bluuebunny/crossref_metadata_2025 huggingface dataset:
Device for assessing the fracture toughness of giant magnetostrictive materials
Authors: Cunningham J. , Hyatt C. V. , KarrisAllen K. J.
Published: July 2002

A device for mode II fracture testing of giant magnetostrictive materials has been developed. With this device, the driving force for crack initiation can be generated from applied stress, applied magnetic field, or a combination of both. Stresses and magnetic fields of up to 320 MPa and 57 kA/m, respectively, have been applied with the device.
Theoretical analysis of optimal conditions in quantum structure semiconductor lasers for low threshold current
Authors: Nambu Yoshihiro , Asakawa Kiyoshi
Published: July 2002

Optimal conditions for reducing threshold current are investigated for quantum structure (QS) semiconductor lasers. The filling factor of whole QSs to an active region is introduced. A general procedure is presented for obtaining the relation between the threshold current and filling factor from the relation of gain to injected carrier density of the individual QS. It is shown that there is a filling factor that minimizes the threshold current. From this value, the optimal areal coverage is shown to be about 0.1 for a quantum box and 0.8 for a quantum wire for an ordinary surface emitting laser with a single In0.53Ga0.47As/InP. The effects of various imperfections in actual QSs are also discussed.
High-pressure equilibrium cell for solubility measurements in supercritical fluids
Authors: Hansen Brian N. , Lagalante Anthony F. , Sievers Robert E. , Bruno Thomas J.
Published: July 2002

This paper describes the design, construction, and operation of an ultraviolet-visible light-transmission cell for high-pressure fluids. The cell can be operated at pressures as high as 70 MPa and at temperatures up to 100 °C. This instrument was specifically designed to measure the solubility of solutes in supercritical fluids. The cell has an internal saturator and fluid circulator that are easy to remove and clean. The solubility of ferrocene in supercritical carbon dioxide was measured in the high-pressure cell described here. At 40 °C, the mole fraction of ferrocene in carbon dioxide increased from 0.00005 to 0.0015 as the solvent density was increased from 5 to 17 mol/L.
Penumbral imaging made easy
Authors: Barnea Gideon
Published: July 2002

A new and most direct method of penumbral imaging is presented. It is shown that for square (or polygonal) apertures, the source distribution is given by the second-order mixed Cartesian derivative of the penumbral image intensity distribution. Use of this approach is illustrated by computer simulation. Two different source sizes (3.2 mm and 10 μm) of high-energy gamma sources were reconstructed. The effect of noise in the recording system is studied and a simple noise reduction technique is shown to be quite effective.
Further measurements of the temperature dependence of the voltage response of piezoelectric tube scanner PZT-5A for use in scanning tunneling microscopes
Authors: Vandervoort K. G. , Zasadzinski R. K. , Galicia G. G. , Crabtree G. W.
Published: July 2002

We report further measurements of the temperature dependence of the piezotube coefficient for material PZT-5A. These new results support our earlier findings that the temperature dependence of the piezoresponse is linear to within 10% and is reduced by a factor of 5.5 on decreasing temperature from 300 to 4.2 K. Our new data imply that the piezocoefficient temperature dependence is reproducible for tubes of various sizes, even when the room temperature coefficients differ by more than 20% from their published values.
Silicon surface tunnel transistor
Authors: Reddick William M. , Amaratunga Gehan A. J.
Published: July 2002

A silicon surface tunneling transistor structure, based on lateral band-to-band tunneling, is presented. The theory, fabrication, and operation of the device is described. Band-to-band tunneling is controlled by the bias on the gate of the device which modulates the width of the tunneling barrier. The operation of the device is confirmed in both experimental results and two-dimensional computer simulations. Dramatic differences in drain current are observed for different gate bias.
Wireless single-electron logic biased by alternating electric field
Authors: Korotkov Alexander N.
Published: July 2002

A new type of ultradense logic based on single-electron tunneling between conducting islands is proposed. The basic element is a short chain of islands which shows bistable polarization and affects the polarization of neighboring chains. The power needed for computation is delivered by ac external electric field.
A count-rate safety circuit for high-voltage single-particle detectors
Authors: Trantham K. W.
Published: July 2002

A common cause of single-particle detector failures is high input fluxes. A digital circuit designed to turn off the detector’s high voltage when this occurs is presented.
NMR probe for high pressure and high temperature
Authors: de Langen M. , Prins K. O.
Published: July 2002

A description is given of a probe which is designed for nuclear magnetic resonance (NMR) experiments at 180 MHz on samples at hydrostatic pressure up to 10 kbar. Temperature control has been designed to allow experiments from room temperature up to 600 K, regulated with an accuracy of 0.1 K. Radio frequency feedthroughs can sustain high-voltage pulses of considerable length. The probe has been used successfully in a proton spin relaxation study at 180 MHz of polyethylene near the melting line.
Characterization and in situ monitoring of a novel compact electron cyclotron resonance plasma source
Authors: O’Keeffe Patrick , O’Morain C. , Den S. , Hayashi Y. , Komuro S. , Morikawa T.
Published: July 2002

For plasma-assisted processing of future semiconductor devices, a new compact electron cyclotron resonance (ECR) plasma source has been specifically designed. The source is novel in that the magnets required for the production of ECR plasma are movable even in vacuum, and in situ monitoring of the discharge zone is also possible. Typical plasma characteristics were evaluated for nitrogen gas using Langmuir probe diagnostics and ion energy analysis. The measured plasma parameters include electron densities in excess of 1010 cm−3 and low ion energies (<30 eV) with narrow distributions, which can be easily controlled by varying the discharge pressure and downstream position. Moreover, changing the aperture size of the discharge cavity enables one to control the relative ratio of the ionic and atomic species in the plasma. In determining plasma stability, changes in plasma parameters after plasma start-up were investigated. The results show a correlation between changes in the plasma potential and the total plasma optical emission. In situ monitoring of the total plasma emission is suggested as a simple means of providing valuable information in real time about physical plasma parameter changes during processing.
Sub-Ångstrom resolution with a phonograph cartridge as bidimensional nanodisplacement sensor
Authors: Mariani Tullio , Frediani Carlo , Ascoli Cesare
Published: July 2002

A simple and reliable displacement sensor is proposed, which is able to detect axial and transverse displacement with a resolution of the order of 0.01 Å. It is based on an inexpensive device borrowed from old-style audio reproducers.
Compact, piezo-driven, vacuum compatible rotation device
Authors: van der Wulp H. , de With E. , Pistecky P. V. , Spronck J. W.
Published: July 2002

A new, vacuum compatible piezo-driven rotation device (piezo-rotor) based on inertial sliding has been developed. The piezo-rotor has one degree of freedom, nanoradial resolution, and unlimited range. As a result of the simple configuration and the use of piezo-actuators, the piezo-rotor is extremely compact. It is well suited for specimen rotation in the vacuum chamber of a transmission electron microscope because the piezos do not create a magnetic field. Although the piezo-rotor has been designed to work in a vacuum, it can be used in many other rotation and positioning applications. To test the performance of the piezo-rotor, a simple, easy-to-manufacture setup was used, whose dimensions are larger than we wanted in our application. Nevertheless, scaling laws show that further miniaturization will not affect the working of the piezo-rotor, so it can be used as an alternative in some volume-critical applications. The tested configuration has a maximum rotation speed on the order of 1 rad/s at drive frequencies of some kHz. Torques on the order of 10−3 Nm have been measured. The positioning resolution depends on the drive electronics, the quality of the bearing surfaces, and the rotor dimensions. Theoretically, the highest angular resolution is 1 nrad. The spindle speed or torque can be optimized by studying the friction process, the application of special coatings, the variation of the wave form frequency, its amplitude, and the axial preload. The piezo-rotor has been shown to be reliable and robust.
Scaling up the colliding shock lens
Authors: Kuppen M. , Michaelis M. M. , Buccellato R. , Lisi N.
Published: July 2002

In this paper we characterize the behavior of a new pulsed gas lens, the colliding shock lens. We show how input energy, electrical diameter, number of discharge electrodes, and enclosing the discharges, affect its optical aperture and focal length. Experimental results are presented for three different lenses and for a 1 cm aperture lens with a focal length of 1.5 m. We derive a simple colliding shock lens scaling law.
Phase discrimination in void fraction measurements via genetic algorithms
Authors: Žun I. , Filipič B. , Perpar M. , Bombač A.
Published: July 2002

The paper deals with the difficulties of reconstructing a hydrodynamic structural function from a time-dependent raw signal produced by a sensor. In the presence of two fluid phases, the deformation of a phase interface at a sensor leads to a lag between the occurrence and the detection of the event, and the probe response characteristics may be altered with time for several reasons. A new phase discrimination technique is presented based on man–machine interaction and utilizing genetic optimization. To discriminate the phases, two-point threshold discrimination is proposed at first. In addition, a man–machine method is introduced which can mimic a human expert observation of a raw signal and his intuitive discrimination procedure. Finally, genetic algorithms are used to search for those threshold settings that produce solutions closest to those defined by an expert. The proposed new method is capable of adaptation to specific flow conditions.
An automated recording system for page oriented volume holographic memories
Authors: Sharp James H. , Budgett David M. , Tang Pei C. , Chatwin Chris R.
Published: July 2002

A system for the automatic acquisition and recording of images from video input scenes to a volume holographic optical memory has been designed and constructed. This memory is intended for use as a template database for reference images for an optical correlator. The system has been tested and commissioned; initial results indicate that system parameters such as hologram reconstruction quality are of a sufficiently high standard for the application.
Frequency stabilization and control of a mode-locked dye laser
Authors: Krüger E.
Published: July 2002

The mode comb of a synchronously pumped mode-locked dye laser is stabilized in frequency by locking one of its modes to a transmission maximum of a reference Fabry–Perot interferometer. The frequency error signal, obtained by a conventional modulation–demodulation technique, is fed back to permanently readjust the cavity length of the laser via an integrating servo amplifier and a piezo-positioned end mirror. Insertion of an appropriate loop filter prevents loop oscillations on the dominant mechanical resonance of the transducer–mirror combination. A special ramp automatic reset function is introduced to avoid saturation of the servo amplifier. To verify the improvement in laser stability the emission spectrum was scanned with a high-resolution optical spectrum analyzer. A laser linewidth of 3 MHz has been achieved. Extended linear sweeps of the stabilized mode comb for spectroscopic measurements were realized by simultaneously tuning the reference cavity and tilting the intracavity etalon.
A simple optical fiber axial speed detector
Authors: Serban A. , Lee S.
Published: July 2002

An optical fiber detector is developed to measure simply and accurately the axial speed of the plasma sheath in a plasma focus device. Using a suitable model, self-consistent information on the distribution of ionized mass and current inside the structure of the plasma sheath may also be inferred. The thickness of the sheath is also obtained.
Two dimensional fiber-optical accelerometer
Authors: Dinev Petko D.
Published: July 2002

A new type of simple and reliable two-dimensional fiber-optical accelerometer is developed to measure constant (dc) and variable (ac) accelerations simultaneously in two perpendicular directions (vector acceleration) with a linearity error of less than 0.1%. The sensor is based on a deflection of a uniform round elastic cantilever beam sensed by an optical lever and a continuous position optical sensor. The accelerometer has a resolution of 0.3 m s−2, dynamic range of 62 dB, −48 dB crosstalk and a natural frequency ω=1970 rad s−2 , when accelerations of up to 400 m s−2 are measured. The compact shielded construction, high responsivity photosensor and high power photodiode make the proposed sensor stable in the environment of strong electromagnetic interference. Varying the sensor’s parameters, the proposed sensor can be designed to have almost any desired response and sensitivity, and natural frequency.
Description and performance of a highly versatile, low-cost fiber-optic confocal Raman microscope
Authors: Stellman C. M. , Booksh K. S. , Reddic J. E. , Myrick M. L.
Published: July 2002

A versatile fiber-optic confocal Raman microscope has been developed. Fiber optics provide remote capabilities for the microscope and the ability to use multiple excitation sources and detection schemes. The horizontal and vertical resolutions of the instrument have been determined by monitoring spectral changes while scanning known interfaces and microparticles. The mini- mum detectable particle size has been determined via the spectroscopic analysis of calibrated polystyrene microspheres. The horizontal resolution has additionally been tested in the imaging of a 10 μm glass fiber embedded in an epoxy matrix.
High-temperature high-pressure oscillating tube densimeter
Authors: Chang R. F. , Moldover M. R.
Published: July 2002

We describe an oscillating tube densimeter for use at temperatures up to at least 575 K and at pressures up to 20 MPa. After the densimeter was calibrated under vacuum and filled with water, it was used to measure the density of toluene from 298 to 575 K at 13.8 MPa. The results agree (0.1% rms deviation) with those obtained using other techniques. In the present densimeter, an alternating current is passed through the tube containing the sample to force the tube to oscillate in the field of a permanent magnet. This design avoids the use of electromagnets (with their attendant polymer or ceramic insulations) and does not require attachment of appendages to the oscillating tube. This densimeter oscillates in an overtone rather than in its fundamental mode, thereby achieving improved isolation from environmental noise and a shorter response time. The densimeter is small, weighing 370 g. If transformers are used to couple electrical signals to the oscillating tube, the densimeter itself may be constructed entirely out of metal.
A continuous wave method for simultaneous sound velocity and attenuation measurements
Authors: Jin C.
Published: July 2002

We describe a cw method for simultaneous ultrasonic phase velocity and attenuation measurements. This method uses a phase locked loop technique to lock the carrier frequency of a frequency modulated drive to the center of the mechanical resonance of the composite oscillator consisting of the sample and the transducers. At the same time, by measuring the rf amplitude modulation index at twice the modulation frequency, the change in the resonator Q factor, and therefore the attenuation, can also be measured. We have applied this method to measure the sound velocity and attenuation of a heavy fermion superconductor UPt3 down to 5 mK. With only 5 nW of rf excitation, we could detect changes in the phase velocity as small as Δv/v∼5×10−9.
Measuring the regression of a burning solid propellant
Authors: Frederick Robert A.
Published: July 2002

A new instrument is presented that measures the regression of a burning solid propellant surface. The system extracted the diffuse reflection of a laser beam from the burning surface using synchronous detection. The incoming beam had a 4000 Hz angular modulation that served as the basis of a synchronous detection scheme. A galvanometer kept the beam spot centered under a sensor as the burn surface regressed. Theoretical analysis of the system using the component response properties resulted in the design of a controller for optimal bandwidth and stability. Laboratory evaluation on diffuse surfaces revealed a system bandwidth of 200 Hz, a range of 50 mm, and a resolution of 0.03 mm. Experiments conducted on burning propellants showed that the instrument successfully tracked the position of the surface at combustion pressures up to 17 atm. Under these conditions, the combustion environment reduced the beam transmission by up to 24 dB. This lowered the system bandwidth to 20 Hz and the resolution to 0.08 mm. The instrument demonstrated the first tracking of a local area on a burning propellant with a laser device.
Microcomputer based instrument for measuring a novel pulmonary function test
Authors: Craine Brian L. , Craine Eric R.
Published: July 2002

The design of a prototype instrument for measuring the end-tidal concentration of carbon monoxide during human respiration is presented. The instrument automatically samples the final sixty cubic centimeters of exhaled breath, from successive breathing cycles, by coordinating a pump and the breathing cycle with a set of vacuum and pressure sensors. The concentration of carbon monoxide is measured using a nondispersive infrared spectrophotometer. The amount of carbon monoxide present is measured relative to the source air concentration eliminating the need for calibrating the instrument. The testing protocol and measurements can be controlled by a microcomputer connected to the instrument through a standard RS-232 serial interface. When at equilibrium, the end-tidal concentration of CO can be measured in a simple and reproducible fashion. This simplified technology allows for the construction of a small, portable, easy to use instrument that will allow the application of this new pulmonary function test at the point of contact with patients.
A wavelength detector for monochromatic light beams
Authors: Ngo Phong L. , Shih I.
Published: July 2002

Wavelength detection of monochromatic light beams can be achieved with a pair of optical sensors located behind a linear variable filter. The active area of one sensor increases, whereas that of the other sensor decreases along the direction of increasing value of transmission wavelength of the filter. By computing the ratio of the photoresponse of one sensor to the other, the wavelength can be obtained from a calibration chart. Proof-of-concept wavelength detectors were constructed using photoresistive superconductor sensors. Results obtained for the spectral range of 700–1100 nm are presented and discussed.
Long-term stabilization of the frequency and power of a laser diode
Authors: Lee Ho Seong , Yang Sung Hoon
Published: July 2002

We report a method to stabilize the frequency of a laser diode for a long time by means of four feedback loops including a digital feedback circuit. The laser frequency was locked at a saturated absorption peak of cesium atoms. In addition, by feeding back the frequency error signal to the temperature controller of the laser diode, the power as well as the frequency was stabilized at the same time. The power stability of 0.03% was obtained, which was 260 times better than that obtained without the feedback. The frequency stabilization continued for over 1 week and the fluctuation width was about ±0.5 MHz around the locking point.
Scintillating fiber hodoscope for a bremsstrahlung luminosity monitor at an electron–positron collider
Authors: Brown D. H. , Orlov D. H. , Varner G. S. , Worstell W. A. , Redin S. I.
Published: July 2002

The performance of a scintillating fiber (2 mm diameter) position sensitive detector (4.8×4.8 cm2 active area) for the single bremsstrahlung luminosity monitor at the VEPP-2M electron-positron collider in Novosibirsk, Russia is described. Custom electronics is triggered by coincident hits in the Y and Y planes of 24 fibers each, and reduces 64 photomultiplier signals to a 10-bit (X,Y) address. Hits are accumulated (10 kHz) in memory and display (few Hz) the VEPP-2M collision vertex. Fitting the strongly peaked distribution (∼3–4 mm at 1.6 m from the collision vertex of VEPP-2M) to the expected QED angular distribution yields a background in agreement with an independent determination of the VEPP-2M luminosity.
Combination high-sensitivity alternating current susceptometer and high-frequency B–H looper
Authors: Slade S. B. , Kassabian G. , Berkowitz A. E.
Published: July 2002

A combination high-sensitivity alternating current (ac) susceptometer and high-frequency B–H looper is described. Based on the well-known inductance technique, the design uses modern low-noise components and stable temperature control to achieve the high sensitivity. The mechanical assembly is designed for use inside a glass Dewar, enabling measurements to be made at any temperature between 4.2 and 300 K. Initial ac susceptibility can be measured over a frequency range of 10 Hz to 120 kHz with sensitivity of 1×10−8 emu, comparable to a superconducting quantum interference device (SQUID) magnetometer. B–H loops are measured at 2 kHz with a low duty cycle, damped oscillatory field pulse, and have sensitivity of 4×10−8 emu. The instrument can thus measure ac susceptibility at higher frequencies than ac-equipped SQUID magnetometers and commercially available inductive ac susceptometers, and can also measure B–H loops at much higher frequencies and with greater applied fields than steady-state loop tracers.
Cam-driven pulsed Laval nozzle with a large optical path length of 50 cm
Authors: Okada Yoshiki , Isomura Shohei , Satooka Sakae , Takeuchi Kazuo
Published: July 2002

This article describes the design and performance of a pulsed valve developed as a gas source for a 500-nm-long supersonic Laval nozzle with a 3-mm-wide throat. The valve consists of a plate cam and a valve seat equipped with O-rings on both the upper and lower faces. The duration of quasi-steady-state expansion is measured to be 12 ms at the nozzle throat when the pulsed valve is filled with Ar gas at 100 Torr.
Partial rejuvenation of Bayard–Alpert ionization gauge tubes
Authors: Siska P. E.
Published: July 2002

We describe a simple procedure for the partial restoration of Bayard–Alpert ionization gauge tubes that have been contaminated by a combination of mechanical and silicone diffusion pump oil vapors. The method consists in filling the tube with 1 M NaOH, immersing it in a hot water bath (>80 °C, ca. 1 h), thorough rinsing with deionized water and reagent acetone, and air drying. This procedure was tested on nine inoperable gauges; after restoration seven of the gauges read within a factor of 2 of a new gauge.
Electro-optic sampling of 1.5-ps photoresponse signal from YBa2Cu3O7−δ thin films
Authors: Hegmann F. A. , Jacobs-Perkins D. , Wang C.-C. , Moffat S. H. , Hughes R. A. , Preston J. S. , Currie M. , Fauchet P. M. , Hsiang T. Y. , Sobolewski Roman
Published: July 2002

Photoresponse signals with widths as short as 1.5 ps are observed from epitaxial YBa2Cu3O7−δ  thin films using electro-optic sampling techniques. Voltage transients less than 2 ps wide are seen in 100- and 200-nm films exposed to 150-fs laser pulses and cooled to 79 K. At low bias currents, the amplitude of the fast response varies linearly with the bias current, suggesting a kinetic inductive mechanism. A negative transient about 15-ps long is also seen that may provide evidence for nonequilibrium recombination of excited quasiparticles into Cooper pairs. At high bias currents or large laser fluences, a fast tail with a decay time of about 10 ps appears in the response followed by a slow, resistive bolometric component due to sample heating. Nonequilibrium aspects of the photoresponse and the origin of the fast tail are discussed.
New digital phase meter concept and its application
Authors: Lio H. P. , Young M. S.
Published: July 2002

A new concept for digital phase meters, which in practical embodiment provides most of the commonly desired performance features such as wide bandwidth, high resolution, high speed measurement, etc., is presented. This meter emulates a Vernier caliper and inherits its characteristics. Phase difference may be measured in any period of the measured signals. In the basic theory, two phase-locked-loop circuits are used as frequency multipliers which divide each period of the input signals into multiple equal time slots, thereby emulating the divisions of space inscribed on the scales of a caliper. A simple “pseudophase detector” made of a D-type flip–flop is used to compare the location of the time slots on both of the scales, just as we use the Vernier caliper. The new meter’s resolution remains very high at both very high input frequencies and output data rates and while maintaining a wide input bandwidth; a resolution of 100 at 10 MHz input and 10 MHz output is easily attainable with off-the-shelf components requiring no clock rate higher than 100 MHz. In addition to a discussion of the theory, experimental results of a test embodiment are presented. Using a 10 MHz clock, a rather crude test circuit could detect a delay time of 400 ns between an original and delayed 40 kHz signal, equivalent to a resolution of ∼65 000.
Superconducting contacts for use in niobium thin film applications
Authors: Garfield James R. B.
Published: July 2002

A simple method is described for forming superconducting contacts to niobium thin films, as used for current perpendicular to the plane measurements of the resistance of magnetic multilayers, using an indium–Roses alloy (Bi 50/Pb 28/Sn 22) solder alloy. This solder alloy has a critical magnetic field of approximately 1.2 T.
Measurement of the stationary thermal nonlinear refraction light wave-front distortions by image processing
Authors: Marcano O. A. , Escalona R.
Published: July 2002

The thermal stationary nonlinear refraction is determined with enhanced sensitivity by measuring the profile distortions of a cw probe light beam in the presence of absorption of a collinearly propagating pump light beam. By measuring the total profile distortion of the probe beam for different position of the sample cell, a signal similar to the well-known Z-scan signal is obtained. Using the Gaussian decomposition method a simple formula is deduced which relates the induced thermal phase shift to the magnitude of the observed signal. Phase shifts as low as λ/40000 with a signal-to-noise ratio of unity becomes detectable with this technique.
Study of large travel tube scanner for photon scanning tunneling microscopy and its investigation for soft materials
Authors: Du Sidan , Gao Duntang , Zhang Baoping , Han Tao , Wu Yunfei , Zhang Shuyi
Published: July 2002

The tube scanner is a key part of the photon scanning tunneling microscope (PSTM). The sensitivity, resolution, scanning range and the linearity of PSTM are quite relevant to the study of the tube scanner. In this article, a new experimental method to measure the deflection sensitivity of the PZT tube is reported. The tube travel range, its linearity, and the coupling between x or y and z direction are analyzed. The theoretical formula for the coupling effects are also derived. With careful design the tube scanner coupling can be neglected and the experimental results show that the linearity of the large travel tube is satisfactory. Some images of PSTM demonstrate convincingly the system performance. The imaging of Langmuir–Blodgett (LB) films and fish scale plates is a significant application of PSTM in the fields of organic materials and living specimens.
Measurement instrumentation for electrical transport experiments in extreme pulsed magnetic fields generated by flux compression
Authors: Kane B. E. , Dzurak A. S. , Facer G. R. , Clark R. G. , Starrett R. P. , Skougarevsky A. , Lumpkin N. E. , Brooks J. S. , Engel L. W. , Miura N. , Yokoi H. , Takamasu T. , Nakagawa H. , Goettee J. D. , Rickel D. G.
Published: July 2002

We describe purpose-built instrumentation that has proved successful in making transport measurements of materials in ultrahigh magnetic fields generated by explosive-driven flux compression. The experimental arrangement minimizes severe problems of heating and pick-up associated with the microsecond pulsed field, for which dB/dt can be as large as 109 T/s. Electrical connection to multiple samples in the high field region is via long, lithographically-defined, nested coplanar transmission lines. Contactless measurements by capacitive coupling, as well as resistively coupled measurements, are made at frequencies of order 1 GHz so that pick-up from the microsecond pulse can be effectively filtered. We demonstrate our technique with data on semiconductor samples taken to 450 T using Russian MC-1 type flux compression generators combined with U.S. explosives at the Ancho Canyon firing point, Los Alamos National Laboratory. We discuss the obstacles encountered during these experiments, and outline improvements and refinements of our technique that should enable transport measurements to be made in the highest obtainable magnetic fields (∼1000 T) in samples at temperatures not exceeding a few kelvin. This technology may also be valuable for transport measurements in nondestructive pulsed fields of millisecond duration, now available in many laboratories worldwide.
Large-field high-resolution x-ray microscope for studying laser plasmas
Authors: Sauneuf Richard , Dalmasso Jean-Michel , Jalinaud Thierry , Le Breton Jean-Pierre , Schirmann Daniel , Marioge Jean-Paul , Bridou Françoise , Tissot Gérard , Clotaire Jean-Yves
Published: July 2002

In 1948, P. Kirkpatrick and A. V. Baez developed an x-ray microscope (energy range about 100 eV–10 keV) composed of two concave spherical mirrors working at grazing incidence. That device, named KB microscope, presents a 3–5 μm resolution within a field having a radius about 100 μm; outside that field, its resolution lowers rapidly when the object point recedes from the center. The adjunction of two similar mirrors can notably increase the useful field (typically, the resolution can be better than 10 μm within a 2-mm-diam field of view), which is necessary for studying laser plasmas. Its main advantage with respect to more simple optics, as the pinhole, is that it can be located far enough from the plasma to avoid any destruction during the shot. We describe such a microscope that we call KBA microscope and present some images of fine metallic grids. Those grids were backlighted by x-ray sources, either a cw one or a series of laser plasmas from the Octal–Héliotrope facility. Examining the films in detail shows that the experimental results are very close to the theoretical characteristics; hence the interest of this device for the x-ray diagnostics on the future powerful laser facilities.
Beam current density distribution of a vacuum arc ion source
Authors: Nikolaev A. G. , Oks E. M. , Zhang Xiaoji , Cheng Cheng
Published: July 2002

The distribution of the beam current density for metal ion vacuum arc ion sources (MEVVA-type) lacks sufficient uniformity and its original form is similar to the Gaussian one. This is because of the plasma generation in a small space near the cathode spot. Further expansion of the plasma to the emission region does not improve this situation which poses a serious problem in creating a broad beam ion source. This article presents experimental results on the influence of various factors on the beam current density distribution. Experiments were carried out in Beijing with the MEVVA-IIA ion source. An additional magnetic field was applied to the arc gap and a small metal grid covering the emission electrode was used.
Recommissioning the deuterium negative ion source experiment ion source for studies in support of ignition device to test engineering concepts
Authors: McNeely P. , Boilson D. , Curran N. , Hopkins M. , Vender D.
Published: July 2002

As part of the international collaborative effort into fusion research, work has begun to recommission the deuterium negative ion source experiment (DENISE) at Dublin City University (DCU). Modifications to the original apparatus to allow easier access to both the ion source and the extraction region for diagnostic systems are nearing completion. A new source chamber that can be used with both the standard Langmuir probe, and a new laser photo-detachment probe, currently under construction, was installed. The source chamber can be operated in any one of three modes: filament driven, continuous wave (cw), radio frequency (rf) driven, or pulsed rf driven (up to 3 kW of 13.5 MHz rf at 250 Hz). A PC computer control system based on LabView™ is nearing completion and is intended for both system control and data logging. An investigation into the production and extraction of H− ions has begun. Langmuir probe measurements on a hydrogen plasma have yielded information on the plasma parameters for three radial probe positions over the pressure range 5–100 mTorr, and the rf power range 25–600 W cw. The article will present the current status of DENISE.
Exploration of the afterglow of the pulsed electron cyclotron resonance source under the injection of neutral fluxes
Authors: Mironov V. , Shirkov G. , Strekalovsky O. , Tokareva N.
Published: July 2002

The results of numerical simulation of highly charged ion production in the electron cyclotron resonance ion source (ECRIS) during the afterglow of the pulsed operation mode are presented in this article. The influence of the short neutral flux injected into the plasma on the parameters of afterglow is studied. It is shown that a pulse of neutral atoms reduces the duration and increases the amplitude of afterglow. The free expansion of laser ablation plasma was experimentally studied to find the ways for neutral flux production. A Q-switched YAG:Nd+3 laser of 60 mJ focused onto the surface of a Zn target was used for this purpose. A neutral density up to 1013 cm−3 at a distance of 5 cm from the target was obtained. The plasma pulse duration is 10 μs, the ionization degree in the flux is about 5%, and the velocity of neutrals is in the range of 106 cm/s. These parameters of the neutral flux are quite enough to test the afterglow enhancement as well as for the load of metal or solid elements into the ECRIS.
Measuring the instantaneous arrival times of a long series of consecutive photoevents
Authors: Stoyanov Dimitar V.
Published: July 2002

A novel technique for measuring the instantaneous arrival times of a long series of consecutive photoevents effective at shorter intrapulse intervals up to 10 ns with an accuracy of better than 1 ns has been developed and tested experimentally and by simulations. It is based on linear processing without dead time effects of detector pulses by excitation of a resonant system, analog/digital sampling, deconvolution, and calculation of single pulse centers and electric charges. The maximum number of processed photoevents exceeds 103 at 108 pulse rate. In an accumulation regime the method can be used for temporal profiling of the number of photocounts with very high resolutions up to 0.1 ns. This method covers the intermediate range of photon rates, where the well known techniques are ineffective. It can be applied for high order photon statistics, in lidar sensing, time-resolved spectroscopy, as well as in typical electronic measurements of instantaneous frequencies, periods etc.
A moving coil ac magnetic susceptometer
Authors: de Souza R. R. , Magon C. J.
Published: July 2002

A mutual inductance bridge which may be used for automatic measurement of ac magnetic susceptibilities from 4 K to room temperature at frequencies up to 1 kHz is described. An alternative and new arrangement of the probe is described in details. The coil set is kept at room temperature and moves in such a way to place the sample in the center of each of the secondary coils. The sample, motionless, has its temperature controlled by a helium flow refrigerator. Use of a magnetic shield minimizes coupling of the probe with nearby magnetic materials. The movement of the probe and the operation of the bridge are fully controlled by a personal computer. This probe has a sensitivity of 10−7 emu in an ac magnetic field of 8 G rms and frequency of 100 Hz. The frequency range employed can easily be extended to 10 kHz without seriously affecting the accuracy of the measurements.
Automated fluid mixing in glass capillaries
Authors: Evensen H. T. , Meldrum D. R. , Cunningham D. L.
Published: July 2002

A fast method and compact device for mixing sub-microliter fluid samples contained in glass capillaries is presented. The fluid is rapidly moved back and forth by air volume displacement driven by a piezo-ceramic actuator. Rapid mixing of different fluids is achieved via diffusion between the main fluid volume in the capillary and the thin fluid film it deposits on the capillary wall through its motion. Bubbles in the fluid are processed out of the capillary by use of an asymmetric velocity profile. A simple analysis model is used to optimize the design of the device and to elucidate the mechanisms involved in mixing. The mixing time is found to be inversely proportional to the fraction of the fluid volume that is left in the film layer for each cycle, which is determined by the wetting properties and the viscosity. The mixing time is therefore controlled by the dead-air volume of the system, the fluid volume, the capillary size, and the displacement limits of the piezo-ceramic actuator, in addition to the intrinsic properties of the fluid being mixed. The device described can mix two 1 μl water solutions in under 3 s. The possible shear breakage of DNA in solution is investigated, and λ-DNA is found to remain intact at aggressive mixing parameters. No evidence of aerosol contamination in polymerase chain reaction reactions was found to date.
A new digital all-sky imager experiment for optical auroral studies in conjunction with the Scandinavian twin auroral radar experiment
Authors: Kosch M. J. , Hagfors T. , Nielsen E.
Published: July 2002

Studies of the relationship between the optical aurorae and the ionospheric electric fields, as observed by the bi-static Scandinavian twin auroral coherent backscatter radar experiment (STARE) and the tri-static European incoherent backscatter radar facility (EISCAT), are to be undertaken in Scandinavia. For this purpose, an unmanned and fully automatic low-light-level television camera system, coupled to an all-sky lens, has been constructed. A personal computer controls all aspects of the instrument, operating it for all dark and moon-free periods. Monochrome optical data, usually at 557.7 nm, are pre-processed in real time at the recording site. The transformed images are stored digitally to magneto-optical disk with a temporal and spatial resolution directly compatible with the STARE radar data, thus making comparisons easy. Simultaneous TV recordings to tape may be made on a campaign basis. The camera has been calibrated for all gain settings, thereby permitting auroral images to be recalled in any sequence with the same absolute intensity scale. Modem communication permits remote control, trouble shooting and quick-look data transfers.
Response time of light emitting diode-logarithmic electrometer
Authors: Acharya Y. B. , Vyavahare P. D.
Published: July 2002

In a logarithmic electrometer which uses a transistor as a nonlinear element, a capacitance is generally connected across the feedback element of the operational amplifier. This stabilizes the loop but degrades the response at low current levels. However the stability problem is not so serious when a junction diode is used. In the present work an attempt was made to study the response time of a logarithmic electrometer which uses a light emitting diode (LED) as a nonlinear element and without external capacitance. The calculated values of rise time are based on an equivalent circuit with a depletion layer capacitance and voltage dependent conductance. These values are found to be in reasonable agreement with the experimentally measured values. This study will be useful in the estimation of dynamical errors in logarithmic electrometers using junction diode/LED, LED photometers and will be helpful in the techniques for improvements of the response time of logarithmic electrometers using a junction diode, particularly at low currents.
Report on the workshop on ion sources for hadron colliders (invited)
Authors: Alessi J. G.
Published: July 2002

A workshop on Ion Sources for Hadron Colliders was held September 4–5, 1997 in Gelnhausen, Germany. This workshop, organized by the WE-Heraeus-Stiftung Foundation, the University of Frankfurt, Brookhaven National Laboratory, and CERN, directly followed the 7th Symposium on Electron Beam Ion Sources and Traps. Various options were reviewed for the development of a high current, intermediate charge state heavy ion source for use on colliders such as RHIC and LHC. In addition to status reports on electron cyclotron resonance, electron beam ion source, and laser sources, there was also discussion of issues relevant to the scaling of these sources to intensities as required by RHIC and LHC. The presentations and discussions from this workshop are summarized.
Review of electron beam macroinstabilities and other EBIS related stability and issues
Authors: Hershcovitch Ady
Published: July 2002

Plasma magnetohydrodynamics and macroinstability theories are briefly reviewed. Although the configuration of any EBIS is inherently susceptible to a number of classical beam instabilities, the small radial dimension of an EBIS plasma prevents modes from occurring in EBIS traps with low beam compression due to physical limitation. In EBIS devices with high electron beam compression, where the potential for beam instabilities is great, the radial dimension is smaller than the Debye length, which renders any plasma theory invalid. However, a RHIC EBIS is expected to have a diameter which is much larger than the Debye length. Hence, it may be the first EBIS, in which the various plasma theories could be valid. For this and similar future devices, a framework is established to analyze and offer remedies plasma instabilities in EBIS.
Investigations on liquid alloy ion sources for rare-earth elements (abstract)
Authors: Machalett F. , Wesch W. , Mühle R. , Barth S.
Published: July 2002

We have developed liquid alloy ion sources for the rare-earth elements Er and Pr. They can be used in focused ion beam systems for ion implantation into optical materials and superconductors. The rare-earth elements incorporated into ternary alloys to achieve lower melting points and lower vapor pressures as well as better wetting properties and easier handling of the sources at atmosphere. The melting properties of the alloys were determined by differential thermal analysis. The emission current stability and the mass distribution using a magnetic mass spectrometer and a time-of-flight mass analyzer have been measured. The mass spectra show a high intensity of double charged and a considerable intensity of triple charged Er and Pr ions. The ion sources exhibit a good performance even after storage for several weeks in air.
Development of a high-current microwave ion source for Korean Multipurposed Accelerator (abstract)
Authors: Hwang Y. S. , Hong I. S. , Kim H. J. , Eom G. S. , Cho Y. S. , Choi B. H.
Published: July 2002

A high-current, proton linear accelerator, named as Korean multipurposed accelerator (KOMAC), is being proposed mainly for accelerator-driven transmutation technology (ADTT) by Korea Atomic Energy Research Institute (KAERI). High-current, low emittance continuous power (cw) linear accelerators favor electron cyclotron resonance (ECR) microwave ion sources as an injector (Ref. Reference 1). Recently, these microwave sources are developed and constructed by several institutes especially for high-current cw linear accelerators. A high-density microwave ion source has been designed and constructed as a prototype ion source for the proposed KOMAC linear accelerator. The design of microwave power injection system is similar to that of the 75 keV proton injector at Los Alamos National Laboratory (Ref. Reference 2). A 2.45 GHz, 1.5 kW magnetron source is introduced into the stainless steel plasma chamber with 10 cm diam and 20 cm length through a tapered, double-ridged waveguide and a quartz window. The microwave power supply is separated from the plasma chamber by a high-voltage waveguide break. Axial magnetic fields up to 1 kG can be provided by two sets of water-cooled solenoid coils. A single-hole extraction system is designed for extraction current up to 50 mA at 50 kV extraction voltage. The design and initial operations of the ion source in ECR regimes will be presented.
Photoreflectance spectroscopy with white light pump beam
Authors: Ghosh Sandip , Arora B. M.
Published: July 2002

Using a dual chopping scheme where both the pump beam and the probe beam are chopped, we show that it is possible to perform photoreflectance spectroscopy with a broadband white light source as the pump beam instead of a laser source. We show that although the signal strength is reduced by a factor of 1/π in the dual chopping scheme, it nevertheless has several advantages. A white light pump beam provides a wide range of excitation energy values, enabling one to characterize semiconductors of different band gaps spread over a wide energy range with a single modulation source. In the case of semiconductor heterostructures, simultaneous as well as selective excitation of different interfaces can be achieved easily. This technique is not plagued by the problem of background due to luminescence often encountered in low-temperature photoreflectance measurements. In this article, we present the details of this technique and demonstrate its usefulness by applying it to selected semiconductor heterostructure samples.
Application of singular value decomposition in average temperature measurement using fluorescence decay techniques
Authors: Sun T. , Zhang Z. Y. , Grattan K. T. V. , Palmer A. W.
Published: July 2002

Average, rather than point specific temperature measurement is important in a number of industrial situations. In this work, a method to improve this type of measurement using the fluorescence lifetime-related mathematical parameter, the singular value (SV), is discussed in detail. The analysis reported shows that with rare-earth doped fibers used as temperature sensor probe elements, for average temperature measurement, such a system works well especially when the lifetimes obtained from different sensing probes are very close to each other. The SV scheme, based on matrix theory, is important because the average temperature-dependent singular value possesses the characteristics of both high speed and high precision. Using the method, an average temperature sensing scheme is demonstrated in experiments carried out over the region from 20 to 100 °C, in which Nd3+ doped fibers are employed as the intrinsic temperature sensor elements. When two temperature sensing probes are used in the measuring region, the precision determined for the average temperature estimation is ±3.6 °C. When three sensors are employed instead of two, the precision is similar at ±3.4 °C. Results obtained indicate that with more sensor elements used in the sensing region, the accuracy achieved is not diminished due to the averaging effect in the measurement.