bluuebunny/crossref_metadata_2025 huggingface dataset:
Microcomputer-based system for the measurement of transpiration rate in trees by the heat pulse method
Authors: Ben-Yaakov Sam , Cohen Yeheskel , Roshansky Magenia
Published: July 2002

A microcomputer-based system was designed to measure water transport in trees by the heat pulse method. The system comprises a heater probe as a heat source and a thermistor, incorporated into a bridge which is automatically balanced by the microcomputer. The overall dynamic range of the system for temperature is 22 bits and the resolution for temperature determination is about 1.45×10−4 °C. The elapsed time between the heat pulse injection and the thermal peak at the thermistor is calculated by the microcomputer. The computation program includes algorithms for base-line slope correction and a noise immune derivative evaluating routine for peak recognition. The system was tested in the laboratory and in the field on a citrus tree.
Electron impact heated atomic hydrogen oven
Authors: Glass G. A. , Andersen L. H. , Elston S. B. , Engar Peter , Holmes R. , Rozet J.-P. , Taylor D. A. , Thoe R. S. , Berry S. D. , Breinig M. , Sellin I. A.
Published: July 2002

The design, construction, and performance of an electron impact heated hydrogen dissociation oven for use in producing an atomic hydrogen gas target for ion–atom collision experiments are described. This novel design utilizes an electron beam focused by a spherical lens system to heat the oven to temperatures in excess of 2400 K. High dissociation fractions are found with cell pressures ≥5 mTorr. The compact design allows placement of an electron spectrometer close to the interaction region (length ∼1.5 cm), as well as direct measurement of the oven temperature by means of an optical pyrometer. The electron beam produces magnetic fields ∼40 mG ∼1 cm from the center of the interaction region. These low magnetic fields offer distinct advantages compared to low-voltage, high-current oven designs when observing relatively low-energy electrons ejected in ion–atom collisions.
Device to cryofracture cultured cells for ion microscopy
Authors: Bernius Mark T. , Chandra Subhash , Morrison George H.
Published: July 2002

A cryofracture device has been developed for freeze-cleaving cultured cells grown on a polished substrate wafer. The fracture is made under liquid nitrogen and results in specimens suitable for ion microscopic analysis to reveal the intracellular elemental distribution. In performing this operation the nutrient media is also removed, precluding any need of prewashing the specimen and introducing any contamination or loss in subcellular ion concentrations. The design and performance of this device are described.
FTIR sample cell thermal lag calibration using phase transitions in three molecular solids
Authors: Casson L. M. , Herber R. H.
Published: July 2002

The temperature dependence of four characteristic infrared absorptions accompanying phase transitions in three molecular solids have been used as ‘‘infrared thermometers’’ to estimate the thermal lag of KBr pellets held in an Invar sample cell in a Fourier transform infrared spectrometer at (variable) cryogenic temperatures. Due to the low power deposition on the sample in a typical FTIR spectrometer, thermal lags of less than 0.5 K can be routinely achieved at temperatures in the range 77≤T≤300 K.
Measurement of neutral beam species ratio by solid-state detector
Authors: Ohara Y. , Miura Y. , Kimura H. , Konagai C. , Takeuchi H.
Published: July 2002

Energy spectra of neutral hydrogen beams produced at the prototype JT-60 neutral beam injector unit were measured by the solid-state detector which was developed for a neutral particle analyzer for fusion devices. The ion beam species ratio estimated from the energy spectra agreed well with that measured by the Doppler-shift spectrometer.
Microprocessor-controlled laser tracker for atmospheric sensing
Authors: Johnson Robert A. , Webster Christopher R. , Menzies Robert T.
Published: July 2002

An optical tracking system comprising a visible HeNe laser, an imaging detector, and a microprocessor-controlled mirror, has been designed to track a moving retroreflector located up to 500 m away from an atmospheric instrument and simultaneously direct spectrally tunable infrared laser radiation to the retroreflector for double-ended, long-path absorption measurements of atmospheric species. The tracker has been tested during the recent flight of a balloon-borne tunable diode laser absorption spectrometer which monitors the concentrations of stratospheric species within a volume defined by a 0.14-m-diameter retroreflector lowered 500 m below the instrument gondola.
Biomolecular deposition on multiple field-emitter tips
Authors: Panitz J. A.
Published: July 2002

A deposition fixture is described for placing proteins and nucleic acids onto field-emitter tips from aqueous solution. The fixture allows the coverage of these species on each of four tips to be independently selected by an appropriate choice of deposition parameters. Common rinsing volumes can be used without cross contamination of the tips. Four tips can be dosed in 20 min, the time previously taken to cover one tip with biological molecules. The fixture makes molecular deposition from aqueous solution both simple and routine.
Improved diamond anvil high-pressure cell for single-crystal work
Authors: Koepke J. , Dieterich W. , Glinnemann J. , Schulz H.
Published: July 2002

A diamond anvil high-pressure cell especially designed for single-crystal x-ray diffraction studies is described, and with its commercial STOE goniometer head the new cell fits to almost every diffractometer type in use. In this high-pressure cell the x-ray beam passes nearly perpendicular to the pressure generating force. This geometry also allows the cell to be used on Weissenberg cameras, but with double-radius film cylinders and adequately enlarged layer line screens. A knee-type lever arm system generates the thrust. In the path of the beams there are no longer larger beryllium parts, which has improved the signal-to-noise ratio. Approximately 90% of all possible non-Friedel reflections for Bragg angles up to 45° can be measured in the bisecting (ϑ=ω) position, up to 95% with general diffractometer settings. An analytic absorption correction was used with beryllium gasketing to eliminate the need to know the thickness of the gasket between the two diamonds. The highest pressure reached which gave satisfactory results was 2.3 GPa. Inconel gaskets were used to collect data at pressures up to 10.2 GPa. Corrections for shadowing by the beams of the cell, absorption, and overlapping of sample reflections from other single crystals inside the cell are calculated using a special control program.
Television memory and display unit
Authors: Kuriański J. M. , Thai V. T. , Storey J. W. V.
Published: July 2002

An inexpensive memory unit has been developed to store and display a grey-scale image. The format is 512×256×8 bits, and expansion to larger formats or color is straightforward. The memory unit can be loaded from a small microcomputer such as the Apple IIe, and thus brings image processing within reach of the small laboratory.
Simple electronic resistance bridge with μΩ resolution at low current
Authors: Sundqvist Bertil
Published: July 2002

A simple electronic resistance bridge is described. The bridge compares an unknown four-terminal resistor in the mΩ range with a precision resistance decade in the kΩ range. A lock-in amplifier is used as zero detector. With 10-mA exciting current a resolution better than one part in 3000 is obtained for unknown resistors in the range 3–100 mΩ. Experimental results are shown for a gold sample under pressure in the range 0–35° C and 0–1.3 GPa.
Replacing filaments in glass Bayard–Alpert ion gauges
Authors: Bedding David , Moran Thomas , Brown Allan
Published: July 2002

A simple method allows unlimited replacement of filaments in glass Bayard–Alpert vacuum gauges.
Pulsed operation of a segmented longitudinal discharge CO2 laser without ballast impedance
Authors: Kukreja L. M. , Sehgal S. K. , Chatterjee U. K.
Published: July 2002

It is shown that a longitudinal CO2 laser with two discharge tubes electrically coupled in parallel can be operated in pulsed mode without ballast impedance. This scheme not only yields much higher efficiency (up to 13% at the maximum output energy) and eliminates component failure at high pulse repetition frequency (prf) but also facilitates short pulse availability. In the absence of ballast, current and laser pulse width decrease on increasing the voltage applied to the discharge tubes but these quantities remain unaffected on varying the value of the energy storage capacitor. This enables an independent control of the laser pulse duration and energy. Threshold energy for the onset of nonuniformities in the glow discharge reduces almost exponentially on increasing the discharge current pulse duration but rises on decreasing the operating value of E/N, the electric field to neutral gas density ratio. The maximum output laser energy of about 1 J/pulse, adjustable pulse duration from 30 μs to about 2 ms, and prf up to 50 Hz have been obtained.
X-ray characterization of thin films using a Read camera—An improvement
Authors: Qadri S. B. , Cukauskas E. J. , Carpenter E. R.
Published: July 2002

An improvement to the modified Debye–Scherrer camera is described which allows for the accurate determination of the lattice parameter for thin films. The x-ray collimator assembly has been altered to allow the thin film sample to cut the x-ray beam in half at zero angle of incidence resulting in a ‘‘D’’ spot on the x-ray film. The lattice parameter of an aluminum film was measured using this modified camera and compared with that determined by an x-ray diffractometer scan and the published value. The results agree within 3 mÅ. An additional method using difference angles is also described which can be employed when the origin has not been determined.
Temperature stage for ultralow-temperature oxygen plasma ashing (L2TA)
Authors: Bernius Mark T. , Brenna J. Thomas , Morrison George H.
Published: July 2002

This paper describes an apparatus that allows the decomposition of organic materials by a radio frequency excited oxygen plasma afterglow at temperatures as low as −70 °C prior to analytical study. The usefulness of this technique is demonstrated by the freeze drying and ashing of frozen-hydrated biological samples. Subsequent analysis indicates that the cell morphology seen in two dimensions remains intact after such treatment.
Low-inductance capacitive probe for spark gap voltage measurements
Authors: Barrett David M. , Byron Stanley R. , Crawford Edward A. , Ford Dennis H. , Kimura Wayne D. , Kushner Mark J.
Published: July 2002

A novel high-voltage (>50 kV) capacitive probe has been developed to measure the voltage drop across a laser-triggered spark gap. The capacitors which comprise the voltage probe consist of three flat, annular rings that are housed within the spark gap chamber. The rings are oriented perpendicular to the spark column axis such that the column is formed in the open center of the rings. Polyethylene and Kapton foil are employed as dielectrics. The resistive portion of the divider is housed in a shielded enclosure external to the switch chamber. The inherent simplicity of the probe design ensures low inductance while minimizing stray capacitance; thus, the probe has excellent response characteristics (≊1-ns theoretical rise time), and does not interfere with the performance of the switch. The probe has also been designed to permit access for laser triggering and interferometric measurements of the spark column formation. The voltage, current, and resistance characteristics of a laser-triggered spark gap for various gas mixtures are also discussed.
Self-matched high-voltage rectangular wave pulse generator
Authors: Ishii M. , Yamada H.
Published: July 2002

This article describes the self-matched pulse generator, an efficient high-voltage generator which produces a rectangular wave pulse. It generates rectangular wave pulses with a duration from a few nanoseconds to a few microseconds. The waveform of the generated pulses is maintained regardless of the resistivity of the load. The principles of its operation and applications are described.
Effect of resonant microwave power on a Penning ionization gauge ion source
Authors: Brown Ian G. , Galvin James E. , Gavin Basil F. , MacGill Robert A.
Published: July 2002

Microwave power resonant to the local electron cyclotron frequency has been coupled into the plasma discharge chamber of a hot-cathode PIG (Philips or Penning Ionization Gauge) ion source. The extracted ion beam was monitored for changes in characteristics of the beam with and without application of the microwave power. No change was seen in the ion charge state distribution. A small but significant reduction in the beam noise level was seen, and this technique may thus find application in situations where beam quiescence is important.
Continuous sinusoidal wave modulation of the three-grid Bayard–Alpert gauge
Authors: Kanaji Toru , Honda Tatsuro , Urano Toshio
Published: July 2002

A continuous sinusoidal wave (10 Hz) potential was supplied to the intermediate grid (G2) of a special three-grid Bayard–Alpert (BA) gauge. The ion collector current corresponding to the instant maximum potential of G2 was regarded as Ion and that corresponding to the instant minimum potential was regarded as Ioff. It was confirmed that this peak-to-peak value, Ion−Ioff, was equal to the difference between the two dc currents, ΔI, which was obtained by manual switching modulation. In order to reduce the effect of noise, a low-pass filter was used. Although the waveform of the signal current was deformed by the filter, the error by this deformation was negligible. Corresponding to the modulation, a considerably strong induced current flowed in the collector circuit, and to avoid the effect of this current, two methods were used in conjunction. One was phase-sensitive detection and the other was compensation. The theoretical concept and electronic circuits are shown with some experimental data.
Programmed temperature controller using ‘‘MEMORIODE’’ for solution crystal growth
Authors: Tanase S. , Takahashi T.
Published: July 2002

A simple programmed temperature controller has been developed to grow single crystals from an aqueous solution. Linear temperature versus time ramps of several days or longer have been achieved with this instrument. From this we have been able to obtain large crystals. An analog ramp generator with an electrochemical device, named MEMORIODE, forms the basis of this design.
Compact magnetic electron energy analyzer
Authors: Schneider R. F. , Luo C. M. , Rhee M. J. , Smith J. R.
Published: July 2002

A compact magnetic energy analyzer designed for the measurement of electron energies in the range from 20 keV through 1.5 MeV is described. The simple device, based on the semicircular focusing principle, is constructed from a high induction permanent magnet enclosed in a soft iron case. The design and operation of the analyzer in pulsed electron beam devices are discussed.
Microcomputer logarithmic time base generator
Authors: Wills L. J. , Ly Nhan G.
Published: July 2002

A new circuit is introduced to generate the logarithmic time base function with good resolution. By using a single-chip microcomputer with EPROM program storage, the circuitry is simplified and can be easily reproduced. The output function covers more than six decades of time and has 590 discrete points per decade with an accuracy of one discrete point per decade or ±0.16%. The design overcomes two well-known problems in using the logarithmic time base. First because the time increments are derived from a real-time register there is a precise reference for zero time, and second a series of time base interval marks are output for correctly calibrating the time axis.
Digital complex demodulation applied to interferometry
Authors: Choi D. W. , Powers E. J. , Bengtson Roger D. , Joyce G. , Brower D. L. , Luhmann N. C. , Peebles W. A.
Published: July 2002

The objective of this paper is to describe the principles of digital complex demodulation, and to summarize its advantages with respect to rapid time response and insensitivity to noise. These advantages are demonstrated by application to interferometry data collected on the Texas experimental tokamak (TEXT).
Integrated development facility for the calibration of low-energy charged particle flight instrumentation
Authors: Biddle Alan P. , Reynolds John M.
Published: July 2002

A system has been developed specifically for the calibration and development of thermal ion instrumentation. The system is optimized to provide an extended, approximately 80-cm2 beam, with usable current rates ∼1 pA/cm2 at beam energies as low as 1 eV, with much higher values available with increasing energy. The beam energy spread is typically less than 2 eV/charge and the average angular divergence is approximately 2.5°. A tandem electrostatic and variable geometry magnetic mirror configuration within the ion source optimizes the use of the ionizing electrons, thus decreasing the gas and nonthermal electron throughput to the instrument chamber while improving the current density uniformity. The system is integrated under microcomputer control to allow automatic control and monitoring of the beam energy and composition and the mass- and angle-dependent response of the instrument under test. The data can be transmitted in nearly real time to the interested investigators for comparison with expected results over existing computer networks. The system is pumped by a combination of carbon vane and cryogenic sorption roughing pumps and ion and liquid-helium operating pumps. This allows testing and final calibration of flight instrumentation in an ultraclean environment.
Emittance measurements of space-charge-dominated electron beams
Authors: Namkung Won , Chojnacki Eric P.
Published: July 2002

A diagnostic technique for measuring beam emittance is developed for electron beams with diverging envelopes under strong space-charge forces. Radial profiles of current density, local temperature, and divergence angle are measured by the slit–pinhole method for axisymmetric beams. The particle distribution function in transverse phase space is then constructed and the rms emittance is obtained by numerical integrations. A 5-kV, 200-mA, 3-μs, and 60-pps electron beam is used in the comparison between theory and this experimental diagnostic method.
Simple system for fluid flow visualization and measurement using a chronophotographic technique
Authors: Kostrzewsky Gregory J. , Flack Ronald D.
Published: July 2002

A delay, split-timer circuit is described for use in streak photography. The unit provides the capability for relatively simple yet accurate flow visualization where conventional methods of visualization are not applicable due to high flow velocities. The basic system uses four timers and two separate strobe flashes. One timer allows synchronization with any event. Another timer controls the split time between discharges of the two strobes. By photographically recording two instantaneous positions of particles in a flow, one can draw pathlines of the particles, allowing a qualitative understanding of the flow. Delay and split times can be varied linearly (within 0.75%) to accommodate different flow rates (split times) and synchronization (delay time). The circuit design described yields predictable and repeatable time periods (to 1.5%) and is easily calibrated. To demonstrate the technique the timer was used to study steady-state secondary flows in curved ducts of square cross section and the oscillatory flow field in the tongue region of an industrial centrifugal pump.
Method for measuring complex permeability at radio frequencies
Authors: Goldfarb Ronald B. , Bussey Howard E.
Published: July 2002

An established method for measuring complex rf magnetic permeability is based on the change in inductance and resistance of a coaxial transmission line upon insertion of a sample toroid. It is not necessary to wind coils on the toroid or correct for geometric demagnetization factors. The use of modern commercial impedance analyzers, as described in this paper, makes measurements from 1 kHz to 1 GHz particularly easy, fast, and accurate.
Combination of a scanning tunneling microscope with a scanning electron microscope
Authors: Vázquez L. , Bartolomé A. , García R. , Buendía A. , Baró A. M.
Published: July 2002

We have placed a scanning tunneling microscope (STM) in the sample stage of a scanning electron microscope (SEM). This allows us to focus the tip on a preselected spot for STM operation with a precision of 0.5 μm. We are able to check the state of the sample and the tip during STM operation by simultaneous use of the SEM. We are also able to correlate the images given by both techniques.
Spatial charge cloud distribution of microchannel plates
Authors: Edgar Michael L. , Kessel Robert , Lapington Jonathan S. , Walton David M.
Published: July 2002

We describe an experiment to measure the spatial charge distribution produced by a microchannel plate intensifier with a new type of charge division readout, the ‘‘split strip’’ anode. This anode is a modified strip and strip anode which determines both the amount of charge deposited on each half of the anode and the centroid position for each event. We present experimental measurements of microchannel plate charge cloud distributions for a variety of detector operating conditions. We find that, as a first-order approximation, one can assume the charge cloud to be azimuthally symmetric. Additionally, the charge cloud remains virtually unchanged from event to event and pore to pore. The general form of the radial distribution is best described by the sum of two exponential components whose scale and relative weights vary with detector operating conditions. The central component of the distribution is three to six times smaller than the outer, or ‘‘wing’’ component. Typically most of the charge is in the central component. We have determined the scale and relative weights of the two exponentials for a fixed microchannel plate/anode gap of 6.2 mm and a range of detector operating conditions. The most significant variable determining the charge cloud distribution is the voltage between the back of the microchannel plates and the anode. As this voltage is increased from 50 to 800 V, the scale length of the central component shrinks from 1.4 to 0.5 mm and the weight increases from 50% to 85%.
Magnetic sphere rheometer
Authors: Hilfiker Rolf , Chu Benjamin , Shook Jeffrey
Published: July 2002

A magnetic sphere rheometer which is fully controlled by a personal computer has been developed. It is capable of measuring viscosities in the range of 0.1–5×104 Pa (100–5×107 cP). It can operate at shear rates between 1 and 2×10−4 s−1 and measure relaxation times down to 100 ms. The precision of the determined viscosities is in the order of 0.3%. The present rheometer is an improvement compared to existing magnetic sphere rheometers both concerning the precision and the viscosity range of the measurements. Measurements on viscosity standards, as well as on semidilute solutions of poly(isobutylmethacrylate-t-butylaminoethylmethacrylate) [poly(IBMA-tBAEMA)] in dimethylacetamide (DMAA) and tetramethylethylenediamine (TMEDA) were performed.
Influence of misfit dislocations on the surface morphology of Si1−xGex films
Authors: Lutz M. A. , Feenstra R. M. , LeGoues F. K. , Mooney P. M. , Chu J. O.
Published: July 2002

The influence of misfit dislocations on the surface morphology of partially strain relaxed Si1−xGex films is studied by atomic force microscopy and transmission electron microscopy. Surface steps arising from the formation of single and multiple 60° dislocations are identified. The role of such steps in the development of a cross-hatch pattern in surface morphology is discussed.
High precision calorimetric apparatus for studying electrolysis reactions
Authors: Närger U. , Hayden M. E. , Booth J. L. , Hardy W. N. , Whitehead L. A. , Carolan J. F. , Balzarini D. A. , Wishnow E. H. , Blake C. C.
Published: July 2002

We have developed a low cost continuous flow labyrinth calorimetric system which attains 0.3% accuracy in absolute energy balance and has a minimum sensitivity of 20 mW. This system is ideally suited to measure the energy balance of electrolytic reactions for output powers ranging from 0 to at least 25 W. By employing a catalyst to recombine the gaseous reaction products, the electrolysis cell can be operated as a closed system, thus eliminating many uncertainties associated with calorimetric measurements on open cell electrolytic processes. Careful calibrations using different electrical heater configurations inside the calorimeter demonstrate insensitivity to temperature gradients and local heating. We present measurements of energy balances of electrolytic reactions using Pd and Pt cathodes in 0.1 M LiOD in D2O as electrolyte. No anomalies are observed in the energy balance of either sample.
A variable bandpass filter for ultraviolet/visible Fourier transform spectroscopy
Authors: Manning Thomas J. , Winefordner James D.
Published: July 2002

A novel optical filter with variable bandpass and central wave number position is described. It is used to eliminate unwanted wavelengths, thereby decreasing the multiplex disadvantage in Fourier transform ultraviolet/visible (UV/VIS) spectroscopy.
Apparatus for the study of the IR multiple-photon resonances of polyatomic molecules via the optothermal technique. I. Description of the apparatus
Authors: Sanna G. , Nardi M. , Tomassetti G.
Published: July 2002

An apparatus for observing the IR multiple-photon resonances of jet-cooled polyatomic molecules using the optothermal technique is described. For experiments in the spectral region 9/11 μm, a commercially available, high-pressure CO2 laser with an improved wave number resolution (∼0.05 cm−1) is used as the pulsed radiation source. Although a moderate pumping capacity is available, high intensity, supersonic beam pulses are obtained by an expressly developed nozzle source. A superconducting bolometer with a responsivity of ∼2×104 V/W and an effective time constant of ≂60 ns (for radiation) has been developed to detect the energy flux carried by the irradiated molecular beam. The time-resolved detector signal is then passed through an analogic processor which separates the fast, small amplitude component generated by the irradiated molecules from the larger component due to the unexcited beam. After further amplification, the useful signal is digitized and stored in a computer to be averaged over several repetitions and then time integrated. A detector input NEP of ∼1.5×10−12 W/(Hz)1/2 is obtained in a single laser pulse. This figure can be further reduced by averaging. Complementary information such as the laser fluence, the intensity of the molecular beam pulse, the optoacoustic signal from a reference gas, as well as the time-of-flight of the molecules can be simultaneously monitored. Part I of this article gives a general description of the apparatus, while Part II gives a detailed description of the bolometer and the related electronics.
Quantitative two-dimensional dopant profile measurement and inverse modeling by scanning capacitance microscopy
Authors: Huang Y. , Williams C. C. , Slinkman J.
Published: July 2002

Quantitative dopant profile measurements are performed on a nanometer scale by scanning capacitance microscopy (SCM). An atomic force microscope is used to position a nanometer scale tip at a semiconductor surface, and local capacitance change is measured as a function of sample bias. A new feedback method has been demonstrated in which the magnitude of the ac bias voltage applied to the sample is adjusted to maintain a constant capacitance change as the tip is scanned across the sample surface. A quasi-1D model is used to extract dopant density profiles from the SCM measurements. The inverted SCM dopant profiles are compared with profiles obtained by process simulation and secondary ion mass spectroscopy measurement. Good agreement was found between the SCM measured profile and the lateral profile predicted by SUPREM 4 over the concentration range from 1017 to 1020 cm−3.
Technique for measuring ultrasonic velocity and attenuation changes in attenuative materials at temperature such as during sintering processes
Authors: Gieske John H. , Frost III Harold M.
Published: July 2002

This paper describes a PC-based automatic measuring system for ultrasonic velocity and attenuation changes in highly attenuating green-body ceramics during sintering temperatures. The system uses pulse-echo/through-transmission buffer rod technique and records pulse-echo and through-transmission waveforms at programmed time or temperature intervals. Data can be taken without interruption during temperature schedules lasting many days. Archival files of the waveform data are saved on disks for later analysis. Accuracy of the technique is demonstrated for solid fused silica for which dynamic resonance and Brillouin scattering data of the longitudinal velocity are compared at temperatures up to 1200 °C. The system has been used successfully for measuring longitudinal velocity and attenuation changes at 5 MHz during sintering of ZnO-based varistor materials and YBa2Cu3Ox superconducting ceramics.
Design, construction, and properties of the large plasma research device−The LAPD at UCLA
Authors: Gekelman W. , Pfister H. , Lucky Z. , Bamber J. , Leneman D. , Maggs J.
Published: July 2002

The large plasma research device (LAPD), a large, linear plasma research device designed to study space plasma processes, has been constructed at UCLA over the past four years. The LAPD has a 0.5×0.5 m2 oxide-coated cathode as a source which produces a 10-m-long plasma column with densities up to the mid 1012/cm3 range. The linear machine is surrounded by a set of 68 magnet coils which can generate an axial magnetic field of up to 3000 G. The vacuum chamber has 128 radial ports to ensure excellent access for probes and antennas. An internal probe drive capable of moving a set of probes to any position within the plasma column is described in a companion paper. This machine is a scientific instrument in its own right and was designed to be versatile enough to study a large variety of phenomena. The techniques employed in the design and construction are sufficiently useful to be discussed here so that others can benefit from our experience.
Hard x-ray continuum crystal spectrograph for inertial confinement fusion (ICF) diagnostics
Authors: Burek A. J. , Armentrout C. J. , Bird C. R. , Frazier R. E. , Geddes J. B. , Gorzen D. F.
Published: July 2002

We describe absolutely calibrated instrumentation for measuring hard x-ray continuum produced during laser irradiation of ICF targets. The instrumentation includes a crystal spectrograph and two collimated filtered scintillators. The absolutely calibrated crystal spectrograph achieves high sensitivity to x-ray continuum over the energy range of 5 to 35 keV with continuous energy coverage and a resolving power E/ΔE between 20 and 100. Time integrated spectra are recorded and stored electronically on a shot basis using two dimensional charge coupled device (CCD) camera readout of a proximity focused MCP detector close coupled to the x-ray diffracting crystals. The filtered scintillators provide discrete, time-resolved, high energy channels for recording integrated continuum in the 40–60 and 60–90 keV bands. End-to-end calibration of the crystal spectrograph was performed over the design energy interval. We discuss instrument design, calibration, and alignment and the factors affecting sensitivity and resolving power.
A vacuum protection system for the front end of SPring-8
Authors: Munekawa Shigeru , Sakurai Yoshiharu , Tong X. M. , Nagasawa Hisao
Published: July 2002

The design of a high-speed movable heat absorber (HA) to protect a fast closing valve (FCV) is presented and a unique safety system to protect the storage ring ultrahigh vacuum from a vacuum break accident in downstream beamlines is proposed. The speed of the incoming shock wave upon a vacuum failure can be measured by two sensors separated by a given distance. If the measured speed does not exceed the prescribed critical speed calculated from both the operating time of the HA and the distance between the sensors and the FCV, the storage ring vacuum can be maintained without dumping the electron beam. If the measured speed exceeds the critical speed, beam dumping will be requested. Fortunately the vacuum sensor can be installed at a distance 14 m from the FCV for the SPring-8 and the operation of the HA can be completed in 40 ms. The acceleration for moving at 40 ms is approximately 2 G, which is a practical value. Therefore the critical value of the shock wave speed is 350 m/s. In order to perform thermal analysis for the absorber plate, the fluorescent x rays and Compton scattered rays emitted from 3° inclined copper absorber can be calculated as 4.7% and 0.41% of the SPring-8 undulator power, respectively. Hence the highest temperature at the absorber surface exposed to intense undulator radiation of the total power of 2.06 kW was about 350 °C.
Spectroscopic study of the plasma of the 10-GHz CAPRICE source
Authors: Hitz D. , Druetta M. , Khardi S.
Published: July 2002

A vacuum ultraviolet spectrometer has been installed on the axis of a 10-GHz CAPRICE source in order to study the relative intensity of some spectral lines in connection with the main parameters of the source, i.e., rf power and gas pressure. Measurements were performed with oxygen ions and preliminary results are presented.
Metal ion production in ECRIS (invited)
Authors: Geller R. , Ludwig P. , Melin G.
Published: July 2002

The most popular methods of producing ions of solid elements are recalled: (a) utilization of gaseous compounds; (b) oven techniques; (c) insertion techniques, which thanks to the ECRIS plasma confinement enable heating the metallic sample up to unparalleled temperatures (yielding enough vapor even for the most refractory elements); and (d) wall recycling techniques which play an important role in the ECRIS behavior. Typical ion yields for various elements are shown, comparisons are done, and a few practical hints are given.
Polarized ion sources (invited)
Authors: Schiemenz Peter
Published: July 2002

Sources producing beams of nuclear spin polarized atoms or ions of H, D, 6Li, 7Li, 23Na are routinely used in many laboratories. Principles and performances of these sources are described, with emphasis on the light particles (H, D). Recent progress in these sources as well as some physical or technical limits are discussed. An updated table comparing working sources of H+,D+ and H−,D− is given.
Metal vapor vacuum arc ion sources (invited)
Authors: Brown Ian G.
Published: July 2002

High current beams of metal ions can be produced efficiently using a metal vapor vacuum arc to establish the metal plasma from which the beam is formed. Pulsed beam currents of several amperes of metallic ions have been produced from nearly all of the solid metals of the periodic table, and in some recent tests dc beams have been produced also. Beam extraction voltage up to 100 kV has been used and since the ions produced in the vacuum arc plasma are in general multiply ionized the ion energy is up to several hundred keV. These kinds of sources are finding application for heavy-ion synchrotron injection, metallurgical ion implantation, and other uses. A number of different embodiments of the source have been developed at Berkeley and elsewhere around the world. Interesting features include multiple cathodes and the ability to switch between up to 18 separate cathode materials simply and quickly, and broad beam source versions (up to 50 cm diameter) as well as miniature versions (about ‘‘thumb size’’). Here we review the design features, operational behavior, and beam performance characteristics of these sources from the perspective of the Berkeley program.
Nanocomposites of lead-zirconate-titanate glass ceramics and metallic silver
Authors: Kundu T. K. , Chakravorty D.
Published: July 2002

Glass ceramics containing lead-zirconate-titanate (PZT) have been synthesized by a sol-gel route. After ion exchange and reduction composites containing PZT and nanoparticles of silver with diameters in the range 3.6–13.7 nm have been made. Samples prepared by hot compaction of these powders have dielectric constant values in the range 350–1050 with dissipation factor ∼0.05 at a frequency of 1 kHz at 300 K. Bergman’s model of inhomogeneous dielectric cannot explain these results. An interrupted metal strand model has been explored for these materials.
An inexpensive Wilhelmy balance for the study of Langmuir monolayers
Authors: Buontempo Joseph T. , Novak Frank A.
Published: July 2002

We have designed and constructed an easy to use, high performance Wilhelmy balance for the study of Langmuir monolayers. This balance is based on a leaf spring and a linear variable differential transformer and was built at a fraction of the cost of a commercial instrument. The balance calibration does not rely on any specific monolayer properties so that we could obtain an independent estimate of accuracy: approximately ±0.2 dyn/cm. In our calibration we follow the standard practice of ignoring the buoyancy of water; we show that this is fine to within the accuracy reported here, but to achieve a higher accuracy not only must the accuracy of the balance be improved, but also the buoyancy of water must be taken into account, which includes knowing and controlling the width and thickness of the Wilhelmy plate to a high degree. The relatively high precision of our Wilhelmy balance is consistently better than ±0.1 dyn/cm, obtained in part by designing an apparatus with very precise temperature regulation, typically ±0.02–0.03 °C. We discuss the conditions necessary to increase this performance. The balance was constructed to achieve good sensitivity while insuring that the Wilhelmy plate travels only a very small distance through the liquid subphase to minimize problems with nonzero contact angle. The control electronics are homemade and have been designed to allow electronic zeroing of the balance. In addition to low cost and good performance, this Wilhelmy balance can be easily adapted to work in many environments differing in available space, mechanical construction, and electronic and computer interfacing.
Comparison of laser and conventional heating in thermoluminescence dosimetry dosemapping
Authors: Jones Scott C. , Sweet J. A. , Fehl D. L. , Sujka B. R. , Vehar D. W. , Westfall R. L.
Published: July 2002

A new, laser-based system has been developed for rapid evaluation of monolithic thermoluminescence dosimetry (TLD) arrays. A precision-controlled CO2 laser is used to sequentially heat 1.5-mm-diam, 38-μm-thick TLDs, deposited on a 0.125-mm-thick polymer substrate in a 3 mm×3 mm grid. Array areas up to 30 cm×30 cm are used (≳10 000 TLD elements), with evaluation times of 45–90 min. Isodose contours and various analysis functions are available on the system-operating PC. This system allows for greatly expanded dosimetry compared to standard TLDs, simultaneously decreasing effort and record keeping. We compared the dosimetric characteristics of this system with standard techniques, using near Si-equivalent CaF2:Mn TLD elements, in a test with 19 MeV end-point x radiation. The results show the laser system performs as well as the standard system.
Some peculiarities of the luminescence of inorganic scintillators under excitation by high intensity synchrotron radiation
Authors: Pustovarov V. A. , Krymov A. L. , Shulgin B. V. , Zinin E. I.
Published: July 2002

The time-resolved studies of luminescence for scintillators based on oxides, alkaline-earth fluorides, and alkaline halides excited by x-ray synchrotron radiation with flux density Nhy=6×(1014–1016) photon s−1 cm−2 are reported. The changes of spectral and time luminescence properties of above-mentioned materials were observed. Two various models for understanding the observed effects are suggested. Presented peculiarities must be taken into account by scintillation detector users dealing with high intensity synchrotron radiation.
Differential absorption spectrometer for pulsed bremsstrahlung
Authors: Gorbics Steven G. , Pereira N. R.
Published: July 2002

We describe a differential absorption spectrometer that measures the energy spectrum (from 20 to 800 keV) of flash x rays whose intensity precludes pulse-height analysis methods. The spectrometer uses individually calibrated thermoluminescent dosimeters, each inside its own spherical absorber, to accommodate isotropic radiation from pulsed bremsstrahlung sources. An iterative perturbation unfolding code determines the spectrum from the detector responses and the computed energy response functions. Unfolding works best with a good guess for the initial spectrum, and data with less than a few percent error.
Integrated windows-based control system for an electron microscope
Authors: Ruan Shengyang , Kapp Oscar H.
Published: July 2002

A Windows application has been developed for management and operation of beam instruments such as electron or ion microscopes. It provides a facility that allows an operator to manage a complicated instrument with minimal effort, primarily under mouse control. The hardware control components used on similar instruments (e.g., the scanning transmission electron microscopes in our lab), such as toggles, buttons, and potentiometers for adjustments on various scales, are all replaced by the controls of the Windows application and are addressable on a single screen. The new controls in this program (via adjustable software settings) offer speed of response and smooth operation providing tailored control of various instrument parameters. Along with the controls offering single parameter adjustment, a two-dimensional control was developed that allows two parameters to be coupled and addressed simultaneously. This capability provides convenience for such tasks as ‘‘finding the beam’’ and directing it to a location of interest on the specimen. Using an icon-based display, this Windows application provides better integrated and more robust information for monitoring instrument status than the indicators and meters of the traditional instrument controls. As a Windows application, this program is naturally able to share the resources of the Windows system and is thus able to link to many other applications such as our image acquisition and processing programs. Computer control provides automatic protection and instant diagnostics for the experimental instrument. This Windows application is fully functional and is in daily use to control a new type of electron microscope developed in our lab.
Design of a high speed, high resolution thermometry system for 1.5 GHz superconducting radio frequency cavities
Authors: Knobloch Jens , Muller Henry , Padamsee Hasan
Published: July 2002

Presented in this paper are the description and the test results of a new stationary thermometry system used to map the temperature of the outer surface of 1.5 GHz superconducting single-cell cavities during operation at 1.6 K. The system comprises 764 removable carbon thermometers whose signals are multiplexed and scanned by a Macintosh computer. A complete temperature map can be obtained in as little as 0.1 s at a temperature resolution of about 0.2 mK. Alternatively, it has been demonstrated that if the acquisition time is increased to several seconds, then a temperature resolution on the order of 30 μK is possible. To our knowledge, these are the fastest acquisition times so far achieved with L-band cavities at these resolutions.
Electron optical benches for in-line and branched systems. A new bench designed for mirror-based aberration correction and low energy electron microscopy
Authors: Skoczylas Walter P. , Rempfer Gertrude F. , Griffith O. Hayes
Published: July 2002

A review of electron optical bench literature is presented, and the designs of two optical benches used by the authors are described. One bench was designed for testing individual electrostatic electron lenses and in-line optical systems, for example, emission electron microscopes and transmission electron microscopes. It has been in operation for many years. The second electron optical bench is new. It is a branched system designed for several purposes: to study correction of spherical and chromatic aberration with an electron mirror, and to gain experience with low energy electron microscopy (LEEM) optics. The alignment of the electron optical support structure is independent of the vacuum housing, and the bench is designed to be operated either horizontally or vertically. As a demonstration of the performance of the new bench in the horizontal mode, a test pattern on a silicon surface was imaged with LEEM optics.
Construction of a high-energy Bonse–Hart ultrasmall-angle x-ray scattering instrument
Authors: Chu Benjamin , Yeh Fengji , Li Yingjie , Harney Paul J. , Rousseau Jean , Darovsky Alex , Siddons D. P.
Published: July 2002

A Bonse–Hart ultrasmall-angle x-ray scattering (USAXS) instrument, employing a synchrotron x-ray source at an energy of 18.86 keV (wavelength λ=0.06573 nm), has been designed, constructed, and tested. Solid as well as suspensions of polystyrene and poly(chlorostyrene) latex spheres were used as reference standards in order to demonstrate the range of this instrument. The USAXS results measured at λ=0.06573 nm were also compared with those from a calibrated Bonse-Hart instrument operating at λ=0.154 nm, i.e., the standard Cu Kα radiation. The higher-energy synchrotron x rays permit us to study absorbing and/or opaque materials having long range inhomogeneities in the order of microns. Furthermore, for many polymer systems, the optimal sample thickness at λ≂0.066 nm is increased to ∼10 mm and thin-walled glass windows become acceptable. Thus, a cylindrical light-scattering cell with a wall thickness of 0.3 mm could be used for both USAXS and laser light scattering measurements. The main hurdle for performing simultaneous static and dynamic light scattering as well as USAXS experiments on polymer solutions and gels with the same sample has been resolved. This capability should open up new frontiers in structural and dynamical studies of systems involving a large range of length scales from angstroms to microns.
Time domain operation of the TRAPATT diode for picosecond-kilovolt pulse generation
Authors: Baker R. Jacob
Published: July 2002

Operation of the trapped plasma avalanche transit time (TRAPATT) diode in the time domain is presented. When operated in the time domain, pulses with amplitudes greater than 1,000 V and risetimes well under 300 ps can be achieved. Selection of a diode for use as a TRAPATT diode is discussed. Experimental results demonstrate pulse generation with an amplitude of 2000 V into 50 Ω and a risetime of 200 ps using a single diode and a power MOSFET driving circuit.
Digital frequency synthesizers for nuclear magnetic resonance spectroscopy
Authors: Momo F. , Sotgiu A. , Testa L. , Zanin A.
Published: July 2002

The use of integrated digital frequency synthesizers has made it possible to design a low-cost multifrequency nuclear magnetic resonance pulsed spectrometer. The three frequencies necessary for heterodyne detection are derived by just one DSP. This approach can be useful to set up an apparatus for multifrequency correlation and relaxation time measurements.
Triggerable spark gap switches for pulsed gas lasers
Authors: Golnabi H. , Samimi H.
Published: July 2002

Two simple three-electrode spark gaps have been constructed to operate at high voltages up to 30 kV for use in a gas laser triggering system. The performance of each spark gap has been tested in a nitrogen laser system designed for this purpose, and the results are described in this report. The pressure-controlled spark gap has shown better results in terms of stability and lifetime, and it is highly reliable for high repetition rate switching.