bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature and frequency dependence of anelasticity in a nickel oscillator
Authors: Berg Robert F.
Published: July 2002

The frequency dependence of the real and imaginary parts of a nickel oscillator’s transfer function is described over 3 decades in frequency by the use of simple expressions. These expressions incorporate only the resonance frequency ω0, the quality factor Q, and a characteristic exponent β determined by a single measurement of creep. They are based on the ansatz φ(ω)=Q−1(ω/ω0)−β, where φ is the imaginary part of the spring constant. Over a 100 K range of temperature T, the exponent β≂0.18 was constant even though Q(T) changed by a factor of 8. These expressions are potentially useful for accurately describing a mechanical oscillator whose transfer function must be modeled at frequencies far below ω0. Examples include accelerometers based on a flexure element and suspensions for interferometric gravitational wave detectors.
Variable gain, zero offset, dc coupled video amplifier for microwave detector diodes
Authors: Mathew J.
Published: July 2002

A variable gain, zero offset, dc coupled video amplifier has been developed which uses a recently introduced ±5 V operational amplifier with 1.6 GHz gain-bandwidth product. The amplifier is inexpensive and it is particularly suited for amplifying the outputs of microwave diode detectors and driving 50 Ω loads. The large input bias currents of wideband operational amplifiers increase the sensitivity of positive polarity diode detectors, but they decrease the sensitivity when a negative polarity diode detector is used at the amplifier input. To eliminate this effect, matched N-channel junction field-effect transistors (JFETs) are used to buffer the operational amplifier inputs, which reduces the input bias current to ∼1 pA. An added benefit of the JFETs is that the amplifier offset voltage is unaffected by changes in gain or source impedance. Once the offset is zeroed out, it remains zero for all gains and for any combination of diode detectors connected at the input. The maximum attainable gain-bandwidth product is somewhat lower with the JFETs (typically 400 MHz), but the amplifier operates reliably for gains up to 40–50 dB.
Simple very low cost high speed 2 input AND gate
Authors: Podoleanu Adrian Gh. , Jackson David A.
Published: July 2002

A low cost subnanosecond AND gate is presented based upon a double-gate GaAs metal-oxide semiconductor field-effect transistor. Applications are presented for ANDing coincident pulses, narrowing pulses (from 310 to 120 ps), and discrimination to improve the operation of a photodetector-based AND used in the configuration of a fiber optic multichannel correlator.
Ultrahigh vacuum manipulator for sample rotation in secondary ion mass spectrometry depth profile analysis
Authors: Konarski Piotr
Published: July 2002

The construction and application of an ultrahigh vacuum manipulator for sample rotation in secondary ion mass spectrometry (SIMS) measurements is presented. The design is a modification of the classical xyzΘ manipulator with a sample carousel. The sample stage is motorized with a Cardan junction by a rotation feedthrough. Simple procedures for positioning the scanning beam center with respect to the axis of rotation, without the use of a secondary electron imaging, are presented. The solution shown simplifies the equipment necessary for indispensable adjustment when used in SIMS with a rotating stage.
Electrochemical method to determine the local composition of a liquid phase within a solidifying NH4Cl–H2O system
Authors: Song Myungho , Viskanta Raymond
Published: July 2002

Knowledge of liquid composition distribution is needed for improved understanding of energy and species transports occurring during mixture solidification. This paper describes an experimental diagnostic technique for monitoring the solute concentration of the ammonium chloride aqueous solution undergoing a phase change without resort to a sampling procedure. The method is based on the principles of an electrochemical cell and can be extended to any binary salt solution having chloride anions. The successive chloriding and dechloriding of the working electrode is employed to eliminate the influence of the drift caused by the dissolution of the silver chloride layer in a high concentration environment. The diagnostic technique was applied to the diffusion controlled solidification to measure the transient distribution of the liquid composition with the uncertainty of ±2.5%. The simultaneously measured temperature and liquid concentration data confirmed the nonequilibrium undercooling of the interdentritic liquid.
Real-time adsorption/desorption thin-film optical monitor using a windowless reflective silicon photodetector
Authors: Azzam R. M. A. , Howlader M. M. K.
Published: July 2002

A thin-film deposition monitor is described that employs a windowless reflective Si photodetector as the sensing element. When the detector is illuminated by a monochromatic light beam at oblique incidence, the generated photoelectric signal becomes a sensitive function of the thickness and refractive index of the deposited film. For high sensitivity, the incident light is linearly polarized perpendicular to the plane of incidence, and an angle of incidence ≳60° is used. Further, the passivation SiO2 layer thickness is also judiciously selected for this application. A sensor of this kind is employed to follow the adsorption/desorption kinetics of an H2O film at the detector surface (at 633 nm wavelength) and the results are interpreted with the help of Bruggeman’s effective medium theory.
A simple inexpensive Couette cell for flow-oriented linear dichroism
Authors: Vogt H. , Hänisch G. , Hochstrasser R. A.
Published: July 2002

We describe the design and performance of a simple, inert, easy to handle and inexpensive Couette cell for flow oriented linear dichroism. The cell consists of three easily fabricated parts. It has only one moving part and there are neither any complex inlet or outlet connections nor any high precision bearings required. The inner moving cylinder self-adjusts by virtue of the forces imposed by the flowing liquid.
Flux measurement for x-ray photoelectron spectroscopy
Authors: Wieliczka David M. , Wagner Eric , Wintergerst Jose
Published: July 2002

A simple modification of a commercial aluminum anode x-ray source allows for the direct measurement of the x-ray flux. The modification involves a biased wire after the Al filter used to block the bremsstrahlung radiation. The current collected by this wire was measured to be logarithmic in bias voltage but linear in power supply setting. The collector wire was used to monitor the x-ray flux over a period of approximately 1 yr and shows the degradation of the flux due to anode contamination. Using the measured x-ray flux platinum photoelectron spectra were normalized to within 20% over a 1 yr period and to 2% over a 1 week period.
Phased injection of microparticles in a Paul trap near atmospheric pressure
Authors: Holler S. , Arnold S. , Wotherspoon N. , Korn A.
Published: July 2002

A method for improving the trapping of microdroplets in a Paul trap in air is introduced. Dynamical simulations demonstrate that injection at an optimal phase relative to the trap cycle facilitates trapping. A circuit is designed for implementing phased injection.
Simultaneous temporal, spectral, and spatial resolution of laser scatter from parametric plasma instabilities
Authors: Cobble J. A. , Fernández J. C. , Wilde B. H. , Evans S. , Jimerson J. , Oertel J. , Montgomery D. S. , Gomez C. C.
Published: July 2002

A spatially discriminating optical streaked spectrograph is employed as a plasma diagnostic on the Nova laser. The instrument, which makes use of a spectrometer coupled to a streak camera with CCD readout, observes a small region of Nova target plasmas with a Cassegrain telescope. It yields simultaneous temporal and spectral information about emission and scattered light from the small plasma region.
Thermocouple sensor for rapid temperature measurements during ignition and early phase combustion of packed propellant beds
Authors: Howard Stephen L. , Chang Lang-Mann , Kooker Douglas E.
Published: July 2002

Flame-spreading processes during the ignition of ballistic events have long been studied by pressure measurements and visual records from high-speed film. While optical temperature measurements have been utilized, they are not useful much below 1500 K. A fine-wire platinum versus 10% Rh/platinum thermocouple probe was designed to measure gas temperature in a packed propellant bed over the range from the initial bed temperature (295 K) to more than 2000 K. Probe mounts were designed to provide sufficient physical support and protection for the thermocouples and yet minimally perturb the flow environment. Three diameters of fine-wire thermocouples were tested for survivability and time response in the simulated pressure-wave environment of ignition of a propellant bed. The largest diameter thermocouple (3 mil or 76 μm) exhibited a response time too great (3 ms). The smallest diameter (1 mil or 25 μm) exhibited the shortest response time (0.4 ms) and would be the thermocouple of choice for this experiment; however, it was not used in the current experiments due to difficulties in probe fabrication and consideration of wire strength. For this application, a 2 mil (51 μm) diameter thermocouple was chosen. The lag time for this thermocouple was estimated at approximately 1.5 ms. Corrections to the temperature for catalytic activity (<1 K) and radiative cooling (60 K in the plateau region) were estimated. Examples of temperature histories during ignition of M30A1 and M43 propellants are also included.
High pressure Stokes’ viscometry: A new in situ technique for sphere velocity determination
Authors: LeBlanc G. E. , Secco R. A.
Published: July 2002

A new method that allows real time determination of the velocity of a sphere moving through a liquid in high pressure Stokes’ viscometry studies is described. Our electro-detection method relies on the electrical conductivity contrast between sphere and liquid. The method has been tested on a jadeite melt at pressures of 2.4 and 2.9 GPa and at temperatures of 1350 and 1450 °C, respectively, and yields viscosities (with an associated error of 25%) which are consistent with those determined by the quench and probe method.
Long-base-line multiple reflection cell for UV and visible spectroscopy
Authors: Amoruso Antonella , Crescentini Luca , Fiocco Giorgio
Published: July 2002

A long-base-line (90 m) multiple reflection cell has been constructed to carry out spectroscopic measurements on gases for atmospheric sciences purposes. The cell is installed in the Laboratori Nazionali del Gran Sasso at Assergi (L’Aquila). The optical path ranges from about 180 m up to about 1500 m in the UV and up to about 2100 m in the visible region. Tests of the instrument by measuring the Rayleigh cross section of molecular nitrogen have been performed.
2D imaging ellipsometric microscope
Authors: Pak Hyuk K. , Law Bruce M.
Published: July 2002

A two-dimensional (2D) imaging ellipsometric microscope (IEM) has been constructed. It overcomes several problems inherent in existing 2D imaging ellipsometers. One can use IEM to measure and map the 2D film thickness profile with high spatial resolution and thickness sensitivity. The performance of the device is demonstrated through the study of the thin-film profile of a spreading liquid drop on a molecularly smooth silicon wafer surface.
A two color mm-wave interferometer for the JET divertor (abstract)a)
Authors: Prentice R. , Edlington T. , Smith R. T. C. , Trotman D. L. , Wylde R. J. , Zimmermann P.
Published: July 2002

An interferometer with compensation for vibration and large scale mechanical movements has been designed and built to measure the line integral electron density along three different lines of sight through the JET divertor plasma. Overcoming the effects of a long transmission path, having an estimated 65 dB loss, requires oversized waveguide transmission lines, sensitive heterodyne detection, low loss quasioptical circuits, and highly stable sources. The sources are frequency doubled, phase-locked, Gunn oscillators producing 15 mW at 130 GHz and 10 mW at 200 GHz. Waveguide Schottky mixer diodes generate reference and output signals at an IF of 10.7 MHz and the LO Gunn diodes are phase locked to the reference IF. Corrugated feedhorns and ellipsoidal mirrors are used for beam control and polarizing wire grids for beam splitting and recombination. To minimize unwanted, direct coupling of source power into the signal detectors, Brewster angle beam dumps and Faraday rotation isolators are used in the transmit and receive QO circuits, which in turn are separated, on opposite faces of a vertical plate. Martin–Pupplet polarizing interferometers are used to multiplex the two colors into a single coaligned, copolar output beam and to demultiplex the return beam. Constant fraction discriminators are used to optimize the accuracy of the phase detectors, which have sampling and recording rates of 1 MHz and a resolution of ∼7° (0.02 fringe).
Target emission probe for suprathermal electron detection
Authors: Martin P. , Antoni V. , Murari A. , Peruzzo S. , Serianni G.
Published: July 2002

The design and preliminary results of a target emission probe (TEP), applied to the continuous detection of suprathermal electrons in the edge of fusion plasmas, is presented in this paper. This diagnostic, developed for the RFX reversed field pinch experiment, is based on the measurement of the x-ray emission from a material target, exposed to the edge plasma, due to the bremsstrahlung of the electrons. The diagnostic has been successfully tested in RFX and a clear indication of the presence of a mostly unidirectional fast electron flow in the RFX plasma edge has been found.
Poloidal magnetic flux measurement on TEXT using a heavy ion beam probe (abstract)
Authors: Schwelberger J. G. , Crowley T. P. , Connor K. A. , Schoch P. M.
Published: July 2002

The displacement out of the toroidal plane of the heavy ions of the beam probe diagnostic is caused by forces due to the poloidal magnetic field. In a nearly toroidally symmetric device such as the TEXT tokamak, the toroidal position of the ions at the detector consists of a part proportional to the poloidal magnetic flux at the sample volume and an integrated contribution of the poloidal magnetic flux along the trajectory. The local part in the relation between beam position and magnetic flux is used in an iterative algorithm that calculates the trajectories in the magnetic field of the tokamak. The q profile can be derived from the measured poloidal flux. Errors of the measurements can be due to uncertainties in the analyzer position and also in the knowledge of the location of the sample volume. Also, uncertainties in the plasma current and position contribute to the error in the q measurement. It is essential to know the magnetic field outside the plasma. The calculation of the outside field is difficult due to the presence of the iron core and is still a matter of investigation, since it has a strong effect on the measurement. A description of the measurement and an error analysis is presented with examples of q profiles for discharges with ECH heating and strong magnetic fluctuations.
Improvement of a 500 keV heavy-ion-beam probe for JIPP T-IIU tokamak
Authors: Hamada Y. , Kawasumi Y. , Nishizawa A. , Narihara K. , Sato K. , Seki T. , Toi K. , Iguchi H. , Fujisawa A. , Adachi K. , Ejiri A. , Hidekuma S. , Hirokura S. , Ida K. , Kawahata K. , Kojima M. , Joong K. , Kumazawa R. , Kuramoto H. , Liang R. , Minami T. , Sakakita H. , Sasao M. , Sato K. N. , Tsuzuki T. , Xu J. , Yamada I. , Watari T.
Published: July 2002

Several improvements in the high-voltage heavy-ion-beam probe (HIBP) are discussed. (1) It is clearly found that the precision slide mount of the detector plates 30° parallel to the base electrode is very effective for the determination of the in-plane entrance angle of the beam in the analyzer to estimate the error in the potential measurement. (2) A two-staged optical trap in the HIBP greatly reduced the effect of the UV radiation in the analyzer. (3) A multiple-plate detector up to 13 measurement points clearly showed the direction of the propagation of the turbulence and path-integral effects.
Performance of an imaging plate as an x-ray area detector used for plane-wave x-ray diffraction topography
Authors: Kudo Y. , Kojima S. , Liu K.-Y. , Kawado S. , Ishikawa T. , Hirano K.
Published: July 2002

We report the linearity, spatial resolution, and granularity of x-ray intensity images recorded on imaging plates (IPs). The IP-processing system, designed for use with a transmission electron microscope (TEM), was used to evaluate the influence of these characteristics on profiles of local lattice distortion in silicon obtained by plane-wave x-ray diffraction topography (PWT). The signal intensity was linear with x-ray doses over four orders of magnitude of intensity, as has also been reported in the case of TEM. The modulation transfer function and root mean square of x-ray intensity images were measured to evaluate the spatial resolution and granularity. The results indicate that profiles of lattice distortion with a period of more than 0.5 mm can be reproduced by PWT in combination with the present IP-processing system.
High-pass filtering extends the dynamic range for recording pulse shapes
Authors: Erskine David J.
Published: July 2002

When a roughly flattopped pulse electrical pulse is recorded by a digitizer, signal clipping can destroy information that is crucial to the experimenter. This is particularly true in release-overtake shock experiments, where the occurrence time of a change in slope at the top of a photomultiplier pulse is sought. We have invented a simple and accurate method to record the pulse that is robust to clipping. The digitizer records the signal through a high-pass circuit. The inverse of the high-pass filter is applied via fast Fourier transform during analysis. The insensitivity to clipping allows one to record the change in slope signature at a higher gain, and thus with an improved signal to noise ratio. The technique is generically applicable to any recording of a roughly flattopped pulse.
Pulverized solid injection system. Application to laboratory burners and pyrometric temperature measurements
Authors: Therssen E. , Delfosse L.
Published: July 2002

The design and setting up of a pulverized solid injection system for use in laboratory burners is presented. The original dual system consists of a screw feeder coupled to an acoustic sower. This laboratory device allows a good regularity and stability of the particle–gas mixture transported to the burner in a large scale of mass powder and gas vector rate flow. The thermal history of the particles has been followed by optical measurements. The quality of the particle cloud injected in the burner has been validated by the good agreement between experimental and modeling particle temperature.
Fiber-optic-bundle delivery system for high peak power laser particle image velocimetry illumination
Authors: Anderson D. J. , Jones J. D. C. , Easson W. J. , Greated C. A.
Published: July 2002

We demonstrate the design and implementation of a fiber-optic-bundle beam delivery system for particle image velocimetry (PIV) applications. The system is designed for the transmission of high peak power pulses (≳20 mJ) from a Q-switched and frequency doubled Nd:YAG laser. A fiber bundle offers advantages over a single fiber in beam delivery systems for light sheet formation. The damage-limit-maximum power that can be transmitted is greater for the bundle than for any of its component fibers, and the quality of the derived light sheet is higher than that obtainable from a single large core fiber of power handling capacity equivalent to that of the bundle. The beam delivery system was demonstrated in PIV measurements on a premixed propane-air flame.
Improved interferometer for measuring unsteady film thickness
Authors: Nosoko T. , Mori Y. H. , Nagata T.
Published: July 2002

An interferometer previously developed for measuring instantaneous film thickness of the order of 10 μm–1 mm [T. Ohyama, K. Endoh, A. Mikami, and Y. H. Mori, Rev. Sci. Instrum. 59, 2018 (1988)] has been improved with respect to both facility of handling and accuracy of thickness determination. The improved version of the interferometer uses an expanded laser beam focused aslant on the subject film. The rays reflected from the front and rear surfaces of the film form interference fringes on a screen, which are then recorded in the form of a single snapshot interferogram or as a set of serial interferograms to be geometrically analyzed. Experiments with thin glass plates as sample films verified the expected advantages of the new version over the original one. The improved version of the interferometer was also tested on a liquid film asymptotically thinning as it drained down a vertical plate. The test indicated that the accuracy and precision of the new improved version far exceed those of other transient film-thickness measuring techniques.
Use of transport delay to avoid compensatory effects in sonic orifice-based gas concentration probes
Authors: Radcliff Thomas D. , Parsons J. Roger , Johnson W. Stan , Ruggles Arthur E.
Published: July 2002

As part of a mixing test, an instrument to measure transient concentration of several different binary gas mixtures was required. A combination sonic nozzle/hot film instrument was selected for this measurement, but for certain gas mixtures the output from this device was unexpectedly small. A study of the dynamics of the instrument reveals that this is caused by the compensatory nature of the two principal contributors to convection: change in constant velocity convection coefficient and change in sonic velocity. The problem is addressed by introducing a physical delay line between the hot film element and the sonic nozzle. Results show that a finite interval of constant velocity thermal convection data can be taken before sonic velocity effects are introduced. A second variation is proposed where the hot film sensor is replaced by a simple orifice flowmeter. Orifice pressure drop and sonic velocity effects, normally strongly compensatory, are also separated by a delay line such that nearly constant velocity orifice discharge coefficient data can be taken over a finite time interval. Results show that this instrument design has higher sensitivity and lower cost than the hot film variant, albeit with slower time response.
Alternating techniques to measure magnetoresistance effects with a sensitivity of 2 pΩ under 3 T down to 60 fΩ in zero field
Authors: Dauguet P. , Gandit P. , Chaussy J.
Published: July 2002

Two methods have been developed to measure variations with magnetic field of electrical resistances in the range 0.1 nΩ–1 μΩ, for applied magnetic fields up to 3 T, and for temperatures less than 9 K. The first method provides direct access to R(H). Its absolute sensitivity is 3×10−14 V/√Hz with a short circuit at input. It becomes on a 1 μΩ sample: 6×10−14 V/√Hz in zero field, and 2×10−12 V/√Hz under 3 T. Averaging the signal over 100 s, the sensitivity is 6×10−15 V in zero field and 2×10−13 V under 3 T. In terms of resistance, using a sensing current of 100 mA, it corresponds to a sensitivity of 6×10−14 Ω in zero field and 2×10−12 Ω in the maximum field. The reproducibility of this method is 0.3%. The second method is a sinusoidal field modulation technique giving the field derivative of the resistance: dR/dH. It has the same absolute sensitivity as the R(H) method and it achieves ultrahigh resolution. It is sensitive to variations of the resistance as small as 6×10−14 Ω in zero field and 2×10−12 Ω in 3 T independent of the absolute resistance of the sample, thus the resulting resolution ΔR/R is, for example, 6×10−8 in zero field and 2×10−6 in the maximum field for a 1 μΩ sample. To demonstrate the high sensitivity of the setups, we measured the magnetoresistance of a magnetic multilayer with the current applied perpendicular to the multilayer plane.
The improvement on the falling needle viscometer
Authors: Sha Zhen-Shun
Published: July 2002

To overcome the shortcomings of the conventional falling needle viscometer, many improvements have been made, e.g., adopting new design of needle structure, collector, and launcher. Furthermore, Hall magnetic sensors and single-board computer are used in the system, which makes the measurement automatic and intelligent. It is proved in the experiment that the instrument is accurate enough and has excellent performance. The technique can also be applied in falling ball viscometers.
Beam characteristics using stable isotopes from a multicusp source for the TRIUMF ISAC facility
Authors: Kuo T. , Yuan D. , Jayamanna K. , McDonald M. , Baartman R. , Mackenzie G. , Bricault P. , Dombsky M. , Schmor P. , Dutto G. , Lee Y. , Leung K-N , Williams D. , Gough R.
Published: July 2002

A multicusp source for positive ion beams has been designed and constructed in collaboration with the Ion Beam Technology Department of LBNL for the TRIUMF ISAC project. This type of source has demonstrated a high yield of singly charged ions, a low energy spread, a good emittance, and is compact and simple. Several stages of tests and measurements using nonradioactive beams to characterize the source performance are being carried out both at LBNL and at TRIUMF prior to the final phase of radioactive target-source system tests. Results of these nonradioactive tests and certain problems encountered are reported and discussed in this article.
Development of a high current H− source for European spallation source
Authors: Volk K. , Beller P. , Klein H. , Maaser A. , Weber M.
Published: July 2002

For the European spallation source, a volume source based on the high efficiency source is being developed. The source will be optimized to produce high current densities in pulsed operation. A pulse generator delivering 1–1.5 ms pulses was installed. Furthermore, cesium was supplied to the plasma generator from an external oven. The cesium injection was optimized for a low e/H− ratio and a high current. We obtained a current density of 70 mA/cm2. This way, with an aperture radius of 4.25 mm, an H− current of 40 mA was extracted at an extraction voltage of 22 kV. After a description of the source and the experimental setup, measurements of the beam current density and the e/H− ratio will be presented in this article.
Absolute measurements of characteristics of tantalum ion current from laser-produced plasma
Authors: Woryna E. , Parys P. , Wol/owski J. , Krása J. , Láska L. , Rohlena K. , Stockli M. P. , Winecki S. , Walch B.
Published: July 2002

The work presents results of absolute measurements of the energy distribution of ions, the ion current density, and the number of ions emitted from a tantalum laser-produced plasma. The results were obtained using two types of calibrated windowless electron multipliers. The number of ions with the individual charge state in the range z=37–42 was about 2.5×108 ions/cm2 and the maximum ion current density was about 0.5 mA/cm2 at the distance of 174 cm from the target. Moreover, the ion signals, the one measured by means of an ion collector and that reconstructed on the basis of measurements performed with an electrostatic ion energy analyzer, are also compared as well the influence of the secondary electron emission effect on the ion collector signal applied in the experiment is estimated.
Off-line efficiency measurements of the microwave discharge source (MIDAS) at the Laboratorio Nazionale del Sud
Authors: Gammino S. , Ciavola G. , Celona L. , Torrisi L. , Castro M. , Chines F. , Marletta S. , Messina E. , Qin J. , Wang Z.
Published: July 2002

The aim of the EXCYT project at the Laboratorio Nazionale del Sud (LNS) is the production of radioactive beams, and for this we need to carry out the ionization of recoils produced in a target with as high an efficiency as possible. In order to obtain efficient positive ionization the microwave discharge ion source (MIDAS) has been designed to be followed by a charge exchange canal. A prototype of this source has been designed, built, and tested at the LNS and a description of this source is presented in this article along with the preliminary results and a design of the final version.
Studies on MEVVA ion source
Authors: Biehe Sun , Hongwen Xiang
Published: July 2002

This article reports the research results of a MEVVA ion source. The structure and working mechanism of the source are briefly described. In order to further upgrade the source’s operating function, we have systematically studied the circuit characteristics and the cathode structure of the source. Thus, the time characteristic of the extracted beam current has been improved and the continuous operating lifetime of the source has been greatly prolonged. The typical working parameters are: the high voltage trigger pulse voltage of the cathode is 12 kV, the trigger pulse width is 20 μs, the extracted beam pulse width is 250 μs, and the pulse repetition rate is 1–5 pps. At an extraction voltage of 30 kV and an arc voltage of 100, 250, and 200 V, respectively, the extracted beams intensity are 290, 300, and 310 mA for Al, Fe, and Cu cathode material.
The operational parameters for the Texas A&M high B mode electron cyclotron resonance ion source
Authors: May D. P.
Published: July 2002

The Texas A&M 6.4 GHz electron cyclotron resonance (ECR) ion source uses conventional water-cooled copper coils and a moderate strength neodymium-iron-boron permanent magnet hexapole to obtain magnetic fields close to those used by the Michigan State superconducting SCECR ion source operating in its 6.4 GHz, high B mode. Despite its simple construction, the intensities of high-charge state, medium to heavy ion beams produced by the Texas A&M ECRIS are comparable to those produced by SCECR and to those produced by some other ECR ion sources that operate at much higher microwave frequencies. In this article the Texas A&M ECRIS run parameters, including the shape of the magnetic confinement field, are described and compared with those of SCECR. The possibility of two-frequency microwave heating is also explored.
Installation for ion-beam treatment of high-precision optical parts
Authors: Michnev R. A. , Shtandel S. K.
Published: July 2002

Information is given on development, manufacturing, testing, and industrial approval of the automatic numerical control installation for microsize ion-beam treatment (IBT), and retouching and finishing of surfaces of high-precision large-sized optical parts (HPOP) 200–600 mm in diameter. The results of automatic microsize IBT of a surface 244 mm diameter obtained in the process of installation approval are presented.
Pulse modulation for plasma parameter control and optimization of volume H− ion source
Authors: Fukumasa Osamu , Shinoda Masahiro
Published: July 2002

Pulse modulation of a negative ion volume source was investigated, both with and without a magnetic filter for various operating conditions. Without a magnetic filter, afterglow negative ion peak is observed, which was reported by some authors. Variation of afterglow peak was discussed as a function of gas pressure, discharge power, and extraction voltage. With a magnetic filter, on the other hand, there is no remarkable afterglow peak and the negative ion current during the discharge pulse exceeds all the afterglow currents for the present experimental conditions. Finally, comparison of afterglow negative ion peak (no magnetic filter case, i.e., temporal filter) with negative ion current during the discharge pulse (with magnetic filter case, i.e., spatial filter) was discussed.
Hollow cathode magnetron ion source with axial extraction. II
Authors: Miljević Vujo I.
Published: July 2002

Characteristics of plasmas in a magnetron ion source with a hollow mesh cathode have been studied. It was found that depending on conditions of discharge and ion current in the cylindrical mesh cathode, the plasma column is always formed in such a way as to ensure necessary ion concentration for extracted ion current.
Numerical simulation of highly charged ion production in RIKEN 18 GHz electron cyclotron resonance ion source
Authors: Shirkov G. , Nakagawa T.
Published: July 2002

Numerical codes based on the model of ion confinement and losses in the electron cyclotron resonance (ECR) source have been applied to the mathematical simulation of krypton and xenon ion production in the 18 GHz ECR ion source at RIKEN. An equation of complete plasma energy is introduced to estimate the rf power of the ECR plasma heating. The final result of fitting is in reasonable agreement with the real experimental data for the Kr and Xe ion production in the source and used to estimate the main plasma parameters.
Development of a femtosecond diffuse reflectance spectroscopic system, evaluation of its temporal resolution, and applications to organic powder systems
Authors: Asahi Tsuyoshi , Furube Akihiro , Fukumura Hiroshi , Ichikawa Musubu , Masuhara Hiroshi
Published: July 2002

An ultrafast time-resolved diffuse reflectance spectroscopic system has been developed as a potential instrument for analyzing photophysical and photochemical dynamics of light scattering materials such as powder and opaque suspension, using an amplified femtosecond Ti:sapphire laser as a light source. Transient absorption spectra of organic powder, covering the wavelength region from 400 to 760 nm, were precisely obtained by using a stable and bright femtosecond white-light continuum as a probe light. An ultrashort light pulse is temporally broadened owing to numerous times of refraction, reflection, and diffraction in scattering materials. This affects the temporal resolution of transient absorption measurements, which was examined and discussed in detail by using a simple numerical model with time-dependent light propagation of a short pulse. From the simulation and experimental results, it was shown that the temporal resolution of transient absorption measurement is less than a few ps under a certain measurement condition, although it strongly depends on the optical properties of the sample; scattering and absorption coefficients. Some applications to the analysis of excited dynamics of organic molecules in polymer latex and molecular microcrystalline powder are also demonstrated.
New technique to control oxygen fugacity in high-temperature/ high-pressure experiments
Authors: Xie Hongsen , Li Heping , Xu Ji-an
Published: July 2002

A new method to control oxygen fugacity in high-temperature/high-pressure experiments is proposed. In this method, use is made of two connected oxygen membrane cells which monitor and regulate the oxygen fugacity in the sample. As an example, all of the possible oxidation states in the Ni–O system were achieved. This method will provide a powerful tool in research on the chemistry of high-temperature/high-pressure environments such as the interior of the Earth.
Use of multiple-discrete-frequency microwave radiation to enhance the performances of traditional B-minimum electron cyclotron resonance ion sources
Authors: Alton G. D. , Meyer F. W. , Liu Y. , Beene J. R. , Tucker D.
Published: July 2002

The performances of electron cyclotron resonance (ECR) ion sources, in terms of high-charge-state yields and intensities within a particular charge-state, can be enhanced by increasing the physical sizes of the ECR zones in relation to the sizes of their plasma volumes. The ECR plasma “volumes” of traditional B-minimum ECR sources can be increased by injecting broadband microwave radiation (multiple-discrete frequency, variable frequency, or broad-bandwidth frequency microwave radiation) derived from standard klystron, gyrotron, or traveling-wave-tube (TWT) technologies (frequency domain). In this work, comparisons were made of the charge-state distributions of Arq+ and Xeq+ extracted from the ORNL Caprice ECR ion source, when excited with single frequency and multiple-discrete-frequency microwave radiation, derived from standard klystron and/or TWT technologies. The charge-state populations for Arq+ and Xeq+ move toward higher values when excited with modest power from two and three discrete frequency, microwave radiation compared to those generated with power from single-frequency radiation. For three-frequency plasma excitation, the most probable charge state for Xe is increased by one charge-state unit while the beam intensities for charge-states higher than the most probable are increased by factors of ∼3 over those for the single frequency plasma case. The results of these measurements along with details on the modifications to the injection system required to couple the microwave radiation into the plasma volume of the Caprice source will be presented in this article.
Duoplasmatron source modifications for He+3 operation
Authors: Schmidt C. W. , Popovic M.
Published: July 2002

A duoplasmatron ion source is used to produce 25 mA of He+3 with a pulse width of ∼80 ms at 360 Hz for acceleration to 10.5 MeV. At this energy, He3 striking water or carbon targets can produce short lived isotopes of C11, N13, O15, and F18 for medical positron emission tomography (PET). A duoplasmatron ion source was chosen originally since it is capable of a sufficient singly charged helium beam with an acceptable gas consumption. Stable long-term operation of the source required a change in the filament material to molybdenum, and a careful understanding of the oxide filament conditioning, operation and geometry. Other improvements, particularly in the electronics, were helpful to increasing the reliability. The source has operated for many months at ∼2.5% duty factor without significant problems and with good stability. We report here the effort that was done to make this source understandable and reliable.
A new concept miniature charge coupled device camera for vacuum ultraviolet and soft x-rays spectroscopy
Authors: Pace E. , Tommasi L.
Published: July 2002

A very compact, vacuum compatible charge coupled device (CCD) camera has been developed for vacuum ultraviolet and soft x-ray imaging spectroscopy. It can house any CCD frame format and two of them have been selected: 385×576 pixels, suitable for normal incidence spectroscopy (300–2500 Å), and 256×1024 pixels, for grazing incidence applications (5–300 Å). Owing to its small and lightweight package, it can be placed at the focus of vacuum spectrometers. A new concept cooling system is based on a three stage thermoelectric cooler in thermal connection with the CCD through a 30-cm-long flexible conductor, allowing the detector to have stress-free movements along the focal plane and a constant temperature. The camera head has been designed to achieve a high cooling efficiency, thus the CCD can be operated at −40 °C. This detector is well suited for applications that require high sensitivity and signal to noise ratio, wide dynamic range, good spatial and spectral resolutions. In addition, it overcomes the limits of fixed detectors and lets the optical performances of the spectrometer remain unchanged. The CCD camera has been tested during an experiment of laser produced plasma spectroscopy and some preliminary results are reported.
A simple scanning mirror mechanism for a Fourier transform spectrometer
Authors: Brasunas John C. , Cushman G. Mark
Published: July 2002

We present a simple scanning mirror mechanism for a Fourier transform spectrometer, consisting of a voice coil actuator, a ball-bearing slide, and a single cube corner mirror or retroreflector. The use of a single cube corner reduces significantly the sensitivity of the Fourier transform spectrometer to the tilt of its moving mirror, enabling the simple mechanism. With simple velocity feedback using a linear velocity transducer, we achieve a scan speed stability of 2%–5% (root-mean-square) for scan speeds from 40 to 440 μm/s for a travel of 2.2 cm, corresponding to a spectral resolution of 0.06 cm−1. Fringe amplitude stability is about 5%. This scan mechanism was operated at standard temperature and pressure, but the relatively minute amount of lubricant in the ball-bearing slide may indicate possible operation under vacuum and/or cryogenic conditions.
A microprocessor controlled pH potentiometric apparatus for titrations in slow equilibrium chemical processes
Authors: Volpicelli R. , Zompa L. J.
Published: July 2002

The use of pH potentiometric measurements in titrimetric analysis is commonplace in chemical and biological systems. The methodology usually works well, but problems arise in chemical systems involving slow equilibrium processes. This article describes a microprocessor controlled system that measures pH during the course of titration and will only allow the addition of titrant when there is no detectible drift in pH with time. The apparatus described has been used in these laboratories for several years and is extremely stable and reliable.
Beam extraction from a laser-driven multicharged ion source (abstract)
Authors: Anderson O. A. , Logan B. Grant
Published: July 2002

A newly proposed type of multicharged ion source has several potential advantages over existing types and a number of useful applications. The basic principle is that multiphoton absorption in an intense uniform laser focus can give multiple charge states of high purity (Ref. Reference 1). Thus, charge state separation downstream is simplified or made unnecessary. Another advantage is that large currents (hundreds of amperes) can be extracted. This type of source could be used for heavy-ion fusion drivers (see Ref. Reference 1) or storage rings. There are also industrial application such as materials processing. We describe conceptual design studies for several specific cases. For example, we discuss extraction and focusing of a 4.1 MV, 144 A beam of Xe16+ ions from an expanding plasma created by an intense laser. The maximum duration of the beam pulse is determined by the total charge in the plasma, while the practical pulse length is determined by the range of plasma radii over which good beam optics can be achieved. The initially diverging beam can be refocused to a small radius or made parallel by a combination of electrostatic and solenoid focusing. Our design studies are carried out first with an envelope code to determine the proper focusing parameters and then with a self-consistent particle code to optimize the beam quality. We present results from both codes and discuss several applications of this type of ion source.
Very high frequency and microwave interferometric phase and amplitude noise measurements
Authors: Rubiola Enrico , Giordano Vincent , Groslambert Jacques
Published: July 2002

The interferometric technique allows close-to-the-carrier measurements of both phase and amplitude noise, improving the instrument noise floor by 10–25 dB as compared to the traditional method based on a saturated mixer. Principles and basic equations describing the noise measurement system are given, together with design strategies suitable to microwave and very high frequency bands. Two prototypes, operating at 9 GHz and 100 MHz are discussed in detail. The relevant features of these prototypes are the capability to operate in a wide power range, below 0 dBm and above 20 dBm, and low noise floor. The latter is about −180 dB rad2/Hz (white) and 150 dB rad2/Hz (flicker) at 1 Hz Fourier frequency, at carrier power from 9 to 15 dBm.
Line integrated density measurements based on Cotton–Mouton polarimetry
Authors: Fuchs Ch. , Hartfuss H. J.
Published: July 2002

A polarimeter based on the Cotton–Mouton effect has been developed and installed at the W7-AS stellarator. It is operated in the submillimeter wave region at frequencies of 500–650 GHz. The polarimeter demonstrated its capability to perform absolute, robust measurements of the line integrated electron density. The change of the state of polarization is calculated with high accuracy using Segre’s formalism. By varying the frequency and the B field, it could be shown that the Faraday effect has negligible influence on the measurements.
Design of a low-cost detection system for laser-induced plasma spectroscopy
Authors: Neuhauser R. E. , Ferstl B. , Haisch C. , Panne U. , Niessner R.
Published: July 2002

A low-cost detection system for laser-induced plasma spectroscopy (LIPS) is described. The system comprises a Rowland spectrometer with photomultiplier detection and a miniaturized multiple gated integrator system. The sensitivity and the spectral band pass of the system were characterized and compared to a conventional Czerny–Turner system with an intensified diode array detector for chromium as representative analyte. Both, the sensitivity and spectral resolution were found to be sufficient for the intended simultaneous multielement LIPS analysis of simple and constant matrices.
Spectral response measurements of an x-ray sensor camera by a fluorescence wavelength dispersive spectrometer
Authors: Wulveryck J. M. , Mouze D.
Published: July 2002

Measurements of the spectral efficiency of an x-ray camera in the 5–25 keV range are presented. The camera consists of a slow scan transfer device (a charge coupled device) optically coupled to a scintillator screen (Y2O2S:Eu). A straightforward method, using laboratory x-ray sources, allows one to carry out measurements in a larger energy range, typically from a few keV to tens of keV by means of a fluorescence wavelength dispersive spectrometer. The spectral responsivity of the x-ray imaging detector, in units of analog-to-digital converter in keV, is discussed. In particular, the assumption of a linear conversion from incident x-ray energy to visible photon energy is confirmed by the experiment.
Compact all-metal high-vacuum gate valve for microwave tube research
Authors: Gold Steven H. , Kinkead Allen K. , Nezhevenko Oleg A.
Published: July 2002

A manually operated all-metal high-vacuum bakable gate valve is described that is designed to attach between an electron gun and an experimental high-power microwave tube. It is designed with a minimal radial extent in order to fit within the 20 cm bore of a magnet that encloses the microwave tube. It also provides a continuous cylindrical metal boundary condition for the electron beam. The valve is used to maintain the electron gun vacuum when the remainder of the tube is brought up to atmospheric pressure for modifications.
A pump-probe photoionization mass spectrometer utilizing tunable extreme ultraviolet laser-produced-plasma radiation
Authors: Flesch R. , Schürmann M. C. , Hunnekuhl M. , Meiss H. , Plenge J. , Rühl E.
Published: July 2002

An experimental device is reported that utilizes time-correlated nanosecond light pulses in combination with photoionization mass spectrometry. A primary light pulse is generated by a tunable dye laser in the ultraviolet regime, which photolyzes neutral gas targets under collision free conditions. Subsequently, a time-correlated extreme ultraviolet-light pulse comes from a laser-produced plasma that is monochromatized in the 10–25 eV regime. The photolysis products are ionized by one-photon absorption, so that the cations are finally detected by time-of-flight mass spectrometry. The performance of this experimental approach is characterized by investigating the primary photolysis products of chlorine dioxide. Finally, possible applications of this approach are briefly discussed.