bluuebunny/crossref_metadata_2025 huggingface dataset:
ac calorimeter for measurements of adsorbed gases on metal films at 4He temperatures
Authors: Kenny T. W. , Richards P. L.
Published: July 2002

An analysis is presented of the performance of an ideal ac calorimeter limited only by thermodynamic noise. A calorimeter based on this analysis is described which is designed for studies of the heat capacity of monolayers and multilayers of atoms and molecules adsorbed on a variety of surfaces. The calorimeter consists of Ge:Ga thermometers and NiCr heaters mounted on one side of a sapphire substrate, with an evaporated film deposited on the other side. The calorimeter is mounted on a 4He cold finger in a UHV system allowing heat capacity measurements down to 1.6 K. In order to verify the performance of the calorimeter, measurements have been made of the heat capacity of 25-μg samples of indium, and of submonolayer coverages of 4He on sapphire. The measured sensitivity corresponds to <10−2 monolayers of 4He adsorbed on the surface of the calorimeter in the gas phase.
An original in situ cleaver for low temperature surface experiments
Authors: Angot T. , Suzanne J. , Hoarau J. Y.
Published: July 2002

A simple, original and easy to construct, in situ crystal cleaver is presented. It is mounted directly on the sample holder and is particularly suitable for low temperature experiments. It is small enough to be adaptable on any low temperature x, y, z, Θ, φ manipulator. Cleaving in situ allows one to obtain a uniform and well-constructed single crystal surface. Adsorption experiments of krypton monolayers on an MgO (100) in situ cleaved crystal at 44 K are presented.
Wide dynamic range current-voltage characterization system for ceramic superconductors
Authors: Kirkup L. , Kalceff W. , Stockton G.
Published: July 2002

Transport current-voltage (I-V) characteristics gathered over several orders of magnitude of current can reveal much about the loss mechanisms in high Tc superconductors. This article describes the design and implementation of a novel, computer-controlled, I-V characterization system which permits a I-V curve spanning five orders of magnitude of current to be captured in 50 ms. The advantages of this system over other methods of obtaining I-V curves are discussed. The system is applied to the study of high Tc superconductors and preliminary measurements are presented. Data obtained at 77 K for polycrystalline YBa2Cu3O7−δ are shown to be consistent with a I-V relation of the form, V=k(I−Ic)n, where Ic is the critical current, and k and n are constants.
Lens induced by stress in optical windows for high-pressure cells
Authors: Shelton D. P.
Published: July 2002

Calculations are described of the elastic stress, strain, and surface displacement for a high-pressure optical window consisting of a transparent cylinder which is supported on a flat seat with an axial hole (Poulter window). Under pressure the window is compressed, and its outside surface bulges through the hole in the support. The net optical effect is to create a weak positive lens and to increase the axial optical thickness of the window.
Measurement of thermal ion profiles in TFTR neutral beamlines
Authors: Kamperschroer J. H. , Grisham L. R. , Kugel H. W. , O’Connor T. E. , Stevenson T. N. , von Halle A. , Williams M. D.
Published: July 2002

A technique is described whereby the ion dumps inside the TFTR Neutral Beam Test Stand were used to measure thermal profiles of the full-, half-, and third-energy ions. 136 thermocouples were installed on the full-energy ion dump, allowing full beam contours. Additional linear arrays across the widths of the half- and third-energy ion dumps provided a measure of the shape, in the direction parallel to the grid rails, of the half- and third-energy ions, and, hence, of the molecular ions extracted from the source. As a result of these measurements, it was found that the magnet was more weakly focusing, by a factor of 2, than expected, explaining past overheating of the full-energy ion dump. Hollow profiles on the half- and third-energy ion dumps were observed, suggesting that extraction of D+2 and D+3 is primarily from the edge of the ion source. If extraction of half-energy ions is from the edge of the accelerator, a divergence parallel to the grid rails of 0.6°±0.1° is deduced. It is postulated that a nonuniform gas profile near the accelerator is the cause of the hollow partial-energy ion profiles, the pressure being depressed over the accelerator by particles passing through this highly transparent structure. Primary electrons reaching the accelerator produce nonuniform densities of D+2 through the ionization of this gas. D+3 is created through subsequent D+2-gas collisions. A technique of rastering the ion beam across the full-energy dump was examined as a means of reducing the power density. By unbalancing the currents in the two coils of the magnet, on a shot-by-shot basis, by up to a 2:1 ratio, it was possible to move the centerline of the full-energy ion beam sideways by ∼12.5 cm. The adoption of such a technique, with a ramp of the coil imbalance from 2:1 to 1:2 over a beam pulse, could reduce the full-energy ion dump power density by a factor of ≳1.5.
Thermal expansion tensor measurement by speckle interferometry
Authors: Gascón F. , Salazar F.
Published: July 2002

Using a block of anisotropic material from the point of view of thermal expansion, six bars are cut in different spatial directions. A double-exposure photograph of speckle is taken of the six bars, one before and one after the temperature is increased. Only one double exposure is required for the six bars altogether. Illuminating two points of the double specklegram of each bar with a narrow laser beam and measuring the angle between the diffraction maxima, the longitudinal expansion is obtained for each bar and the thermal expansion tensor of the material is calculated.
Magnetic error field analysis by measurement of local rotational transform in a low aspect ratio torsatron
Authors: Hartwell Gregory J. , Gandy Rex F. , Hanson James D. , Knowlton Stephen F. , Owens Monte A.
Published: July 2002

In magnetic fusion toroidal confinement devices, the confining magnetic fields may have errors which produce magnetic islands. The standard method of investigating magnetic field errors involves measuring the maximum radial spatial extent of a given magnetic island at a fixed toroidal location and calling this measurement the island width. However, because of magnetic flux conservation inside an island, the spatial width of the island is not toroidally invariant. Magnetic error fields and their associated islands have been investigated in the Compact Auburn Torsatron through the measurement of the local rotational transform about the fixed points of the island. This method of magnetic field error investigation is valid at any poloidal or toroidal angle because the local rotational transform is spatially invariant. The technique of measuring the local rotational transform is described and the results are compared to those obtained using standard methods of measuring island widths.
A novel medium-energy ion emitter for active spacecraft potential control
Authors: Schmidt R. , Arends H. , Pedersen A. , Fehringer M. , Rüdenauer F. , Steiger W. , Narheim B. T. , Svenes R. , Kvernsveen K. , Tsuruda K. , Hayakawa H. , Nakamura M. , Riedler W. , Torkar K.
Published: July 2002

An ion emission instrument has been developed to actively control the electrostatic surface potential of a spacecraft in orbit. Spacecraft surfaces tend to charge positive when their conductive surfaces are partially sunlit, and photoelectrons emitted, and the spacecraft is positioned outside of the very dense plasma region which is referred to as plasmasphere. A small, lightweight instrument with a lifetime of more than 104 h at a nominal emission current of 10 μA was the design goal. The ion emitter is based on the liquid metal ion source principle; a constant stream of liquified indium is evaporated from the tip of a needle and ionized; the ions are then extracted by a strong electric field. The size of the instrument is about 18 by 15 by 23 cm (length×width×height) and the entire instrument weighs about 1.9 kg and consumes 2.4 W of electrical power in the nominal emission mode. An instrument of this type is already operational on the Japanese Geotail spacecraft, while five more instruments are at the stage of flight model assembly for integration on the Russian Interball satellite and the ESA/NASA four-spacecraft Cluster mission. The Geotail instrument is functioning as expected. Preliminary results show that the ion emitter is able to reduce surface potentials of +70 V (highest value observed up to now) down to 2–4 V.
The systematic uncertainty of the heat of hydration of cement
Authors: Gascón F. , Varadé A.
Published: July 2002

A theoretic calculation of the systematic uncertainty of the heat of hydration of cement using the Langavant calorimeter is made. The significant causes of error obtained when following the methodology described by the French Standard NF P15-436-88 and the Spanish Standard UNE 80-118-86 are analyzed. Simple modifications to the said Standards are suggested which would lead to a 70% reduction in the systematic uncertainty of the measurement.
Performance and limitations of laser diodes stabilized to the sides of molecular absorption lines of ammonia
Authors: Bertinetto Fabrizio , Bonanni Paola , Gambini Piero , Puleo Mario , Vezzoni Emilio
Published: July 2002

Performance and limitations of laser frequency stabilization based on the locking to the side of an absorption line are discussed: experimental results of spectroscopic measurements and of the stabilization of 1543-nm DFB laser diodes to ammonia absorption lines are presented.
Apparatus for minority-carrier lifetime measurements on light-emitting devices
Authors: Kot Miroslav
Published: July 2002

The experimental setup has been designed that allows measurements of the minority-carrier lifetime versus drive current in InGaAsP/InP LEDs. The small-signal technique has been used to obtain the lifetime data and a special averaging system has been built for measurements at very low injection levels. The measurement system is controlled by an IBM personal computer and supporting software packages have also been designed.
Vessels for preparing and delivering gaseous solutions
Authors: Keeley Dean F. , Koon William K.
Published: July 2002

Two, inexpensive, easily constructed vessels are described which can be used to prepare and deliver measured volumes of parts per million concentrations of gaseous mixtures.
High-sensitivity magnetometry: An experimental null test of Ampère’s law
Authors: Gerber C. J. , Chernikov M. A. , Ott H. R.
Published: July 2002

A prototype low-frequency ac magnetometer with a sensitivity to circular magnetic induction of (9±5)×10−15 T √Hz is described. Using this device we confirm Ampère’s law at 1.24 K setting an upper limit for possible deviations expressed in terms of the photon mass: mγ≤(8.4±0.8)×10−48 kg.
Multizone, single tracer gas measurement system for ventilation research
Authors: Phillips Duncan A. , Bragg Gordon M. , Weckman Elizabeth J.
Published: July 2002

This paper introduces a high-speed, multizone, infrared absorption spectrometer for use in tracer gas ventilation experiments. This new instrument provides opportunities for experimental ventilation research that were hitherto not possible. In order to investigate ventilation phenomena with fine temporal resolution, instrumentation capable of high-speed tracer gas concentration measurements is required. The instrument presented here uses infrared absorption to measure concentrations of sulfur hexafluoride (SF6) which is seeded into the enclosure under study. The apparatus takes simultaneous, continuous concentration measurements from three sampling locations. Each air sample chamber has a flush time constant of 7 s based on a 16 ℓ/min sample flow rate. The accuracy of a relative concentration measurement is better than 1.0%, while absolute measurements are accurate to 5.0%. The resolution of the instrument is 0.06 ppmV of SF6. Results showing detection of high-speed ventilation phenomena and multipoint simultaneous sampling are presented, and sample calculations of ventilation parameters are included to illustrate the overall utility of the instrument.
An economical x-ray area detector based on an intensified CCD unit
Authors: Gao Tong , Li Yingjie , Rousseau Jean , Linliu Kung , Chu Benjamin
Published: July 2002

An economical charge-coupled device (CCD) based area detector for x-ray experiments was developed and assembled. Although low in cost, careful evaluation shows that this detector consisting of an optical fiber taper, an image intensifier, a relay lens, and a cooled CCD unit has good overall features and is comparable with other reported CCD based x-ray area detectors. The detector is suitable for small-angle x-ray scattering and wide-angle x-ray diffraction experiments employing either synchrotron or conventional x-ray sources. It also has several options which we could utilize under different experimental conditions. The test result, its limitations, and possible improvements are discussed.
Interferometry on diffuse surfaces in high-velocity measurements
Authors: Pronin A. , Gupta V.
Published: July 2002

An interferometer is presented which is capable of measuring the free-surface velocities and displacements of both specular and diffuse surfaces. The setup utilizes a previously used principle of producing a virtual image of one mirror at the same distance from the photodiode as the second mirror of the interferometer, albeit with considerable simplification. It is shown that use of a He–Ne laser of only 5-mW power can produce high contrast displacement fringes from surfaces of materials with nonuniform microstructure, including composites. Substrates of carbon–carbon composites and polycrystalline alumina with nonuniform microstructure on the scale of 5–10 μm, and with peak velocities up to 150 m/s were considered. An experimental strategy which allows one to covert the optical setup to either a velocity or a displacement interferometer is also discussed. It is further shown that use of a fast photodiode and a high-speed digitizer with a 5-ps rise time provides a time resolution of 0.2 ns for recording the displacement fringes, and allows measuring free surface velocities up to 800 m/s. This is demonstrated by measuring such transient surface velocities with rise times of 1 ns on a specular Si surface. In all the experiments reported here, the surface velocities were produced by the reflection of a stress wave, which in turn was generated on the back surface of the substrate, using a Nd:YAG laser pulse.
Measurement of the temperature coefficient of ratio transformers
Authors: Briggs Matthew E. , Gammon Robert W. , Shaumeyer J. N.
Published: July 2002

We have measured the temperature coefficient of the output of several ratio transformers at ratios near 0.500 000 using an ac bridge and a dual-phase, lock-in amplifier. The two orthogonal output components were each resolved to ±1 ppb of the bridge drive signal. The results for three commercial ratio transformers (an ESI DT72A, a Gertsch RT-1665u, and an Eaton PRT-10C) between 20 and 50 °C range from 0.5 to 100 ppb/K for the signal component in phase with the bridge drive, and from 4 to 300 ppb/K for the quadrature component.
Low-temperature intracavity photoacoustic spectrometer
Authors: Boraas Kirk , Reilly J. P.
Published: July 2002

A cryogenic photoacoustic cell has been developed for intracavity use in a tunable ring laser. Its design ensures uniform cooling of the gas sample and minimum loss to the laser cavity. Also implemented is a flexible microphone mounting system that reduces thermal stress during temperature changes.
Design and characterization of a shock wave generator using canalized electrical discharge: Application to lithotripsy
Authors: Bourlion Maurice , Dancer Paul , Lacoste François , Mestas Jean-Louis , Cathignol Dominique
Published: July 2002

During recent years, much work has focused on breaking urinary and biliary stones using extracorporeal shock wave devices. Up to now, in terms of fragmentation efficacy, the ‘‘electrohydraulic’’ principle is the gold standard. In an electrohydraulic shock wave generator, a plasma is created by a high-voltage electrical discharge between two underwater electrodes. This kind of shock wave generator has a significant drawback because of the large variations of pressure pulses. Moreover, the wear of the electrodes is considerable, leading to nonconstant electrical discharge conditions all along the treatment. A new method to canalize the plasma between the electrodes, using highly conductive liquid, was investigated. Based on this principle a new spark plug was designed. This paper deals with the description and the characterization of this new type of spark plug. The electrical and geometrical parameters are presented. Measurements of the focal point pressure amplitude, of the spatial pressure distribution using different voltage settings, are reported. The acoustic energy in the focal zone is computed. We show that using this principle, the wear of the electrodes has been tremendously reduced. A comparison of in vitro results with other shock wave technologies shows that this new spark plug represents a significant breakthrough in terms of stone fragmentation efficacy. This spark plug is not only useful in the medical field, but it should also be of great interest to laboratories.
A rheometer to measure the viscoelastic properties of polymer melts at ultrasonic frequencies
Authors: Thomas V. , Giacomin A. J. , Wolfenden A.
Published: July 2002

A rheometer which uses a piezoelectric ultrasonic composite oscillator has been developed to measure the viscoelastic properties, G′(ω) and G″(ω), of polymer melts at ultrasonic frequencies. The storage and loss moduli of an ethylene–tetrafluoroethylene copolymer melt were measured at six frequencies in the range 0.25×106–1.28×106 rad/s (between 40 and 200 kHz nominal frequency) and at a temperature of 280 °C. This ultrasonic instrument operates at strain amplitudes ranging from about 10−8 to 10−3 and is therefore ideally suited for linear viscoelastic property measurements.
A dual-scan piezo element for scanning probe microscopes
Authors: Porter T. L.
Published: July 2002

A simple method of achieving dual scan ranges with a single piezo element in scanning probe microscope instruments is described. Both high-resolution small-scan ranges and low-resolution large-scan areas are obtainable.
A photoacoustic spectrometer for measuring subgap absorption spectra of semiconductors
Authors: Zegadi A. , Slifkin M. A. , Tomlinson R. D.
Published: July 2002

In this paper we describe the design of a high resolution near-infrared photoacoustic spectrometer of the gas-microphone type intended to be used for measuring impurity absorption spectra of semiconductors. Particular attention has been paid to the design of the photoacoustic cell to find the most suitable one, and as a result, several cells differing in geometry and materials have been investigated. We present results for the PA amplitude dependence on the modulating frequency for carbon black powder and some widely used semiconductors. The sensitivity of the spectrometer and its effectiveness in resolving active defect states existing in the subgap absorption spectra of semiconductors are demonstrated in both optically opaque and transparent thick and thin samples.
Experimental demonstration of the use of a Fabry–Perot cavity as a mirror of variable reflectivity
Authors: Strain K. A. , Hough J.
Published: July 2002

The use of a spherical mirror Fabry–Perot cavity as a mirror of variable reflectivity for near monochromatic light is demonstrated herein. The results of an experimental test of two control systems for the variable mirror are presented. It is shown that the reflectivity of our mirror can be controllably varied over a wide range. This technique has application in laser interferometric gravitational-wave detection.
A precision, low-force balance and its application to atomic force microscope probe calibration
Authors: Smith S. T. , Howard L. P.
Published: July 2002

We present the design and evaluation of a novel precision balance consisting of a thin silica rod suspended on a beryllium copper spring flexure. At opposing ends of the rod are a capacitance sensor and a soleniod/magnet force actuator. When an external force is applied to the silica rod, the resultant deflection of the springs is detected and fed back through a servo controller and current amplifier to the force actuator, thus maintaining a null signal. Consequently, the coil current, which, for relatively small fields, can be considered proportional to its applied force, is monitored as the balance output. Three class I dead weight masses of 2, 5, and 100 mg were used for calibration with six less accurate weights used to verify the linearity of the balance to better than 1%. Using standard vibration isolation techniques and an inexpensive environmental chamber, the present design will measure loading forces up to 1 mN (100 mg) and it has a resolution of better than 70 nN Hz1/2 (7 μg Hz1/2). Presently measuring 40 mm in diameter and 40 mm height this compact design is constructed from low expansivity materials giving a thermal sensitivity of better than 0.03 μN K−1. Results from a calibration of an atomic force probe are also presented and discussed.
Large volume radio-frequency plasma source using a magnetic line-cusp field
Authors: Yabe Eiji , Takahashi Keiji , Takayama Kazuo
Published: July 2002

A large volume cylindrical radio frequency (rf)-plasma source with a magnetic line-cusp field has been developed for large scale plasma processing. In this type of plasma source, a capacity-coupled 13.56 MHz rf plasma is produced in the presence of a magnetic line-cusp field. Two versions of the plasma source have been made and tested. The first version has peripheral rf electrodes placed on the outside of the ionization chamber, and is suitable for preparing a large volume uniform plasma. This plasma source can attain a useful area of uniform plasma over a 30-cm-diam region within 10% nonuniformity. The second version is featured by parallel doughnut-plate electrodes which forms part of the chamber wall and serves as a high current source. The electron density in such a version is proportional to the rf power, being equal to 4×1010 cm−3 at 400 W. The measured electron energy distribution function showed the Maxwellian-like distribution from a drift motion in the magnetic line-cusp field.
Selection and design of ion sources for use at the Holifield Radioactive Ion Beam Facility (abstract)a)
Authors: Alton G. D. , Haynes D. L. , Mills G. D. , Olsen D. K.
Published: July 2002

The Holifield Radioactive Ion Beam Facility now under construction at the Oak Ridge National Laboratory will use the 25-MV tandem accelerator for the acceleration of radioactive ion beams to energies appropriate for research in nuclear physics; negative ion beams are, therefore, required for injection into the tandem accelerator. Because charge exchange is an efficient means for converting initially positive ion beams to negative ion beams, both positive and negative ion sources are viable options for use at the facility. The choice of the type of ion source will depend on the overall efficiency for generating the radioactive species of interest. Although direct-extraction negative ion sources are clearly desirable, the ion formation efficiencies are often too low for practical consideration; for this situation, positive ion sources, in combination with charge exchange, are the logical choice. The high-temperature version of the CERN-ISOLDE positive ion source has been selected and a modified version of the source designed and fabricated for initial use at the facility because of its low emittance, relatively high ionization efficiencies and species versatility, and because it has been engineered for remote installation, removal and servicing as required for safe handling in a high-radiation-level ISOL facility. The source will be primarily used to generate ion beams from elements with intermediate to low ionization potentials. Prototype plasma-sputter negative ion sources and negative surface-ionization sources are under design consideration for generating radioactive ion beams from high-electron-affinity elements. The design features of these sources and expected efficiencies and beam qualities (emittances) will be described in this report.
How to select the best condition for operating a positive ion source of molecular beam surface ionization type (abstract)a)
Authors: Kawano Hiroyuki , Ohgami Katsushi , Funato Kiyohiko , Nakamura Junji
Published: July 2002

In easily attainable high vacua (Pr≊20–0.2 μTorr), the efficiency (β+) for producing ions (M+) from diatomic molecules (MX) incident on a polycrystalline surface of W, Mo, or Re was measured as a function of surface temperature (T≊800–2300 K). Theoretical analysis of β+ elucidated the temperature dependence of the effective work function (φ+) for the ionization. Namely, (1) above ∼2000 K, each surface is kept virtually clean, having φ+≊5.2, 4.9, and 5.4 eV for W, Mo, and Re, respectively. (2) At ∼1400–1200 K, the range of which depends upon Pr, φ+ is increased up to ∼7 eV by adsorption of residual gas molecules (RGM), thereby yielding β+=1 for even Tl and the current density of ∼10 μA cm−2 for the flux of 1014 molecules cm−2 s−1. (3) Below ∼1200 K, however, φ+ is much decreased by coadsorption of MX and RGM. A theoretical diagram of T vs φ+ is devised to predict the best condition for β+=1. The best condition (φ+, T, and Pr) to make β+ as large as possible may readily be selected according to the diagram and the present data on φ+.
Intensive cluster ion beam production by laser radiation impact on the anode of a vacuum diode
Authors: Kondrashev S. A.
Published: July 2002

Characteristics of the ion beam created when the CO2-laser radiation heats the anode of a vacuum diode are investigated. The diode with a carbon plate anode and a high-transparency grid cathode has been used. The gap and the applied voltage were equal to 5 cm and 40 kV accordingly. Laser power density on the anode was varied in the range of 107–108 W/cm2 by changing the focal spot size from 1 to 7 mm. It is shown that the specific regime without breakdown of the vacuum diode can be obtained by adjusting the laser power density and the focal-spot size on the anode. The ion beam with a total current of 100 mA and a pulse duration of 30 mks was obtained in such a regime. The number of carbon clusters C+2 and C+3 constitutes about 60% of the total number of ions in the beam, which is equal to 1013 per pulse. The maximum current density of the carbon cluster beam is equal to 3 mA/cm2, and the emittance of this beam is less than 10 cm mrad. On the basis of results obtained, a new method is proposed for production of intensive cluster and molecular ion beams with different elements and chemical compounds on the target.
Mevva ion source for the application of material surface modification
Authors: Zhang H. X. , Zhang X. J. , Zhou F. S. , Li Q. , Liu F. H. , Han Z. E. , Lin W. L.
Published: July 2002

Several versions of Mevva ion sources have been developed in our institute since 1988. It operates in a pulsed mode with a pulse length of 1.2 ms and a repetition rate of up to 50 pps. A time-averaged beam current of 10 or 50 mA has been extracted at 30–80 kV from Mevva IIA-H and Mevva IIB, respectively. In order to develop surface modification of materials by ion implantation we have constructed three kinds of Mevva ion source implantation systems. High dose (3–5×1017 cm−2) implantation with Ti, Ce, Y, and Ti+C, etc. has been carried out for improving the lifetime of metal cutting tools, relay contacts, dies, and some sophisticated components.
Characterization of a Bernas ion source for multiply charged ion implantation
Authors: Walther S. R.
Published: July 2002

Due to concerns about energy purity and reduced beam current, the use of multiply charged ions to achieve higher effective ion energies with a fixed acceleration potential has not been common for implantation users in the semiconductor industry. Energy purity is compromised primarily by charge exchange in the implanter beamline, caused by neutral gas originating from the ion source extraction aperture. Beam current has been an issue, since traditional implanter ion sources, such as the Freeman source, produce very limited currents of multiply charged species. At low beam currents, the implanter is not economical to use, hence the lack of commercial use of multiply charged ion implantation. Ion sources that address these issues must also meet requirements for adequate source lifetime, simplicity of operation (for computer control) and maintenance, and low cost of ownership. This paper details beam energy purity and usable beam currents for a new medium current Bernas ion source as compared to a standard Freeman ion source. The results show significant performance improvements, while also increasing the ion source lifetime.
H− beam based projection microlithography: A conceptual study of the beam parameters (abstract)a)
Authors: Guharay S. K. , Reiser M. , Dudnikov V. G.
Published: July 2002

The current trends of research and development work in ion-beam microlithography are examined with particular emphasis on the choice of ion sources and the beam parameters. The common approach with duoplasmatron-type ion sources for projection ion-beam lithography is revisited, and the suitability of H− beams is examined. The beam brightness and energy spread, which constitute the figure of merit of a beam, appear to be better in the case of H− beams. From a surface plasma source type discharge operating under stable condition, H− beams with an emission current density of ∼1–5 A/cm2 and a normalized brightness of ∼7×1012 A/(m rad)2 can be extracted. Several key issues of an ion-projection lithography device, such as the ion source parameters, beam optics, and thermal load are discussed.
Discharge characteristics of a 5 cm multipolar electron cyclotron resonance ion source (abstract)a)
Authors: Srivastava A. K. , Sze F. C. , Asmussen J.
Published: July 2002

A compact 5-cm-diam multipolar electron cyclotron resonance (ECR) ion source is characterized. The source is experimentally studied with no grids using argon gas with 50–250 W of 2.45-GHz microwave input power. Using a microcoaxial probe it was confirmed that the exciting electromagnetic fields within the resonant cavity were indeed TE111, as expected from the critical cavity dimensions. Double Langmuir probe measurements indicate high densities of about (4–5)×1011/cm3 near the source, and 5 cm downstream from the source output the densities become very uniform with a value of about 5×1010/cm3 over a 10-cm diameter. Electron energy distribution functions (EEDFs) were measured using a single Langmuir probe. Average electron energies were seen to be about 8–10 eV with an energy distribution function falling between a Maxwellian and a Druyvesteyn distribution. Ion energy distribution functions (IEDF) were measured with a multigrid energy analyzer. It was seen that the distribution functions were narrow and peaked [with a full width half maximum (FWHM) of about 5 eV] except under certain conditions. Above 200-W input power, and also below about 0.5 mTorr there is significant broadening of the ion distribution function. It is speculated that the former may be caused by gas heating, and the latter may be caused by the presence of Ar+2 ions. With its high current densities (≳10 mA/cm2) and low average ion energies (<40 eV), it is expected that this ion/plasma source will be very useful in many etching and deposition applications.
Internal H− ion source for cyclotrons
Authors: Glazov A. , Novikov D. , Vasiliev N.
Published: July 2002

The results of experimental studies of the ion source with a cold hollow cathode for production of H− ions are presented. The cavity parameters for effective hollow cathode operation in the PIG-type of discharge have been found and a H−-ion current up to 2 mA at a small gas flow rate has been obtained. The ion source can be used as an internal ion source in cyclotrons.
State of the art of radio-frequency ion sources for space propulsion (abstract)a)
Authors: Groh K. H. , Loeb H. W.
Published: July 2002

After 30 years of research, development, and qualification work of radio-frequency ion thrusters (RIT), the RIT 10 engine has now been tested successfully in space onboard the European Retrievable Carrier (EURECA). RIT 10 produces a thrust of 10 mN and is designed for north–south stationkeeping of geosynchronous satellites. Besides, the European Space Agency (ESA/ESTEC) plans to implement ion propulsion in their technological satellite ARTEMIS, where ion thrusters shall be used operationally for north–south stationkeeping. In parallel, development and tests of a scaled-up 50 mN engine RIT 15 have been continued successfully with xenon and krypton as propellants. A large ion engine with a 35 cm ionizer diameter, the RIT 35, has been developed for primary propulsion of interplanetary probes aiming at a thrust level in the 250 mN range. A laboratory prototype has been subjected to extensive testing and performance mapping. Recently, this work has been continued in European cooperation due to a redirection of contracts. The ion source diameter has been reduced to 26 cm but the performance should be kept using a British high perveance grid at the German rf-ion source.
Influence on the extracted ion beam of gas added to the MEVVA discharge (abstract)a)
Authors: Spädtke P. , Emig H. , Wolf B. H. , Oks E.
Published: July 2002

The presence of background gas in the discharge chamber of the MEVVA source influences the extracted beam. A strong influence of the background gas pressure in the arc region on the total extracted beam current and on the charge state distribution of the metallic ions have been observed. Different gases have been investigated together with different cathode materials. Up to 90% of the total beam current can be gaseous ions, depending on the arc and gas injection conditions.
Development of MEVVA ion source
Authors: Biehe Sun , Shangbin Hu , Qin Chen , Yongqin Shui
Published: July 2002

Research results of the metal vapor vacuum arc (MEVVA) ion source are reported in this paper. As cathode materials, for example, Al, Ti, Fe, and Cu are used, respectively. A triggering pulse with a pulse height of 12 kV, pulse length of 90 μs, and repetition rate of 1–5 pulses/s is applied between the trigger electrode and the cathode. The pulse duration of the extracted ion beam is 800 μs. When the extraction voltage is 28 kV, the extracted beam current intensity for Al, Ti, Fe, and Cu is 255, 290, 240, and 300 mA, respectively.
A direct-current Penning surface-plasma source
Authors: Smith H. Vernon , Allison Paul , Geisik Carl , Schmitt David R. , Schneider J. David , Stelzer James E.
Published: July 2002

After developing a pulsed 8X source for H− beams, we are now testing a cooled, dc version. The design dc power density on the cathode surface is 900 W/cm2, much higher than achieved in any previously reported Penning surface-plasma source. The source is designed to accommodate dc arc power levels up to 30 kW by cooling the electrode surfaces with pressurized, hot water. After striking the arc using a 600-V pulser, a 350-V dc power supply is switched in to sustain the 100-V discharge. Now our tests are concentrating on arc pulse lengths ≤1 s. Ultimately, the discharge will be operated dc. The source is described and the initial arc test results are presented.
Comment on ‘‘A new powder diffraction method for linear detectors’’ [Rev. Sci. Instrum. 64, 2201 (1993)]
Authors: Beno M. A. , Knapp G. S.
Published: July 2002

In this comment, the authors acknowledge that at the time of publication of their article, they were not aware of the independence of discovery by Megtert et al.1,2 of the powder diffraction technique; hence they did not include Megtert et al.’s reference in their original article. (AIP)
Incorporation of a differential refractometer into a laser light-scattering spectrometer
Authors: Wu Chi , Xia Ke-Qing
Published: July 2002

A new differential refractometer, which mainly consists of a laser light source, a position-sensitive detector, and a temperature-controlled refractometer cuvette has recently been developed. In comparison with a conventional differential refractometer, it has a different optical design so that the effect of laser beam drift can be greatly reduced. In our design, a very small pinhole is illuminated by the laser light and the illuminated pinhole is imaged to the detector by a lens located in the middle between the detector and the pinhole in a 2f-2f configuration. The cuvette is placed just before the lens. The pinhole, the cuvette, the lens, and the detector are mounted on a small optical rail. The refractometer can be easily incorporated into any laser light-scattering spectrometer, in which the laser, the thermostat, and the computer are shared. This not only reduces the total cost (at least ten times cheaper than a commercial differential refractometer), but also enables us to measure the specific refractive index increment and the scattered light intensity under the identical experimental conditions, such as wavelength and temperature. This novel refractometer has a wide linear detection range (±0.035 RI units) with a resolution of 10−6 RI units, which is sufficient for determining the specific refractive index increment of most polymer solutions.
A microalignment system for high precision positioning of collimating pinholes
Authors: Fischer W. , Rando N. , Peacock A. , Venn R.
Published: July 2002

A complete micropositioning unit based on high precision, manually controlled X-Y-Z translators, related metrology system, and sighting microscope is described. It has been specifically developed for the alignment of collimating pinholes (5–10 μm diam) on cryogenic x-ray detectors, 10–50 μm in size, deposited both on transparent and opaque substrates. The main characteristics of this flexible and convenient system are the capability to handle a complete test fixture ready for further measurements at cryogenic temperature, coupled with the possibility to verify the precision attained. Such microalignment equipment will find application in optical/UV/x-ray photon counting experiments, whenever a highly collimated illumination is required or in any test involving precision positioning of small experimental units onto microdevices or detectors.
Inert gas purgebox for Fourier transform ion cyclotron resonance mass spectrometry of air-sensitive solids
Authors: May Michael A. , Marshall Alan G.
Published: July 2002

A sealed rigid ‘‘purgebox’’ makes it possible to load air- and/or moisture-sensitive solids into the solids probe inlet of a Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometer. A pelletized sample is transferred (in a sealed canister) from a commercial drybox to a Lucite(R) purgebox. After the box is purged with inert gas, an attached glove manipulator is used to transfer the sample from the canister to the solids probe of the mass spectrometer. Once sealed inside the inlet, the sample is pre-evacuated and then passed into the high vacuum region of the instrument at ∼10−7 Torr. The purgebox is transparent, portable, and readily assembled/disassembled. Laser desorption FT/ICR mass spectra of the air- and moisture-sensitive solids, NbCl5. NbCl2(C5H5)2, and Zr(CH3)2(C5H5)2 are obtained without significant oxidation. The residual water vapor concentration inside the purgebox was measured as 100±20 ppm after a 90-min purge with dry nitrogen gas. High-resolution laser desorption/ionization mass spectrometry of air-sensitive solids becomes feasible with the present purgebox interface. With minor modification of the purgebox geometry, the present method could be adapted to any mass spectrometer equipped with a solid sample inlet.
The adverse effect of perpendicular ion drift flow on cylindrical triple probe electron temperature measurements
Authors: Tilley D. L. , Gallimore A. D. , Kelly A. J. , Jahn R. G.
Published: July 2002

The cylindrical triple probe method is an attractive technique for measuring electron temperatures (Te) and electron number densities (ne) in a variety of plasmas sources. In practice, however, the cylindrical triple probe can be sensitive to sources of error that affect all Langmuir probe techniques. In particular, the presence of an ion drift velocity component that is perpendicular to the probe axis has been known to result in erroneous measurements of ne. Less obvious, however, is that ion flow perpendicular to the probe has a significant effect on the indicated Te. The purpose of this note is to make researchers aware of such an effect and to demonstrate a technique which can mitigate it. The approach taken to investigate this phenomenon was to make Te measurements in the plume of a 20 kW magnetoplasmadynamic thruster with the probe oriented at several angles with respect to the local ion flow.
The plasma-emitter type ion source
Authors: Lobanov Nikolai R.
Published: July 2002

The model HOLCROSS ion source is designed for the production of high-current and brightness ion beams for application in ion implantation and particle accelerator injection. This ion source has been designed to deliver an ion beam up to a maximum of 30 mA at an energy of 30 keV and will serve as an injector to a radio frequency accelerator. This ion source is equipped with an additional cross-type hollow cathode system placed between the auxiliary plasma generator and the extractor. A negative voltage is applied to the cathode so that dependent low pressure gas discharge (DGD) is observed. High homogeneity and emission density of the plasma (50 mA/cm2) in the extraction region and multiaperture extraction are advantages of this version. The voltage of the DGD has the value 300–1200 V depending on the auxiliary discharge current so the plasma chemical reactions in the extraction region may be controlled. A description of the source is given, together with some recent results.
Single shot charge analyzer for laser-produced plasma studies
Authors: Tsui Y. Y. , Fedosejevs R. , Offenberger A. A.
Published: July 2002

The theory and design of a single shot charge analyzer is described which is capable of separating a multispecies ion beam from an instantaneous point source of plasma, such as laser-produced plasma, into several single species ion beams. A time-dependent deflection in planar geometry is employed which continuously steers each ion beam into a separate Faraday cup. Two important processes, space charge spreading of the ion beams and charge exchange with background gas in the chamber, that may alter the performance of the analyzer, are studied in detail. The charge state distribution of a laser-produced plasma obtained by this device is compared to that obtained by a 45° electrostatic analyzer using multiple laser shots.
Method for evaluating sharpness of tip apex of a cantilever for the atomic force microscope
Authors: Umehara Y. , Ogiso Y. , Chihara K. , Mukasa K. , Russell P. E.
Published: July 2002

A chemically textured alumite disk with micropillar posts on its surface is found to be a good standard sample to evaluate sharpness of atomic force microscope tips in the range of a few to a few tens of nm. The tips evaluated were silicon nitride cantilever with a normal pyramidal tip, one with a carbon microtip deposited by the electron beam method and one with a microtip formed by the focused ion beam method (FIB tip). The FIB tip has a fairly sharp tip apex so it can show very fine ridges around micropillars precisely.
Comments on ‘‘On the photothermal method applied to low thermal diffusivity measurements’’ [Rev. Sci. Instrum. 64, 1576 (1993)]
Authors: Salazar A. , Sánchez-Lavega A.
Published: July 2002

It is shown theoretically and experimentally that the method recently proposed by Bertolloti et al. to measure low thermal diffusivity samples presents errors of the same order as other ‘‘mirage’’ photothermal techniques previously proposed.
Reply to ‘‘Comments on ‘The photothermal method applied to low thermal diffusivity measurements’ ’’ [Rev. Sci. Instrum. 66, 275 (1995)]
Authors: Bertolotti M. , Li Voti R. , Liakhou G. , Sibilia C.
Published: July 2002

An analysis of the thermal diffusivity data for a low diffusivity material is presented, showing that suitable experimental conditions must be carefully chosen to minimize the error in the measurements through the photodeflection method.
Laser and plasma diagnostics for the OMEGA Upgrade Laser System (invited) (abstract)a)
Authors: Letzring S. A.
Published: July 2002

The upgraded OMEGA laser system will be capable of delivering up to 30 kJ of 351-nm laser light with various temporal pulse shapes onto a variety of targets for both ICF and basic plasma physics experiments. ICF experiments will cover a wide parameter space up to near-ignition conditions, and basic interaction and plasma physics experiments will cover previously unattainable parameter spaces. The laser system is the tool with which the experiments are performed; the diagnostics, both of the laser system and the interaction between the laser and the target, form the heart of the experiment. A new suite of diagnostics is now being designed and constructed. Most of these are based on diagnostics previously fielded on the OMEGA laser system very successfully over the last ten years, but there are some new diagnostics, both for the laser and the interaction experiments, which have had to be invented. Laser system diagnostics include high-energy, full-beam calorimetry for all of the 60 beams of the upgrade; a novel, multispectral energy-measuring system for assessing the tuning of the frequency-multiplying crystals; a beam-balance diagnostic that forms the heart of the energy-balance system; and a peak power diagnostic that forms the heart of the power-balance system. Target diagnostics will include the usual time-integrated x-ray imaging systems, both pinhole cameras and x-ray microscopes; x-ray spectrometers, both imaging and spatially integrating; plamsa calorimeters, including x-ray calorimetry; and time-resolved x-ray diagnostics, both nonimaging and imaging in one and two dimensions. Neutron diagnostics will include several measurements of total yield, secondary, and possibly tertiary yield and neutron spectroscopy with several time-of-flight spectrometers. Other measurements will include ‘‘knock-on’’ particle measurements and neutron activation of shell materials as a diagnostic of compressed fuel and shell density.
High pressure cell for solid 3He using Stycast 1264
Authors: Tsujii H. , Ikeya A. , Nozawa M. , Inoue S. , Mamiya T.
Published: July 2002

The nonmetallic susceptibility cell using Stycast 1264 is described. It withstood pressure up to 25 MPa at low temperature. The tensile strength of Stycast 1264 at room temperature was measured to be 56.0 MPa.
Nanosecond spark calibrator for Thomson scattering system
Authors: Kishinevsky M. , Wukitch S.
Published: July 2002

A nanosecond spark system has been built for spectral calibration of a Thomson scattering system based on a ruby laser–MCP detector system. The fast calibration source has the advantage that its pulse duration and signal amplitude are similar to the signal collected in the electron temperature measurements. In the spark system, the duration of the light pulse (30 ns) is determined by the shock-wave expansion of the spark plasma. The light source is very bright due to the high plasma pressure prior to expansion. The calibrator uses an auxiliary spark for preionization to achieve good reproducibility and low jitter.