bluuebunny/crossref_metadata_2025 huggingface dataset:
Extraction of H− and D− ions from a large magnetic multipole source
Authors: Holmes A. J. T. , Lea L. M. , Newman A. F. , Nightingale M. P. S.
Published: July 2002

Results are presented on the production of H− ions in a large (55×31×20 cm3) magnetic multipole discharge, which is sufficiently large to act as the plasma generator for a neutral beam injector. H− ion current densities up to 57 mA/cm2 have been extracted in pulses up to 3 s in length at low energies. When the discharge is operated in deuterium, a maximum D− current density of 27 mA/cm2 is obtained. The scaling laws of the H− production are consistent with production by dissociative attachment to rovibrationally excited molecules and loss by mutual recombination.
Inexpensive automatic Weiss extraction system
Authors: Chang Y. J. , Ng C. F. , Kwan W. K.
Published: July 2002

An inexpensive yet reliable and convenient Weiss extraction system involving a magnet of maximum field strength of 8.9 kOe and a signal collection system coupled to an Apple II computer is described. The data obtained using such a system for H2S and AsH3 adsorption on Ni/SiO2 catalysts are discussed.
Low radioactivity material for use in mounting radiation detectors
Authors: Fong Marshall , Metzger Albert E. , Fox Richard L.
Published: July 2002

Two materials, sapphire and synthetic quartz, have been found for use in Ge detector mounting assemblies. These materials combine desirable mechanical, thermal, and electrical properties with the radioactive cleanliness required to detect minimal amounts of K, Th, and U.
Nonmagnetic metal and glass helium-3 cryostat immersed in a 4.2-K bath
Authors: Nacher P. J. , Tastevin G. , Wiesenfeld L.
Published: July 2002

A simple helium-3 cryostat operating down to 400 mK is described. It is very weakly magnetic, easy to take apart, and allows optical access to the coldest part.
Fast analog chopper multiplexer for oscilloscope recording of single-shot events
Authors: Choi P. , Wyndham E.
Published: July 2002

The design and construction of an electronic circuit to multiplex two analog signals for display by trace chopping on a fast single-beam oscilloscope is presented. The circuit uses a Schottky ring diode modulator as a control switch and is unique in having a chopping frequency of up to 400 MHz with switching times between channels of less than 0.7 ns. Used with an oscilloscope with sufficient bandwidth, it is then possible to obtain pseudosimultaneous display of fast single-shot events. In conjunction with a Tektronix 7834 oscilloscope with a 7A19 plug in, the maximum signal bandwidth of the prototype is measured to be 150 MHz, and the interchannel rejection ratio greater than 24 dB at a chopping frequency of 200 MHz.
Fast calibration of an infrared vidicon
Authors: Freude W.
Published: July 2002

Infrared vidicon tubes of the type N 214 from Hamamatsu have widespread use for various measurements in the field of optical communication, in spite of their severe drawbacks such as poor stability and low accuracy. Usually, they interface with a desktop computer as a controller, so that the influences of dark current, shading, and nonlinearity may be corrected. With a specially designed computer-controlled lamp and an optimized algorithm, it is possible to calibrate the vidicon very fast. Dark current, shading, and nonlinearities result in errors less than 9% and are mainly determined by the strong thermal drift of the tube. Because of the least-squares-fitting technique, the calibration is very noise insensitive.
GaInP–AlGaInP band offsets determined from hydrostatic pressure measurements
Authors: Kowalski O. P. , Cockburn J. W. , Mowbray D. J. , Skolnick M. S. , Teissier R. , Hopkinson M.
Published: July 2002

Low-temperature (1.8 K) photoluminescence spectra of a Ga0.52In0.48P–(Al0.58Ga0.42)0.52In0.48P multiple quantum well have been measured as a function of hydrostatic pressure from 0 to 5.0 GPa. The extrapolation to zero pressure of the energy of the indirect k-and-real-space barrier X to well Γ transition allows the direct determination of the valence band offset for this heterojunction system. A value of ΔEv=(0.35±0.05)ΔEg is found, in good agreement with values previously determined from the theoretical modeling of quantum well transition energies.
Stopped-flow apparatus for x-ray scattering at subzero temperature
Authors: Tsuruta Hirotsugu , Nagamura Toshihiko , Kimura Kazumoto , Igarashi Yoshihiko , Kajita Akihiko , Wang Zhi-Xin , Wakabayashi Katsuzo , Amemiya Yoshiyuki , Kihara Hiroshi
Published: July 2002

A stopped-flow apparatus was constructed for x-ray scattering study at subzero temperature. It can be operated over a wide temperature range down to −20 °C with highly viscous solution (20 cP) successfully. We have applied the stopped-flow x-ray scattering method to many biological reactions. In particular, the association of E. coli ribosomal subunits was detected at −10 °C which was too fast to be detected at room temperature. Dissociation of E. foetida hemoglobin was measured by the stopped-flow x-ray scattering method combined with a time-resolved imaging plate as a detector.
Phase-modulation fluorometry using a frequency-doubled pulsed laser diode light source
Authors: Berndt Klaus W. , Gryczynski Ignacy , Lakowicz Joseph R.
Published: July 2002

We describe the use of a pulsed frequency-doubled laser diode, the Hamamatsu model PLP-01 picosecond light pulser, as a 413-nm excitation light source for frequency-domain fluorescence measurements. The modulated incident light, over a range of modulation frequencies, is provided by the harmonic content of the pulse train. In comparison with the more usual light source for harmonic-content excitation, a sync-pumped/cavity dumped/frequency doubled dye laser, the 413-nm PLP-01 has a longer pulse width (FWHM of 40 ps), a similar pulse repetition rate (up to 10 MHz), much less output power at a fixed wavelength (0.44-mW peak, 220-nW maximum average power), but is less expensive, small-sized, and easy to handle. Using the PLP-01, we were able to perform frequency-domain fluorescence measurements up to an upper modulation frequency of about 2000 MHz, and to resolve mixtures of fluorophores exhibiting different lifetimes. During our tests, we observed remarkable and lasting (2 h) time drifts between the optical output and the electrical trigger input or output. At present, work is in progress at Hamamatsu to eliminate these drifts.
Computer-controlled dual low-level constant current source
Authors: Bortner L. , Clark D. , Pestinger R. L. , Newrock R. S.
Published: July 2002

We present the specifications for a computer-controlled, low-noise, bipolar current source for use with superconducting electronics. Our instrument, which contains two such sources, operates in the 10−7–10−3 A range and has a bipolar output in which the null output is not a unique point on the operating curve. This device has been used successfully with superconducting electronics to measure current-voltage characteristics of superconducting thin films.
Versatile apparatus for etching scanning tunneling microscope tips
Authors: Fiering J. O. , Ellis F. M.
Published: July 2002

We have developed an apparatus for easy and consistent etching of small tips suitable for use with a scanning tunneling microscope. Its unique features are free access to the etching region and a continuous supply of electrolyte for the production of many tips in succession.
Using the second harmonic from a Nd:YAG as a probe beam for determination of free electron density in a plasma induced by the fundamental
Authors: Englert Thad J. , Beik Mostafa A.
Published: July 2002

The higher harmonics are typically generated in Nd:YAG lasers equipped with standard harmonic generator crystals and these harmonics become useful as probe beams of light in applications where optical measurements are required during early stages of laser-induced effects. The system described here makes use of a spatially filtered second harmonic beam for schlieren photography of a plasma created by the fundamental beam of a Nd:YAG laser interacting with a gas. Fringe patterns recorded on schlieren photographs of the plasma region provide measurements of the variation in the index of refraction which in turn yield the variation in electron density within the plasma.
Calibration of the neutron yield measurement system on FTU tokamak
Authors: Angelone M. , Batistoni P. , Bertalot L. , Esposito B. , Martone M. , Podda S. , Pillon M. , Rapisarda M. , Rollet S.
Published: July 2002

This paper describes the in situ calibration of the BF3 detector system used for measuring the total neutron yield from the FTU tokamak. Two different neutron sources, 252Cf (7.23×107 n/s) and AmBe (2.18×106 n/s), were used. The calibration was performed by placing the two sources at different radial and toroidal positions inside the vacuum vessel. Data on the response of the different detectors as a function of the source position are presented. The effect of the different spectra of the neutron sources is pointed out. Finally, the procedure for the computation of the relationship between the local flux at the detectors and the total neutron yield from an extended plasma is presented.
A new force sensor incorporating force-feedback control for interfacial force microscopy
Authors: Joyce Stephen A. , Houston J. E.
Published: July 2002

A new interfacial-force microscope capable of measuring the forces between two surfaces over the entire range of surface separations, up to contact, is described. The design is centered around a differential-capacitance displacement sensor where the common capacitor plate is supported by torsion bars. A force-feedback control system is incorporated which balances the interfacial forces at the sensor, maintaining the common capacitor plate at its rest position. This control therefore eliminates the instability or ‘‘jumping’’ which occurs with conventional cantilever-based force sensors when the attractive force gradient between the fixed sample and sensor exceeds the mechanical stiffness of the cantilever. The operating characteristics of the sensor and its ability to measure interfacial forces using the feedback control at surface separations smaller than this instability point are demonstrated.
A versatile inverse photopyroelectric (IPPE) technique and instrument for real time observation of the condensation of water vapor in the atmosphere
Authors: Chirtoc Mihai , Bićanić Dane , Toşa Valer
Published: July 2002

A novel method and instrument capable of either monitoring continuously a condensation process or estimating the thickness of a liquid layer in the μm range are presented. The underlying physical principle is a variant of the photopyroelectric technique in which the changes in the thermal wave propagation due to the presence of the liquid layer are sensed by the pyroelectric sensor. The theoretical model developed supports the experimental results obtained.
Laser ion sources for highly charged ions (invited)
Authors: Sherwood T. R.
Published: July 2002

The development of laser ion sources is reviewed in the light of possible future requirement for highly charged ions at CERN. After the advent of high power Q-switched pulsed lasers in the 1960’s, there were a number of proposals to use the laser produced plasma as sources of ions. Such ion sources have been constructed for a number of uses, and in particular, for injection of ions into particle accelerators. At CERN, a new test facility has recently started operation. Initial results indicate ion currents in excess of 5 mA for lead ions with charge state about 20.
Real time spectroscopic ellipsometry study of hydrogenated amorphous silicon p-i-n solar cells: Characterization of microstructural evolution and optical gaps
Authors: Koh Joohyun , Lu Yiwei , Kim Sangbo , Burnham J. S. , Wronski C. R. , Collins R. W.
Published: July 2002

Spectroscopic ellipsometry measurements have been performed during the preparation of hydrogenated amorphous silicon p-i-n solar cells in the SnO2:F/p-i-n/Cr configuration. Postdeposition data analysis yields the evolution of bulk, surface roughness, and interface layer thicknesses with ∼0.2 Å sensitivity. In addition, the dielectric functions and optical gaps of the p-, i-, and n-layers are determined in the analysis. With the real time measurement approach, the layer properties are determined in the actual device configuration, rather than being inferred indirectly from studies of thick film counterparts.
Wavelength-modulated interferometric thermometry for improved substrate temperature measurement
Authors: Saenger K. L. , Tong F. , Logan J. S. , Holber W. M.
Published: July 2002

Interferometric thermometry is a promising noncontact technique for measuring the temperature of transparent substrates (with polished front and back surfaces) from thermally induced changes in sample thickness and refractive index. However, for substrates of uniform thickness, the technique is not sensitive to the direction of temperature change, thus restricting its use to situations in which the temperature variation is monotonic. In this paper, we present some new schemes for interferometric thermometry based on the wavelength modulation capabilities of the distributed feedback laser diode. These schemes allow both the magnitude and direction of temperature change to be determined. One scheme utilized to measure temperature changes in a silicon wafer during thermal cycling is described in detail. In addition, the calibration factors required to convert the thermally induced reflectance oscillations (‘‘fringes’’) of known-thickness samples into temperature change are provided for Si and GaAs at wavelengths near 1.5 μm.
Two-dimensional electron density, temperature, and radial drift profiles of a laser plasma by 266 nm collective Thomson scatteringa)
Authors: Cameron S. M. , Tracy M. D. , Estabrook K. G. , DeGroot J. S.
Published: July 2002

Collective Thomson scattering measurements performed at 266 nm on an underdense, long scalelength laser-produced aluminum plasma (nc∼1021 cm−3, Z∼7, Te≥50 eV, L≥100 μm) under moderate irradiance conditions (1011 W/cm2) are used to obtain temporally integrated, spatially resolved (30 μm) electron temperature, density, and radial fluid velocity contours. For an ultraviolet diagnostic wavelength, the effects of inverse bremsstrahlung heating perturbations and refractive turning are significantly reduced, allowing high density coronal conditions in the vicinity of one-tenth critical to be investigated. Detailed knowledge of these plasma conditions are fundamental prerequisites for understanding the distributed absorption process within fusion plasmas and for validation of the modeling accuracy of hydrodynamic codes. Fluid equations with classical coefficients should accurately apply to the plasma in these experiments because electron thermal transport is in the Spitzer regime, and the authors report relatively good agreement between the experimental results and two-dimensional LASNEX simulations.
Midplane Faraday rotation: A densitometer for large tokamaks
Authors: Jobes F. C. , Mansfield D. K.
Published: July 2002

The density in a large tokamak such as International Thermonuclear Experimental Reactor (ITER), or any of the proposed future US machines, can be determined by measuring the Faraday rotation of a 10.6 μm laser directed tangent to the toroidal field. If there is a horizontal array of such beams, then ne(R) can be readily obtained with a simple Abel inversion about the center line of the tokamak. For a large machine, operated at a full field of 30 T m and a density of 2×1020/m3, the rotation angle would be quite large−about 60° for two passes. A layout in which a single laser beam is fanned out in the horizontal midplane of the tokamak, with a set of retroreflectors on the far side of the vacuum vessel, would provide good spatial resolution, depending only upon the number of reflectors. With this proposed layout, only one window would be needed. Because the rotation angle is never more than 1 ‘‘fringe,’’ the data is always good, and it is also a continuous measurement in time. Faraday rotation is dependent only upon the plasma itself, and thus is not sensitive to vibration of the optical components. Simulations of the expected results show that ITER, or any large tokamak, existing or proposed, would be well served even at low densities by a midplane Faraday rotation densitometer of ∼64 channels.
Visible light emission spectra of individual microstructures of porous Si
Authors: Ito K. , Ohyama S. , Uehara Y. , Ushioda S.
Published: July 2002

We have measured the spectra of visible light emitted from the individual structures of porous Si (PS) below the probe tip of the scanning tunneling microscope (STM), and found that the peak energy of the emission spectrum shifts with the size of nanometer-scale structures on the PS surface. Samples with a PS layer ∼50 nm thick were formed by anodic etching of p+Si(100) substrates (∼0.005 Ω cm). The STM images show that protrusions whose dimensions are 3–10 nm in diameter are distributed on the PS surface. The peak energy of the STM light emission spectrum shifts from ∼1.7 to ∼2.1 eV as the diameter of the structure below the STM tip decreases from ∼9 to ∼3 nm. The measured peak shift with the size of the structure is consistent with the shift of the energy gap predicted on the basis of a quantum confinement model.
Ultrafast intermetallic compound formation between eutectic SnPb and Pd where the intermetallic is not a diffusion barrier
Authors: Wang Y. , Tu K. N.
Published: July 2002

An intermetallic compound which grows at a rate greater than 1 μm/s has been observed in the liquid/solid reaction at 250 °C between molten eutectic SnPb solder and solid Pd. The intermetallic PdSn3 does not form as a diffusion barrier between the reactants, rather it grows as lamellae into the molten solder. The growth direction is normal to the liquid/solid interface, where the molten solder between the lamellae serves as fast diffusion channels during the reaction. For comparison, molten Sn (Pb-free) reacts with Pd at a rate slower by one order of magnitude. The intermetallics, in this case, grow as a diffusion barrier between the Sn and Pd. The role of Pb in the extremely fast eutectic soldering reaction is discussed, in view of the trend of searching for a Pb-free solder in electronic packaging.
Applications of resonance ionization mass spectrometry
Authors: Payne M. G. , Deng Lu , Thonnard N.
Published: July 2002

We describe here several types of mass spectrometry in which the mass selectivity is combined with a highly selective laser ionization method to achieve both high sensitivity and very high selectivity. These methods combine the most sensitive and highly selective laser ionization methods with mass selectivity in order to improve on both the sensitivity and the Z and A selectivity previously achievable in detecting atomic species. Applications of these methods include the dating of geophysical specimens, the on line analysis of rare short-lived isotopes produced in high-energy collisions, the detection of low levels of heavy metals or radioactive isotopes in biological samples, the detection of impurities in ultrapure materials, and a host of other applications. Because some versions of this method offer sensitivity to a hundred atoms of a particular isotope of an element in a macroscopic sample, there are new possibilities for fundamental studies of rare events. Several types of facilities for elemental and isotopic analysis will be described.
Ion sources for microfabrication (invited)
Authors: Grotjohn Timothy A.
Published: July 2002

Several microfabrication processes benefit from the application of ion sources including the physical, reactive, and chemically assisted sputtering/etching of surfaces, the deposition/growth of materials, and the modification/cleaning/preparation of surfaces. This paper reviews the types, properties, and requirements of ion sources applied to microfabrication processes including etching, epitaxial growth, ion implantation, and nanostructure formation. Particular emphasis is given to the requirements of ion streams for low-damage semiconductor processing. The types of sources covered include broad-beam ion sources; ECR, helicon, helical resonator, and inductively coupled plasma/ion sources; ion implanters; compact MBE-ECR ion/free radical sources; and focused ion beam sources.
Small electrical lead-throughs in a high-pressure helium cell for wide temperature ranges
Authors: Maire Michel le
Published: July 2002

New compact and easy-to-install electrical lead-throughs for hydrostatic pressure cells have been designed and tested in dielectric measurements at pressures up to 0.55 GPa and temperatures between 20 and 300 K using helium gas as pressure transmitting medium. The electrical leakage resistance of the device at room temperature is larger than 1014 Ω.
Automated polarimeter–macroscope for optical mapping of birefringence, azimuths, and transmission in large area wafers. Part I. Theory of the measurement
Authors: Bajor Andrzej L.
Published: July 2002

A computer-controlled polarimeter–macroscope has been developed to measure birefringence (phase retardation), the principal azimuths and transmission in large area (up to 6 in. diameter) wafers. It consists of two HR-type linear polarizers which can be rotated simultaneously by a stepper motor versus an immobile wafer. The transmission axes of the polarizers can be set at either 90° or 0° (polariscopic mode) or at 45° (polarimetric mode). The ability of observing samples’ images in the polariscopic mode can be useful for, e.g., quick detection of macroscopic defects. In the polarimetric mode the arrangement is capable of collecting input data through a video frame grabber (VFG)/TV camera detecting system and calculate three maps as stated above within a fraction of a minute. In usual circumstances, using a VFG with 256 grey levels enables determination of birefringence with an error not greater than approximately 5×10−7, whereas errors of azimuths and transmission are of a fraction of a degree and of a percent, respectively. In this part of the work a theory of the method and a detailed error analysis are presented.
Electrochemical fabrication of scanning tunneling microscopy tips without an electronic shut-off control
Authors: Bourque H. , Leblanc R. M.
Published: July 2002

We report a modified procedure to fabricate electrochemically etched scanning tunneling microscopy tips under ac voltage. By both confining the etching action to a small region and controlling the etching current on a tungsten wire, we produce ultrasharp tips with low-aspect ratio. No electronic shut-off control is required. Atomic resolution images are routinely obtained.
Multibeamlet focusing of intense negative ion beams by an aperture displacement technique
Authors: Takeiri Y. , Kaneko O. , Oka Y. , Tsumori K. , Asano E. , Akiyama R. , Kawamoto T. , Kuroda T. , Ando A.
Published: July 2002

Multibeamlet focusing of an intense negative-ion beam has been performed using beamlet steering by aperture displacement. The apertures of the grounded grid were displaced as all 270 beamlets (18×15) in an area of 25 cm×26 cm are steered to a common point (a focal point) in both the two-stage and the single-stage accelerators. The multibeamlets were successfully focused and the e-folding half width of 10 cm was achieved 11.2 m downstream from the ion source in both accelerators. The corresponding gross divergence angle is 9 mrad. The negative-ion beamlets are deflected by the electron deflection magnetic field at the extraction grid and the deflection direction reverses line by line, resulting in the beam splitting in the deflection direction. This beamlet deflection was well compensated also using beamlet steering by the aperture displacement of the grounded grid. The beam acceleration properties related to the beam divergence and the H− ion current were nearly the same for both the two-stage and the single-stage accelerators, and were dependent on the ratio of the extraction to the acceleration electric fields.
General method for adjusting the quality factor of EPR resonators
Authors: Pfenninger Susanne , Froncisz Wojciech , Forrer Jörg , Luglio Juan , Hyde James S.
Published: July 2002

Instrumentation for remote control of the unloaded quality factor, Q0, of a loop-gap resonator is described. The value of Q0 can be lowered by weak inductive coupling of the resonator to a loop of wire that contains a carbon resistor. Replacement of the resistor by a PIN diode permits remote control. Theoretical analysis and experiments are carried out in a context of electron paramagnetic resonance (EPR) spectroscopy at X band. Equivalent circuits are solved numerically and predicted performance confirmed experimentally. Two applications are demonstrated: (a) superfine control of critical coupling of the incoming transmission line to the resonator in excess of −80 dB, and (b) dynamic Q spoiling for reduction of the dead time after a microwave pulse. Possible degradation of EPR system performance by shot noise from the PIN diode is considered. Scant literature suggests that it is very low, and noise from this source could not be detected experimentally.
Photoemission starting of induction rf-driven multicusp ion sources
Authors: Pickard D. S. , Leung K. N. , Perkins L. T. , Ponce D. M. , Young A. T.
Published: July 2002

It has been demonstrated that pulsed and continuous wave, rf-driven hydrogen discharges can be started with photoemission. The extracted H− current from a photoemission-started plasma has been investigated and does not differ significantly from that of a filament-started plasma. The minimum pressure for photoemissive starting was found to be higher than that of filament starting, 17 mTorr compared to 7 mTorr, respectively, in this particular configuration.
A compact coaxial electron cyclotron resonance plasma source
Authors: Baskaran R. , Jain S. K. , Ramamurthy S. S.
Published: July 2002

A compact coaxial electron cyclotron resonance (ECR) plasma source is built for plasma deposition experiments. The ECR plasma is produced in a coaxial line configuration and hence the source is compact. The plasma parameters (plasma density and electron temperature) are measured using a Langmuir probe. The plasma parameters are mainly dependent on the center conductor (stub) dimensions of the coaxial line. The characterization of plasma for both conical and cylindrical stubs is carried out and it is found that the conical stub produces relatively denser and more stable plasma than the cylindrical stub. The typical plasma density and electron temperature are 3×1010 cm−3 and 5 eV, respectively, for argon plasma.
Negative ion production in large volume source with small deposition of cesium
Authors: Jacquot C. , Pamela J. , Riz D. , Belchenko Yu.
Published: July 2002

Experimental data on the enhancement of D− (H−) negative ion production due to cesium injection into a large volume multiampere negative ion source (MANTIS) are described. The directed deposition of small cesium amounts (5–100 mg) from a compact, movable oven, placed into the central part of a MANTIS gas-discharge box was used. A calorimetrically measured D− beam with an intensity up to 1.6 A and an extracted current density up to 4.2 mA/cm2 (beam energy 25 kV) was obtained. Exactly 30 mg of cesium provides at least one month of source operation (1000 pulses with a discharge pulse duration of 4 s). The effect of cesium on NI enhancement was immediately displayed after the distributed Cs deposition, but it needed some ‘‘conditioning’’ of cesium by tens of discharge pulses (or by several hours ‘‘pause’’) in the case of a localized Cs deposition. No degradation of extraction-acceleration voltage holding on within the tested range of cesium injection was observed.
A compact electron cyclotron resonance proton ion source
Authors: Boukari F. , Wartski L. , Roy V. , Schwebel C. , Coste Ph. , Aubert J.
Published: July 2002

The demand has increased for a high-current, long lifetime ion source in various fields of application. The present work concerning the production of atomic hydrogen ions H+ in competition with molecular ions H+2 has been essentially motivated by recent trends in the field of passivation of silicon [V. Le Thanh, M. Eddrief, and C. A. Sébenne, Appl. Phys. Lett. 64, 3308 (1994)]. For a given low neutral energy, passivation with a neutral atomic beam H instead of H2 is preferred. The most straightforward method to produce the neutral beams is by the extraction of low energy atomic ions, and neutralization by electron capture. We have thus developed an electron cyclotron resonance coaxial hydrogen ion source that produces a 30-mm-diam ion beam, is operated with a microwave power in the range of 50–130 W, and has a pressure of neutrals in the range of 6×10−4–4×10−3 mbar. We have compared the proportion of extracted H+ and H+2 ions with the two principal parameters of the plasma: the pressure of neutrals and microwave injected power. These parameters have been optimized for the production of an 83% atomic ion beam.
Ion sources for implantation application (invited)
Authors: Matsuda Koji , Tanjyo Masayasu
Published: July 2002

A review of the newly developed ion sources for implantation application is presented. These ion sources include Bernas ion source and electron cyclotron resonance (ECR) ion source. They have advantages of source lifetimes and yields of multiply charged ion-beam current. Typical lifetime of Bernas source is 100 h and the ratio of As2+/As+ is about 25% with wide range beam current controllability. Lifetime of the ECR source is more than 150 h and the ratio of As2+/As+ beams is about 50%. The characteristics of these ion sources for the ion implantation system are also presented on actual uses in factories.
Two novel solid-state nuclear magnetic resonance probes
Authors: Michal Carl A. , Jelinski Lynn W.
Published: July 2002

The design and construction of two novel solid-state NMR probes are described. One probe incorporates a high-resolution goniometer for single-crystal studies, while the other can apply tension (≳5000 N) to fiber bundles. Deuterium spectra demonstrating the sensitivity of both probes are presented.
An impedance based non-contact feedback control system for scanning probe microscopes
Authors: Lee Mark , McDaniel E. B. , Hsu J. W. P.
Published: July 2002

We describe a non-contact, non-optical distance feedback control system for scanning probe microscopes that detects the surface damping of a vibrating probe. The feedback signal is derived from an electrical impedance change in a dithering piezoelectric element with attached scanning tip. The system incorporates an arbitrary-impedance bridge that maximizes detection sensitivity of the surface damping-induced impedance change as the tip approaches and interacts with the sample. In addition, an auxiliary circuit greatly improves reliability by making the feedback signal insensitive to the phase of the impedance change. The complete detection network can sense changes of −80 to −100 dB down to the level of 1 μV in a bandwidth of ≳1 kHz. The feedback system has demonstrated topographic height sensitivity of ∼0.5 Å and dynamic range of ≳60 dB.
Low-cost, heated, and/or cooled flow-through cell for transmission x-ray absorption spectroscopy
Authors: Jentoft R. E. , Deutsch S. E. , Gates B. C.
Published: July 2002

A transmission x-ray absorption spectroscopy cell that can be used for air-sensitive samples with in situ treatment is described. The cell is designed with a relatively small size for use with air-sensitive powdered catalyst samples that must be loaded in a glove box. Samples can be treated in situ with gas flow or vacuum and temperature control up to 500 °C. The cell is constructed of stainless steel and designed for durability as well as ease of repair. The cells are vacuum tight and equipped with beryllium windows sealed with vacuum O-ring flanges for easy loading. Each cell, with all parts excluding the windows, costs about $2700.
Direct-current bias effect on the synthesis of (001) textured diamond films on silicon
Authors: Lee J. S. , Liu K. S. , Lin I-Nan
Published: July 2002

A diamond film consisting of almost 100% [001] grains can be synthesized at a fast rate (∼ 3 μm/h) by a two-step process. First, the nuclei are formed under −160 V dc bias with 3 mol % CH4/H2 at 900 °C substrate temperature and then the films are grown under −100 V dc bias with around 5–6 mol % CH4/H2 at the same temperature. The nucleation of the diamond is enhanced by using bias voltage. The a and b axis of [001] textured diamond films grown under large bias voltage are aligned with a and b axes of silicon, viz. (100)diamond∥(100)Si and [110]diamond∥[110]Si. The effect of bias voltage on the growth behavior of the diamond films is accounted for by the suppression of the growth of the non-[001] grains due to the electron emission under bias.
Surface permeameter for nondestructive measurement of the rf complex permeability spectra of thin surface coatings
Authors: Grimes Craig A.
Published: July 2002

Thin film permeability measurement techniques such as stripline cavities or conventional permeameters require the sample undergoing measurement to be inserted within a fixture; typically, these samples can be no larger than a few square inches. However, certain applications require knowledge of the complex permeability of a coating or film applied to a finished, large product such as films deposited onto a continuous web for use as identification markers, the inside of a computer case for the control of EMI, or a ship mast for reduction of radar reflections. Therefore, a surface permeameter is presented that measures the rf complex permeability spectra of continuous films or coatings that are placed adjacent to the fixture over the frequency range of 10–500 MHz.
Coupling format variations in x-ray detectors based on charge coupled devices
Authors: Tate Mark W. , Gruner Sol M. , Eikenberry Eric F.
Published: July 2002

Three variations of charge coupled device (CCD) based x-ray detectors have been constructed and evaluated, two of which are used for routine data collection on small angle x-ray diffraction beamlines at Princeton. The first detector consists of a commercially available CCD camera system lens coupled to the output of a four-stage magnetically focused image intensifier. The second system, assembled to gather test data, consists of a CCD fiber-optically coupled to an x-ray conversion phosphor via a 5:1 reduction fiber-optic taper. The final detector configuration was comprised of this fiber-optic taper system with the addition of a single stage proximity-focused image intensifier. Rationale is given for choosing components to be used in the assembly of CCD-based detectors.
High-repetition-rate operation of the wire ion plasma source using a novel method
Authors: Urai Hajime , Kurosawa Tadashi , Okino Akitoshi , Hotta Eiki , Yasui Hiroyuki , Tamagawa Toru , Ko Kwang-cheol
Published: July 2002

The wire ion plasma source (WIPS) is a device that can be utilized as a pulsed ion source for ion-induced secondary-emission electron guns. The pulsed discharges of the WIPS are usually ignited by applying over-voltages onto the wire anode using a thyratron. The shortness of lifetime peculiar to such gas filled switching devices is known to be a major problem when utilizing the WIPS as a high-repetition-rate pulsed ion source. In this article a completely new method for the ignition of the pulsed discharges on the WIPS is proposed. This method, named the built-in electrostatic trigger method, does not need an external gas switching device. The new method also gives rise to another advantage in the pulsed-discharge characteristics since it minimizes the series impedance in the discharge circuit. The feasibility of the method is confirmed experimentally. A few improvements are introduced so as to realize high-repetition-rate pulsed operations of the WIPS.
Zone-averaged method to minimize polarizer and analyzer imperfections in a phase-modulated spectroscopic ellipsometer
Authors: You Chun-Yeol , Shin Sung-Chul
Published: July 2002

We have theoretically investigated the effects of polarizer and analyzer imperfections in a phase-modulated spectroscopic ellipsometer adopting a photoelastic modulator. Jones matrices having off-diagonal elements have been introduced to represent the imperfections of the polarizer and analyzer, and the effects of the imperfections were analytically derived to the first-order approximation. It was found that the effects of the imperfections could be completely eliminated by the zone average. Also, the effects of an incorrect setting of the modulation amplitude were found to be largely reduced by the zone average.
An electron cyclotron resonance source for radioactive beryllium ion beam production
Authors: Jayamanna K. , Zyuzin Z. , Buchmann L. , Cojocaru G. , Dombsky M. , Kuo T. , McDonald M. , Schmor P. W. , Yuan D.
Published: July 2002

An ECR ion source is converted to produce a beryllium fluoride beam, which will be stripped to Be+27 beam and used in Be7(p,γ)8B experiments at ISAC. The source consists of an injection chemical chamber and a plasma chamber. Chemically purified (99.9%) BeO is placed in the chemical chamber which can be heated up to 1000 °C. A CF4 leak connected to that chamber serves as the source of CF4 for the reaction to produce BeF2. The BeF2 is then injected into the hot electron layer region of the plasma chamber to enhance the ionization efficiency. A detailed source description, beam parameters and ionization efficiency measurements are presented in this paper.
Evaluation of a prototype Isotope Separator Accelerator surface ionization source
Authors: Dombsky M. , Baartman R. , Bricault P. , Doornbos J. , Jayamanna K. , Kuo T. , Mackenzie G. , McDonald M. , Schmor P. , Yuan D.
Published: July 2002

A prototype surface ionization source coupled with a fixed-geometry extraction electrode system was commissioned on the Isotope Separator Accelerator (ISAC) ion source test stand at TRIUMF. The suitability of the ion source and extraction system for use in the ISAC facility was determined by a series of emittance measurements of the extracted beams. The test stand optics were successfully commissioned using the prototype ion source; emittance measurements of the mass-separated beams demonstrated that second- and third-order beam aberrations (introduced by the magnetic dipole mass separation) could be corrected by the use of multipole electrostatic optics elements. An upper limit of the root-mean-square-energy spread (2 eV) was deduced from the emittance measurements. Emittance measurements were performed at beam energies of 10–50 keV, as well as for ion masses ranging from Li+ to Rb+, to demonstrate the feasibility of the prototype for a variety of beam energies and masses.
High-Q oscillator torque magnetometer
Authors: Biggar R. D. , Parpia J. M.
Published: July 2002

We describe a torque magnetometer for use at low temperatures based on a high-Q silicon torsional oscillator. The oscillator is fabricated using standard lithographic techniques from a single-crystal silicon wafer. The sample stage of the oscillator has an area of 0.57 cm2 and is suitable for deposition of thin magnetic film samples. Oscillator motion is detected through a capacitance measurement. The small torsion constant of the oscillator combined with a Q value >106 allow detection of magnetic moments as small as 10−13 A m2. Magnetometer sensitivity is measured using small superconducting open cylinders machined from aluminum.
Ytterbium-based fluorescence decay time fiber optic temperature sensor systems
Authors: Sun T. , Zhang Z. Y. , Grattan K. T. V. , Palmer A. W.
Published: July 2002

A series of different Yb-doped fibers has been investigated to determine their potential for use as the active elements in fluorescence–lifetime based thermometry, over a wide range from room temperature to 700 °C. Heat treatment (“annealing”) has been shown to be necessary in practical applications to achieve consistent and reproducible calibration curves, each of which is consistent with the results of a simple two level model. Each sample studied was found to possess unique sensitivity characteristics, enabling an optimized selection for specific applications. The response of the thermometer and the error in the measurement was found to be, at <±5 °C, consistent with the stability of the calibrated oven used.
Direct visualization of electromagnetic microfields by interference of three electron waves
Authors: Hirayama Tsukasa , Tanji Takayoshi , Tonomura Akira
Published: July 2002

A method is presented for direct visualization of electromagnetic microfields. Using a transmission electron microscope equipped with a field-emission electron gun and two electron biprisms, an object wave and two reference waves are superposed to interfere for producing a new type of interference pattern in which electromagnetic fields are directly observed. Equal-potential lines of an electric field around a latex particle and magnetic flux lines emerging from a barium ferrite particle have been observed.
The application and status of the radio frequency driven multi-cusp ion source (invited)
Authors: Leung Ka-Ngo
Published: July 2002

The multi-cusp ion source has been operated with 2 and 13.5 MHz in either pulse or cw mode for positive or negative ion beam production. Application of this type of source includes spallation neutron source, ion implantation, ion beam lithography, focused ion beam systems, radioactive ion beam production, and neutron generators. In order to achieve long life and reliable operation, different antenna arrangements have been explored. It is found that several antenna configurations can provide over 100 h of rf induction discharge operations.
Production of He-like light and medium mass ions in laser ion source
Authors: Kondrashev S. , Mescheryakov N. , Sharkov B. , Shumshurov A. , Khomenko S. , Makarov K. , Satov Yu. , Smakovskii Yu.
Published: July 2002

Operation of the laser ion source of He-like light ions designed for the first stage of the ITEP Terra Watt Accumulator (TWAC) project is discussed. A 5 J/0.5 Hz rep-rate CO2 laser was used for generation of highly charged light ions. The absolute number of ions with different charge states for carbon and aluminum ion beams has been measured. The obtained number of C+4 ions (∼1011ions/pulse) is sufficient to start the experimental proof of the accelerator scheme of the TWAC project. The investigation of shot to shot stability indicates significant increasing (∼2–3 times) of highly charged ion yield for the first shot onto the fresh target surface with respect to the next shots onto the same spot of aluminum target. This effect was not observed for the carbon target. Experimental results for highly charged light and medium mass (F, Mg, Al, Ca, Ti) ions produced by of 75 J single pulse CO2 laser consisting of a master oscillator and power amplifier are also presented.
A plasma–cathode electron source designed for industrial use
Authors: Osipov Igor , Rempe Nikolai
Published: July 2002

The article presents a description of the principle of operation, the design, and the performance data of a plasma–cathode electron source. Plasma is produced in a hollow-cathode reflex discharge operating in an axial magnetic field. The discharge unit is filamentless. Air is used as the working gas. The electron source generates a focused continuous electron beam of current up to 0.3 A at an accelerating voltage of up to 60 kV. Owing to the absence of hot electrodes, the system operates reliably under severe gas conditions with a long lifetime. The electron source is currently used as a component of electron-beam welding flow lines. The use of the electron source for electron-beam facing of composite powdered materials is also discussed.
Quantitative imaging of dielectric permittivity and tunability with a near-field scanning microwave microscope
Authors: Steinhauer D. E. , Vlahacos C. P. , Wellstood F. C. , Anlage Steven M. , Canedy C. , Ramesh R. , Stanishevsky A. , Melngailis J.
Published: July 2002

We describe the use of a near-field scanning microwave microscope to image the permittivity and tunability of bulk and thin film dielectric samples on a length scale of about 1 μm. The microscope is sensitive to the linear permittivity, as well as to nonlinear dielectric terms, which can be measured as a function of an applied electric field. We introduce a versatile finite element model for the system, which allows quantitative results to be obtained. We demonstrate use of the microscope at 7.2 GHz with a 370 nm thick Ba0.6Sr0.4TiO3 thin film on a LaAlO3 substrate. This technique is nondestructive and has broadband (0.1–50 GHz) capability. The sensitivity of the microscope to changes in permittivity is Δεr=2 at εr=500, while the nonlinear dielectric tunability sensitivity is Δε113=10−3 (kV/cm)−1.
Impact ionization in GaAs: Distribution of final electron states determined from hydrostatic pressure measurements
Authors: Allam J. , Adams A. R. , Pate M. A. , Roberts J. S.
Published: July 2002

We have measured the avalanche breakdown voltage (Vb) in GaAs p-i-n diodes as a function of hydrostatic pressure up to 14 kbar. The pressure coefficient of Vb was small and opposite in sign compared to that of the band gap. A lucky-drift calculation of Vb including the effects of pressure on both the phonon scattering and ionization rates showed that the ionization threshold energy does not scale with the band gap. Instead, the effective threshold scales with an average of the energies of the Γ, X, and L conduction-band minima. This is direct evidence that pair production yields final electron states distributed between conduction-band valleys.
Magneto-optical response of nanoscaled cobalt dots array
Authors: Takeshita H. , Suzuki Y. , Akinaga H. , Mizutani W. , Tanaka K. , Katayama T. , Itoh A.
Published: July 2002

Magneto-optical (MO) spectroscopic studies were carried out on submonatomic layer coverage of Co atoms deposited on the reconstructed Au(111) surface forming two-dimensional lattice of nanometer scaled Co dots. The MO spectral features were considerably affected by the shape of the Co dots. Strong dependence of the MO peak intensity on the change of the Co dot shape was observed at around the plasma edge of Au.
Cation distribution in NiZn-ferrite films via extended x-ray absorption fine structure
Authors: Harris V. G. , Koon N. C. , Williams C. M. , Zhang Q. , Abe M. , Kirkland J. P.
Published: July 2002

We have applied extended x-ray absorption fine structure (EXAFS) spectroscopy to study the cation distribution in a series of spin-sprayed NiZn-ferrite films. A least-squares fitting of experimental EXAFS data with theoretical, multiple-scattering, EXAFS data allowed the quantitative determination of site distributions for all transition metal cations.
New excimer-laser-crystallization method for producing large-grained and grain boundary-location-controlled Si films for thin film transistors
Authors: Kim H. J. , Im James S.
Published: July 2002

Based on the previously elucidated super lateral growth phenomenon, we have developed an excimer-laser-crystallization method that produces large-grained and grain-boundary- location-controlled Si films on SiO2  and which possesses a wide processing window. For the set of experiments reported in this letter, a patterned SiO2 capping layer on top of Si films is utilized as an anti-reflective coating in order to induce artificially controlled super-lateral growth in the film upon being irradiated with a single excimer laser pulse. For a simple SiO2  stripe pattern, the occlusion among the laterally and directionally solidifying grains permits the eventual development of elongated parallel grains with a single perpendicular grain boundary which is localized in the middle of the completely melted regions, provided that the width of the completely molten region is sufficiently narrow so as to avoid the nucleation of solids in the supercooled liquid.