bluuebunny/crossref_metadata_2025 huggingface dataset:
Transport optics for a space-charge broadening ion beam
Authors: Malafsky Geoffrey P. , Winograd Nicholas
Published: July 2002

The design and performance of a low-energy ion gun system suitable for surface analysis is described. The ion gun system is capable of delivering up to a 0.72 μA beam of Ar+ ions at a potential of 500 eV into a spot diameter of 1 mm. This performance is accomplished by using ion optics to refocus the space-charge diverging beam along the 44-cm path to the target. The ion optics have been optimized by the use of a new simulation program, chden, which can model a series of lenses and the effects of space-charge forces.
CO2 dissociation in sealed rf-excited CO2 waveguide lasers
Authors: McArthur B. A. , Tulip J.
Published: July 2002

A mass spectrometer has been used to study the gas composition in a sealed rf-excited CO2 waveguide laser during operation. CO2 dissociation levels, at 53% to 71%, are similar to those reported for dc-excited waveguide lasers and substantiate prior measurements on rf-excited discharges. The degree of dissociation decreases with increasing pressure and xenon content, but increases as the proportion of helium in the gas mixture is increased. Dissociation has been found to be insensitive to the rf input power per unit discharge length over the range of 2.7 to 4.7 W/cm. This is believed to be the result of increased rates of water vapor outgassing at higher input power levels.
Concentric tube scanning tunneling microscope
Authors: Snyder C. W. , de Lozanne A. L.
Published: July 2002

A small scanning tunneling microscope (STM) for studying surfaces in ultrahigh vacuum is described. It has been designed to have a mechanical tip–sample gap instability of less than 0.002 Å while operating in an environment with relatively large-amplitude, low-frequency vibrations. Thermal fluctuations are minimized by built-in thermal compensation. The microscope has a unique coarse z positioner, and an open design for accommodating various types of tip and sample exchanging manipulators. A novel mechanism for fabricating tips of the same length makes it possible to approach the tip and sample without visual access. Atomic-scale images of graphite have been obtained and are presented.
Semiconducting wafer form shaping with an electric discharge machine
Authors: Yang Yu-Tung
Published: July 2002

Gallium can be used as a temporary glue for semiconducting wafer mounting. The good electric contact between the electrode, the gallium layer, and the semiconducting wafer makes the spark cutting and the semiconducting wafer form shaping much easier. After wafer spark cutting, the residual gallium can be easily removed by a cotton swab from the surface of the wafer in warm isopropyl alcohol (IPA). Also, in this report, improved circuitry of the electric discharge machine for easy and economical construction is described. Gallium arsenide wafers have been form shaped by the present method.
Infrared thermography of the DIII-D divertor targets
Authors: Hill D. N. , Ellis R. , Ferguson W. , Perkins D. E. , Petrie T. , Baxi C.
Published: July 2002

The power flow to the DIII-D divertor targets is routinely measured using infrared (IR) thermography. An IR television camera sensitive to radiation in the 8–12-μm range views the divertor region using a set of germanium optics. Digital signal processing is used to extract the desired surface temperature profiles from the analog data (≂12 Mbytes) stored on videotape. Inversion of these data using a simple matrix formulation of the inverse heat conduction problem then yields the incident heat flux as a function of space and time. Results from a DIII-D discharge are included.
Electron density measurements from cutoff of electron cyclotron emission in the DIII-D tokamak
Authors: Lohr John
Published: July 2002

Cutoff of microwave emission at the second harmonic of the electron cyclotron frequency has been used to infer the local electron density profile in the DIII-D tokamak. Modeling the density profile during the uncontrolled density increase associated with the transition to H-mode operation permits the profile shape factor and line average to be estimated. In special cases, the density fluctuations associated with sawteeth can also be inferred. Independent corroboration of the standard density diagnostics has been performed with this technique.
Design and construction of a rotary kiln simulator for use in studying the incineration of hazardous waste
Authors: Lemieux Paul M. , Pershing David W.
Published: July 2002

Rotary kiln systems are widely used in industrial applications to transfer energy from high temperature flames to irregular solids. Recently these systems have been shown to be suitable for the incineration of hazardous solid waste materials and the thermal treatment of contaminated soils. Destruction and removal efficiencies in excess of 99.99% have been reported for hazardous species, but the rate controlling steps of the incineration process are not well understood. This article describes the design, construction, and operation of a laboratory scale simulator which was developed to investigate the fundamentals of hazardous incineration in a rotary kiln environment. This 2 ft×2 ft refractory-lined kiln allows time-resolved characterization of contaminant evolution and destruction. Continuous thermal and exhaust concentration measurements are used to characterize the fate of the solid charge as a function of residence time within the kiln. Overall destruction efficiency can be measured by subsequent analysis of the solid phase. The initial performance of this facility has been demonstrated by studying the combustion of waste zirconium metal and by characterizing the thermal clean up of solid sorbent contaminated with toluene. The rotary kiln simulator has been shown suitable for investigation of parameters such as amount of charge, contaminate loading, rotation speed, temperature, excess oxygen, and particle size.
X-ray microtomography on beamline X at SSRL
Authors: Kinney J. H. , Johnson Q. C. , Nichols M. C. , Bonse U. , Saroyan R. A. , Nusshardt R. , Pahl R.
Published: July 2002

This article describes a high-resolution three-dimensional CT system which has been tested on the new wiggler beamline X-2 at the Stanford Synchrotron Radiation Laboratory. The present system is a rotate-only design which uses a virtual phase CCD array camera optically coupled to a high-resolution phosphor screen. The spatial resolution of this system is presently somewhat better than 10 μm (50 line pairs/mm at 20% contrast). This resolution is limited by the optical elements in the detector, and we are undertaking an effort to improve this resolution to 1 μm. Nevertheless, the spatial resolution offered by this design is sufficient to begin many studies of interest to materials research, such as, supported catalysts, composite materials, and crack growth and propagation.
Multilayer mirrors for use as a wavelength-selective filter around 100 eV
Authors: Yamamoto M. , Yanagihara M. , Arai A. , Cao J. , Nakayama S. , Mizuide T. , Namioka T.
Published: July 2002

Multilayer mirrors have been designed, fabricated and tested for use as a wavelength-selective filter of ∼100 eV for photo-CVD experiments at the beamline 12C of Photon Factory, KEK. Mo/Si and Rh/Si multilayers were selected in accordance with new simple optical criteria and fabricated on super-polished CVD-SiC substrates by means of ion-beam sputtering. Both mirrors showed a reflectance of over 40% at around the designed angle of incidence of 45°.
Soft x-ray beamline (10–1000 eV) with a plane grating monochromator for surface studies
Authors: Namba H. , Daimon H. , Idei Y. , Kosugi N. , Kuroda H. , Taniguchi M. , Suga S. , Murata Y. , Ueyama K. , Miyahara T.
Published: July 2002

The optical design and mechanical solution for a soft x-ray beamline BL-7A in PF-KEK for the energy range 10–1000 eV with a PGM are described. The optical characteristics of the beamline are tested with gas phase absorption and photoelectron spectroscopy.
A heat transfer study for beamline components in high-power wiggler and undulator beamlines. Part II. Beryllium windows (invited)
Authors: Shen Q. , Bedzyk M. J. , Keeffe M. J. , Schildkamp W.
Published: July 2002

The designs for heat transfer capabilities of beryllium windows and prefilters at Cornell High Energy Synchrotron Source (CHESS) high power wiggler and undulator beamlines are discussed, based on experimental test results and finite element analysis calculations for determining temperature and thermal stress values and distributions.
Performance of the Dragon soft x-ray beamline (invited)
Authors: Chen C. T. , Sette F.
Published: July 2002

We report on the performance of a newly constructed synchrotron radiation soft x-ray beamline. This beamline, dubbed Dragon, is a spherical version of the cylindrical element monochromator design proposed previously. By measuring the K-edge absorption spectra of condensed nitrogen, it is determined that this monochromator has achieved resolving power 104 at 400-eV photon energy, using its full 15 by 1 mrad angular acceptance. The ideas and advantages contained in the CEM design have also been experimentally confirmed.
In situ calibration of TFTR neutron detectors
Authors: Hendel H. W. , Palladino R. W. , Barnes Cris W. , Diesso M. , Felt J. S. , Jassby D. L. , Johnson L. C. , Ku L.-P. , Liu Q. P. , Motley R. W. , Murphy H. B. , Murphy J. , Nieschmidt E. B. , Roberts J. A. , Saito T. , Strachan J. D. , Waszazak R. J. , Young K. M.
Published: July 2002

We report results of the TFTR fission detector calibration performed in December 1988. A NBS-traceable, remotely controlled 252Cf neutron source was moved toroidally through the TFTR vacuum vessel. Detection efficiencies for two 235U detectors were measured for 930 locations of the neutron point source in toroidal scans at 16 different major radii and vertical heights. These scans effectively simulated the volume-distributed plasma neutron source and the volume-integrated detection efficiency was found to be insensitive to plasma position. The Campbell mode is useful due to its large overlap with the count rate mode and large dynamic range. The resulting absolute plasma neutron source calibration has an uncertainty of ±13%.
Contact placement errors for resistive and Hall measurements on cross-shaped samples
Authors: Koon Daniel W.
Published: July 2002

The calculation of lead-placement errors for resistivity and Hall signals is extended to the family of cross-shaped samples. Empirical expressions for errors [Δρ/ρ=− 1/2 (2d/D)2n and ΔRH/RH=− 1/2 (2d/D)n] are given in the limit of large contact displacement (d/D→ 1/2 ). For crosses, the exponent n was found to increase as n ∝ (l/D)−1.42 as the ratio of leg width to overall size, l/D, was reduced. For square and circular cloverleafs, n is less sensitive to the increase of the slit length, giving power laws with exponents of 0.8 and 0.6, respectively, in terms of the parameter λ=2r/D.
Inverse photoemission
Authors: Johnson P. D. , Hulbert S. L.
Published: July 2002

We review the experimental apparatus presently available for use in inverse photoemission spectroscopy (IPES) in the vacuum ultraviolet (5–30 eV) energy range. We consider the design and use of different photon detectors including the gas-filled Geiger Muller counters and the more recent solid-state isochromat detectors. We review the properties of various tunable photon detectors employing either gratings or lenses as the dispersive element. Detection of the polarization of the photons and its role in the emission process is also discussed. A survey of the different electron gun designs is presented with a discussion of the limitations imposed by space-charge effects on both the available current and the achievable momentum resolution. Finally we present a brief review of spin-polarized IPES (SPIPES) and discuss the introduction of spin polarization in the incident electron beam.
An omegatron mass spectrometer for plasma ion species analysis
Authors: Wang E. Y. , Schmitz L. , Ra Y. , LaBombard B. , Conn R. W.
Published: July 2002

An omegatron mass spectrometer which can be used to measure the ion species and charge state distribution in a magnetized plasma is described. In the conventional omegatron, ions are formed as the result of gas ionization by a fine electron beam passing through the center of the analyzer along the magnetic field. In the plasma omegatron, the plasma ions are entering the analyzer through a small floating aperture. We employ a biasing technique to reduce the ion velocity along the magnetic field and, thus, achieve improved ion collection and sensitivity. Experiments have been performed to demonstrate the instrument’s operation in the PISCES-A linear plasma device, at a magnetic field B=1.3 kG. Mass spectra have been obtained in hydrogen, helium, and nitrogen plasmas, and typical results are presented.
A vertical piezoelectric inertial slider
Authors: Renner Ch. , Niedermann Ph. , Kent A. D. , Fischer O/.
Published: July 2002

We have developed a linear translation device using piezoelectric-induced slip-stick motion. Reproducible single steps of about 30 Å, as well as continuous stepping with an overall translation speed of 0.25 mm/s, are routinely realized. The notable feature of this device is that this performance is achieved in the vertical orientation with the translator moving against gravity. This remarkable result is made possible using cycloidal functions instead of sawtooth signals to activate the motion. We have realized a very simple translator which can be used in any orientation with a displacement onset voltage of 15 V. The instrument was successfully tested in the temperature range from 1.6 to 300 K. Since no mechanical connections are required, this design is well suited for many applications, including scanning tunneling microscopy.
Super-polished silicon carbide mirror for high-power operation of excimer lasers in a vacuum ultraviolet spectral range
Authors: Kurosawa Kou , Sasaki Wataru , Okuda Masahiro , Takigawa Yasuo , Yoshida Kunio , Fujiwara Etsuo , Kato Yoshiaki
Published: July 2002

We demonstrate the usefulness of a high-quality SiC mirror for the high-power operation of vacuum ultraviolet lasers. A void free SiC film of 400-μm thickness was deposited onto a high-purity graphite substrate by chemical vapor deposition. The super-polished SiC mirror, whose surface roughness was 0.2 nm rms, was used as a cavity reflector of a high-power Ar excimer laser, which operates at 126 nm. The highest output energy of 400 mJ/cm2 per pulse, which corresponds to the energy density of 1 J/cm2 on the SiC mirror surface, has been obtained without any damage to the SiC mirrors.
P-channel metal–oxide–semiconductor dosimeter fading dependencies on gate bias and oxide thickness
Authors: Ristić Goran , Golubović Snežana , Pejović Momčilo
Published: July 2002

The threshold voltage recovery (‘‘fading’’) of P-channel metal–oxide–semiconductor dosimeters irradiated to 10 Gy(Si), after 3500 h room-temperature annealing, has been investigated. The obtained results have shown that fading decreases with the increase of the absolute value of gate voltage as well as with the increase of gate oxide thickness.
A balanced dual-photodetector optical receiver for daylight operation
Authors: Chien Pie-Yau
Published: July 2002

A balanced dual-photodetector optical receiver with an active optical feedback circuit suitable for daylight operation has been developed. This receiver is suitable for laser range finder or fuse systems operating under high level of sunlight illumination. The design and operation of the receiver is discussed.
A pulsed electron beam time of flight apparatus for measuring absolute electron impact ionization and dissociative ionization cross sections
Authors: Ma Ce , Sporleder C. R. , Bonham R. A.
Published: July 2002

A new electron impact spectrometer has been constructed that utilizes a variable energy (4–500 eV) pulsed electron source with time-of-flight detection of electrons and ions. The apparatus can be used in a beam-beam scattering mode or in a constant pressure mode suitable for absolute measurements. A newly designed data processing system is described that uses standard CAMAC modules (LeCroy model 4208 TDCs) and allows up to 32 separate detectors to be used simultaneously in a single hit mode or up to four separate detectors in a multihit mode with each detector capable of recording up to eight hits in the same experiment. The dead time between experiments is 9.2 μs which allows up to 100 000 experiments/s for experimental flight times not exceeding 1 μs at 1 ns timing resolution. Longer flight times, up to 8.3 ms in duration, can be accommodated but with reduced timing resolution. The determination of the partial ionization cross sections for Ar+, Ar2+, and Ar3+ from threshold up to 500 eV is used as an illustration of some of the capabilities of the new instrument. The results obtained are in excellent agreement with other recent work for Ar+. For the multicharged ions the cross sections were found to lie between earlier reported results. In addition the utility of the variable ion extraction field capability of the instrument is demonstrated by the separation of N+ from N2+2 for the case of electron impact dissociative ionization of N2. A new method for placing the data on an absolute scale is presented.
Comparison of triethylaluminum, triethylgallium, triethylindium, and triethylantimony on GaAs(100)
Authors: Heitzinger John M. , Jackson M. S. , Ekerdt J. G.
Published: July 2002

The surface chemistry of triethylaluminum, triethylgallium, triethylindium, and triethylantimony was studied on GaAs(100) using thermal desorption spectroscopy, static secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy. Ethylene, the major hydrocarbon reaction product, desorbs from the GaAs(100) surface during thermal desorption spectroscopy experiments at 565 K for all four molecules. This indicates an identical rate limiting step for the elimination of ethyl groups from the surface following adsorption of these molecules. We propose that ethyl groups migrate to Ga sites and then undergo reaction at these sites.
Hydraulic fluid as a liquid coolant of high power, cw microwave (2.45 GHz) plasma tubes
Authors: Schlie L. A.
Published: July 2002

Commercially available hydraulic fluid is shown to be an excellent liquid coolant for high power plasma tubes excited in microwave (2.45 GHz) structures such as resonant cavities, ‘‘holes’’ in waveguides, and slotted waveguides. The hydraulic fluid’s very low absorption (tan δ=ε″/ε′=1.87×10−4) at 2.45 GHz makes this liquid useful as a safe and inexpensive coolant of high power, cw microwave plasma tubes. For the spectral region 5700 Å≤λ≤1.1μm, the liquid’s transmission is nearly 100% but greatly reduced for longer wavelengths and non-existent for λ≤5700 Å. Its nonflammable and nontoxic properties plus good viscosity are additional attractive features.
Characterization of two-gated microchannel plate framing cameras
Authors: Failor B. H. , Gorzen D. F. , Armentrout C. J. , Busch G. E.
Published: July 2002

The overall performance of both a single- and a double-microchannel plate framing camera were measured. In the case of the double-plated device, only the front plate was gated. A short-pulse, 20-ps full width half-maximum (FWHM), uv laser was used to create photoelectrons on a time scale rapid compared to the temporal variation of the high-voltage gate pulse (965 V peak amplitude and 270 ps FWHM). Measurements were made of the variation in the light output pulse amplitude (8%–24%), width (85–115 ps), and peak location (±22 ps), the latter corresponding to a temporal jitter. It was found that when a dc bias was applied to the plate (in addition to the high-voltage pulse) the output signal increased as the dc bias to the 13 and 5.2 powers, below and above a bias of 450 V, respectively, and a factor of 20 difference in signal between the single- and double-plate cameras. It was also determined that the rejection ratio drops from 500 to 1300 at a bias value of 450 V to 125–190 at 650 V.
Plastique: A synchrotron radiation beamline for time resolved fluorescence in the frequency domain
Authors: De Stasio Gelsomina , Zema N. , Antonangeli F. , Savoia A. , Parasassi T. , Rosato N.
Published: July 2002

PLASTIQUE is the only synchrotron radiation beamline in the world that performs time resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and dynamics of molecules. We describe the beamline and some initial data.
Seeman–Bohlin linkage for Siemens x-ray diffractometer
Authors: Banerjee R. L. , Richard Aldérice
Published: July 2002

A mechanical linkage attached to a Siemens x-ray diffractometer is designed and constructed to convert it to a Seeman–Bohlin diffractometer, with special emphasis on its suitability for x-ray characterization of polycrystalline thin films. The apparatus employs a pyrolitic graphite monochromator crystal using the full focusing Johansson principle for the diffracted beam to obtain a high intensity low background diffraction pattern. The performance of this Seeman–Bohlin diffractometer is illustrated by recording the diffraction pattern of a 100-Å-thick thin film of gold.
Self-tuning temperature servo regulator
Authors: Grubic M.
Published: July 2002

A self-tuning algorithm is described and applied to a temperature servo control. It allows the regulator to adapt to slowly changing processes while keeping the response of the control system unaffected. Examples dealing with adaptions to set points with different dynamics and a reaction of the self-tuner to changes in the gain of the power amplifier are provided.
Ge thin-film melting point detection for optical pyrometer calibration in a rapid thermal processor
Authors: Dilhac J.-M. , Ganibal C. , Nolhier N. , Rousset B.
Published: July 2002

The reflectivity of a multilayered structure on top of a silicon wafer has been measured in a rapid thermal processor at 0.6328 μm. This structure consisted of a Ge thin film sandwiched between SiO2 and Si3N4 films. The wafer has been submitted to thermal cycles around the melting point of Ge (938 °C). It has been shown that the onset of Ge melting which corresponds to an abrupt reflectivity change can be detected in situ by monitoring the intensity of a reflected laser light. It has therefore been demonstrated that the detection of Ge thin-film melting can serve as a tool for temperature sensor calibration in a rapid thermal processor.
Report of the satellite workshop on synchrotron radiation instrumentation for x-ray absorption spectroscopy
Authors: Greaves G. N.
Published: July 2002

Report of a workshop on synchrotron radiation instrumentation for x−ray absorption spectroscopy, a satellite meeting of the 4th International Conference on Synchrotron Radiation Instrumentation, will be presented. The workshop comprised presentations and discussions in the principal areas of x−ray optics, sources of noise, detectors and new experiments. (AIP)
Production of a high-density state-selected metastable neon beam
Authors: Brand J. A. , Furst J. E. , Gay T. J. , Schearer L. D.
Published: July 2002

We have developed a high-density source of metastable neon and have selectively quenched both metastable species using a standing-wave dye laser. The source is compact, stable, and produces an average intensity of 3.6×1014 sr−1 s−1 and a density on target of 7.7×106 cm−3.
Time-resolved experiments in the frequency domain using synchrotron radiation (invited)
Authors: De Stasio Gelsomina , Giusti A. M. , Parasassi T. , Ravagnan G. , Sapora O.
Published: July 2002

PLASTIQUE is the only synchrotron radiation beam line in the world that performs time-resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and the dynamics of molecules. This technique measures fluorescence lifetimes with picosecond resolution in the near UV spectral range. Such accurate measurements are rendered possible by taking phase and modulation data, and by the advantages of the cross-correlation technique. A successful experiment demonstrated the radiation damage induced by low doses of radiation on rabbit blood cell membranes.
The design of an atmospheric pressure ionization/time-of-flight mass spectrometer using a beam deflection method
Authors: Ma Ce , Michael Steven M. , Chien Mingta , Zhu Jianzhong , Lubman David M.
Published: July 2002

A novel time-of-flight (TOF) mass spectrometer configuration has been designed which can be interfaced to a continuous ion beam source produced by atmospheric pressure ionization. The TOF device uses a beam deflection method to sweep the ion beam past a slit placed near the ionization source in order to generate a start pulse for TOF detection. The beam sweep technique is modeled by computer simulation and optimized for the various experimental parameters. Nonvolatile samples are injected into the TOF device using liquid injection into a glow discharge atmospheric pressure ionization source in helium. A resolution of at least 519 at m/z 311 is obtained, which is limited by the experimental parameters available in our experiment. The mass resolution is computer modeled and it is shown that as the mass increases, the experimental constraints become less important, and the resolution will increase. It is predicted that using the correct experimental conditions and with the addition of an ion reflector that resolution of well over 1000 should be obtained.
High-luminosity system for XEOL spectroscopy (abstract)
Authors: Ivanov S. N. , Kolobanov V. N. , Mikhailin V. V.
Published: July 2002

A high-luminosity system comprising optically matched sample chamber, monochromator-spectrograph, and detectors of luminescences has been designed for XEOL spectroscopy using synchrotron radiation. Exciting x-ray radiation penetrated the sample chamber through a window made of a Be foil. The sample is mounted on the sample holder of a nitrogen cryostat. The entrance slit of the monochromator is fixed on the sample’s surface. Luminescence is excited and detected at the same side of the sample and optical slit; the angle between the exciting radiation and the entrance shoulder of the monochromator is 45°. Sample chamber has two windows made of a Be foil for incident and transmitted x-ray radiation and another one made of MgF2 for outcoming luminescence. A Seya–Namioka mounting with 70.5° has been chosen for the spectra instrument as it is characterized by a flat field in the focal surface in the area of the exit slit, providing the possibility to detect luminescence either in the mode of a monochromator or a spectrograph. In the first case it is detected by a photomultiplier with a sodium salicylate screen or a mirror in front of it depending on the spectral range. In the spectrograph a photodetector array is applied. The switching of the modes is achieved by a mirror in front of the exit slit. Changeable diffraction gratings with radius 250 mm and density of grooves per mm 300 and 600 make the instrument efficient in the spectral range 110 to 1400 nm providing resolution up to 1 nm. The sample chamber and the monochromator are separated by a window made of MgF2. Vacuum in the sample chamber is better than 10−7 Torr, in the monochromator better than 10−4 Torr. Temperature of the sample can be varied in the range 80–600 K. The level of the scattered light in the instrument is lower than 10−4.
A surface-profile measuring system for synchrotron radiation mirrors
Authors: Sato S. , Higashi Y. , Haya S. , Otsuka M. , Yamamoto H.
Published: July 2002

The optical head for a new surface-profile measuring system was constructed on the basis of the Twyman–Green interferometer with heterodyne phase detection method. Stability in optical path difference (OPD) was within 2 nm for a fixed point under the well shielded condition. The measured OPD map at the null fringe condition shows the possibility for direct or segment measurement method of aspheric and/or large size mirrors in SR optics. Based on experiments, a new surface-profile measuring system by phase measurement interferometry and segment method is designed. Designed features of the system are briefly reported.
The new JET 2.5-MeV neutron time-of-flight spectrometer
Authors: Elevant T. , Belle P. v. , Grosshög G. , Hoek M. , Jarvis O. N. , Olsson M. , Sadler G.
Published: July 2002

A major upgrade of the JET 2.5-MeV neutron time-of-flight spectrometer has been completed. The improvement has permitted ion temperature measurements for Maxwellian deuterium plasmas with Ti≳4 keV to be obtained in 0.5-s intervals. By combining observations of neutron and x-ray energy spectra with studies of γ-ray emission from reactions between fast deuterons and impurities, the effects of ICRF heating on the deuterium energy distribution have been studied. The time evolution of neutron energy spectra from deuterium-beam heated deuterium plasmas is illustrated and a method for evaluating the ion temperature from such sequences is indicated. Furthermore, the spectrometer has shown stable performance during high neutron fluxes.
Thermal property measurements of liquid samples using photoacoustic detection
Authors: Leite N. F. , Miranda L. C. M.
Published: July 2002

In this paper we describe the use of so-called open-photoacoustic cell (OPC) for thermal characterization of transparent liquid samples. The samples used to demonstrate the usefulness of the OPC configuration are water, glycerol, and diffusion pump oil.
An extremely low noise, low cost, constant current supply
Authors: Ross S. B. , Davis J. R. , Dutra J.
Published: July 2002

We have constructed an extremely low noise constant current power supply. The design was optimized for low noise at 0.5 Hz. For a 134 mA supply, noise at this frequency is 2.5 nA rms/ √Hz. At 1 Hz, it is 1.0 nA rms/√Hz. The supply is roughly an order of magnitude quieter than the quietest commercial unit we know of.
Determination of ion multiplier sensitivities as a function of ionic mass for use in quantitative mass spectrometry
Authors: Cooper Glyn , Zheng Yenyou , Burton Gordon R. , Brion C. E.
Published: July 2002

An experimental method has been developed for the determination of ion multiplier sensitivity to ions of different mass to charge ratio using the electron-ion coincidence technique of dipole (e,e+ion) spectroscopy. Time-of-flight mass spectra of each of the noble gas atoms He, Ne, Ar, Kr, and Xe are collected using the ion multiplier under investigation. In the present work we have determined relative efficiencies, at 7.5–8 keV ion impact energy, over the mass range 1–140 amu for two different large active area multipliers, a Johnston focused mesh multiplier and a microchannel-plate detector, both operated in the saturated pulse counting mode. Significant variations in detector sensitivity occur at low m/e values for both multipliers. The microchannel-plate detector shows a level response function above m/e=∼30, while the Johnston multiplier exhibits a slow decrease in sensitivity in the same mass range. The applicability of the measured response functions to the correction of molecular mass spectra and experimental photoion branching ratio data has been investigated. It appears that the detection efficiencies for atomic and polyatomic ions of the same m/e may be different.
Measurement of surface impedance versus temperature using a generalized sapphire resonator technique
Authors: Fletcher R. , Cook J.
Published: July 2002

An automated measurement technique to measure the surface impedance, Zs=Rs+iXs, as a function of temperature is presented. Based on the dielectric resonator measurement technique, a general purpose approach is developed which does not neglect dielectric loss and can accommodate a variety of sample sizes and measurement frequencies. By employing a parallel-plate geometry which has a known electromagnetic solution, both the surface impedance of the sample and the induced surface current can be related quantitatively to the measured Q, the resonant frequency, and the applied power. Although the measurement sensitivity depends on the system design and choice of materials, comprehensive equations are presented which serve as a useful tool for designing the system and simulating the measurement. Using a sample size of 1×1 cm2 and a measurement frequency of 19.6 GHz, a measurement uncertainty of 420 μΩ for Rs and 4800 μΩ for ΔXs is demonstrated. For superconducting samples, this translates to a measurement uncertainty of 105 μΩ for Rs and 2400 μΩ for ΔXs at 10 GHz, which is sufficient for routine measurements. Methods to improve the resolution and uncertainty of this measurement technique are discussed, and a general scheme to fully automate this measurement via computer is demonstrated.
A laser vaporization, laser ionization time-of-flight mass spectrometer for the probing of fragile biomolecules
Authors: Schilke David E. , Levis Robert J.
Published: July 2002

We report the design and evaluation of a new spectrometer for probing fragile biomolecules in the gas phase. The spectrometer is based on a laser vaporization method to transfer biomolecules up to several hundred thousand dalton into the gas phase as intact, neutral species. This method requires the formation of a thin film containing a dye molecule and the analyte of interest which is molecularly vaporized using a high energy, pulsed laser. The gas phase, neutral analyte molecules are laser vaporized directly into a laser ionization region without the need of a pulsed nozzle. The molecules are subsequently ionized using multiphoton ionization; two-color, two-photon laser ionization is reported here. The resulting ions are detected using time-of-flight mass spectrometry. The spectrometer employs a four grid extraction system which both filters unwanted ions produced in the initial vaporization step and extracts the laser ionized species into the field free drift region. A hybrid copper–beryllium dynode with a dual microchannel plate detector is employed as the high mass ion detector and amplifier before external amplification. Anthracene-tagged nucleotides and some small test molecules are vaporized and ionized to evaluate the spectrometer.
Low temperature ion source
Authors: Tanabe Shinichi , Tonegawa Akira , Takayama Kazuo
Published: July 2002

A low temperature ion source has been developed to produce a plasma with a low ion temperature and a high plasma density by using a gas contact technique. This ion source is a hybrid type consisting of modified plasma compression type cylindrical hollow cathode plasma source and the gas contact chamber with floating potential mounted on the head of the anode. The temperature of ions and the density in the produced argon plasma are gradually increased in order to compress it by the small canal of the floating electrode and the gas magnetic field. This plasma flow goes into the gas contact chamber and mixes with the cold neutral argon gas, resulting in the production of a low ion-temperature plasma by ion-neutral collisions. The characteristics of the energy distribution of extracted ion beam (Vex=500 V) were measured by an electrostatics analyzer and we determined both the half-value of the energy spread of ion beam ΔE and the mean ion temperature Ti in the plasma flow. The mean electron temperature Te and plasma density ne were determined by means of a plane Langmuir probe. As a result, Te and ΔE decrease from 4.1 to 2.5 eV and 13.3 to 8.3 eV, respectively, though ne is nearly constant at 3.0×1010 cm−3.
A hollow cathode ion source as an electron-beam ion source injector for metallic elements
Authors: Visentin B. , Harrault F. , Gobin R. , Leroy P. A.
Published: July 2002

A hollow cathode ion source (HCIS) has been developed in our Laboratory to produce, by cathodic sputtering in a glow discharge, a one charge metallic ion beam. This source is used as an injector for the electron-beam ion source (EBIS) Dioné that produce, after ion stripping, a highly charged heavy-ion beam for acceleration in Mimas–Saturne synchrotrons. Due to the good pulse-to-pulse repeatability of the HCIS, the very long lifetime of the cathode (several months), as well as the very good value of the normalized emittance (εnorm=4×10−9 π mrad), this source appears as an ideal EBIS injector for metallic and gaseous elements. In this paper we report the description of the HCIS and the experimental results achieved, after injection in the EBIS, by the production of heavy-ion beams like Fe20+, Au50+, and U55+ (from 4×107 to 9×106 ions/cycle).
Initial emittance measurements of the superconducting electron cyclotron resonance at NSCL
Authors: Harrison K. A. , Antaya T. A.
Published: July 2002

We report on preliminary emittance measurements of oxygen and argon ions extracted from the superconducting electron cyclotron resonance (SCECR). For oxygen, charge states 1+ through 8+ have been measured for 100% intensity with the SCECR tuned to maximize highly charged ions, at a 10 kV extraction voltage. For argon, charge states 6+ through 14+ have been measured under the same conditions. For both species, both normalized and unnormalized emittances show the same trend—increasing with charge Q for low charge, and falling sharply for highly charged ions. The increase in emittance with Q for low Q implies an expected magnetic field dependence. The decreasing emittance for high Q is unexpected, and possible explanations for this effect will be discussed.
A large negative-ion source immersed in the vacuum vessel on the NBI test stand at the NIFS
Authors: Oka Y. , Takeiri Y. , Kaneko O. , Ando A. , Tsumori K. , Akiyama R. , Kawamoto T. , Kuroda T.
Published: July 2002

To develop the powerful negative-ion-based neutral beam injection system for the large helical device, a 1/3 scaled H− source has been tested, which is immersed in the vacuum vessel. Intrinsic features of the vacuum-immersed large H− source are described. Plasma density of higher than about 1012 e/cm3 is produced. During the beam extraction, it was found that a beam-induced thin plasma exists in the vacuum vessel. In order to get a long pulse beam, this plasma was shielded and then the beam conditioning was completed up to the total beam energy of 70 keV for 100 ms, with the arc power up to about 50 kW. It is confirmed that H− current scaling as well as the plasma parameters would be similar to the scaling which is achieved by the previous 1/3 source.
The superconducting electron cyclotron resonance 6.4 GHz high-B mode and frequency scaling in electron cyclotron resonance ion sources (abstract)a)
Authors: Antaya T. A. , Gammino S.
Published: July 2002

We would like to present the initial results and description of the superconducting electron cyclotron resonance ion source (SCECR) operating in the high-B mode—a new high magnetic field, low-frequency mode of operation. First, we describe the operating characteristics of this mode, which include very high mirror confinement in all directions, yet having a minimum field low enough for electron cyclotron resonance heating of 6.4 GHz. The source performance for oxygen, neon, argon, krypton, and xenon is presented and comparisons are made with several existing high-performance ECR sources. In this high-B mode the SCECR matches or exceeds the performance of all existing ECR sources. These results perhaps invalidate the classical frequency squared source performance scaling law, and suggest the new possibility of high-performance, low-frequency (and hence low cost) sources as will be discussed.
Status of the pulsed magnetic field electron cyclotron resonance ion source
Authors: Mühle C. , Ratzinger U. , Bleuel W. , Jöst G. , Leible K. , Schennach S. , Wolf B. H.
Published: July 2002

Synchrotrons like the heavy-ion synchrotron SIS at GSI need an efficient low duty cycle injector (typical 1-pulse/s and 200-μs pulse length). To improve the peak current, an electron cyclotron resonance (ECR) ion source has been designed using a pulsed magnetic field (PuMa) to force ion extraction. We replaced the hexapole of a 10-GHz Minimafios ECR ion source by a vacuum chamber containing a water-cooled bilayered solenoid coil and a decapole permanent magnetic structure. A pulse line feeds the solenoid with a 250-μs pulse which increases the magnetic field in the minimum B region by 0.3 T. This process opens the magnetic bottle along the beam axis resulting in an extracted ion pulse. First tests of the PuMa ECR configuration in cw and pulsed operation are presented and analyzed.
Intense high charge state ion sources (invited)
Authors: Kutner V. B.
Published: July 2002

A review of Penning ionization gauge (PIG), duoplasmatron (DP), laser-plasma ion source (LPIS), Electron cyclotron resonance ion source (ECRIS), and electron beam ion source (EBIS) used for the production of intense and high charge state ion beams is given. The outputs of high charge states of different elements of the Periodic Table from ion sources of these types are compared. Bare nuclei up to Ar can be obtained from EBIS and ECR and Xe+54 from EBIS. Comparisons are made of compilations of the output (high average current of 107–1017 pps) for different charge states of Xe for PIG, DP, ECRIS, EBIS ion sources and Ta, Pb for different charge states of the LPIS. The present level and perspectives of development (a pulsed gas feed, stationary electric field) of the PIG ion source are presented. The beam performance and future development of these intense and high charge state ion sources are discussed from the point of view of the perspectives of the cyclotron programs at FLNR and JINR.
Novel implementation of laser heated pedestal growth for the rapid drawing of sapphire fibers
Authors: Phomsakha V. , Chang R. S. F. , Djeu N.
Published: July 2002

A new version of laser heated pedestal growth system is described which is amenable for the rapid growth of single crystal fibers. The system incorporates a Gaussian reflector to reshape the radial intensity profile of the CO2 laser beam. When He is used as the growth atmosphere, high optical quality sapphire fibers can be produced at rates as high as 2 cm/min with this apparatus.
In situ monitoring of the relative distribution of radicals by a two probe system
Authors: Lee Pyung-Woo , Kim Yong-Jin , Chang C. S. , Chang Hong-Young , Moon Jong
Published: July 2002

A new technique to determine the relative spatial distribution of radical concentration without Abel transformation is presented. By monitoring spatial light intensities with an optical probe inserted into the plasma, the relative spatial distribution of the radical species is investigated. The relative spatial uniformity of the radical atom is also investigated by normalizing the emission intensity of the radical atoms to the plasma parameters (electron-impact excitation rate coefficient and plasma density). The movable probe technique has a simple configuration and provides accurate information on the relative spatial distribution of radicals in any plasma source.
Cosmic ray simulator: A versatile apparatus for quantitative studies on the interaction of cosmic rays with frozen solids by on line and in situ quadrupole mass spectrometry and Fourier transform infrared spectroscopy
Authors: Kaiser R. I. , Gabrysch A. , Roessler K.
Published: July 2002

The cosmic ray simulator consists of a 50 ℓ cylindrical stainless steel chamber. A rotable cold finger milled of a silver (111) monocrystal optimizes heat conductivity and is connected to a programmable, closed cycle helium refrigerator allowing temperature control of an attached silver wafer between 10 and 340 K (±0.5 K). Oil-free ultrahigh vacuum (UHV) conditions of ≊10−10 mbar are provided by a membrane, drag, and cryopump, hence guaranteeing a vacuum system free of any contamination. Ice layers of defined crystal structures and reproducible thickness of (5±1) μm are achieved by depositing gases, e.g., CH4, CD4, CD4/O2, and CH4/O2, with a computer-assisted thermovalve on the cooled wafer. These frosts are irradiated at 10 and 50 K with 7.3 MeV protons and 9 MeV α particles of the compact cyclotron CV28 in Forschungszentrum Jülich up to doses of 150 eV per molecule, i.e., simulating the distribution maximum of galactic cosmic ray particles interacting with primordial matter in space during 0.7×109 yr. During the experiments, gas phase and solid state are monitored for the first time quantitatively on line and in situ by a quadrupole mass spectrometer (QMS) via matrix interval arithmetic and a Fourier transform infrared spectrometer (FTIR) in an absorption-reflection mode at 62.5°.

For the first time, a cosmic ray simulator allows detailed and reproducible mechanistic studies on the interaction of cosmic ray particles with frozen gases in space based on pressure conditions (hydrocarbon free UHV conditions, the limitation of condensations of residual gases during an experiment to less than one monolayer), temperature regime (the use of silver monocrystals, FTIR in reflection, optimized ion currents, and target thicknesses <5 μm restrict temperature increasing to 14 K), and defined target systems. In combination with two on line and in situ analyses techniques, i.e., FTIR and QMS, the machine yields unprecedented options such as computing the heating of the ice surfaces directly exposed to the ion beam by a calibrated QMS and a complete quantification of product distribution. Preliminary results indicate a strong temperature-dependent component of the reaction mechanisms in the frosts: surface layers are heated by impinging ions to (14±1) K and yield (70%–100%) of higher molecular weight species, such as C11D24, whereas 10 K regions produce majority of simpler hydrocarbons, e.g., C3D8. Second, O2 contaminations influence the experiments dramatically by trapping of diffusive H atoms as O2H and, thus, yield oxygen-containing yellow to brown residues after heating to 293 K. Irradiation of pure methane targets, however, produce no residues. But an increasing concentration of H atoms exceeding (6%±3%) leads to ejection of up to 90% of the frosts into vacuum.
Oxides as thermionic sources of Mg+, Ca+, Sr+, and Ba+ ions
Authors: Tan T. L. , Zhou Z. L. , Ong P. P.
Published: July 2002

Group II metal oxides (MgO, CaO, SrO, and BaO) were coated on tungsten or tantalum filaments to form thermionic emitters of positive metal ions. The choice between tungsten and tantalum for optimum performance was empirically found to depend on the oxide material. Total ion emission current and ion purity were generally found to increase with temperature. A stable source of high purity (up to 97%) Ba+ ions could be obtained from the BaO-coated filament at 1800 °C after 150 min of heating. At 1600 °C, the SrO-coated filament could produce a relatively stable ion current and purity of 97% of Sr+ ions. Very pure (99.8%) Ca+ ions were emitted at 1950 °C. However more stable ion current though less pure ions (87% of Ca+ at 1800 °C) were obtained at lower temperatures. MgO-coated filaments using tungsten or tantalum wires were found to be unsuitable as a source of Mg+ ions. All the filaments of MgO, CaO, SrO, and BaO were found to produce larger ion current and higher ion purity at higher temperatures. In general, the relative isotopic abundances of ions produced by a thermionic source are reproduced by the natural isotopic abundances of the corresponding metal. It implies that the slight differences in the nuclear masses of the isotopes do not introduce any significant effect on their ion production efficiency. Between tantalum and tungsten as a choice for the filament material, tantalum was found to be a better choice for Ba+ and Sr+ ions, while tungsten was better for Ca+.