensity required by the element. The resultant output signal is a series of ‘‘spikes’’ whose height corresponds to the level of beam intensity. Profiles of a high-power CO2 laser beam were obtained by using the detector to acquire a series of radial data points which were then graphed to yield the beam profile. Experiments were also conducted to measure the amount of attenuation of the laser beam during the ignition of solid propellants. This was done by mounting a small sample of propellant on a thin plate above the detector, cutting a 1.5 mm hole through the propellant and the plate, and aligning the hole with the sensing element. The gases and particles evolved during ignition and subsequent combustion of the propellant attenuated the laser beam as it passed through the gaseous plume and the small hole in the sample before being measured by the sensor. The intensity measured by the sensor was then used to quantify the level of transmittance of the beam through the gaseous plume to the propellant sample surface. Results are presented and discussed for a beam profile test and two attenuation tests performed on different energetic materials.
An ultrahigh vacuum tip transfer system for the scanning tunneling microscopy/field ion microscopy
Authors: Sugihara Kazuyoshi , Sakai Akira , Akama Yoshiaki , Shoda Naohiro , Kato Yoshihide , Tokumoto Hiroshi , Murakami Hiroshi
Published: July 2002

The authors have developed a magnet-type tip transfer system for use in an ultrahigh vacuum scanning tunneling microscopy/field ion microscopy (UHV-STM/FIM) system. The construction of the tip transfer system ensures that a tip can be introduced into the STM and the FIM in situ without any chances of tip crushing during handling. The new tip transfer system is extremely simple and reliable, and is particularly suitable for rapid tip exchange in the STM. An atom-resolved image of a highly oriented pyrolytic graphite has been obtained with a tungsten tip characterized by an FIM and transferred to an STM via this transfer system.
Angle-resolved inverse photoemission spectroscopy with longitudinally spin-polarized electrons
Authors: Grentz W. , Tschudy M. , Reihl B. , Kaindl G.
Published: July 2002

We have built and tested a spin-polarized electron source based on photoemission from negative electron affinity GaAs(100). It provides 5–10 μA of longitudinally spin-polarized electrons in the energy range 5–20 eV. Following the design of Erdman and Zipf, the electron optics are simple and consist of only five elements. Their voltages are all proportional to each other and are linearly driven by one ramping voltage. The spin-polarized electrons are used for angle-resolved inverse photoemission measurements from magnetized sample surfaces. Our first results obtained from Ni(110) mounted on a horseshoe magnet agree well with the literature. From these measurements the degree of spin polarization is determined to be 35%±5%. We also checked the spin polarization using an absorbed-current spin detector in combination with a 90° cylindrical deflector.
Ion spectra of the metal vapor vacuum arc ion source with compound and alloy cathodes
Authors: Sasaki Jun , Brown Ian G.
Published: July 2002

In metal vapor vacuum arc (MEVVA) ion sources, vacuum arc plasma with cathodes of single, pure elements has been utilized for the production of metal ions. In this study, we have investigated the charge state distributions of ions produced in vacuum arc plasmas in a MEVVA ion source for the case when the cathode is an alloy or a compound material. The ion charge state spectra were analyzed by means of a time-of-flight apparatus. We have compared the ion spectra for a cathode of an alloy or a compound material with its constituent elements: TiC/TiN/TiO2/Ti/C, SiC/Si/C, WC/W/C U/UN/(UN-ZrC)/Zr/C, and brass/Zn/Cu. We find that the MEVVA produces ions of all constituent elements in the compound and the alloy cathodes. The charge state distribution of each element differs, however, from the charge state distribution obtained in the vacuum arc with a cathode made of the pure, single constituent element. Fractional values of the total ion numbers of each constituent element in the extracted beam depart from the stoichiometry of the elements in the cathode material. In an operation with a TiC cathode, we irradiated a 304 stainless-steel plate with the extracted beam. Results from glow-discharge spectroscopy (GDS) of the surface show that both titanium and carbon are implanted in the substrate after the irradiation.
Focused high-intensity proton beam from a lithium source by using an E×B stigmatic selector
Authors: Leal-Quiros Edbertho , Prelas Mark A.
Published: July 2002

This article describes the design and operation of a system that produces a high-intensity proton beam. The system consists of a lithium proton source and an E×B stigmatic selector that produces a stigmatic proton beam at the mass focus. The protons are produced by bombarding electrons against a lithium surface. These protons are accelerated toward a special tilted-pole Wien filter (stigmatic selector), which eliminates astigmatism in the proton beam at the mass focus. The stigmatic E×B selector was also tested with electron beams, and their astigmatism was also eliminated. A classical E×B Wien filter with parallel poles (astigmatic selector) was used for comparison. The experimental spectral curves of both the proton current and the electron current, each using both types of selectors, are shown.
Intense negative ion beams and their diagnostics
Authors: Papadichev V. A. , Shelkovenko T. A.
Published: July 2002

Using negative ions for accelerators and CTR has some peculiarities. High-power beams of fast atoms obtained by charge exchange of negative ions can have advantage over positive ion beams for ICF since they do not experience any deviation, instabilities, and scattering. H− current up to 7 kA in a 100–200-ns pulse with densities up to 200 A/cm2 and a voltage of 0.8 MV were obtained in experiments on magnetically insulated diodes at the Lebedev Physical Institute. The cathode plasma was formed by surface discharge of a dielectric. Diagnostics of high-power H− beams is described, which includes target activation, prompt gamma-ray recording, registration of ion traces on Mylar foils, and others. It was concluded that up to 1 kA/cm2 of H− can be obtained.
Calibrated high-energy x-ray continuum crystal spectrometer for ICF diagnostics
Authors: Burek A. J.
Published: July 2002

Two separate crystal spectrometers are being developed for high-energy x-ray continuum measurements at Aurora and NOVA for ICF diagnostics. Both spectrometers are required to record hard x-ray continuum over the wide energy range of 5–35 keV. Continuous spectral coverage is required with low-energy resolution E/ΔE of the order of 10 to 20. The spectrograph for NOVA will use a Laue transmission geometry while the Aurora spectrograph will use a de Broglie curved crystal geometry. The instrumentation for Aurora will also include two discrete, time-resolved, high-energy channels for recording integrated continuum in the 40–60 keV and 60–90 keV bands. Individual component and end-to-end system calibration and alignment for both spectrographs will be done using the high-energy x-ray calibration facilities at KMS. We describe these spectrograph designs and discuss and compare the factors that affect their performance.
Amplitude and phase-modulation (AM-PM) wide-band photothermal spectrometry. II. Experiment
Authors: Power J. F.
Published: July 2002

Amplitude and phase-modulation (AM-PM) wide-band photothermal spectrometry is experimentally demonstrated, using apparatus constructed from readily available components. Theoretical AM-PM wide-band waveforms were digitally synthesized, filtered, and used as excitation waveforms in a wide-band spectrometer using photopyroelectric effect detection. The frequency domain dynamic range of the AM-PM wide-band technique was clearly superior to linear FM photothermal spectrometry. Multiband spectrometry was also demonstrated, in which several arbitrary narrow-band regions or ‘‘slices’’ of the frequency response were recovered simultaneously. The procedure shows great promise for image enhancement in thermal-wave applications, where selective target features of interest may be studied in the absence of neighboring interference.
Charge state distribution studies of the metal vapor vacuum arc ion source
Authors: Galvin James E. , Brown Ian. G. , MacGill Robert A.
Published: July 2002

We have studied the charge state distribution of the ion beam produced by the MEVVA (metal vapor vacuum arc) high current metal ion source. Beams produced from a wide range of cathode materials have been examined and the charge state distributions have been measured as a function of many operational parameters. In this article we review the charge state data we have accumulated, with particular emphasis on the time history of the distribution throughout the arc current pulse duration. We find that, in general, the spectra remain quite constant throughout most of the beam pulse, as long as the arc current is constant. There is an interesting early-time transient behavior when the arc is first initiated and the arc current is still rising, during which time the ion charge states produced are observed to be significantly higher than during the steady current region that follows.
Alignment system for 9–10 GHz longitudinal sound waves in a quartz etalon at 1.5 K
Authors: Lockerbie N. A. , Chapelier C. , Blanchard J. J.
Published: July 2002

We report the results of a system that employs four small superconducting repulsion coils and their respective niobium force-plates to restore the parallelism of a quartz-rod acoustic etalon, used for the measurement of acoustic transmission across quarter-wave matching layers into liquid 4He. In the 9–10 GHz frequency range we find up to an eightfold improvement in the number of usable echoes for some quartz-rod samples.
Simultaneous in situ conductivity and ESR measurements of electroactive polymers in electrochemical cell
Authors: Kruszka J. , Nechtschein M. , Santier C.
Published: July 2002

Experimental aspects of conductivity and spin susceptibility measurements of conducting polymer films as a function of the redox state are discussed. An apparatus for in situ measurements in an electrochemical cell is described. The working electrode consists of two parts separated by an insulating gap which is bridged by the polymer film. Special geometry has been designed to make the cell compatible with utilization inside an ESR microwave cavity. A signal proportional to the film conductivity is recorded continuously as a function of the applied potential. Data obtained on polyaniline are reported. In particular a case of spinless conductivity is evidenced.
Modification of a Princeton Applied Research FM-1 vibrating sample magnetometer
Authors: McKinstry Kevin D. , Patton Carl E. , Edmondson Charles A. , McClure Paul J. , Kern Sanford
Published: July 2002

A Princeton Applied Research model FM-1 vibrating sample magnetometer (VSM) has been modified using lock-in detection, automatic data acquisition, and microcomputer control. The practical sensitivity in the updated version has been improved to 10−4 emu. Data collection and data management are quicker and greatly simplified. Through menu driven software and modular design, the overall ease of use has been enhanced. The original layout of the FM-1 has been retained so that no versatility is lost for either the original or modified version.
Fluorescence x-ray absorption fine structure measurements using a synchrotron radiation x-ray microprobe
Authors: Hayakawa Shinjiro , Gohshi Yohichi , Iida Atsuo , Aoki Sadao , Sato Kohei
Published: July 2002

X-ray absorption fine structure (XAFS) measurements in regions less than 20 μm in diameter were realized using an x-ray microprobe employing the fluorescence detection method. To realize an energy tunable intense small x-ray beam, an ellipsoidal mirror was used as the synchrotron radiation focusing element combined with a double-crystal monochromator. Distortion of a XAFS spectrum due to the self-absorption effect is discussed in detail. The degree of the distortion was experimentally evaluated from the measurement of the x-ray fluorescence intensity as a function of takeoff angle, and the distortion was significantly reduced with the small takeoff angle detection geometry. Utilizing this technique, reliable XAFS spectra were obtained from a rock sample containing several minerals.
A flow cryostat for cooling of eight independent pipe guns
Authors: So/rensen H. , Hansen J. E. , Sass B.
Published: July 2002

A flow cryostat allowing independent cooling of eight pipe guns in a multishot deuterium pellet injector is described. The pipe guns are placed symmetrically around the flow cryostat and with a liquid helium consumption of 4–5 l/h the cooling is sufficient for simultaneous formation of eight pellets at 8–9 K with a diameter of 2.1 mm containing up to 8×1020 atoms/pellet. The thermal interaction between the eight pipe guns is sufficiently low to allow successive firing of the guns with time intervals of up to 1 s.
Interferometric angle encoder
Authors: Mertz Lawrence N.
Published: July 2002

Four unusual features are combined in the construction of an interferometric angle encoder: (1) a robust optical configuration, (2) a three-port lenticular fringe receiver, (3) a hexaflash phase-analysis circuit, and (4) a recursive phase unwrapping and smoothing filter. Raw performance of the instrument is about 600 prad resolution at 2 MHz sample rate. That is about a factor of 25 away from the shot noise limit. Resolution is improved to about 13 prad by on-the-fly smoothing to a 500 Hz bandwidth and data acquisition of 32-bit values is implemented at up to 5376 samples per second. The overall range of the system can be up to 18°.
Measurement of internal bore diameter at inaccessible locations by manometry
Authors: Giardini W.
Published: July 2002

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.
End-loss analyzer for plasma diagnosis
Authors: Vandegrift Guy , Loomis Richard
Published: July 2002

An end-loss analyzer to study the plasma escaping from a magnetic mirror has been constructed at low cost. It consists of 163 independently biased Langmuir probes arranged in a honeycomb array.
Electron-beam welded Cu-to-Ag joints for thermal contact at low temperatures
Authors: Yin Shi , Hakonen Pertti
Published: July 2002

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.
A wide-band high-sensitivity laser strainmeter
Authors: Crescentini L. , Renzella G.
Published: July 2002

A new laser strainmeter, inspired by those used in the first gravitational waves detectors, is presented. A wide-band feedback circuit controls the optical length of the reference arm of an unequal-arm Michelson interferometer by means of a Pockels cell. No modulation is added to the Pockels cell supply, since laser power fluctuations are proved to be of negligible effect if some care is taken in balancing the two outputs of the interferometer. A reset circuit follows variations in arm length greater than λ, obscuring the servo for 50 μs. As a consequence, an analog signal combined with a digital signal allow to detect any change in the arm length greater than 10−3 λ. The frequency band extends from continuous signals to 100 kHz.
Vibration isolation analysis for a scanning tunneling microscope
Authors: Oliva A. I. , Sosa Victor , de Coss R. , Sosa Raquel , López Salazar N. , Peña J. L.
Published: July 2002

We analyze the efficiency of a vibration isolation system (VIS) for a scanning tunneling microscope as a function of the different parameters involved. The VIS consists of a stack of several metallic plates, separated by rubber elements with known properties. We show three-dimensional graphs obtained for different values of parameters such as rigidity (spring) constant (K), damping constant (C), mass (M), and the number of stages (n). Analyzing the K dependence of the position of the main peaks, we find a parabolic behavior when the damping constant is small, with a slight deviation for larger values.
A combined Thomson–Rayleigh scattering diagnostic using an intensified photodiode array
Authors: van de Sanden M. C. M. , Janssen G. M. , de Regt J. M. , Schram D. C. , van der Mullen J. A. M. , van der Sijde B.
Published: July 2002

A combined Thomson–Rayleigh scattering device is discussed. It consists of a Nd:YAG laser as a light source in combination with a multichannel detection technique consisting of a gated light amplifier in combination with an optical multichannel analyzer. Special attention is focused on the analysis of the measured spectra. Including convolution methods and taking into account weak coherent effects increases the dynamic range and the accuracy of the measured electron density ne and temperature Te and neutral particle density n0. Accuracies of 1%–4% for ne, 2%–6% for Te, and 10%–50% for n0 depending on the plasma condition are obtained. The dynamic range for ne is 7×1017–1021 m−3, for n0 is 1020–1023 m−3 and for Te is 1000–50 000 K.
Chemical milling−Determination of depth and rate of etch based on sacrificial dissolution of one arm of a ratiometric transducer
Authors: Blake-Coleman B. C. , Hutchings M. , Hutchinson R. W. , Millar G.
Published: July 2002

The change in electrical resistance during the chemical dissolution of one arm of a variable ratio potentiometric bridge under constant current conditions is shown to offer a high precision, high resolution method of determining depth and rate of etch in immersed alloy work pieces undergoing chemical milling. The method is stable and repeatable, displaying negligible interference or disturbances due to electrochemical or electrothermal e.m.f.’s. Solution shunt conductivity is shown to have no significant effect on measurement accuracy allowing the sacrificial test piece to directly resolve etch depths to better than 10−5 m (10 μm) with comparable measurement of etch depth in the work piece. The principle is reliable and permits rugged construction, making it ideal for an industrial environment.
Radiant heater assembly for limited reaction-rate processing applications
Authors: Parker G. J. , Bonar J. M. , Starbuck C. M. K.
Published: July 2002

We discuss the design and performance of a radiant heating assembly for limited reaction-rate processing applications. The heating assembly is fabricated in stainless steel on a 300 mm bore flange for incorporation with an ultrahigh vacuum compatible low-pressure chemical vapor deposition system. The heating source is an array of 18 tungsten-halogen lamps; each lamp is rated at 360 W and has its own integral parabolic reflector. A 55-mm-diam ‘‘O’’ ring sealed quartz window is mounted in front of each lamp allowing the transmission of infrared radiation into a water-cooled stainless-steel deposition chamber.
Optimization of the performance of a digital voltmeter for synchronous detection
Authors: Bajaj Kapil M. S. , Lakshmikumar S. T. , Mehrotra Ravi
Published: July 2002

A procedure for performing synchronous detection of signals using a digital voltmeter (DVM), beyond the frequency limit set by a straightforward consideration of the sampling theorem and the conversion time of the DVM, is presented. This is achieved by using an independent timer to produce a number of time series with appropriate phase relationships. These time series are then combined by a computer to give a single series with a smaller effective sampling time. A regular fast Fourier transform routine is used for the detection of signals. For a DVM with a minimum sampling time of 16 ms, the procedure has been implemented successfully up to 150 Hz. The limits on the applicability of the procedure for higher frequencies are discussed.
Design of an isothermal cavity with nonuniform local instrinsic emissivities to give true blackbody radiant characteristics
Authors: Ma C. K. , Bedford R. E.
Published: July 2002

Blackbody simulators in the form of heated cavity radiators are widely used to calibrate IR radiation thermometers. The values of the local effective emissivities along the internal surface of an isothermal cavity decrease from the rear towards the aperture; the integrated value is always smaller than unity and is different for different calibration configurations. A simulator for which all of the local effective emissivities, and so also the integrated values, have the same value would be convenient for calibration purposes. We show that this can be simply achieved, in principle, by arranging for the intrinsic emissivity of the cavity surface to vary in such a way as to compensate for the change in effective emissivity. The method is exemplified by application to a right-circular conical cavity.
Depth of focus in velocity interferometer system for any reflector systems
Authors: Sweatt William C.
Published: July 2002

Velocity interferometer system for any reflector (VISARs) are used to measure the velocity of targets by monitoring the Doppler shift of laser light backscattered from them. In the design of these systems, there is a trade-off between signal-collecting efficiency and depth of focus. We present a VISAR architecture that maximizes the efficiency for any specified depth of focus for velocity sensitivities ranging from 20 m per second per fringe to several kilometers per second per fringe. We consider the usual system where the light going to and from the target is relayed with lenses. We also study fiber optically coupled systems. Our analysis shows that well-designed fiber-coupled systems can be as efficient as the equivalent lens-coupled systems, assuming that the divergence of the fiber-coupled laser beam is small.
Improvements in a laser heterodyne vibrometer
Authors: Yusheng Sun , ZiDong Zhang , Kanze Cai
Published: July 2002

This paper introduces an improved laser heterodyne vibrometer, describes improvements in the instrument, and gives its characteristics. A Bragg modulator is not used. So its optical structure and electrical circuits are relatively simple. An improved processing circuit is used. The data processing is controlled by microcomputer. The vibrating amplitude and frequency in a wide range can be measured simultaneously; the measuring results are accurate.
A 14.6-GHz ECR ion source for atomic physics and materials research with highly charged slow ionsa)
Authors: Zschornack G. , Birke U. , Hofmann D. , Mühle C. , Musiol G. , Schmidt-Böcking H. , Schneider M. , Stiebing K. E. , Streitz H. , Zippe C.
Published: July 2002

A 14.6-GHz electron cyclotron resonance ion source has been designed and will be installed at the TU Dresden. Contrary to other ECR sources some features are foreseen for atomic physics experiments to study the source plasma. Beside the description of source construction and computer-aided source control first physical experiments on the source are discussed.
A multielement solid-state detector system for use on the SRS materials science Station 9.3
Authors: Derbyshire G. E. , Dent A. J. , Dobson B. R. , Farrow R. C. , Felton A. , Greaves G. N. , Morrell C. , Wells M. P.
Published: July 2002

This article describes the design of a multielement solid-state detector system for use on the SRS materials science Station 9.3. The detector system is discussed in detail and test data are presented. The current system consists of 13, 8-mm diam, germanium diodes mounted in a single cryostat. The system operates with a 0.5-μs shaping time and achieves better than 200-eV resolution at 5.9 keV. Rate and resolution characteristics of the system are discussed with a view to future improvements in the system.
The extraction of signal to noise values in x-ray absorption spectroscopy
Authors: Dent A. J. , Stephenson P. C. , Greaves G. N.
Published: July 2002

The assessment of signal to noise (S/N) values in x-ray absorption spectroscopy is important for a number of reasons. Two methods will be described that remove the signal to give the noise. The first uses polynomials and the second Fourier filtering. Having extracted the noise the signal can then be used to calculate the S/N ratio. The method described operates on a background subtracted spectrum and is quick so it can be done on line in an experimental situation.
Real time x-ray studies of rapidly annealed epitaxial layers
Authors: Lowe Walter , Clarke Roy , Dos Passos Waldemar , Rodricks Brian , Brizard Christine
Published: July 2002

Time-resolved x-ray scattering studies of epitaxial overlayers are presented. The results illustrate the usefulness of high-brightness synchrotron probes for studying the cooperative kinetics of interfaces during rapid thermal processing.
Kirkpatrick–Baez microprobe on the basis of two linear single crystal Bragg–Fresnel lenses
Authors: Bonse U. , Riekel C. , Snigirev A. A.
Published: July 2002

X-ray microprobe on the basis of two linear single crystal phase Bragg–Fresnel lenses in Kirkpatrick–Baez geometry has been suggested and realized for hard x rays. The Kirkpatrick–Baez optics has been tested by two-dimensional imaging the x-ray source spot of a conventional sealed-off x-ray tube with Cu target (λ=1.54 Å). The possibility of applying this kind of microprobe at a synchrotron radiation source is discussed.
Synchrotron radiation as a light source in confocal microscopy
Authors: van der Oord C. J. R. , Gerritsen H. C. , Levine Y. K. , Myring W. J. , Jones G. R. , Munro I. H.
Published: July 2002

The optical properties of a confocal scanning microscope that was designed to utilize a synchrotron as light source are presented. The usable spectral range is from 200 nm up to 700 nm. Using 325-nm laser light, it is shown that the lateral resolution is about 125 nm, and the axial resolution better than 250 nm. After transport of the microscope from Utrecht to the Daresbury Synchrotron Source, 200-nm excitation can be applied, and the lateral resolution will drop to below 100 nm.
Microwave electron gun theory and experiments
Authors: Gao J.
Published: July 2002

A general microwave electron gun (rf gun) theory and some new ideas about further reducing the emittance of electron beams are reviewed and introduced briefly. Experimental results are presented from a thermionic cathode rf gun which has been developed for Beijing Free-Electron Laser Project (BFELP) at Institute of High Energy Physics (IHEP), Academia Sinica as the injector of 30 MeV constant gradient linac. LaB6 is used as the thermionic emitter with 100 crystal surface and the temperature around 1620 °C. Back bombardment heating effect and another effect connected with the cathode surface temperature was observed. An electron beam with macropulse length 4 μs, repetition rate 12.5 Hz, greater than 500 mA beam current during macropulse and around 1 MeV maximum energy has been obtained. In the last section of this article, two useful formulas used to determine electric field distribution near the cathode surface and coupling coefficient β of a rf gun are introduced.
An X–Y encoder with fast centroid calculation for large multiwire proportional chambers
Authors: Bahri A. , Bosshard R. , Santiard J. C. , Kahn R. , Fourme R.
Published: July 2002

The system described here is part of a data acquisition system for macromolecular crystallography using a two-dimensional wire chamber with a spherical drift space. The readout consists of 2×128 cathode strips (4 mm width) which are connected to shaping amplifiers coupled to a fast high precision position encoder. Cathode amplitudes are converted digitally with flash analog-to-digital converters and valid cathode clusters give between 3 to 5 digital amplitudes. A specialized VME module calculates the center of gravity of the cluster. The entire system is constructed as a VME structure and is under program control from a VALET-plus VME microcomputer system (developed at the CERN) which allows fine tuning of the electronic system. Data acquisition rate is presently 200 kHz with less than 20% data loss. The useful sensitive area of the detector is a disk (diameter 486 mm). Local positional resolution is around 150 μm root-mean-square and long range positional reproducibility is better than 200 μm.
Method for measurement of integral intensity of reflections in KARD-5 area detector diffractometer
Authors: Kheiker D. M. , Garmash A. A. , Andrianova M. E. , Popov A. N.
Published: July 2002

An improved method for integral intensity measurements with variable interval of scanning for all reflections for macromolecular crystal diffractometry has been developed and tested in the KARD-5 area detector diffractometer. The programs are written in FORTRAN and assembler.
Absolute spectral brightness and polarization characteristics of radiation from a polarizing undulator in the visible region
Authors: Yagi K. , Onuki H. , Sugiyama S. , Yamazaki T.
Published: July 2002

A polarizing undulator has been constructed utilizing crossed and retarded magnetic fields that can provide arbitrary polarized radiation. The absolute brightness and polarization characteristics have been studied in the visible region from 350–700 nm at 230 MeV of stored electron energy by varying the observation angle θ. Any desired elliptically polarized radiation was obtainable by adjusting the retardation between the two pairs of magnet arrays.
A superconducting electron cyclotron resonance source for the L.N.S.
Authors: Ciavola G. , Gammino S.
Published: July 2002

At the ‘‘Laboratorio Nazionale del Sud’’ (L.N.S.) the K-800 Superconducting Cyclotron (C.S.) is under construction and by the end of 1992 it will be completed in order to work as a booster for the 15-MV Tandem. With this facility fully stripped light ions will reach 100 MeV/amu, while the heaviest ions are foreseen to get 16 MeV/amu. In order to increase both charge states and intensities, mostly for the heaviest ions, of the beams injected into the C.S. a project for a superconducting electron cyclotron resonance (ECR) ion source has been developed and it will be carried out as a joint venture between the L.N.S. and the C.E.N. of Grenoble. This source will be the first superconducting ECR source to be coupled to a superconducting cyclotron in Europe, and it is particularly suited to exploit the capabilities of our K-800 superconducting cyclotron. The source will be working at 14.5 GHz and the confinement will be performed by superconducting magnets able to give 1.3 T on the plasma chamber wall, permitting attainment of a very good confinement. The design is at a preliminary level, but the main characteristics of the source have been established. The construction is scheduled to begin in 1992 and the source is expected to be working in 1995.
Synthesis of GaN by N ion implantation in GaAs (001)
Authors: Lin X. W. , Behar M. , Maltez R. , Swider W. , Liliental-Weber Z. , Washburn J.
Published: July 2002

Both the hexagonal and cubic GaN phases were synthesized in GaAs (001) by 50 keV N ion implantation at 380 °C and subsequent furnace annealing at 850–950 °C for 10 min–2 h. For a fluence of 1.5×1017 cm−2, transmission electron microscopy revealed that cubic GaN epitaxially crystallizes as precipitates in the GaAs matrix. A cubic-to-hexagonal GaN phase transition was observed for extended thermal anneals. By increasing the N fluence to 3×1017 cm−2, a continuous buried layer of randomly oriented hexagonal-GaN nanocrystals was produced.
Electron storage ring BESSY as a source of calculable spectral photon flux in the x-ray region
Authors: Arnold D. , Ulm G.
Published: July 2002

The electron storage ring BESSY is shown to be a primary standard of spectral photon flux ΦE from the infrared to the x-ray region. During the last years we have improved the measurements of the important storage ring parameters involved in the determination of ΦE and extended the usable spectral range to the x-ray region. We have achieved a relative uncertainty for ΦE of 0.18% (√3σ level) at a photon energy E=1 eV, 0.35% at E=5 keV and 0.57% at E=15 keV. In order to investigate and prove possible deviations between the calculated photon flux ΦE of BESSY and the flux of well established calibration sources in the x-ray region, the radionuclide x-ray standards, an intercomparison was made using a Si(Li) detector. At two different photon energies, 6.4 and 8.0 keV, agreement within the combined uncertainties was found.
Using a straightness reference in obtaining more accurate surface profiles from a long trace profiler
Authors: Irick S. C. , McKinney W. R. , Lunt D. L. J. , Takacs P. Z.
Published: July 2002

The long trace profiler (Takacs et al.) has found significant applications in measuring the surfaces of synchrotron optics. However, requirements of small slope errors at all spatial wavelengths of the synchrotron optics mandate more accurate slope measurements. A straightness reference for the long trace profiler greatly increases the accuracy of the instrument. Methods of using the straightness reference by interpreting the sequential interference patterns are discussed and results of measurements are presented.
Soft x-ray beamline BL7A at the UVSOR
Authors: Murata T. , Matsukawa T. , Naoé S. , Horigome T. , Matsudo O. , Watanabe M.
Published: July 2002

A vacuum-compatible double-crystal monochromator with constant exit-beam height has been installed and operated for several years at beamline BL7A at the UVSOR facility at the Institute for Molecular Science, Okazaki, Japan, The beamline is used both for the photons from a normal bending-magnet section and those from a 4 T superconducting three-pole horizontal wiggler. Various pairs of monochromator crystals are being used with sufficient intensity and signal to noise ratio of the output signal. Basic structure of the beamline, the mechanism of the monochromator, and some typical spectra of materials with absorption edges between 850 eV and 4 keV are reported.
An x-ray spectrometer for Compton scattering
Authors: Sakurai Y. , Ito M. , Urai T. , Tanaka Y. , Sakai N. , Iwazumi T. , Kawata H. , Ando M. , Shiotani N.
Published: July 2002

An x-ray spectrometer has been designed and constructed for Compton scattering measurements using 40–70 keV x-rays from an ellipsoid multipole wiggler (EMPW) installed in the accumulation ring of the National Laboratory for High Energy Physics at Tsukuba. The spectrometer has four sets of a Cauchois-type energy analyzer and an imaging plate, which are arranged on the surface of a cone and share a scattering angle of 160°. In each energy-analyzing system, to increase signal to noise ratio a set of vertical and horizontal slits are inserted between the analyzer and the imaging plate. A resolution of 0.13 a.u. in terms of electron momentum was achieved. A Compton profile of a vanadium single crystal was measured with an integrated counting rate of 400 counts/s.
The low-energy toroidal grating monochromator beamline at the synchrotron radiation source at Daresbury Laboratory
Authors: Hoyland M. A. , Harrington J. Q. , Weston M. I.
Published: July 2002

The bending magnet beam line 1.2 low-energy toroidal grating monochromator of the synchrotron radiation source (SRS) at Daresbury Laboratory, was designed1 to deliver moderately high fluxes (∼ 5 × 1011 photons s−1), of linearly polarized, medium resolution (∼0.2 eV) radiation in the energy range 5–85 eV. The colinear optical system utilizes platinum-coated silicon-carbide mirrors to focus the broad-band radiation emergent from the SRS at the entrance slits of the three grating monochromator. A single ellipsoidal mirror is then used to doubly focus the desired narrow-band radiation at the sample position. The colinear arrangement of the optical elements ensures that the radiation at the sample point is strongly horizontally plane polarized (estimated to be of order 90%). The entire system has been the subject of detailed analyses using the raytracing program shadow,2 and standard optical theory. These calculations have been compared with experimental determinations of photon flux outputs and resolution measurements.
Characterization of ion behavior in Ti cathode N2 vacuum arc using plane probe diagnostics and spectroscopic measurements
Authors: Sakaki Mamoru , Sakakibara Tateki
Published: July 2002

This study characterizes ion behavior of cathodic arc plasmas which have been used for the TiN coating. The ion currents are measured using a plane probe. The probe plane is vertical and parallel to the arc axis. Spectral intensities of Ti+ and Ti++ ions are also measured as a function of pressure (0.01–30 Pa). As a result of these measurements, it was found that at pressures below 0.1 Pa, the predominant ions in the plasma are Ti++ which have a tendency to be directional or to have a beam component, whereas at pressures above 0.1 Pa, mainly Ti+ ions of random motion are present.
Effect of beam-attenuation modulation on fluctuation measurements by heavy-ion beam probe
Authors: Ross D. W. , Sloan M. L. , Wootton A. J. , Schoch P. M. , Heard J. W. , Crowley T. P. , Hickok R. L. , Simcic V.
Published: July 2002

Beam-attenuation modulation arising from density fluctuations along the orbit of the heavy-ion beam probe (HIBP) in a plasma can distort the local amplitude, coherence, and phase derived from one- and two-point correlation measurements. Path-integral expressions for these effects are derived and applications to the TEXT tokamak are discussed. The work is part of an effort to account for previously reported wave-number data. However, the analysis is general and bears on any correlation measurement in turbulent media that depends on beam propagation or might otherwise be affected by spurious common-mode signals. In the HIBP case the effects depend critically on the ratio of the average fluctuation amplitude ñe along the beam path to the local ñe at the sample volume. Because the fluctuation amplitude is small in the core and rises sharply toward the plasma edge, the contamination effect is negligible in a radial zone near the edge but rises sharply to the interior of a critical radius. With increasing average plasma density n̄e the interior contamination increases strongly and the critical radius moves outward. The conclusion is that beam-modulation fluctuations affect the data but do not fully explain the disagreement with theoretical predictions of drift waves. The effects are expected to decrease with increasing beam energy.
A capacitance displacement sensor with elastic diaphragm
Authors: Roth P. , Gmelin E.
Published: July 2002

We have developed a capacitance displacement sensor based on the elastic deformation of a 150 μm thick diaphragm made up of Cu0.98Be0.02. Displacements up to 50 μm can be detected. The resolution is about 0.1 nm. The time dependence of the dilatation of a relaxor-ferroelectric (Sr0.61Ba0.39)Nb2O6 single crystal after removing an electric field is investigated using this sensor.