bluuebunny/crossref_metadata_2025 huggingface dataset:
Generation of an intense metal-ion beam by a pulsed ion diode
Authors: Nakagawa Yoshiro , Ariyoshi Takeshi
Published: July 2002

Intense pulsed metal-ion beams (∼100 keV, ∼1 kA, 0.5 μs, Pb and Cu) were generated by a pulsed magnetically insulated ion diode driven by a long-pulse Marx generator. The ion current density exceeded the Child–Langmuir value by a factor of 50. The ion beams were extracted from either an anode plasma produced by electron bombardment on a metal anode or by a vacuum-arc metal-plasma source. Metal-ion beams rich in high-energy multi-ionized ions and also impurity ions of H+, C+, and O+ were measured by a Thomson-parabola ion spectrometer and a magnetic mass analyzer. The amount of impurity ions were reduced by conditioning of the anode surface. A design was considered to develop an intense metal-ion source with a total ion current of 1 kA, an ion energy of 100–200 keV, a pulse width of 10 μs, and repetition rate of 10 Hz, all of which correspond to a 100 mA steady-state metal-ion beam.
Development of the BOLVAPS lithium vapor source for the PBFA-II accelerator
Authors: Dreike P. L. , Appel D. B. , Cap J. S. , Gerstle F. P. , Lamppa K. P. , Mattox D. M. , McCollister H. L. , Moore R. H. , Neilsen M. K. , Peeples C. R. , Tisone G. C.
Published: July 2002

A pulsed, large area, Li vapor source for use in the PBFA-II ion beam diode is described. BOLVAPS (boil-off lithium vapor source) produces a 1–2 mm thick layer of Li vapor with a density approaching 1×1017 cm−3 by rapid ohmic heating of a thin-film laminate, one layer of which contains Li. The principal design issues of the vapor source being built for use on the PBFA-II accelerator are described. Results of small-scale development experiments are summarized.
Multiple arc ion sources for heavy ion fusion
Authors: Rutkowski H. L. , Johnson R. M. , Greenway W. G. , Gross M. A. , Hewett D. W. , Humphries S.
Published: July 2002

Heavy ion fusion requires high current density, low-emittance ion sources that are reliable and long lived. We report experimental and simulation results on the performance of carbon arc ion sources intended for use in a scaled induction linac experiment. These sources use a planar electrostatic plasma switch to prevent plasma from entering the extraction gap before the extraction voltage pulse is applied. This provides good beam optics for short pulse extraction. Measurements of current density and emittance are presented. Both double-slit and channel plate-pepper pot techniques are used for emittance measurement. Data presented are from a compact three-arc source with plasma coupling of the cathodes. Data on lifetime and multiple arc triggering are also presented. The plasma switch performance has been modeled with a 2D explicit electrostatic particle-in-cell code. Results showing plasma shutoff phenomena and behavior during extraction are presented. A 2D steady-state ion flow model is also used to predict the optimum plasma switch geometry for producing minimum emittance generation at the switch surface.
A simple rf-ion source of high efficiency with respect to power and gas consumption
Authors: Abdelaziz Mohamed E. , Zakhary Safwat G. , Abdel-Ghaffar Amin M.
Published: July 2002

An rf-ion source has been constructed which is featured with its small size, low power, and low gas consumption as well as the use of magnetic mirrorlike configuration at the source’s axis. The source could yield an ion current up to 12 mA at 3 kV extracting voltage, magnetic field of 0.056 T, and argon discharge pressure of 20 mTorr. The use of magnetic field increases the extracted ion current in values ranging from three to eight times it original value. The extracted ion current has been investigated as a function of the discharge parameters, i.e., the oscillator input power, discharge pressure, magnetic field, and extracting voltage.
A PIG ion source with single-crystal LaB6 cathodes
Authors: Song Zhizhong , Yu Jinxian , Yuan Zhongxi , Li Renxing
Published: July 2002

A new PIG ion source has been developed with the cathodes made of single-crystal LaB6 and a permanent magnet. The experiment shown that the single-crystal LaB6 is better than the common multicrystal LaB6 in electron emissivity, ion bnombardment resistance, and cathode lifetime. That ion source can produce a total beam current of about 1 mA at the low arc power of about 30 W.
Testing of a H2+-enriched ion source for deuterium simulation
Authors: Williams M. D. , Leung K. N. , Brennen G. M. , Burns D. R.
Published: July 2002

We have tested a McDonnell Douglas short milticusp plasma generator, designed to generate a positive hydrogen ion beam which is enriched with H2+ ions. Initial testing shows that the prototype source is capable of producing a positive hydrogen ion beam with H2+ percentage greater than 85%. The total ion-current density was 56 mA/cm2. For a higher current density of 110 mA/cm2, the percentage of H2+ ions is approximately 73% as measured by a magnetic deflection spectrometer. A comparison between tungsten and lanthanum hexaboride cathodes shows that tungsten filaments can provide better performance.
A high charge state multicusp ion source
Authors: Leung K. N. , Keller R.
Published: July 2002

Attempts have been made to generate high charge state ion beams by employing a multicusp plasma source. Three experimental investigations have been performed at Lawrence Berkeley Laboratory (LBL) and at Gesellschaft fuer Schwerionenforschung, Darmstadt (GSI) to study the charge state distributions and the emittance of the extracted beam. Results demonstrate that charge state as high as +7 can be obtained with argon or xenon plasmas. The brightness of a 11-mA xenon ion beam is found to be 26 A/(π mm mrad)2.
Operating experience with the Argonne PIIECR ion source system
Authors: Pardo Richard C. , Billquist Peter J.
Published: July 2002

The Argonne PIIECR ion source is the first ECR ion source system to operate on a high-voltage (350 kV) platform. The system is the injector into a new superconducting linac which will eventually provide beams over the entire periodic table, including uranium. The experience we have had with the system to date will be discussed. Emphasis will be placed on the source performance with solid materials and the initial performance of the system as an injector to the superconducting linac. The bunching system which is part of the overall source system allows a determination of the system longitudinal emittance. Results of these initial measurements will be presented.
Production of H− in a new type compact electron cyclotron resonance ion source
Authors: Tamba Moritake , Amemiya Hiroshi
Published: July 2002

A new type compact electron cyclotron resonance ion source is constituted by using permanent magnets and a 2.45-GHz microwave. A cylindrical vessel of Pyrex glass is mounted inside a TE11-mode waveguide. A cusp field is formed in the vessel by two water-cooled permanent magnets, the one being a SmCo cylinder and the other being a ferrite doughnut-shaped ring. The cusp field is modified from the conventional one in that the field at the upper part serves commonly as a wave radiator and a plasma confinement space. As a result, an overdense plasma can be realized with typical parameters Ne=2.5×1011 cm−3 and Te=3.5 eV at 5×10−4 Torr. The field at the lower section is opened toward the bottom extraction part to allow a downward drift of the produced plasma. This facilitates the extraction of the H− beam from the bottom electrode system. The beam current density showed a maximum value of 0.5 mA cm−2 at 4×10−4 Torr. The result is compared with the calculation by using rate equations.
High current ECR source for oxygen implantation: Life tests and comparison to duopigatron performance
Authors: Hipple J. , Hayden C. , Dionne G. , Torii Y. , Shimada M. , Watanabe I.
Published: July 2002

An ECR source has been built for production use on Eaton’s NV200 oxygen implanter. It can be retrofitted in place of the duopigatron normally used on that machine. This article reports results of 200 continuous hours of operation of the source, producing 95 mA of O+ ions, on a special test stand which emulates the injector of the NV200. Currents up to 200 mA at 45 kV were briefly obtained on this stand, the upper limit being set by thermal capacity of the beam dump. The ECR source was installed on an NV200 and used to implant wafers at 200 keV. Its performance is compared to that of the duopigatron source under similar conditions.
Comparison of multimode and single-mode optical fibers for quasi-elastic light scattering
Authors: McClymer J. P.
Published: July 2002

A comparison is made between the use of single and multimode optical fibers in a homodyne quasi-elastic light scattering experiment using simple optical hardware. The single-mode fiber is used without a spatial filter and gives a larger signal-to-noise ratio and counting rate than a multimode fiber with a spatial filter.
Modified stepwise expansion method for the measurement of compressibility isotherms of gases up to 10 kbar
Authors: Biswas S. N. , van de Ridder J. J. , ten Seldam C. A.
Published: July 2002

The stepwise expansion method for the measurement of compressibility isotherms of gases, developed recently in this laboratory, has been modified in order to measure those gases for which only low-pressure fiducial density data are available. The modified method has been tested with CH4 as a measuring gas at 298.15 K and up to 9.9 kbar.
Visible spectroscopy on the Tokamak de Varennes with high spatial resolution
Authors: Lafrance D. , Boileau A. , Stansfield B. L. , Zuzak W.
Published: July 2002

A vertical slice of a tokamak plasma is imaged onto the entrance slit of a spectrometer, giving at the exit plane both the spectral (horizontal axis) and the spatial (vertical axis) distributions of the collected light. An intensified CID (charge injection device) camera is mounted at the exit plane to record the spatially and spectrally resolved emission profiles of low-Z impurities, with a temporal resolution of 1/60 s. The large number of lines of sight allows for inversion of chord-integrated signals to obtain local emissivities. Profiles from several ionization stages of carbon and oxygen are compared to the predictions of the impurity transport code MIST (multi-ionized species transport) to deduce impurity diffusion coefficients.
Error analysis of a new asymmetric Abel-inversion method
Authors: Park Hyeon K.
Published: July 2002

Propagation of the various errors in a new asymmetric Abel-inversion method [Hyeon K. Park, Plasma Phys. Controlled Fusion 31, 2035 (1989)] is investigated. In order to provide a meaningful error analysis of the inversion process, both the effects of geometrical factors and measuremental errors are studied. The dominant source of uncertainty in the determination of local electron density is due to the spline fitting of the interferometric measurements with uneven spacings. The propagation of these errors is highly spatially localized and heavily damped in this inversion method. The absolute range of error in the local electron density is ±1.5×1012 cm−3.
Reflections (invited)
Authors: Green Tom
Published: July 2002

The interplay between three issues—ion sources, electrostatic beam formation and acceleration, and beam transport—is considered from a historical perspective, with reference to several important innovations.
A time-resolved x-ray scattering technique for observation of non-equilibrium phonons
Authors: Chapman L. D. , Ehrlich S. N. , Lazarz N. M.
Published: July 2002

We have demonstrated a time-resolved x-ray diffraction technique for observing nonequilibrium phonons. We have used this technique to observe phonons in α-quartz at low temperatures. Phonons were generated by direct stimulation of near zone center transverse-optical phonons using infrared light from a powerful Q switched CO2 laser. We show data taken at a Brillouin zone boundary confirming the presence of nonequilibrium phonons initially generated by the laser and their resulting decay products.
Electrohydrodynamically driven, large-area liquid metal ion source for inertial confinement fusion
Authors: Pregenzer Arian L.
Published: July 2002

Analysis of the electrohydrodynamic (EHD) equations of motion of a planar liquid-lithium surface in the presence of a normal electric field suggest that liquid lithium may provide a large-area ion source for intense ion-beam diodes. Such sources are being developed for the Particle Beam Fusion Accelerator II at Sandia National Laboratories. In this paper, theoretical and experimental studies of the planar EHD ion source will be reviewed. When a planar liquid surface is subjected to an electric field of sufficient magnitude, EHD instabilities produce an array of cusps on the surface. The electric field enhancement at the apex of each cusp is sufficient to permit field evaporation of ions. The time delay between application of the electric field and ion emission depends on the magnitude and rate of increase of the applied electric field, and on the initial amplitude of the surface perturbation. Above 10 MV/cm, theory indicates that field emission will occur on a nanosecond time scale and that the characteristic spacing of emitters will be <1 μm. At these fields, the source should have an intrinsic divergence of <6 mrad and the effects of space charge from neighboring emitters should not inhibit emission significantly. Experimental measurements of wavelengths and cusp-formation-times for water and ethanol at electric fields near the critical field for instability have agreed well with theory.
Sputtering ion source with simultaneous use of microwave and Penning-ionization-gauge discharge
Authors: Yoshida Yoshikazu , Ohnishi Teruhito , Hirofuji Yuichi , Ikeda Tanejiro
Published: July 2002

Characteristics of Penning-ionization-gauge-type compact microwave metal-ion source are described. This ion source can operate with two different discharge modes: the positive-resistance region mode and the negative-resistance region mode. In the positive-resistance region, a normalized emittance of a Ta+-ion beam is 1.8×10−7 m rad, the plasma density is 4×1012 cm−3, and the electron temperature is about 6 eV. In the negative-resistance region, the emittance is 2.7×10−7 m rad. This ion source is suitable for operation in the positive-resistance region where the microwave discharge is dominant.
Production of ions from solids using chemically assisted sputtering
Authors: Rosenblum S. S. , Doniger K. J. , Helmer J. C.
Published: July 2002

Boron ions are universally used as a p-type dopant for ion implantation of silicon wafers. In today’s technology, ions are produced from gases in a hot filament magnetron plasma, known as the Freeman ion source, using BF3 as a feedstock. Two problems are that the hot filament corrodes in the fluoride environment and the BF3 is quite toxic. In order to overcome these limitations, we have developed a cold cathode magnetron source which uses a conductive boride cathode liner (B4C and B6Si have been used successfully), and a nontoxic gas feed (such as CF4 or SF6), which produces boron ion fraction yields as high as 15% in beam extraction experiments performed on a low voltage ion source test stand. This is comparable to the performance obtained using a Freeman source and BF3 feed gas.
Characteristics of a seven-element electrostatic lens system studied by an exact beam-tracing method
Authors: Sakae Takeji , Tsumura Yoshihiko , Matsumoto Yuzuru , Ishibashi Kenji , Katase Akira
Published: July 2002

A lens system has been designed for an electron energy analyzer by the numerical beam-tracing method using the paraxial equation of motion for electrons. Three new modes are investigated, in addition to a usual one, as methods for applying voltages to the lens electrodes. The emittance diagrams are obtained for the system by solving the exact equation of motion, and they clearly show the effects of aberrations. The transmission for electrons is calculated for each of the four modes by using the diagrams. The lens system can be used with considerable efficiency in the different energy regions appropriate to the respective modes.
Pulse-periodical high-intensity ion sources for multielement implantation
Authors: Ryabchikov A. I.
Published: July 2002

In this paper we present results on the formation of multicomponent ion beams with controlled composition for ion implantation. The principles of control of the beam composition and energy are formulated by consideration of the requirements of beams for multielement ion implantation. It is shown that variation of the composition and energy can be obtained by repetitively pulsed beam formation with spatial separation of the different components. Results are presented of different versions of our high current ion sources, and of the means for controlling the beam composition and energy on a pulse-to-pulse basis and also within each pulse.
A three-axis spherical void electrodynamic levitator trap for microparticle experiments
Authors: Arnold S.
Published: July 2002

By adding two additional electrodes to the equator of a spherical void electrodynamic levitator trap (SVELT) one can balance static forces on a microparticle independently along three perpendicular axes. The balance equations are derived and a joy stick based controller is introduced for manipulating the electric field vector at the center of the SVELT. With this device one can eliminate stray fields at the ‘‘null’’ point and center a particle to a limit set only by Brownian forces in the electrodynamic pseudopotential. This limit is calculated and its importance for microphotography is discussed.
A dual beam total internal reflection fluorescence spectrometer for dynamic depth resolved measurements of biochemical liquid-solid interface binding reactions in opaque solvents
Authors: Liebmann Lars W. , Robinson John A. , Mann Kenneth G.
Published: July 2002

The initiation of many physiologically important biochemical reactions is dependent on the binding of a molecule or molecules from solution to an appropriate solid surface such as a cell membrane. The quantitative study of dynamic interactions of molecules in solution with immobilized surfaces under physiologically relevant conditions presents a significant physical problem. Traditionally these measurements have been performed by discontinuous, nonequilibrium assays that cannot accurately model in vivo reaction mechanisms. Total internal reflection fluorescence spectroscopy (TIRFS) is an analytical technique that is based on the excitation of fluorescence by means of an exponentially decaying surface energy wave called the evanescent wave. The limited ‘‘penetration depth’’ of the evanescent wave leads to excitation of fluorescent molecules at or near the surface. This phenomena makes TIRFS uniquely qualified for the dynamic fluorescence study of liquid-solid interface binding reactions. The instrument described here permits the powerful technique of TIRFS to be used by biomedical researchers in their investigation of biochemical interface reactions. The fully automated, menu driven instrument allows the real time dynamic measurement of binding of fluorescent-labeled molecules in solution at physiologically relevant concentrations to appropriate immobilized surfaces.

The novel design of the total internal reflection element enables the study of binding from essentially opaque and highly scattering solutions such as whole blood. Measurements may be performed under static, stirred, or flow conditions. The presently described TIRFS instrument is capable of tracking a binding reaction with evanescent fields established by two identical reflecting light beams with different reflection angles. This instrumental feature allows the dynamic measurement not only of the primary binding event but also of fluctuations in the distance between the optical interface and the point of signal generation. Data from experiments involving fluorescently labeled molecules binding to cell monolayers as well as binding experiments performed in whole blood are shown to verify the instrument performance. Due to its extraordinary capabilities and its user friendly design, the developed TIRFS instrument opens up a large number of relevant but previously unmeasurable experimental systems for investigation.
A diamond-anvil cell for the study of fluid binary mixtures at high temperatures
Authors: Vos Willem L. , van Anrooij Fred. C. J. , Jongeneelen Ton , Schuijlenburg Wim J. , Schouten Jan A.
Published: July 2002

In order to study phase equilibria in aqueous systems at high temperatures, a diamond-anvil cell that can be loaded with compressed-gas mixtures and a matching thermostat were developed. Care was taken to ensure a stable (0.1 K) and homogeneous (<0.5 K) temperature distribution inside the cell by using a two-stage heating system. Experiments were performed up to 50 kbar at 650 K on pure nitrogen. The observed melting line of nitrogen is in very good agreement with previous results.
Transverse mode selection in a convectively cooled cw-CO2 laser with a cyclonic flow configuration
Authors: Sehgal S. K. , Nundy U. , Chatterjee U. K.
Published: July 2002

Strong cyclonic flow induced discharge confinement has been used for the first time to efficiently select the lower order transverse modes in a fast axial flow high power cw-CO2 laser. The laser performance with and without the cyclonic flow has been compared. Comparison has also been made with the conventional aperture method of selection of lower-order transverse modes.
A digital integrator and scan generator coupled with dynamic scanning for scanning tunneling microscopy
Authors: Robinson R. S. , Kimsey T. H. , Kimsey R.
Published: July 2002

A novel digital integrator circuit has been engineered for constant-current mode STM feedback control. In contrast to analog integrators that rely on charging or discharging of a capacitor in an amplifier feedback loop, the integrator uses a 16-bit digital counter that is rapidly incremented or decremented depending on whether the tunneling current is higher or lower than a reference value. The counter drives a digital-to-analog converter (DAC) whose output is amplified and used to control the STM Z-axis scanner. A computer’s parallel input port records the DAC output word at each sampling point, directly giving the digital value of the tip position. The integrator is used in conjunction with a two-axis 16-bit scan generator. The Z-axis feedback reference circuit is used to dynamically control the STM’s lateral scanning rate, and scan rates of 300 μm s−1 are demonstrated. The digital integrator and scan generator facilitate fast switching between different modes of STM operation, allowing glitch- and drift-free locking of tip position, interchange of axes, scanning or switching the sign of the tip bias, and flexible tailoring of the feedback response.
Magnetic penetration depth measurements of superconducting thin films by a microstrip resonator technique
Authors: Langley B.W. , Anlage S. M. , Pease R. F. W. , Beasley M. R.
Published: July 2002

The microstrip resonator technique is a convenient way to sensitively measure the temperature dependence of the magnetic penetration depth, λ(T), in superconducting thin films. Because the method relies on measuring the resonant frequency of a microwave transmission line resonator, one can very precisely measure small changes in λ(T). This technique can resolve changes in λ on the order of several angstroms, allowing a direct measurement of the low-temperature behavior of λ(T), which is a measure of the low-lying pair breaking excitations of the superconductor. Absolute penetration depth values can also be obtained from a self-consistent fit to the data to an assumed temperature dependence. Measurements of the penetration depth of Nb and NbCN film give results that are consistent with the predictions of BCS theory in which 2Δ/kTc is treated as an adjustable parameter, while YBa2Cu3O7−δ films give results that are not completely understood at this time. We also compare this technique with other methods of measuring the penetration depth of superconducting thin films, and discuss the systematic errors present in the measurement.
Split-ring resonators for measuring microwave surface resistance of oxide superconductors
Authors: Bonn D. A. , Morgan D. C. , Hardy W. N.
Published: July 2002

A cavity perturbation technique using split-ring resonators has been developed for measuring the surface resistance of metals in the frequency range 0.3–5.0 GHz. The system is designed particularly for measurements of films and crystals of high-Tc oxide superconductors. The small size of split-ring resonators in this frequency range makes them useful for measuring crystals with areas as small as 0.1 mm2. The measurement geometry is favorable for the study of films because the sample screens its substrate from the microwave fields. The resonator temperature can be kept fixed at 4.2 or 1.2 K for sample temperatures as high as 120 K and this thermal isolation from the sample allows the use of a superconducting split-ring resonator. An unloaded Q of 1.2×106 has been achieved with a superconducting resonator at 1.78 GHz and this makes it sensitive enough to detect surface resistances of the order of a few μΩ. This resonator has been used to measure the surface resistance (25 μΩ/⧠) of a 1-mm2 crystal of Bi2Sr2CaCu2O8.
Ozone jet generator as an oxidizing reagent source for preparation of superconducting oxide thin film
Authors: Hosokawa Shunsuke , Ichimura Shingo
Published: July 2002

An ozone jet generator to supply precisely controlled ozone flux to a specimen was constructed with the particular aim of its application for the preparation of superconducting oxide thin films by an MBE (molecular beam epitaxy) method. The ozone jet is supplied to the thin film growth chamber by evaporating the liquid (or solid) ozone accumulated in the ozone vessel of the generator. The necessary condensed ozone is produced from the ozone-oxygen mixture gas generated by a commercial ozonizer. The ozone flux can be changed by adjusting the temperature of the ozone vessel (i.e., the temperature of liquid ozone). Precise pressure and temperature control of the ozone vessel in liquefying ozone makes it possible to minimize dissolution of diatomic oxygen in the liquid ozone. As a result, the ozone jet generated from the liquid ozone possesses high purity. The precise temperature control also enables a very stable supply of the ozone jet, with a stability of less than 2.5% over 1.5 h. For the experimental condition of liquefying ozone at 95 K and 800 Pa, and evaporating at 85 K, an ozone jet with an ozone flux of 1×1016 molecules/s and an ozone concentration of higher than 70% was obtained in the test vacuum chamber installed with this ozone jet generator. It was also confirmed by XPS spectra of Cu after oxide film formation that the ozone jet possesses a very high reactivity.
Effect of interface composition and growth order on the mixed anion InAs/GaSb valence band offset
Authors: Wang M. W. , Collins D. A. , McGill T. C. , Grant R. W. , Feenstra R. M.
Published: July 2002

We have used x-ray photoelectron spectroscopy (XPS) to measure the dependence of the InAs/GaSb valence band offset on both interface composition and growth order. Molecular beam epitaxy was used to grow InAs-on-GaSb and GaSb-on-InAs interfaces with both InSb-like and GaAs-like interface compositions. Analysis of XPS core level separations showed no dependence of the valence band offset on interface composition; however, a 90 meV increase in the valence band offset was observed for InAs grown on GaSb compared to GaSb grown on InAs. This difference is attributed to the extended nature of the InAs-on-GaSb interface. Results from analysis of an intentionally extended GaSb-on-InAs interface were consistent with this conclusion.
Emission properties of broad-beam vacuum arc ion sources
Authors: Ryabchikov A. I.
Published: July 2002

Investigation results on emission properties of repetitively pulsed vacuum arc ion sources with a broad-beam diameter are presented in this report. Influence of the arc discharge current, geometric dimensions and shape of the anode on the arc discharge stability, and extraction efficiency of the ion current are analyzed. It is shown that under formation of broad ion beams due to plasma expansion of the cathode spot within the anode expander, it is expedient to utilize the conical geometry of the anode. Influence of the grid cell size or port diameter in multiaperture diaphragms on emission properties of the ion source is investigated. It is illustrated that under certain conditions the decelerating voltage drop can occur near the anode reducing the efficiency and operating stability of the source.
Focused ion beams in microfabrication (invited)
Authors: Prewett P. D.
Published: July 2002

Ion probes from liquid metal ion sources are increasingly used in microfabrication R&D and commercial systems are being considered for manufacturing applications in the semiconductor industry. Among the applications of focused ion beams, the repair of x-ray masks and chip surgery are two important areas of growing interest. The use of micromachining and microdeposition techniques to repair and modify a gold on membrane x-ray mask and an advanced prototype integrated circuit are described and discussed.
A novel position-sensitive detector using an image-sensing integrated circuit
Authors: Hatfield J. V. , Burke S. A. , Comer J. , Currell F. , Goldfinch J. , York T. A. , Hicks P. J.
Published: July 2002

A novel position-sensitive detector has been developed which consists of an array of electron-sensing electrodes and a corresponding array of amplifiers and counters all integrated onto a single silicon chip. The integrated circuit is coupled with a microchannel plate electron multiplier so that it counts individual charged particles or photons. The detector array is capable of being extended by abutting individual detector chips side by side in the form of a hybrid circuit. The detector is currently in use on both electron-energy-loss and photoelectron spectrometers.
Scanning surface harmonic microscopy: Scanning probe microscopy based on microwave field-induced harmonic generation
Authors: Michel B. , Mizutani W. , Schierle R. , Jarosch A. , Knop W. , Benedickter H. , Bächtold W. , Rohrer H.
Published: July 2002

A scanning probe microscope has been integrated into a microwave resonator tunable from 2.2 to 3.4 GHz with a quality factor Q larger than 1000. Nonlinear phenomena caused generation of higher harmonics when rf fields in the range of 109 V/m were applied between tip and sample. Higher harmonic signals were detected at a bandwidth of 10 kHz on conductor surfaces as well as on thin insulating films and were used as feedback to the control loop for imaging graphite surface features and oxidized silicon surfaces with subnanometer resolution.
Design, construction, and testing of an infrared–far-infrared–radio frequency (IR–FIR–rf) cell
Authors: Rob Mohammad A.
Published: July 2002

Practical considerations in designing a far-infrared waveguide laser and a radio frequency/microwave transmission line applicable to double- or triple-resonance spectroscopy are discussed. It is shown that a transmission line is preferable in the radio frequency (∼1 kHz–1 GHz) region, and a waveguide is preferable in the microwave (∼1–100 GHz) region. A near-optimum radio frequency transmission line was constructed and a double-resonance experiment was carried out to show the usefulness of the transmission line. It is found that a small mismatch between the impedance of the transmission line and that of other instruments does not appreciably modify the characteristics of the transmission line.
An integrated-circuit based wide range electrometer implemented with automatically ranged linear display
Authors: Shaw Sen-Yen
Published: July 2002

An electrometer using a complementary metal-oxide semiconductor bilateral switch for automatic range control has been built. This circuit provides linear analog output over six orders of magnitude for current measurement without the need for constant adjustment of offset at different ranges. The application of integrated circuits makes the whole system stable and can be readily constructed.
Digital phosphorimeter with frequency domain signal processing: Application to real-time fiber-optic oxygen sensing
Authors: Alcala J. Ricardo , Yu Clement , Yeh Gong Jong
Published: July 2002

An instrument to measure the excited-state lifetimes of phosphorescent materials in real time is described. This apparatus uses pulsed and frequency-doubled Nd:YAG solid-state laser for excitation, sampler for data acquisition, and frequency domain methods for data fitting. The instrument amplifies the ac components of the detector output and band limits the signal to 25 kHz. The fundamental frequency of the excitation is then set to obtain a desired number of harmonics. This band limited signal is sampled and averaged over few thousand cycles in the time domain. The frequency domain representation of the data is obtained by employing fast Fourier transform algorithms. The phase delay and the modulation ratio of each sampled harmonic is then computed. Ten to a hundred values of the phase and modulations are averaged before computing the sensor lifetime. The instrument is capable of measuring precise and accurate excited-state lifetimes from subpicowatt luminescent signals in 100 μm optical fibers. To monitor oxygen for biomedical applications the response time of the system is decreased by collecting only 8 or 16 harmonics. A least-squares fit yields the lifetimes of single exponentials. A component of zero lifetime is introduced to account for the backscatter excitation. The phosphorescence lifetimes measured reproducibly to three parts in a thousand are used to monitor oxygen. Oxygen concentrations are computed employing empirical polynomials. The system drift is less than 1% over 100 h of continuous operation. This instrument is used to measure oxygen concentrations in vitro and in vivo with 2 s update times and 90 s full response times. Examples of measurements in saline solutions and in dogs are presented.
A versatile laser beam deflection sensor utilizing optical fibers
Authors: Vattulainen Juha , Hernberg Rolf
Published: July 2002

A compact, fast (τ≊10 ns) and sensitive (δ≊0.1 μrad) laser beam deflection sensor has been developed. The device consists of a passive fiber optic sensor head and a separate detector and amplifier unit. Subsequent signal processing is performed using a fast digital storage oscilloscope. The sensor head can be adjusted according to the probe beam spot size to optimize the deflection measurement sensitivity. The passive sensor head having no electrical components makes the system especially suitable for applications where rf noise pickup may constitute a problem. A differential operating principle is utilized to reduce common-mode noise such as probe laser intensity fluctuations. The possibilities of high-pass filtering and averaging of the deflection signal to enhance the measurement sensitivity are discussed.
Measurement of frequency response in short thermocouple wires
Authors: Forney L. J. , Meeks E. L. , Ma J. , Fralick G. C.
Published: July 2002

Experimental measurements are made for the steady-state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire (type K) and a two material wire (type T) with unequal material properties across the junction. The data for the amplitude ratio and phase angle are correlated to within 10% with the theoretical predictions of Fralick and Forney (1992) for a laser-heated junction with no bead. This is accomplished by choosing a natural frequency ωn for the wire data to correlate the first-order response at large gas temperature frequencies. Moreover, it is found that a large bead size (roughly twice the wire diameter) will increase the amplitude ratio at low frequencies and distort the phase angle. In the latter case, it is necessary to increase the thermocouple wire length by 20% in the theory to correlate the data when the junctions have beads (silver soldered).
A dc SQUID for use below 1 K
Authors: Geng Z. K. , Adams P. W. , Hamilton W. O. , Johnson W. W. , Solomonson N. D.
Published: July 2002

For detection of weak signals, and for use on ultralow temperature experiments, it would be useful to have a robust superconducting quantum interference device (SQUID) amplifier that works below 1 K. We report on a test of a commercial SQUID amplifier that has lower noise than others we have tested, and works well while attached to a 50-mK chamber. The SQUID noise was improved only modestly when cooled from 4 K to 50 mK. The best energy resolution measured was 2200 ℏ.
Flow cytometer for resolving signals from heterogeneous fluorescence emissions and quantifying lifetime in fluorochrome-labeled cells/particles by phase-sensitive detection
Authors: Steinkamp John A. , Yoshida Thomas M. , Martin John C.
Published: July 2002

A phase-sensitive flow cytometer has been developed that combines flow cytometry and fluorescence lifetime spectroscopy measurement principles to provide unique capabilities for making phase-resolved measurements on fluorochrome-labeled cells and particles. Stained cells are analyzed as they intersect a high-frequency intensity-modulated (sinusoid) laser excitation beam. Fluorescence is measured orthogonally using only a single-channel optical detector. The detector output signals, which are phase shifted from a reference signal and amplitude demodulated, are processed by phase-sensitive detection electronics to resolve signals from heterogeneous fluorescence emissions and quantify single-component decay times. Results show signal phase shift and amplitude demodulation on fluorospheres; a detection limit threshold of 300–500 fluorescein molecules equivalence for excitation frequencies 1–30 MHz; a measurement precision (coefficient of variation) of 1.8% on alignment fluorospheres and 3.6% on cells stained for DNA content; the resolution of fluorescence signals from cells stained in combination with two fluorochromes, based on differences in their decay times; and the measurement of fluorescence lifetimes directly by the two-phase ratio method.
A novel force microscope and point contact probe
Authors: Jarvis S. P. , Oral A. , Weihs T. P. , Pethica J. B.
Published: July 2002

The mechanical properties of very small volumes of material can vary greatly from bulk properties. These modified properties are of interest in many areas including the operation of atomic force microscopy (AFM), the study of adhesion and fracture, and the evaluation of electrical contact response. Despite the importance of these properties, AFM has not yet been successfully utilized for their investigation. Most existing AFMs still rely on the control and monitoring of displacements, with forces being inferred from spring constants. This would be fine if other interactions, such as those between the tip and the surface, were minor perturbations. However, this is frequently not the case, particularly for contact mode AFM. Hence very little is known about the forces applied in the contact and their affect on both the tip and the sample. In this article we describe an AFM probe where forces rather than displacements are applied to the tip. This allows absolute determination of contact compliance and hence provides a measure of the tip–surface interaction. As an example of its use we show quantitatively the effect of the adsorbed water and meniscus forces present in ambient probe microscopy.
An ultrahigh vacuum Czochralski crystal growth system using either hot or cold crucibles
Authors: Fort D.
Published: July 2002

An ultrahigh vacuum Czochralski crystal growth system intended primarily for use with metallic elements and intermetallic compounds is described. The equipment can be used with either hot or cold crucibles and utilizes radio frequency heating. By designing the equipment so that the crucible is suspended from above, and thereby dispensing with the normal pedestal arrangements, it has been possible to employ a simplified design of a vacuum system, which, in turn, permits rapid loading and unloading of samples.
Technique for measuring thermal diffusivity/conductivity of small thermal-insulator specimens
Authors: Miller M. S. , Kotlar A. J.
Published: July 2002

An experimental technique to measure simultaneously the thermal diffusivity and thermal conductivity of small specimens of thermal-insulator materials is described. Experimental conditions are developed which approach the mathematical idealization of a one-dimensional, infinite, two-component, composite solid whose planar interface is subjected to a step-function heat flux. The heat flux is generated by resistive heating of a thin metallic foil. Although this principle has been exploited previously, the present technique permits specimens with volumes two orders of magnitude smaller than prior work based on the same idealization. A number of difficulties related to small specimen volume are identified and overcome. Another improvement over past efforts is the use of the nonlinear least-squares analysis to determine the optimum values for diffusivity and conductivity. A comparison of measurements of these properties for acrylic and Pyrex glass with literature values suggests that the technique affords accuracies of about 5% for materials in this range.
Narrow-line, low-amplitude noise semiconductor laser oscillator in the 780 nm range
Authors: Hilico L. , Touahri D. , Nez F. , Clairon A.
Published: July 2002

We present a narrow-band and low-intensity noise laser oscillator around 780 nm built from a commercially available laser diode. We have stabilized the frequency of two extended cavity diode lasers on the same high finesse Fabry–Pérot cavity using a wide-band electronic feedback loop. We have reduced the relative linewidth of the two lasers down to 570 Hz and strongly concentrated their energy: 95% in a relative bandwidth smaller than 10 kHz. The intensity noise of this device corresponds to the shot noise for Fourier frequencies larger than a few megaHertz.
A fast extraction instrument of a 1-GeV electron synchrotron
Authors: Tsukishima Chihiro , Nakata Shuhei
Published: July 2002

A kicker magnet and a modulator were developed as a fast extraction instrument of a 1-GeV electron synchrotron. A 1-kG pulsed magnetic field was generated by the kicker magnet with the rise time of 40 ns. The ripple of the flattop of the current wave form was less than ±1%, and the shot-to-shot fluctuation of the peak current was no more than 0.1%. The modulator consists of two Blumleins in series which operate at a quarter of the charging voltage as compared to a pulse forming network (PFN) type modulator. The damped oscillating wave form of the current could decrease the residual field to be less than 0.5 G. The effect of the residual field of the kicker magnet on the dynamic aperture of the low-energy electron beam was estimated by the tracking calculation. The result shows the dynamic aperture decreases as the residual field increases. To obtain enough accelerated current, the residual field must be less than 1 G. This restriction could be satisfied by the developed kicker magnet and the modulator. Successful extraction of eight bunches out of 15 bunches in the synchrotron were measured by a wall current monitor located in the extraction transport line.
Fabrication of Wolter-type x-ray focusing mirror using epoxy resin
Authors: Hasegawa Masaki , Taira Hideki , Harada Tatsuo , Aoki Sadao , Ninomiya Ken
Published: July 2002

We have developed a new fabrication method for Wolter-type x-ray focusing mirrors. In this method, a slight gap between the master mandrel and the glass replica produced by vacuum replication was filled with epoxy resin to decrease the roughness and the figure displacement of the mirror surface. The mirror was evaluated both by taking x-ray microphotographs of No. 1000 and No. 2000 copper meshes with Al Kα and C Kα x rays, and by focusing x rays with several wavelengths using synchrotron radiation. No apparent degradation was found in the micrographs even when we changed the irradiating x rays from the C Kα to the Al Kα. The focused beam profile remained unchanged even at the wavelength of 1.24 nm. The beam size in the meridional plane also decreased to 50% of the beam size focused by a mirror fabricated only by vacuum replication. These results indicate that the present method successfully decreases the surface roughness to less than 6.2 nm (peak-to-valley) and improves the figure accuracy of the mirror surface.
Complex dielectric constant measurement of samples of various cross sections using a microwave impedance bridge
Authors: Joo J. , Epstein A. J.
Published: July 2002

A microwave impedance bridge covering from 8.2 to 12.4 GHz used for measuring complex dielectric constants over a wide temperature range is described. This apparatus is suited for materials formed into solid posts having different cross sections. The effective diameters for use in the analysis of circular, elliptical, or rectangular cross-section posts are presented. The effective diameters are applied to determine the complex dielectric constant of rectangular-shaped conducting polymer film. The frequency and temperature dependence of the dielectric constant and conductivity are presented, and compared with those obtained using a microwave cavity perturbation technique at 6.5 GHz. The bridge results are well suited for independent determination of the depolarization factor of a rectangular post for use in analysis of results of the cavity perturbation method.
Supersonic cluster source with mass selection and energy control
Authors: Laaksonen R. T. , Goetsch D. A. , Owens D. W. , Poirier D. M. , Stepniak F. , Weaver J. H.
Published: July 2002

We have developed an apparatus that produces an ionized beam of mass selected clusters of controllable energy. It uses a pulse of second-harmonic light from a Nd:YAG laser to vaporize atoms from a target disk. The clustering rate of the atoms in this expanding plume is controlled with the pressure of a He pulse injected from a fast pulsed valve. A Wiley–McLaren type time-of-flight mass spectrometer with a shield lens is used to monitor the cluster distribution and to optimize the control parameters of the system. The shield lens doubles the resolution and the signal-to-noise ratio of the spectrometer. A 4000 amu rf quadrupole with 1.2 amu resolution is used to select the mass of charged clusters. An electrostatic quadrupole is used to separate the charged clusters from the neutral clusters and the He gas. The ionized clusters are then focused onto a suitably prepared substrate by using electrostatic lenses. Time averaged deposition current densities on the order of 100 pA cm−2 have been measured when the vaporization laser is fired at 10 Hz. The deposition energy of the clusters is controlled by applying a bias voltage to the substrate. A mobile vacuum chamber is used to transfer samples to various diagnostic systems.
Apparatus for the in situ kinetic study of reactions involving air sensitive materials using energy-dispersive powder diffraction
Authors: Clark S. M. , Irvin P. , Flaherty J. , Rathbone T. , Wong H. V. , Evans J. S. O. , O’Hare D.
Published: July 2002

A novel sample chamber has been developed for the study of chemical reactions involving air sensitive samples using energy-dispersive powder diffraction. The apparatus consists of a reaction vessel, automatic reactant dispensing system, heating jacket, stirrer, and gas purge system. The use of this apparatus is illustrated with data collected on station 9.7 of the UK Synchrotron Radiation Source during a study on the intercalation of cobaltocene into tin disulfide.
Dielectric resonator-based stopped-flow electron paramagnetic resonance
Authors: Sienkiewicz Andrzej , Qu Kunbin , Scholes Charles P.
Published: July 2002

We present the technical details and relevant performance aspects of a dielectric resonator-based electron paramagnetic resonance probe for stopped-flow kinetic studies. The major benefits of this system are: (1) It incorporates a small, high sensitivity resonator system that is insensitive to stopped-flow induced noisy transients. (2) The resonator system is cheap, robust, and easily assembled. (3) It contains a microwave coupling scheme that provides finesse in tuning and freedom from microphonics.