bluuebunny/crossref_metadata_2025 huggingface dataset:
A self-crowbar switch for a gas-puff z-pinch driven by a pulsed power generator
Authors: Akiyama H. , Shimomura N. , Takasugi K. , Miyamoto T. , Sato M. , Tazima T.
Published: July 2002

A self-crowbar switch for a gas-puff z-pinch, driven by a pulsed power generator with output voltage 600 kV, pulse width 70 ns, and characteristic impedance of 3 Ω, has been built and tested successfully. Discharges with pulsed gas injection are placed into four groups dependent on the delay between the pulsed power generator trigger time and the gas-puff trigger time. For short delay times (<2.8 ms), vacuum discharge occurs. For moderate delay times (2.8–3.8 ms), a z-pinch plasma is produced without using the self-crowbar switch, and the plasma exists for a much longer time than the voltage pulse, that is, 700 ns compared to 70 ns. For relatively longer delay times (3.8–6 ms), the self-crowbar switch operates, and the decay time of the current becomes approximately 2.5 μs. Moreover, a z-pinch occurs after self-crowbarring. For long delay times (>6 ms), a z-pinch does not occur. The self-crowbar switch is believed to operate by photoionization of puffed gas which has reached the switch region.
Use of replaceable dynode electron multiplier for comparative measurements of opaque cesium iodid photocathodes in the ultraviolet
Authors: Roberts Ed
Published: July 2002

A simple means of performing comparative assessment of opaque cesium iodide ultraviolet photocathodes was developed in order to study sensitivity variation with means of deposition. A replaceable dynode electron multiplier was modified to accept a removable metal plate on which was deposited an ultraviolet photocathode. This allowed a large number of photocathode samples to be rapidly compared in a low-cost manner.
A time-of-flight mass filter for ion and cluster ion photodissociation studies
Authors: Syage J. A. , Steadman J.
Published: July 2002

A sensitive method is described for detecting photodissociation products from a specific ion or cluster ion in the absence of the initially formed fragment ions that would otherwise interfere with the signals of interest. By using a simple pulse sequence, the conventional three-grid time-of-flight (TOF) assembly can be operated as a low-mass rejection filter capable of eliminating all ions below an adjustable threshold mass value. The method has been applied using different ionization sources [e.g., picosecond and nanosecond photoionization, and electron impact (EI) ionization]. Molecular-beam applications are demonstrated for (1) high-resolution resonance ion dissociation spectroscopy of rovibrationally cold ions, and (2) stepwise solvation of neat and seeded cluster ions formed by either photoionization or EI ionization. The low-mass filter (LMF) is especially powerful for cluster ion photodissociation studies. For example, the elimination of successively larger cluster ions leads to photofragment mass spectra that can uniquely establish the photodissociation and metastable decay fragments from specific cluster ions.
Emittance characteristics of negative ion beams generated by the sputter technique
Authors: Alton G. D.
Published: July 2002

Average emittance data for ion beams extracted from cesium-sputter negative ion sources equipped with spherical, ellipsoidal, and cylindrical geometry cesium-surface ionizers are presented. The attributes of the respective source geometries are described in terms of their cesium ion optical properties. The results of recent measurement of the emittances of momentum-analyzed beams extracted from the ellipsoidal geometry source are also presented. These measurements indicate the presence of a species-dependent effect. The effect is believed to be attributable to differences in the energy spreads of the respective negative ion beams introduced by the sputter generation process.
Current status of development of ion sources in Japan from a standpoint of materials science (invited)
Authors: Takagi Toshinori , Ishikawa Junzo
Published: July 2002

The current status of development of novel ion sources for materials science in Japan is reviewed. Several types of microwave ion sources which permit a reactive gas discharge have been developed for the production of high intensity and low-charge-state ion beams. The plasma cathode technique, as an electron source, provides conventional ion sources with a long lifetime. Metal ion sources which can deliver a pure metal ion beam have been developed, extracting metal ions from a high temperature discharge chamber of large volume or a porous tip surface. A new principle metal ion source by use of a metal cluster, which consists of hundreds to thousands of metal atoms, has been developed. High current negative ion sources have been developed for both light and heavy ions, resulting from in-depth investigation of negative ion production mechanisms.
High-current metal ion beam extraction from a multicusp ion source
Authors: Inouchi Yutaka , Tanaka Hideki , Inami Hiroshi , Fukumaru Fumio , Matsunaga Kouzi
Published: July 2002

Improvements have been made in a multicusp ion source, which made it possible to produce metal–vapor plasma and extract a high-current metal ion beam. In the discharge chamber, double radiation shields were set and the inner shields were heated to 1860 K. Therefore, it became possible to maintain enough metal–vapor density to produce plasma without the use of support gas. For the extraction of a high-current metal ion beam, we used multislit electrodes in the accel–decel electrode structure. Experiments of the metal ion beam extraction were performed with several kinds of metals (Al, Cr, Si). For example, the extracted Al ion beam current reached 65 mA. As a result of mass analysis, it was found that more than 90% of an Al ion beam is Al+. Furthermore, stable operation could be achieved. For Al (58 mA) and Si (28 mA) ion beam extraction, the temporal drift of each ion beam current was within ±5% for 3 h.
Development of microwave plasma cathode for ion sources
Authors: Matsubara Yoshio , Tahara Hideaki , Nogawa Shuichi , Ishikawa Junzo
Published: July 2002

A new type of electron source for ion sources, which serves as a cathode has been developed. In this cathode, a high-density microwave plasma is produced under the electron-cyclotron-resonance (ECR) condition, and a high electron current of several amperes can be extracted from it. The structure of this microwave plasma (MP) cathode is very simple and compact. A rod antenna connected to a coaxial line for introducing the microwave power (2.45 GHz) and a rare-earth metal permanent magnet for producing the ECR condition are major components. Since there is no filament in this MP cathode, it has a longer lifetime than the equivalent thermionic filament electron emitter. It offers a great advantage to the operation with reactive as well as inert gases. This MP cathode has been adapted in Kaufman-type ion source and have successfully obtained an argon ion-beam current of 110 mA and an oxygen ion-beam current of 43 mA in 25 mm diameter.
Measuring the tensor nature of stress in silicon using polarized off-axis Raman spectroscopy
Authors: Loechelt G. H. , Cave N. G. , Menéndez J.
Published: July 2002

Polarized off-axis Raman spectroscopy is a technique for measuring the complete tensor nature of stress fields in semiconductors. By combining incident light tilted away from the normal axis with polarization of the incident and scattered beams, any Raman-active optical phonon mode can be selectively studied. Once the frequencies and intensities of these phonons are measured, the complete stress tensor can be uniquely determined. This technique has been applied macroscopically to mechanically deformed silicon wafers under biaxial tension. The results of this approach compare favorably with the stress calculated by means of the theory of elasticity.
Lithium fluoride ion source experiments on PBFA II
Authors: Bieg K. W. , Pregenzer A. L. , Woodworth J. R. , Lockner T. R. , Johnson D. J. , Gerber R. A. , Bailey J. E. , Kensek R. P. , Leeper R. J. , Maenchen J. E. , Mehlhorn T. A. , Olson R. E. , Ruiz C. L. , Stygar W. A.
Published: July 2002

Lithium fluoride, field-enhanced ion source experiments are being performed on PBFA II. The source consists of a thin coating of LiF on a microscopically rough substrate. Diagnostics to measure ion beam energy, purity, and transport include electrical monitors, Faraday cups, nuclear activation, ion pinhole camera, Rutherford magnetic spectrograph, and shadowbox aperture array. With PBFA II operating at three-quarters energy, the source has produced 16 TW of ion power and 550 kJ of ion energy with 70% diode efficiency. Over 26 kJ of lithium beam energy has been focused to the diode center axis with a peak energy density of about 1.3 kJ/cm2 . PICDIAG simulations of the lithium focus indicate the intrinsic source divergence is about 45 mrad with a 20-μm-grade porous stainless-steel substrate.
The suppression of electrons extracted from a negative-ion source
Authors: Lea L. M. , Holmes A. J. T. , Thornton M. F. , Naylor G. O. R.
Published: July 2002

When a suitable accelerating voltage is applied to extract negative ions from a volume production source, electrons are also extracted. If no means of suppression is utilized, the electron current in a hydrogen plasma would typically be of the order of 80–100 times the negative-ion current. In the accelerator designs in use at Culham Laboratory, electrons entering the accelerator are dumped in a trap within the second electrode at a small fraction of the beam energy. Even using this technique, a considerable amount of power would be expended unnecessarily in accelerating electrons to the trap. The suppression of electrons at the source/accelerator interface can be achieved by means of a magnetic field applied across the extraction aperture. This traps electrons, which are then collected on an electrically biased subsection of the first electrode. Experiments performed with an electromagnet configuration have shown that the electron flux entering the accelerator can be reduced as approximately the reciprocal of the square of the magnetic field strength.
Improved metal compound ellipsoidal-spherical mirror condenser for xenon short-arc lamp
Authors: Luthjens L. H. , Hom M. L. , Vermeulen M. J. W.
Published: July 2002

The total light flux through a small aperture, for application in time-resolved optical absorption spectrophotometry, e.g., pulse radiolysis and flash photolysis, has been increased. This was achieved by redesigning the ellipsoidal mirror condenser of the high-intensity xenon short-arc lamp system. The essence is replacement of part of the ellipsoidal mirror, between the lamp arc and the nearest ellipsoid vertex, by a hemisphere with the first focus point of the ellipsoid as center. This results in a smaller beam focus spot, shown by calculation and experiment. A reliable alignment procedure, including the use of a smoke vessel to visualize the beam, is described. A relative increase in the total light flux through a 0.5-cm-diam aperture in the beam focus up to 50% has been obtained with a 450-W xenon short-arc lamp at a current of 25 A. Comparative measurements, using different aperture sizes in the beam focus, with the original ellipsoidal mirror condenser system and the new design are discussed. The improvement in signal to noise by a factor of 1.2 is particularly useful in transient absorption experiments where many small signals with poor signal-to-noise ratio have to be averaged. The new condenser can save 33% in time and cost of investigated materials, and decrease the relative effect of interference and other disturbances. The 50% higher light flux at no additional cost of energy may easily find application in other optical instruments, e.g. irradiators and fiber optic illuminators.
The evolution of ion sources for implanters (invited)
Authors: Rose Peter H.
Published: July 2002

Ion sources have improved in performance and reliability to such a degree that they can be operated completely under computer control. The improvements in design and fabrication that have made this possible are the result of many years of effort, and yet there are still serious shortcomings. For example, there is still a need for a several times improvement in lifetime and it is questionable whether this can be achieved by further evolution of existing designs. Perhaps the answer to better performance may be found by replacing the electron emitting filament used in almost all sources today by a source using rf or microwaves for plasma excitation.
High-intensity plasma-sputter heavy negative-ion source (invited)
Authors: Alton G. D. , Mori Y. , Takagi A. , Ueno A. , Fukumoto S.
Published: July 2002

A multicusp magnetic field plasma-surface ion source, normally used for H−ion-beam formation, has been modified for the generation of high-intensity, pulsed, heavy-negative-ion beams suitable for a variety of uses. A brief description of the source and basic pulsed-mode operational data (e.g., intensity versus cesium oven temperature, sputter probe voltage, and discharge pressure) are given. In addition, illustrative examples of intensity versus time and the mass distributions of ion beams extracted from a number of samples, along with emittance data, are also presented. Preliminary results obtained during dc operation of the source under low-discharge-power conditions suggest that sources of this type may alo be used to produce high-intensity (mA) dc beams.
Luminescence lifetime measurements from spectrofluorimeters employing low-cost analog input interfaces
Authors: de Lucas C. Marco , Rodríguez F.
Published: July 2002

This work describes an easy method of adapting a standard spectrofluorimeter for lifetime measurements which is based on a low-cost analog input interface. The different aspects of this method are discussed in detail, including the excitation light system, triggering for multiple scan detection, and the program used to control and analyze data. This technique provides good sensitivity and a large sample memory (up to 30 000 points per scan) for detecting emission decay curves in the lifetime range 100 μs–1 s. Its performance has been successfully tested for two different luminescent materials (CaF2:Mn2+ and TMMC).
A high-current density and long lifetime ECR source for oxygen implanters
Authors: Torii Y. , Shimada M. , Watanabe I. , Hipple J. , Hayden C. , Dionne G.
Published: July 2002

A high-current ECR source has been developed for oxygen implanters for use in fabricating separation by implanted oxygen (SIMOX) substrates. The new source has the following features: (1) high-current density (150 mA/cm2) and large extracted current (more than 200 mA), (2) stable and long lifetime operation (more than 200 h), (3) high O+ ratio (more than 80%), and (4) low-divergence beam. The improved performance is obtained by incorporating the following: (1) Localized high-density plasma generation at the center of the plasma chamber. (2) A newly developed multilayer window to satisfy two requirements: efficient coupling of the microwave with high-density plasma and high resistance to high-speed backstream electrons. (3) Optimized combination of plasma chamber length and axial magnetic field distribution. (4) Sophisticated compact magnetic circuit that yields the optimum magnetic field for obtaining high-density plasma. An industrial-version ECR source was developed for production use on EATON NV-200 implanters. The source was installed on an NV-200 and used to implant oxygen ions to Si wafers. Good performance compared to a duopigatron source was obtained in terms of beam transport efficiency and reliability of source operation.
Microwave ion beam sources for reactive etching and sputter deposition applications
Authors: Jolly T. W. , Blackborrow P.
Published: July 2002

There are important industrial applications for broadbeam microwave ion beam sources which give current densities in the range 0.1–4.0 mA/cm2 at energies between 100 and 1500 eV. These include machines for the production of multilayer optical coatings by means of ion beam sputter deposition, and cassette-to-cassette machines for inert and reactive ion beam etching of semiconductor wafers. In both cases, the ability to run reliably, and at high power for several hundred hours without unscheduled maintenance is most valuable, and may well justify the extra cost of such a source over the conventional Kaufman hot-filament source. The sources discussed in this article use dual high-power grids of pyrolytic graphite, using a self-aligning design, to produce uniform ion beams with diameters of up to l2 cm. Stabilities of better than 1% over several hundred hours of operation are achieved. The design of the discharge chamber and grids enables operation on most inert and reactive gas mixtures. Typical run data and beam profiles obtained when running on argon, oxygen, and chlorine will be presented.
Beam qualities of a microwave ion source
Authors: Sakudo N. , Tokiguchi K. , Seki T. , Koike H.
Published: July 2002

Beam characteristics of a microwave ion source for implantation were studied with an apparatus that can evaluate the degree of matching between the ion source and mass-separator optics. The principal cause that limits the beam transmission of mass separator optics was clarified and an approach was taken to eliminate it. The emittance for the length depends on the plasma density distribution along the slit, which was found to be closely related to the vapor inlet system of the plasma chamber. In order to make the plasma density distribution uniform, several vapor inlets were arranged in a line along the slit. This resulted in a lower emittance.
A parallel plate resonator technique for microwave loss measurements on superconductors
Authors: Taber R. C.
Published: July 2002

A simple method for the evaluation of microwave surface loss of superconductive samples is discussed. The method allows the evaluation of small (∼1 cm×∼1 cm), flat samples over a broad range of temperatures. It can accurately characterize samples with surface resistances as low as 5 μΩ or as high as 1 mΩ at 10 GHz. In addition to high resolution, it has several advantages: sample preparation requirements are minimal; the current distribution within the sample under test is relatively uniform and can be accurately calculated; no other superconducting or normal conducting material is required for the resonator, so no additional corrections for such materials are needed; and the procedure is comparatively rapid and can be performed in the necktube of a liquid-helium storage Dewar.
New double constant-fraction trigger circuit for locking on laser pulse trains up to 100 MHz
Authors: Cova S. , Ripamonti G. , Lacaita A.
Published: July 2002

We describe a new technique for picosecond synchronization on a 80-MHz mode-locked laser. An implementation of such technique is described, and experimental results are presented. Better than 30-ps FWHM synchronization jitter is demonstrated, with an optical pulse amplitude fluctuation of a decade. Such results confirm that single-photon-timing experiments with picosecond resolution are possible by using high-repetition-rate light pulses (i.e., without any cavity dumper).
An automatic focus/hold system for optical microscopes
Authors: Hellen Edward H. , Axelrod Daniel
Published: July 2002

A system for maintaining long-term focus of samples under high-magnification quantitative observation in an epi-illumination optical microscope is described. A negative feedback signal is generated from focus-dependent changes in the backreflection of an off-axis HeNe laser. This reflection is intercepted by a small prism downbeam from the standard trinocular head, and detected by a small two-photodiode array. Spontaneous drifts in sample focus (presumably due to thermal and mechanical relaxations) are detected as a nonzero difference signal, which is used to drive a dc motor mechanically coupled to the fine-focus knob of the microscope. This system has several advantages: (1) it is completely compatible and nonobstrusive with concurrent data acquisition of sample intensities; (2) it requires no alteration of the sample, sample stage, or objective; (3) it monitors the focal position of sample areas very near to those under observation; (4) it is inexpensive. In an experimental test, the system can hold a thin glass coverslip sample (a common substrate for biological cell cultures) to within 0.5 μm of its preset focus position, well within the depth of focus of the microscope. Without the system, such samples typically drift several micrometers over periods of 10 min. In response to a disturbance of the focus knob, the system can restore the focus to within 0.5 μm of the preset position.
An Auger photoelectron coincidence spectrometer
Authors: Thurgate S. , Todd B. , Lohmann B. , Stelbovics A.
Published: July 2002

The feasibility of photoelectron Auger electron coincidence spectroscopy from solid surfaces has been demonstrated by Haak et al. [Ph. D. thesis, University of Groningen, The Netherlands, 1983; Phys. Rev. Lett. 41, 1825 (1978); Rev. Sci. Instrum. 55, 696 (1984)]. They were able to show the considerable power of the technique in deconvoluting the L23M45M45 line of Cu by finding those parts of the line that were due to a 2p3/2 hole and those which were due to a 2p1/2 hole. However, the technique is a difficult one, requiring two analyzers rather than one and complex coincidence electronics. Even then a single spectrum can take weeks to acquire. This initial work was followed up by Jensen et al. [Phys. Rev. Lett. 62, 71 (1989); Physical Electronics Conference abstract A-5, July, 1988] using a synchrotron to provide the radiation and a means of getting very good timing resolution. They were able to acquire Cu spectra in 2–3 days using this system. We have constructed a set of electron analyzers specifically for this experiment. We used the ideas of Völkel and Sandner [J. Phys. E 16, 456 (1983)] to produce analyzers that have good angular acceptance, good energy resolution, and very good timing resolution. With this system we are able to measure coincidence line shapes, for elements with large enough cross section, within a few days using a standard laboratory dc x-ray source.
Line focus of an elliptic cone for an x-ray crystal spectrograph
Authors: Phillion D. W. , Hammel B. A.
Published: July 2002

The crystal in any flat crystal x-ray spectrograph with the film plane at any angle and any position may be bent sagittally into an elliptic conical shape such that a perfect line focus is formed on the film plane for a point source at a fixed location. However, for high spectral resolution, only a narrow strip along the cone can be utilized. This strip will be near the plane formed by the axis of the cone and the source point. The elliptic cone has mirror symmetry in this plane. The equation of this cone is determined and its properties are discussed. Any conical surface has zero intrinsic curvature since one of the two principal radii of curvature is zero, so it is no more difficult to bend a crystal to this shape than to a concave circular cylinder with the same principal radius of curvature.
Measurement of the internal magnetic field in tokamaks utilizing impurity pellets: A new detection technique
Authors: Marmar E. S. , Terry J. L.
Published: July 2002

Measurements on impurity pellet ablation trails indicate that the emission from these clouds extends much farther along the magnetic field than across it. For carbon pellets on TFTR, the aspect ratio of this cigar-shaped plume is of the order of 10. Strong visible line emission from one of the ionization states can be imaged with high time resolution, and since ions should be well confined along the field lines, it should be possible in this way to measure the radial profile of the pitch of the total internal magnetic field. For a pellet injected along a major radius in the plasma midplane, the appropriate viewing geometry consists of imaging the pellet along its flight from behind. A detector scheme capable of accomplishing the measurement, consisting of an array of 1-D spot-imaging photodiodes, is described. In order to make meaningful measurements with regard to the tokamak physics of interest, it is highly desirable to measure the field angle profile with a precision of ±10 mrad or better. In order to achieve this for a cigar with aspect ratio of 10, measurement of the mean vertical position for each slice of the cigar must be made with a precision of about 10% of the vertical thickness of the cigar on that slice.
ATF two-frequency correlation reflectometer
Authors: Hanson G. R. , Wilgen J. B. , Anabitarte E. , Bell J. D. , Harris J. H. , Dunlap J. L. , Thomas C. E.
Published: July 2002

The Advanced Toroidal Facility (ATF) density fluctuation reflectometer system consists of two individual reflectometers operating in the 30–40 GHz band. Each reflectometer consists of a tunable microwave source and a quadrature phase detector connected to the same antenna system. This arrangement allows two-frequency operation along the same radial chord for radial coherence measurements. The technique used in making radial coherence measurements is discussed and the results of such experiments are given. Initial experiments have shown high coherence when the frequencies of the two reflectometers are tuned close together and a clear loss of coherence as the radial separation of the cutoff layers is increased by increasing the frequency separation of the two reflectometers. Recent results have shown that local measurements of density fluctuations in plasmas with electron cyclotron heating (ECH) are possible and that detailed structure can be seen in the fluctuation spectra. In addition, radial correlation lengths have been found to be from 0.5 to 1.0 cm in ECH plasmas, with some frequency structures having correlation lengths up to 3 cm. In plasmas with neutral beam injection (NBI), the radial correlation lengths in the edge region have been found to be approximately 0.1–0.2 cm.
A difluoromethane laser interferometer system on ATF
Authors: Ma C. H. , Hutchinson D. P. , Vander Sluis K. L.
Published: July 2002

A 15-channel far-infrared (FIR) interferometer system has been constructed to measure the electron densities in the Advanced Toroidal Facility (ATF) device. The system consists of a pair of cw 214 μm difluoromethane (CH2F2) lasers, optically pumped by separate CO2 lasers. The large number of channels is achieved by the use of reflective beam expansion optics to create a beam of 2 cm×45 cm. After passing through the plasma discharge, the beam is dissected by an array of 15 off-axis paraboloid reflectors, each of which illuminates a single Schottky-diode detector. The system can also be operated at a wavelength of 119 μm for high density experiments by changing the gas in FIR laser cavities to methanol. Details of the system are described and the recent results of the measurements are presented.
TEXT upgrade far-infrared interferometer system
Authors: Hallock G. A. , Gartman M. L. , Castles R. L. , Chiang K. , Rahman A. S.
Published: July 2002

A high-resolution 2-D interferometer is being developed to measure electron density profiles in the TEXT-upgrade tokamak. Excellent port access allows both horizontal and vertical chords, which will be used to resolve plasma asymmetries. Close channel spacing is employed to give good spatial resolution. In addition, the system can be operated in an imaging mode to resolve the steep gradients expected in H-mode operation.
A balloon borne 19-GHz radiometer
Authors: Boughn S. P. , Cheng E. S. , Cottingham D. A. , Fixsen D. J.
Published: July 2002

The design and performance of a 19-GHz one-horn maser radiometer is discussed. The antenna is a lensed, conical horn with 3° angular resolution. The radiometer is stabilized by chopping against an internal cold load. A novel chopping scheme allows continual calibration of maser gain fluctuations with only a modest penalty in noise. The method of calibrating this instrument is described. The instrument has been used to map the sky with an equivalent blackbody temperature sensitivity of 1 mK per 3°×3° resolution element.
An indium-free substrate holder for radiative heating of quarter-wafer molecular-beam epitaxy samples
Authors: Kuhn K. J.
Published: July 2002

The design and test of a new type of fractional-sample indium-free substrate holder is discussed. This holder has been used for the growth of indium-free material from quarter-wafer slices of 50-mm GaAs material. The power required to bring the quarter-wafer indium-free holder to the desorption temperature of 582C is compared with that of a 50-mm full wafer holder and found to be approximately 7.5% lower under equivalent growth conditions.
Reply to ‘‘Comment on High-spatial and high-mass-resolution SIMS instrument for the surface analysis of chemically complex materials’’ [Rev. Sci. Instrum. 6
, 203 (1989)]
Authors: Schuetzle D. , Prater T. J. , Kaberline S. , deVries J. E. , Bayly A. , Vohralik P.
Published: July 2002

This comment summarizes the historical development of a new high-spatial and high-mass resolution SIMS instrument developed in our laboratories. Reference is given to the lack of published material on similar developments which may have taken place in other laboratories.
A new method to determine ion temperatures in magnetized plasmas by means of an electrical probe
Authors: Höthker K. , Belitz H.-J. , Bieger W. , Amemiya H.
Published: July 2002

The particle flow to a probe in a magnetized plasma is anisotropic. Because of this effect a probe pin generates a shadow in the plasma. From the measurement of the density profile of this shadow the ion temperature can be inferred for specified plasma conditions by comparison with results from Monte Carlo calculations. The probe presheath and sheath are accounted for in the calculations only by use of the Bohm criterion. This implies that the calculated results of the present article pertain strictly only for plasmas with an ion temperature that is large compared to the electron temperature, although the principle of the method is not restricted to these temperature ratios. The space resolution of the measurement in the direction perpendicular to the magnetic field is a few times the ion gyro radius and the time resolution is <100 ms. We present an application of this method of the ion temperature measurement for the scape-off layer of the tokamak TEXTOR.
Field configurations in Helical magnetic wigglers
Authors: Calvo Miguel , Rendon Otto
Published: July 2002

We consider the field configuration produced in a system of two intercalcated concentric coils of radius a and pitch Λ carrying currents in opposite directions (magnetic wigglers). The magnetic field and vector potential inside are obtained exactly at the coils axis and in a multipole-type expansion off the axis. The effect of finite coils is also considered.
Video-based analog tomography
Authors: Garvie Andrew M. , Sorell Graham C.
Published: July 2002

A high-speed analog tomographic reconstruction device is described. The device uses convolution filtering of the projection data to improve the image quality. This filtering was performed using a tapped analog delay configured as a transversal filter. Filtered back-projections were displayed on a raster, rotated using a dove prism, and integrated using analog techniques. Images of high-contrast objects are presented and are a better approximation to the object than those obtained without filtering and have a spatial resolution of approximately 1 in 300. The electronics used to perform the Radon inversion were analog and provided real-time computations introducing a delay between data input and data output of only 2 ms. The shortest time attained for total data collection and processing was 8 s; however, it is suggested that with new commercially available technologies reconstruction times could be further shortened. The individual components of the device were tested and the final results compared with digital reconstructions.
Multiple pulsed ion and electron beams produced by the multiplate chamber
Authors: Jiang Xing-liu , Xu Ning
Published: July 2002

Intense pulsed ion and electron beams with energies below 100 keV are difficult to create using the normal ‘‘vacuum diode.’’ In this paper, the generation of intense multiple pulsed ion and electron beams by the multiplate chamber (MPC) based on the field escalation effect is described. Various kinds of target material ions can be produced by bombardment by the electron beam created in the last gap near the anode. Studies of the propagation of intense pulsed particle beams can be conducted with such a MPC.
A versatile secondary transmitter unit for nuclear magnetic resonance spectroscopy
Authors: Retournard A. , Brondeau J. , Diter B. , Canet D.
Published: July 2002

A transmitter unit for homo- or heteronuclear double-resonance experiments has been designed so as to be independent of the NMR spectrometer main console. It features capabilities similar to the principal transmitter unit, with respect to rf phases, amplitudes, and pulses. It can be run manually and under computer control and possesses several modulation schemes or sequences specific to liquid-state or solid-state NMR spectroscopy. Its general organization as well as particular circuits is described. Its performances are demonstrated by illustrative examples.
Beam dynamics of a liquid-metal ion source
Authors: Whealton J. H. , Meszaros P. S. , Rothe K. E. , Raridon R. J. , Ryan P. M.
Published: July 2002

rms emittance growth of liquid-metal ion sources is studied. Processes included are nonlinear expansion through extractor and accelerator fringe fields, nonlinear beam space charge, plasma effects near needle, and waves [either ion acoustic or space charge limited as considered by Dudnikov (private communication, 1988)]. This investigation consists of 2-D analysis of appropriate Vlasov–Poisson equations in both steady-state and time-dependent formulations. Various geometries will be considered such as some used by Alton of ORNL.
Photon counting dead time measurement in commercial laser light scattering instrumentation
Authors: Dorshow Richard B.
Published: July 2002

A straightforward, simple, and convenient method is described for measuring the dead time in a photomultiplier/amplifier–discriminator/counter system when employed as the photon counting detector in a commercial laser light scattering spectrometer. The rotating pinhole turret on the spectrometer collection optics is used to ratio measured count rates (output), thus eliminating the necessity of calibrating the incident source (input). Dead time measurements are reported which demonstrate and validate this method. Alteration of the commercial analysis software to reflect the true detector response, as determined by these measurements, is enumerated.
A compact low thermal conductivity support for cryogenic use
Authors: Gush H. P.
Published: July 2002

A low thermal conductivity support is described, rigid in all three directions, based on a taut band of Kapton, a strong plastic film. It is compact and readily fabricated.
An apparatus for measuring D
T/K without in-vacuum mechanical motion
Authors: Ong P. P. , Hogan M. J.
Published: July 2002

A new drift-tube apparatus has been developed for measuring DT/K, the ratio of the transverse diffusion coefficient to the mobility of ions in a neutral gas under the influence of an electric field. It harnesses existing technology in mechanical, electronic, materials, and computer engineering. The main features are the ion current detector, which comprises 65 parallel rods, and an external mechanical multiplexer, which was designed to have extremely low (fA order) leakage currents and noise levels. Unlike with other earlier systems, the need for precise mechanical motion or adjustments of experimental conditions inside the drift tube during data collection has been circumvented. Its design therefore simplifies construction and makes operation less error prone. Data collection is computer controlled. A value for DT/K can now typically be obtained in less than 20 min, which greatly increases the rate at which results can be obtained as well as reduces the chance of unwanted variations in experimental conditions occurring during data collection. Results are estimated to be accurate to within 3%.
Simulated lock-in amplifier deep level transient spectroscopy
Authors: Ball C. A. B. , Conibear A. B.
Published: July 2002

A technique is presented for the analysis of digitally recorded capacitance transients in order to determine the energy and capture cross section of deep levels. The method is essentially a digital simulation of the measurement carried out by a lock-in amplifier. This technique in principle allows trap parameters to be determined in a single temperature scan. The more efficient use of data brought about by the method permits a detailed study of the Arrhenius plot and in particular gives insight into cases where the capacitance transient is nonexponential. The method may be adapted to allow more efficient data usage in conventional lock-in amplifier deep level transient spectroscopy.
Thermal lens technique for sensitive kinetic determination of fast chemical reactions. Part II. Experiment
Authors: Franko Mladen , Tran Chieu D.
Published: July 2002

A novel thermal lens spectrophotometer which can be used for simultaneous measurements of thermal lens and absorption has been constructed to verify the developed theories (which were described in the previous paper) and to implement the thermal lens technique for sensitive kinetic determinations. The measured experimental results agree well with the values predicted by the developed theories. Compared to other conventional kinetic methods, the thermal lens technique provides kinetic results which are not only accurate and precise but also can be obtained with reagents whose concentrations are about 100 times lower. Other potential applications of this method, including the kinetic determinations of fast chemical reactions, are discussed.
A high-pressure volumetric gas adsorption system
Authors: Giacobbe F. W.
Published: July 2002

A unique, all-metal, volumetric gas adsorption system has been described. This device was capable of facilitating precise and semiautomatic measurements which could be used to produce complete adsorption isotherms. Isotherm temperatures could be controlled and maintained at the boiling point of liquid nitrogen, argon, and oxygen. In addition, relatively high-pressure adsorption isotherms could be measured due to the all-metal construction of the adsorption system.
A scanning force microscope with a fiber-optic-interferometer displacement sensor
Authors: Mulhern P. J. , Hubbard T. , Arnold C. S. , Blackford B. L. , Jericho M. H.
Published: July 2002

We present a simple optic-fiber displacement sensor for a scanning force microscope (SFM). The design minimizes the alignment difficulties after a cantilever is changed and is easily adaptable to tube scanners so very compact SFM designs should be possible for imaging at low temperatures or in strong magnetic fields. We also provide a theoretical analysis and results to show that the sensitivity of the device can be improved by increasing the reflectivity of the fiber end. The increased sensitivity makes it possible to work under fluids.
Cooled submillimeter Fourier transform spectrometer flown on a rocket
Authors: Gush H. P. , Halpern M.
Published: July 2002

A detailed description is given of a liquid-helium-cooled. Fourier transform spectrometer recently flown on a rocket. The instrument was used to make new precise measurements of the spectrum of the cosmic background radiation in the wave number range 2–30 cm−1, as reported by H. P. Gush, M. Halpern, and E. Wishnow [Phys. Rev. Lett. 65, 537 (1990)].
The use of magnetostrictive film transducers in the measurement of elastic moduli and ultrasonic attenuation of solids
Authors: Kuokkala V.-T. , Schwarz R. B.
Published: July 2002

The authors describe a novel method and apparatus for measuring the elastic moduli and ultrasonic attenuation of small samples (millimeter dimensions) over a wide temperature range. In the most general case, a nonmagnetic sample is coated with a thin film of a magnetostrictive material (e.g., nickel or iron-cobalt alloy). This film performs both as a driving transducer and as a receiving transducer. An alternating magnetic field of variable frequency generates a periodic stress in the film and drives the sample into mechanical resonances. The permeability of the film changes when the sample is resonating and allows the detection of the resonances. The operation of the system and the mathematical procedures to deduce the elastic moduli and ultrasonic attenuation from the measured resonance spectra are exemplified with measurements on amorphous Ni80P20 in the temperature range of 80–520 K.
Microwave-mode analyzer with dispersive reflector antenna
Authors: Kiwamoto Y. , Kira F. , Saito T. , Kurihara K. , Kawamura M. , Miyoshi S. , Nakajima M.
Published: July 2002

A new method is developed for mode analysis of microwaves propagating in an oversize waveguide. A curved reflector is used to disperse the different modes in different directions. The locations of the mode powers are systematically distributed on an intercepting absorber plane. An infrared camera is used for quick visual analysis of the mode map produced as a temperature distribution on the absorber sheet. Detailed analysis is also made by numerically processing the image data. Polarizations of the constituent modes can be determined with a rotated microwave receiver. Usefulness of this method is experimentally demonstrated by comparison with other techniques.
The combination of electrotransport and zone refining techniques for the growth and purification of metallic crystals
Authors: King C. A. , Brown S. V.
Published: July 2002

The combination of zone refining and electrotransport techniques is considered with the aim of obtaining an improved method for the growth and ultrapurification of metallic crystals. A complete ultrahigh vacuum crystal growth system using induction heated vertical float zoning with up to 400 A of electrotransport current simultaneously passing through the molten zone has been developed. Preliminary tests on nickel show that the two techniques are indeed compatible and the purification process is substantially enhanced by their combination.
A laser Doppler flowmeter using variable coherence to effect depth discrimination
Authors: Dougherty G.
Published: July 2002

A novel means of investigating blood flow at different depths within the skin is described. By varying the coherence length of the diode laser source, the depth of the sampling volume over which Doppler signals are received could be controlled in a simple model system. The instrument has a variety of potential applications in dermatology.
Automatic wide-range scanning and calibration over 220–740 nm using a dye laser with a rapid cell exchanger
Authors: Oki Yuji , Tashiro Eiji , Maeda Mitsuo , Honda Chikahisa , Hasegawa Yoshio , Futami Hiroshi , Izumi Jun , Matsuda Keiichi
Published: July 2002

A pulsed dye laser system fully controlled by a microcomputer has been developed as a tunable light source for analytical spectroscopy. The system has 13 dyes with a rapid replacement mechanism and a frequency doubler inside, and any desired wavelength from 220 to 740 nm can be instantaneously generated by the aid of the microcomputer control. The absolute wavelength can be automatically calibrated with a newly developed optogalvanic wavemeter with an accuracy of ±1 cm−1 over the whole spectral range.
Performance characteristics of an acousto-optic tunable filter for optical spectrometry
Authors: Tran Chieu D. , Bartelt Mark
Published: July 2002

The development and implementation of the paratellurite (TeO2) acousto-optic tunable filter as the novel dispersive device are described. It will be demonstrated that this all solid state, rugged filter which contains no moving parts can be used to rapidly diffract white incident light into a selected color beam whose amplitude is kept constant in either pulsed or continuous mode.
The improvement of phase modulated spectroscopic ellipsometry
Authors: Kim Charles C. , Raccah P. M. , Garland J. W.
Published: July 2002

Spectroscopic ellipsometry using photoelastic modulator [phase modulated spectroscopic ellipsometry (PMSE)] has been improved in the spectral range. Spectroscopic ellipsometry using the rotating analyzer [rotating analyzer spectroscopic ellipsometry (RASE)] has demonstrated its capability of measuring the reflectivity ratio, ρ(ω), from 1.5 to 6 eV with a single scan, but PMSE has not been able to do so. We demonstrate that PMSE also can measure ρ(ω) from 1.5 to 6 eV with a single scan. We discuss the problems and show their solutions to achieve this goal. We also discuss the accuracy of our PMSE by comparing the spectral data by RASE with those by our PMSE. We find that the simplest possible procedure with our system provides reasonably accurate values, after including the zone average which is easy to perform with our system. The extension of the spectral range is a decisive advantage, especially in studying the E1 structure of the wide band gap materials such as ZnSe.
Performance characteristics of a capacitively coupled 3 cm rf ion sourcea)
Authors: Korzec D. , Engemann J. , Rapp J.
Published: July 2002

A novel 13.56 MHz radio frequency capacitively coupled ion source has been developed and characterized with special emphasis on low-energy (<1 keV) broad ion beam extraction. When operating the source with chamber pressures ranging from 1 × 10−4 to 1.7 × 10−3 mbar (O2 and Ar), rf-power levels from 5 to 120 W, axial air coil magnetic fields up to 70 mT, and maximum extraction voltages of 650 V extractable ion currents were as high as 50 mA. With a total grid area of 7 cm2 and a transparency of 46%, this amounts to a grid current density of more than 7 mA/cm2 while the ion saturation current density is calculated as 9.3 mA/cm2. The potential oscillation amplitude of the rf excitation electrode can be as high as 650 V. Due to an external axial magnetic field, a dc bias up to 70 V is induced between the grounded accelerator grid and cylindrical anode. The performance data are traced back to constructional source details such as plasma excitation geometry, axial magnetic field, and floating electrostatic end confinement. Under all operating conditions, the source shows an excellent long-time stability even with reactive gases (e.g., more than 100 h without maintenance with oxygen).
Introduction of cesium vapor into the arc chamber of a high-brightness H−/D− volume source and resulting beam characteristicsa)
Authors: Debiak T. W. , Gammel G. , Kuehne F. , Ng Y. , Sredniawski J.
Published: July 2002

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