bluuebunny/crossref_metadata_2025 huggingface dataset:
Precise calibration of a microwave cavity with a nonideal waveguide system
Authors: Sauer B. , van Leeuwen K. A. H. , Mortazawi-M. A. , Koch P. M.
Published: July 2002

We describe in detail a method that permits determination to an accuracy of 5% or better of the absolute amplitude of a microwave electric field inside a resonant cavity. The method is based on an analysis of the frequency dependence of sampled-power measurements that record the response not only of the cavity but also of the waveguide circuit to which it is connected. Even small reflections from real, nonideal waveguide components lead to a frequency-dependent interference pattern that extends over a much wider range in frequency than does the sharp, resonant response of the cavity. The microwave cavity is modeled with an equivalent circuit model, and the interference pattern in the waveguide circuit is modeled in much the same way as is a Fabry–Pérot interferometer. From this one may obtain accurate values for the Q factor of the cavity resonance and the coupling factor that quantifies how well the cavity is matched to the rest of the waveguide circuit. We also discuss a method to determine accurately the power absorbed by the cavity, using the same waveguide circuit. We confirm the accuracy of the method by comparing to a microwave field-amplitude-dependent physical process, which can be calculated from first principles.
Trend studies of standard and regular gauge block sets
Authors: Tan A. , Miller III J. R.
Published: July 2002

Trend studies of standard and regular gauge block sets were undertaken by studying their total deviations summed over individual blocks in a set. The standard sets exhibited volumetric shrinkage and wear but no volumetric expansions. The regular gauge block sets frequently exhibited expansions, mostly in the earlier and middle stages of their calibration history. The rates of total deviations were smaller for the standard sets than for the regular sets, and were the least for the carbide sets. The Pratt & Whitney gauge blocks showed a significantly larger shrinkage as compared with gauge blocks made by DoAll and other manufacturers. A factorial experiment with gauge blocks is proposed to separate the volumetric change from wear.
A new resistor network for an electrostatic octupole deflector combined with a stigmator
Authors: Ohnishi T. , Hosaka S. , Tamura H. , Ishitani T. , Noda T.
Published: July 2002

A new resistor network for an octupole deflector combined with a stigmator is proposed. Improvement on the time constant due to the octupole’s stray capacity, which is made by connecting phase-compensative capacitors parallel to the resistors, is also described.
Passive Q switching of the Er3+:Y3Al5O12 laser at 1.64 μm
Authors: Camargo Marly B. , Stultz Robert D. , Birnbaum Milton
Published: July 2002

Saturable-absorber Q switching of an erbium-doped Y3Al5O12 (YAG) laser at 1.64 μm using U2+:SrF2 and U2+:CaF2 was demonstrated. The Er:YAG was longitudinally pumped using a free-running 1.534 μm Er:glass laser. Q switched 1.64 μm pulses of 1.7 mJ and 25 ns pulse widths were obtained.
Low-temperature anneal of the divacancy in p-type silicon: A transformation from V2 to VxOy complexes?
Authors: Trauwaert M.-A. , Vanhellemont J. , Maes H. E. , Van Bavel A.-M. , Langouche G. , Clauws P.
Published: July 2002

Deep level transient spectroscopy of electron irradiated p-type silicon reveals a defect level at Ev+0.19 eV, which during anneal treatments at 200 °C gradually transforms into a band with Ev+0.24 eV. Both energy levels however, are reported in literature to be the donor level of the divacancy. In the present study it is proposed that during the low-temperature anneal the divacancy interacts with oxygen, forming a V2O complex. During heat treatments at temperatures in the range between 250 and 450 °C a further shift of the deep level to higher energy positions is observed which might be related with other vacancy-oxygen complexes.
Design and calibration of the JET time of flight neutral particle analyzer with high noise rejection capability
Authors: Bracco G. , Betello G. , Mantovani S. , Moleti A. , Tilia B. , Zanza V.
Published: July 2002

This paper describes the design and calibration of a time-of-flight neutral particle analyzer used on the Joint European Torus (JET) tokamak in the diagnostics of plasma close to thermonuclear fusion conditions. The 15 channels of the analyzer can select energy and mass of charge exchange neutrals in the energy range from 0.5 to 250 keV. The analyzer has been calibrated for hydrogen, deuterium, and helium atoms. The utilization of the coincidence technique in the measurement of the time of flight of the detected neutrals also permits discrimination of the particle signal from a random background. Thus, the NPA operates successfully in the presence of the high neutron and gamma fluxes that are characteristic of the high-performance fusion plasmas produced in large tokamaks. The calibration data processing, the signal analysis, and the signal-to-noise evaluation are reported in detail.
Hall mobility measurements in semi-insulating GaAs by electro-optic voltage probing
Authors: Vickers A. J. , Tsui E. S-M. , Robert F. , Lyons V.
Published: July 2002

The Hall mobility in semi-insulating GaAs has been measured by probing the Hall voltage dropped across the thickness of the sample optically. This is achieved by exploiting the linear electro-optic (Pockels) effect in the material. The method only involves two electrical contacts to the sample which gives a distinct advantage over the conventional Hall or Van der Pauw techniques. It permits, in principle, the direct measurement of the time evolution of carrier populations, a useful corollary to transient photoconductivity. It also makes possible the measurement of a Hall voltage dropped across the width of a quantum well.
Correction-free radiometry on specular spheres for containerless processing in microgravity
Authors: Thomas A. S. W.
Published: July 2002

An analysis is presented that establishes how correction-free radiance measurements or pyrometry can be performed on targets in furnaces where there may be significant additional radiance from heated furnace walls or from reflecting surfaces close to the target. These configurations are common in microgravity and containerless processing applications where a specular target is radiantly heated in a hot-wall furnace, or inductively heated from the fields arising from nearby closely spaced electromagnetic coils. Proper design requires that the pyrometer does not view any images of the background features in the specular target so that stray radiation will not be reflected into the viewing optics of the pyrometer. To analyze the problem, conventional paraxial optics analysis is shown to be significantly in error. Instead a method of nonparaxial ray tracing, based on the derivatives of the ray paths, shows how the images must be located. This leads to analytical results that can be used to design such systems. The findings are applied to the furnace geometries that are presently being considered for flight in low-earth orbit. However, the same results may be used in other applications where any radiance measurement is being made on a specular target, as is the case for any molten material in a furnace.
Ultrahigh frequency thin film rf-SQUID magnetometer with a cryogenic preamplifier employing a high-electron-mobility transistor
Authors: Cavalleri A. , Cerdonio M. , Fontana G. , Jung G. , Macchietto R. , Mezzena R. , Vitale S. , Zendri J. P.
Published: July 2002

Ultrahigh frequency rf-SQUID magnetometer employing a cryogenic preamplifier and a commercially available thin film rf-SQUID sensor have been designed, manufactured, and tested. The system has been operated at 316 MHz, which is the maximum pump frequency accepted by the thin film sensor. The cryogenic preamplifier has been built around a microwave high-electron-mobility transistor which was made unconditionally stable at ultrahigh frequency band by means of an appropriate circuit design, namely, a cascode configuration. The total flux noise of the magnetometer has been found to be 8.4 × 10−6Φ0/√Hz at 4.2 K and 5.8× 10−6Φ0/√Hz at 1.4 K. The temperature dependence of the fractional step rise α of the current-voltage rf characteristic has been measured to be proportional to the 2/3 power of the SQUID sensor temperature. The noise performance of the system at 4.2 K has been limited by the intrinsic SQUID noise only, in good agreement with theoretical predictions.
Beam divergence and ion density measurements for an induction coupled ion beam source
Authors: Pai J. R. , Venkatramani N.
Published: July 2002

In this article the ion beam of H+ and Ar+ produced from the low-pressure radio frequency ionized plasma is analyzed for beam divergence. The divergence measurement method adopted for a low-energy beam is described. The divergence values for H+ and Ar+, respectively, are 0.4° and 1.1° for a beam energy of 2.5 kV. It is found that the beam divergence varies with the extraction voltage. In case of H+ beam, the divergence value varies from 2.8° to 0.4° for the extraction voltage of 500 V to 2.5 kV, and in the case of Ar+ beam this value is from 1.3° to 1.1° for the extraction voltage of 1000 V to 2.5 kV. The extraction electrode is concave outward as shown in the figure of the extraction system. The rf plasma is diagnosed using the double-probe technique for ion density estimation. The axial variation of the electron density and the electron temperature are obtained for both hydrogen as well as argon plasmas. The electron density is maximum, near the end of the coil.
A fast operating laser device for measuring the thicknesses of transparent solid and liquid films
Authors: Fedortsov A. B. , Letenko D. G. , Churkin Yu. V. , Torchinsky I. A. , Ivanov A. S.
Published: July 2002

A fast operating device for thickness measurement of transparent films has been designed and tested. Its principle of operation is based on the film reflection dependence on the laser beam incidence angle. The alteration of the incidence angle is produced by means of nonspherical optics. The single measurement time is less than 0.001 s, so this device allows the measurement of film thickness irregularities and investigation of the spreading liquid film thickness kinetics. The measurement frequency is 50 per second.
On the origin of spurious peaks in pseudorandom time-of-flight analysis
Authors: Zeppenfeld Peter , Krzyzowski Michael , Romainczyk Christoph , David Rudolf
Published: July 2002

The pseudorandom time-of-flight analysis overcomes the classic trade-off between resolution and transmission and has become a standard tool in inelastic low-energy neutron and atom scattering. However, systematic errors in the machining of the chopper slots as well as the finite thickness of the chopper disk can lead to the appearance of spurious peaks in the time-of-flight spectrum. These spurious peaks are mirror images of the real time-of-flight distribution shifted in the spectrum by a constant number of channels which is uniquely determined by the nature and length of the chopper-slot sequence. These effects can easily be corrected for and will in general not impede the actual time-of-flight analysis. We report a systematic study of the origin of the spurious peaks and show how one can discriminate between the effects stemming from machining errors or from the finite thickness of the chopper disk.
Pulsed, gridded electron reversal ionizer
Authors: Boumsellek S. , Chutjian A.
Published: July 2002

The design and performance of a new-type source of negative ions is presented. This device retains the idea of the so-called reversal electron attachment detector [READ, M. T. Bernius and A. Chutjian, J. Appl. Phys. 66, 2783 (1989)] to produce low-energy electrons by reversing electron trajectories at an electrode. Electrons are produced in the present device by several ribbon filaments that surround a cylindrical wire grid. They are accelerated through the grid, then decelerated to zero, or near-zero velocity at the surface of a tube. The tube (anode) is perforated with small holes through which effuse the target molecules. Electrons attach to form either parent and/or fragment negative ions. Attachment takes place at a location above the anode corresponding to a match between the electron energy and the attachment resonance energy. Negative ions are pulsed out of the attachment region and focused onto the entrance plane of a quadrupole mass selector. Electron and ion trajectory calculations are presented, and the performance illustrated with six molecules having attachment resonances in the range 0.0–2.2 eV. The detection sensitivity as measured using the method of standard additions is below 1 part-per-trillion, with a calculated conversion rate (ions/electrons) of 1.3%. Signal nonlinearity is discussed in terms of ion space-charge effects. The device also produces positive ions, and an analogous treatment may be carried through to characterize its performance in this mode.
A novel aircraft-based tandem mass spectrometer for atmospheric ion and trace gas measurements
Authors: Möhler O. , Reiner Th. , Arnold F.
Published: July 2002

A novel aircraft-based triple-quadrupole mass spectrometer (TQMS) has been developed for improved detection and collisional analysis of atmospheric ions and trace gases. The instrument is also suitable for laboratory collision-induced dissociation (CID) measurements, studies of ion–molecule reactions, and analytical applications. Highly sensitive and selective trace gas detection by chemical ionization mass spectrometry (CIMS) methods is also possible using a novel ion injection technique. Unambiguous identification of atmospheric ions is possible by comparing atmospheric fragment ion spectra with the fragment ion spectra of known ions measured in the laboratory under conditions similar to those of the aircraft-based CID measurement. The overall efficiency of the CID process, that is, the ratio of the fragment ion signal in the CID mode and the signal of the parent ion in the normal mass scan mode, varies between some 10−3 and 5×10−2, depending on the mass resolution of the mass selecting and mass analyzing quadrupoles. The sensitivity for ambient ion measurements is about a factor of 3 larger compared to previous aircraft-borne measurements. The TQMS was successfully used on five aircraft flights between September 27 and October 2 1991. The identification of various atmospheric ions was investigated by CID and the concentrations of various atmospheric trace gases including nitric acid, sulfuric acid, sulfur dioxide, acetone, and acetonitrile were measured by CIMS. In this article, the novel chemical ionization-triple quadrupole mass spectrometer is described and its potential is illustrated by describing the detection and unambiguous identification of atmospheric acetone.
Role of dangling bond centers on radiative recombination processes in porous silicon
Authors: Mochizuki Yasunori , Mizuta Masashi
Published: July 2002

The role of Si dangling bonds (Pb center) on the broad luminescence band around 1.1 eV of porous Si is discussed, based on transient wave form measurement of optically detected magnetic resonance. The observed wave form is compatible with the nongeminate shunt path scheme and the characteristic time constant of this nonradiative process is deduced to be 15 μs at 1.6 K, whereas the competing radiative channel has a shorter decay time of 3 μs. Therefore, Pb centers are unlikely to be involved as a radiative state in this infrared luminescence. Results are also discussed in conjunction with the visible luminescence process.
A new detection method used to calibrate Fabry–Perot interferometers in the infrared range
Authors: Talvard M. , Javon C. , Garcin M. , Thouvenin D.
Published: July 2002

Fabry–Perot interferometers are routinely used in the Tore Supra tokamak in order to measure the time evolution of the electron temperature of the confined plasmas. Calibration of such interferometers requires the detection of very low dc levels (0.1 nV) with signal-to-noise ratios less than 10−5, which is generally not compatible with standard detection methods. A new correlation method is proposed to achieve this absolute calibration. It is based on a proper noise autocorrelation technique combined with an optimized filtering involving Fourier analysis. The advantages of the method are detailed and experimentally compared to standard averaging techniques, such as coherent addition and synchronous detection. The method can be used in a more general context every time very small amplitude signals are to be measured.
Clean GaP(001)-(4×2) and H2S-treated (1×2)S surface structures studied by scanning tunneling microscopy
Authors: Sanada N. , Shimomura M. , Fukuda Y. , Sato T.
Published: July 2002

Clean GaP(001)-(4×2) and H2S-treated (1×2) surfaces are studied by scanning tunneling microscopy (STM). We have observed a (4×2)/c(8×2) STM image for the cation-stabilized GaP(001) surface. The result suggests that the unit cell of the (4×2) structure consists of two Ga dimers with two missing Ga dimers. For the (1×2)S surface, the previous model that sulfur atoms are adsorbed on the Ga dimer and that a missing row of sulfur is formed along the [11̄0] direction is supported by the STM result.
Catastrophic degradation lines at the facet of InGaAsP/InP lasers investigated by transmission electron microscopy
Authors: Snyder C. W. , Lee J. W. , Hull R. , Logan R. A.
Published: July 2002

Material transformations occurring at the facets of optically ‘‘stressed’’ planar InGaAsP/InP diode lasers have been investigated by transmission electron microscopy and energy dispersive x-ray spectroscopy. Catastrophic degradation lines (CDLs) which are characteristic of catastrophic optical damage are observed for optical power densities ∼107 W/cm2. Analysis of the microstructure reveals a series of 150 nm wide GaAs-rich tracks and the formation of unique void/InGa-rich precipitate pairs within the InGaAsP active layer. These observations suggest that the formation of local group III-rich regions is the first stage in the formation of CDLs. Subsequently, the strong absorption of the impinging laser beam leads to propagation of an InGa-rich melt, thereby producing the GaAs-rich tracks through a process similar to liquid phase epitaxy. These results are discussed in the context of standard physical models for CDLs.
Disorder and synchronization in a Josephson junction plaquette
Authors: Landsberg A. S. , Braiman Y. , Wiesenfeld K.
Published: July 2002

We describe the effects of disorder on the coherence properties of a 2×2 array of Josephson junctions (a ‘‘plaquette’’). The disorder is introduced through variations in the junction characteristics. We show that the array will remain one-to-one frequency locked despite large amounts of the disorder, and determine analytically the maximum disorder that can be tolerated before a transition to a desynchronized state occurs. Connections with larger N×M arrays are also drawn.
Development of a 1.8 T permanent magnet wiggler system (abstract)
Authors: Robinson K. E. , Gottschalk S. C. , Jander D. R. , Quimby D. C. , Valla A. S.
Published: July 2002

The design, development, and realization of a 1.8 T permanent magnet hybrid wiggler system is presented. This 3.0 m wiggler has a 200 mm period, operating at a minimum gap of 22 mm. It has 27 poles and integrated end correctors and field clamps. The magnetic design for this device is pushed to a regime where few hybrid devices have operated. The very large peak field causes a significant increase in the saturation of the vanadium permendur poles. The operating point also significantly impacts the transverse uniformity of the field and the magnet operating point. The magnetic design approach and the development of a mechanical structure which provides adequate strength and stability are discussed. The system is a complete stand-alone system with a fully integrated controls system and complete insertion device magnetics measurement system. The adjustment of the end compensation of the device with the presence of the field clamps requires particular attention. The distinctive elements of the design and the result of the magnetic and mechanical testing of the device are presented. This wiggler is being delivered to the Synchrotron Radiation Research Center for installation at the beginning of 1995.
Studies of beam dynamics of a compact storage ring using superconducting bending magnets
Authors: Tanaka H. , Nakanishi T.
Published: July 2002

A compact storage ring has been designed with a method that uses a numerical integration of exact equations of motion and exact three-dimensional magnetic fields measured. A beam test has shown that betatron tunes and chromaticities can be calculated within accuracies of 0.2% and 10%, respectively. An agreement of measured and calculated closed orbit errors and the good corrections have shown that an alignment of nonisomagnetic bending magnets, the manufacture of coils, and measurements of magnetic fields have been made accurately.
Commissioning and operation of the beamline for photoelectron spectroscopy in NSRL
Authors: Xu P. S. , Wang Q. P. , Lu E. D. , Yu X. J. , Xu S. H. , Zhou H. J.
Published: July 2002

A grazing incidence spherical grating monochromator (SGM) for photoelectron spectroscopy has been set up in NSRL. It covers the energy range 10–1000 eV. The primary results of commissioning and operation of the beamline have been described. The resolution power could be obtained from 500 to 1000 (E/ΔE) with 50 μm of slit opening in a wide range of photon energy. The improvement of the beamline performance is continuing.
An ultrafast mechanical shuttering system for separating single x-ray pulses from a synchrotron (abstract)
Authors: LeGrand Alan D. , Pradervand Claude , Schildkamp Wilfried , Bourgeois Dominique , Wulff Michael
Published: July 2002

A mechanical shutter system for conducting time resolved experiments at the APS and ESRF storage rings which is suitable for use with white and monochromatic x-ray beams has been developed. The system is able to isolate single x-ray pulses from synchrotron sources with large orbit times, such as the APS, ESRF, and CHESS when they are operated in single bunch mode. It consists of three components: a slotted rotating disk which opens for 3.28 μs every 2 ms, a fast magnetic shutter which can open and close in less than 1.5 ms, and dedicated electronics which can predict when the arrival of the x-rays from the storage ring and the opening of the rotating disk will coincide. When this occurs, the electronics open the magnetic shutter, allowing the x-ray pulse through, and generates a trigger signal with an adjustable delay of up to 2 ms with an accuracy of 10 ns or better before the arrival of the x-ray pulse. This system has been tested at both the CESR and the ESRF storage rings where it has been used to collect Laue data from three crystals: a small organic molecule and two forms of the protein lysozyme. We present results from these tests and discuss their implications for future experiments.
Thermo-mechanical analysis of the white-beam slits for an undulator beamline at the Advanced Photon Source
Authors: Nian H. L. Thomas , Shu D. , Kuzay Tuncer M.
Published: July 2002

A set of precision horizontal and vertical white-beam slits has been designed for an undulator beamline at the Advanced Photon Source. Due to the powerful x-ray heat flux emitted by the undulator, it is difficult to control the thermal distortion within the desired range of 1–2 μm. We analyzed many conceptual designs in an attempt to minimize the thermal distortion of the slits. Even with 1-mm-thick, low-Z material (graphite) coated on the heating surface of a traditional slit, the maximum thermal distortion is over 25 μm. A three-piece slit was then designed to satisfy the requirements. It consists of one large block, two tungsten knife edges, and an OFHC cooling tube (filled with copper mesh) brazed inside the large block. The thermal distortion at the knife edges of this three-piece slit is less than 2 μm.
Control of six degree-of-freedom parallel manipulators for synchrotron radiation applications
Authors: Fajardo P. , Rey-Bakaikoa V.
Published: July 2002

This high precision parallel manipulator is a well-adapted support for optical instrumentation in synchrotron radiation beamlines. It consists of a single moving element that obtains its six degrees-of-freedom from the combined movement of six independent actuators. This arrangement offers new control possibilities, together with fewer constraints for instrument mounting and alignment. Control of this kind of manipulator requires a special approach in order to exploit its full capabilities while keeping a reasonable simplicity of operation. In this paper the details of the control procedure and associated software package are presented. Special emphasis is given to the geometry: definition and ability to follow smooth trajectories, optimized calculations and special interface features like the possibility of defining virtual axes: logical motors associated with any particular rotation or translation of the instrument. By defining adequate virtual axes, it is now simple to execute a sequence of movements that were difficult with serial manipulators. The program includes special help for the alignment and calibration process and global instrument security features. It was written in a modular way, so that it can be easily adapted to different geometries, motor controllers and other site-dependent parameters. At present three ESRF beamlines have installed and used these programs and around ten new installations are foreseen.
Testing of submicrometer fluorescence microprobe based on Bragg–Fresnel crystal optics at the ESRF
Authors: Snigirev A. , Snigireva I. , Engström P. , Lequien S. , Suvorov A. , Hartman Ya. , Chevallier P. , Idir M. , Legrand F. , Soullie G. , Engrand S.
Published: July 2002

An x-ray fluorescence microprobe with circular Bragg–Fresnel lens was tested at the European Synchrotron Radiation Facility Microfocus beamline. A focal spot of 0.7 μm was observed using the knife-edge technique at the energy 7.6 keV (wavelength 1.6 Å). The intensity in the focal spot was measured to 108 ph/s in energy bandwidth of 10−5. The fluorescence microprobe was applied for mapping 100 μm size micrometeorite at 13.5 keV.
Signal-to-noise improvements with a new far-IR rapid scan Michelson interferometer
Authors: Hirschmugl C. J. , Williams G. P.
Published: July 2002

In this paper signal-to-noise issues in the infrared spectral region are discussed, presenting an update on instrumentation developments that have focused on this topic. Reproducibilities in the 0.01% range for spectra measured in around 1 min on samples with an area of 1 mm2 illuminated with an f/10 beam were achieved. It is shown how this result is consistent with the synchrotron source intensity and detector noise and a comparison with a conventional globar source is also shown. For these new studies, a NicoletTM Impact 400 rapid scan Michelson interferometer was modified by Pike Technologies and installed in vacuum at the U4IR infrared beamline at the NSLS. The instrument is capable of scanning at an optical retardation rate of 3.2 cm/s, and of a data-collection frequency of 50 kHz triggered by the colinear reference beam of a HeNe laser. A proprietary NicoletTM solid-state beam splitter was used to cover the range from 10 to 2500 cm−1. Spectra were taken in reflection at grazing incidence off a single-crystal Cu surface in ultrahigh vacuum using liquid helium cooled detectors of the photoconductive type (Cu/Ge) or bolometric type (B/Si). The sample throughput for this system was 0.05 mm2 sr.
The time-of-flight neutral particle analyzer and its calibration system for the RFX experiment
Authors: Costa S. , Frascati F. , Guatieri R. , Molon I. , Sardella A. , Toigo V.
Published: July 2002

A simple and low cost time-of-flight neutral particle analyzer has been operated on the RFX experiment. Simplifications have been introduced with respect to already existing similar devices, obtaining a low cost and reliable system. Good performance has been reached for hydrogen plasmas producing charge exchange H neutrals whose energy is lower than 3000 eV. Moreover a simple ion beam system has been projected and built to calibrate the electron multipliers used on the time-of-flight analyzer.
Undulators at the Advanced Light Source
Authors: Hoyer E. , Akre J. , Chin J. , Gath W. , Hassenzahl W. V. , Humphries D. , Kincaid B. , Marks S. , Pipersky P. , Plate D. , Portmann G. , Schlueter R.
Published: July 2002

At Lawrence Berkeley Laboratory’s Advanced Light Source, three 4.6 m long undulators have been completed, tested, and installed. A fourth is under construction. The completed undulators include two 5.0 cm period length, 89 period devices (U5.0s) which achieve a 0.85 T effective field at a 14 mm minimum gap and a 8.0 cm period length, 55 period device (U8.0) that reaches a 1.2 T effective field at a 14 mm minimum gap. The undulator under construction is a 10.0 cm period length, 43 period device (U10.0) that is designed to achieve 0.98 T at a 23 mm gap. Undulator magnetic gap variation (rms) is within 25 μm over the periodic structure length. Reproducibility of the adjustable magnetic gap has been measured to be within ±5 μm. Gap adjusting range is from 14 to 210 mm, which can be scanned in 1 min. The 5.1 m long vacuum chambers are flat in the vertical direction to within 0.74 mm and straight in the horizontal direction to within 0.08 mm over the 4.6 m magnetic structure sections. Vacuum chamber base pressures after UHV beam conditioning are in the mid-10−11 Torr range and storage ring operating pressures with full current are in the low 10−10 Torr range. Measurements show that the uncorrelated magnetic field errors are 0.23% and 0.20% for the two U5.0s and the U8.0, respectively, and that the field integrals are small over the 1 cm×6 cm beam aperture. Device description, fabrication, and measurements are presented.
Three-dimensional neutral atom imaging of tokamak plasmas
Authors: Scime Earl E. , Funsten Herbert O. , McComas David J. , Hokin Samuel
Published: July 2002

Recent technological advances in neutral atom imaging of space plasmas can be applied to the next generation of long pulse, high density fusion experiments. In particular, the small size of these neutral atom imagers makes them ideal for measurements of charge exchange neutrals in the edge and divertor region of tokamaks. In the edge of tokamak plasmas, the lower energy neutrals are created locally and the higher energy neutrals are generated within a few mean free paths of the edge. This charge exchange neutral flux can be imaged and its energy spectrum analyzed. The energy spectrum measurements provide the radial information necessary for a three-dimensional (3D) image of the convolved ion and neutral populations.
Narrow pulse shaping for high-counting-rate x-ray measurements
Authors: Harada Masaaki , Sakurai Kenji
Published: July 2002

A fast main amplifier for x-ray measurements has been developed through the modification of a commercially available delay-line amplifier. The characteristics of this amplifier were investigated by combining it with x-ray absorption fine structure equipment and it was found that counting rates in excess of 106 cps are attainable at 34% counting loss. The output pulse width of the amplifier has been narrowed from 0.3 μs to 0.12 μs (FWHM), which is not obtained by conventional pulse-shaping amplifiers.
Effect of misfit dislocations on leakage currents in strained multiquantum well structures
Authors: David J. P. R. , Chen Y. H. , Grey R. , Hill G. , Robson P. N. , Kightley P.
Published: July 2002

The reverse leakage current in strained multiple quantum well (MQW) p-i-n structures has been measured for a range of different dimensions and strain. The magnitude of the leakage current is found to be dependent on the average strain of the MQW, the total MQW thickness and the thickness of the capping layer. Plan view transmission electron microscopy shows that misfit dislocation arrays form primarily at the upper and lower MQW interfaces and the total density of these determine the leakage current.
High-temperature thermal resistors based on silicon carbide
Authors: Avramenko S. , Kiselev V. , Pavlenko A.
Published: July 2002

The technique of high-temperature cheap thermal resistor fabrication, based on polycrystal and fast neutron irradiated silicon carbide single crystals, is presented. The operating temperature range is 20–600 °C for polycrystal devices and 200–800 °C for single crystal devices and coefficient B in the expression R=R0 exp(B/T) is equal to 4500 and 10 000, respectively.
Effect of coupling condition on vibration-induced noise in fiber lead used in an optical current measurement system
Authors: Zhang W. , Ning Y. N. , Palmer A. W. , Grattan K. T. V.
Published: July 2002

When using a multimode fiber lead in an optical current measurement system, the optical power in the guided modes is often determined by the coupling conditions at the input end of the fiber. If only the skew rays are excited in the fiber lead—under appropriate coupling conditions—the vibration-induced noise normally experienced in the fiber lead in such an optical current measurement system can be effectively suppressed, especially when a low coherence source and a long length of multimode fiber is used. The experimental conditions for this are considered and discussed in this article.
A newly designed molecular beam Fourier transform microwave spectrometer in the range 1–4 GHz
Authors: Storm V. , Dreizler H. , Consalvo D. , Grabow J.-U. , Merke I.
Published: July 2002

We report on a new design for a Fourier transform microwave spectrometer in the spectral region 1–4 GHz, specially constructed for the investigation of rotational spectra of heavy van der Waals complexes. In contrast to the commonly known molecular beam spectrometers using a Fabry–Perot resonator working with TEM00q modes, the proposed design employs a different type of resonator operating with TE01q modes. This resonator allows for compact dimensions even at cut-off wavelengths above 0.1 m. Details of the design, performance data, and example spectra of stable molecules and complexes are given.
High-current-density gun with a LaB6 cathode
Authors: Ebihara K. , Hiramatsu S.
Published: July 2002

To develop a high-current electron gun for an induction linac, a prototype of a Pierce-type electron gun using planar 12-mm-diam lanthanum hexaboride (LaB6) is studied as a thermionic emitter at high current densities. The cathode is heated up to temperatures of 1750 °C by electron bombardment and thermal radiation from a tungsten heater. The heater that has the highest temperature in the gun is thermally isolated from the outer vacuum chamber with heat shields. The bombardment voltage of ∼1 kV is typically applied to a gap between the cathode and the heater. The gun has been operated up to voltages of 55 kV, obtaining a maximum current density of 20 A/cm2 with a pulse width of 250 ns at a cathode temperature of 1600 °C. High-voltage pulsing results show that the gun, with applied voltages of over 40 kV, is operated in space-charge-limited region at temperatures of over 1600 °C; also it is operated in a temperature-limited region at temperatures of less than 1500 °C. An effective work function of 2.68 eV is obtained. The cathode, when heated up to 1600 °C, emits over 7 A of electrons with a ∼20% reduction after 850 h of continuous operation. These measurements were made between vacuum pressures of 10−6 and 10−7 Torr.
Studies on quantitative x-ray diffraction characterization of phase depth profiles
Authors: Luo Jian , Tao Kun , Yin Hong , Du Yong
Published: July 2002

A fitting method using parallel beam x-ray diffraction (XRD) for profiling phase content changing with depth is presented. This method depends on measurements of XRD intensity at various incident angles, and numerical procedures are employed for obtaining the true depth profiles quantitatively. The procedures were then applied to a nitrided steel sample without preferred orientation and a thin-film sample with preferred orientation. Both model-independent and model-dependent ways were used in fitting.
Multiple wavelength Fabry–Pérot lasers fabricated by vacancy-enhanced quantum well disordering
Authors: Hofstetter D. , Zappe H. P. , Epler J. E. , Riel P.
Published: July 2002

Wavelength-shifted GaAs/AlGaAs Fabry–Pérot ridge waveguide lasers were fabricated by vacancy-enhanced quantum well disordering using dielectric cap annealing. 500 μm long and 4 μm wide Fabry–Pérot lasers with emission wavelengths selectively shifted by 20 nm were integrated with unshifted lasers on the same chip, characterized and further compared with lasers fabricated from as-grown material. These investigations showed that the absorption edge of a single-quantum well double heterostructure can be selectively blueshifted after epitaxial growth without compromising diode laser performance.
Spatially resolved in situ diagnostics for plasma-enhanced chemical vapor deposition film growth
Authors: McCauley Thomas S. , Israel Andrew , Vohra Yogesh K. , Tarvin John T.
Published: July 2002

The most critical factors for materials grown by chemical vapor deposition (CVD) are the local substrate temperature distribution and gas-phase concentration/distribution of activated growth species near the substrate surface. We present a micro-optical system design which can perform spatially resolved in situ spectroscopic measurements of both local substrate temperature and gas-phase species concentrations/distributions in real time. We present spatially resolved emission spectra from a high density plasma showing variation in CH, C2, and H radicals near the substrate during diamond growth. Substrate temperatures can be calculated from the measured blackbody emission spectra, using standard linearization methods. These techniques provide a flexible tool for temperature measurement and process optimization during CVD film growth, as well as means of studying the complex surface chemistry underlying the growth of diamond films and other technologically important materials.
Performance of a 1.5 m augmented railgun using a permanent magnet
Authors: Katsuki S. , Akiyama H. , Sueda T. , Koga Y. , Sato K. N.
Published: July 2002

A 1.5 m augmented railgun using a permanent magnet (ARGPM) has been assembled and tested. The goal of this work is to demonstrate fusion pellet injection with an extremely high velocity, in excess of 5 km/s. In this work, a wood fiber projectile is accelerated up to a velocity of 3.3 km/s in a plasma armature railgun without preaccelerators. Also, the velocity possible for a very light projectile accelerated by the ARGPM is discussed.
Image characteristics of a channel plate collimator for low energy x rays
Authors: Aota Tatsuya , Yamaguchi Naohiro , Ikeda Katsunori , Aoki Sadao , Yoshikawa Masayuki , Mase Atsusi , Tamano Teruo
Published: July 2002

Imaging characteristics of channel plate x-ray collimators have been investigated in the low energy range for applications of two-dimensional x-ray spectrometer. Improvement of the degradation of spatial resolution due to x-ray reflection inside a hollow channel has been considered by utilizing a focusing action of the channel plate collimator. Spatial extent of images through the channel plate collimator have been measured systematically by using a low energy point x-ray source and have been compared with results of ray-tracing calculations. It is shown that the spatial extent of the image consisting of the focusing component is limited by the geometrical divergence of the channel plate collimator. The possibility of two-dimensional imaging spectroscopy as well as the focusing action is discussed.
Possible developments of high power targets for radioactive beams
Authors: Bennett J. R. J. , Drumm P. V.
Published: July 2002

The development of the RIST tantalum foil target for the production of radioactive nuclei by bombardment with energetic (∼1 GeV) proton beams of high intensity (100 μA) has shown that targets capable of dissipating 20–60 kW of thermal power can be constructed. Tantalum is a good material for high power dissipation because, as a metal, it has a relatively good thermal conduction and is able to stand very high temperatures. However, for a full range of unstable beams, it will be necessary to have targets made from many different materials. Developments of high power target and ion source designs are discussed with particular emphasis on non-metallic, non-refractory powder and liquid target materials. Also, the possibilities of combining targets and ion sources to reduce effusion times are considered, as well as methods to increase the surface-desorption rates of the radioactive particles.
Formation of uniform titanium dioxide films by sputtering of tapered targets in an electron cyclotron resonance plasma
Authors: Ishii S. , Morishita N. , Kato Y. , Tani F. , Koizumi Y. , Sunagawa M.
Published: July 2002

A rectilinearly wide plasma has been formed by electron cyclotron resonance (ECR). The ECR magnetic field is generated in the long range using a pair of 300-mm length magnets with oppositely facing poles. Microwave of 2.45-GHz frequency is supplied through a quartz window from a slotted waveguide placed between the magnets. A preliminary experiment is conducted to acquire basic data for sputtering targets to fabricate wide, uniform thin films. It is established by simulation that sputtering directivity obeys the square-root cosine law. Two planar titanium targets are lined up in parallel with the slotted waveguide. They are so tapered as to point their edges at each other and soaked in the uniform plasma. Uniform films are formed within an area of 180×180 mm2 in a 200-mm width plasma by sputtering the tapered targets and varying the direction of substrate surface to the targets.
Ion sources for microsize ion-beam treatment of optical parts
Authors: Michnev R. A. , Shtandel S. K. , Belokurov A. P. , Martynov M. I.
Published: July 2002

The requirements of ion sources (IS) for ion-beam treatment (IBT) of high precision optical parts are substantiated. The ion source feature is presented. There are developed and investigated differences for ion-optical systems forming the beams featuring preset ion current distribution and cross section (on the 0.1 level) in the range from 5 to 30 mm. The ion beam characteristics are measured. IS has been tested while processing different materials. The source is recommended for employment in installations designed for automatic microsize processing of high precision optical parts.
Polarized ion sources for high-energy accelerators (invited)
Authors: Levy C. D. P. , Zelenski A. N.
Published: July 2002

Motivated by experimental requirements at high energy accelerators, very large increases in polarized H− ion source current have been achieved recently. Polarized H− current of 1 mA dc from the optically pumped source (OPPIS) and 1 mA pulsed H− current from the atomic beam source (ABS) have been demonstrated. High current development of both the ABS and OPPIS is continuing. Pulsed current of more than 10 mA has been proven to be feasible from the OPPIS. An OPPIS is also used in the high precision parity violation experiment at TRIUMF, in which helicity-correlated changes to beam properties must be extremely small.
A microwave driven off-line ion source for ISAC at TRIUMF
Authors: Jayamanna K. , Cojocaru G. , Dombsky M. , Kuo T. , Laxdal R. , McDonald M. , Schmor P. W. , Yuan D. , Zyuzin A.
Published: July 2002

An off-line microwave ion source (TE111 mode resonator at 2.45 GHz) is being developed to produce stable ion beams for ISAC commissioning as well as to produce intermediate and long half-life radioactive ion beams for initial experiments. Two different sources have been constructed and tested. In the standard source configuration the microwave power is injected and the beam is extracted on axis. In the second source microwave power is injected radially. In this case, the beam is extracted radially. Each of the sources is capable of handling gaseous, metallic and volatile compounds. A three electrode extraction system and a mass spectrometer with a resolution of 1600 are used to analyze the beams. The performance of the two sources is compared. In a number of parameters, efficiency, power requirements, tuning simplicity and lifetime, the radial source out performs the axial source. The test results with both sources are present.
Experiments on 5 MeV proton beam focusing by plasma lens
Authors: Belan V. N. , Butenko V. I. , Ivanov B. I. , Kiselev V. A. , Linnik A. F. , Onishchenko I. N. , Prishchepov V. P. , Yegorov A. M.
Published: July 2002

The plasma lens is investigated for focusing of a proton beam of energy 5 MeV, current 10 mA, and pulse duration 30 μs, obtained on the accelerator “Ural-5” with radio-frequency quadrupole (RFQ) radial-phase focusing. The parameters of the plasma flow produced by a coaxial plasma gun are the following: plasma density 1011–1015 cm−3, temperature 1–3 eV, velocity 107 cm/s, and time duration 500 μs. The magnetic-field value of a short coil is 500–1000 Oe. The focusing coefficient is ten times the compression at the length of 30 cm obtained. The dependence of ion-beam size upon various parameters of the plasma lens is investigated.
Modified arc ion source of multicharged ions of metals and gases
Authors: Il’enko B. P. , Nekludov I. M. , Onishchenko I. N.
Published: July 2002

In the ion source described here, a heated 1500 °C discharge chamber was used and a special configuration of crossed E×B fields, thereby providing several times more ion-beam current. The design of this multicharged ion source has been developed to work for long periods and use moderate power in continuous operation.
Automated measuring instrument of the surface electric potential and potential distribution
Authors: Sakalauskas S. , Sodeika A.
Published: July 2002

An automated measuring instrument of the surface electric potential and its distribution was presented. The schematic instrument diagram, metrological assessment, the relation of measured voltage with the sample electrophysical parameters are discussed. Possibilities of measuring instruments are demonstrated by some physical investigations.
A pulsed power system for generating multiple high voltage pulses with a short pulse repetition interval
Authors: Masugata Katsumi
Published: July 2002

A new type of multipulse generator is proposed for the generation of high power pulses with extremely short pulse repetition interval. In this system, an air-core step-up transformer is used with a magnetic switch and the pulse forming line is charged on a double resonance mode. Numerical simulations of the system have shown that 56 ns duration pulses matched to a 20 Ω impedance can be produced with a minimum pulse separation of 2.7 μs. The voltages and the efficiencies of the output pulses are 0.63 MV and 93% for the first pulse and 0.56 MV and 69% for the second pulse.
Software architecture considerations for ion source control systems (invited)
Authors: Sinclair John W.
Published: July 2002

General characteristics of distributed control system software tools are examined from the perspective of ion source control system requirements. Emphasis is placed on strategies for building extensible, distributed systems in which the ion source element is one component of a larger system. Vsystem, a commercial software tool kit from Vista Control Systems was utilized extensively in the control system upgrade of the Holifield Radioactive Ion Beam Facility. Part of the control system is described and the characteristics of Vsystem are examined and compared with those of the Experimental Physics and Industrial Control System (EPICS).