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Nov 1999

Volume 70, Issue 11, pp. 4131-4438

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The superconducting gravimeter

John M. Goodkind

Rev. Sci. Instrum. 70, 4131 (1999); http://dx.doi.org/10.1063/1.1150092 (22 pages) | Cited 35 times

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The superconducting gravimeter is a spring type gravimeter in which the mechanical spring is replaced by a magnetic levitation of a superconducting sphere in the field of superconducting, persistent current coils. The object is to utilize the perfect stability of supercurrents to create a perfectly stable spring. The magnetic levitation is designed to provide independent adjustment of the total levitating force and the force gradient so that it can support the full weight of the sphere and still yield a large displacement for a small change in gravity. The gravimeters provide unequaled long term stability so that instrumental noise can be either below geophysical and cultural noise or indistinguishable from it over periods ranging from years to minutes. This article reviews the construction and operating characteristics of the instruments, and the range of research problems to which it has been and can be applied. Support for operation of the instruments in the United States has been limited so that operation of multiple instruments for periods much longer than a year has not been possible. However, some of the most appropriate applications of the instrument will require records of several years from arrays of instruments. Commercial versions of the instruments have now been purchased in sufficient numbers elsewhere in the world so that a world-wide array has been organized to maintain instruments and share data over a period of six years. © 1999 American Institute of Physics.
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93.85.-q Instruments and techniques for geophysical research: Exploration geophysics
84.71.Ba Superconducting magnets; magnetic levitation devices
01.30.Rr Surveys and tutorial papers; resource letters
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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

Construction and performance of a figure-8 undulator

Takashi Tanaka, Toru Hara, Masaki Oura, Haruhiko Ohashi, Hiroaki Kimura, Shunji Goto, Yoshio Suzuki, and Hideo Kitamura

Rev. Sci. Instrum. 70, 4153 (1999); http://dx.doi.org/10.1063/1.1150044 (8 pages) | Cited 20 times

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The figure-8 undulator is a novel insertion device adopted as a light source at the soft x-ray photochemistry beamline of the Super Photon ring-8GeV. It was designed to produce linearly polarized soft x rays between 100 and 5000 eV with low on-axis power density. Magnetic fields of the constructed device were measured with compensation for the planar Hall effect using two different methods. After magnetic-field corrections, it was found that the first-harmonic intensity and the on-axis power density calculated using the measured fields were almost the same as ideal ones. After installation in the storage ring, a power-distribution pattern was observed by a fluorescent screen and it was found that the shape corresponded to expectation. The quantity of fluctuation of the photon-beam axis was estimated by measuring spectra at various observation angles and it was found to be small compared to the photon-beam size. In addition, it was also found that the measured spectrum at the gap of 77 mm agreed well with the calculated one. © 1999 American Institute of Physics.
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07.85.Qe Synchrotron radiation instrumentation
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
29.20.db Storage rings and colliders
41.60.Ap Synchrotron radiation

X-ray focusing test and x-ray imaging test by a microcapillary x-ray lens at an undulator beamline

Yoshiki Kohmura, Mitsuhiro Awaji, Yoshio Suzuki, Tetsuya Ishikawa, Yu. I. Dudchik, N. N. Kolchevsky, and F. F. Komarov

Rev. Sci. Instrum. 70, 4161 (1999); http://dx.doi.org/10.1063/1.1150045 (7 pages) | Cited 12 times

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A first focusing test of the undulator radiation at SPring-8 has been done using two types of x-ray refractive lenses in thin glass capillaries. One (lens No. 1) contained bubbles in a glue whereas the other (lens No. 2) contained bubbles in glycerol. The capillaries had inner diameters of 0.2 and 0.8 mm, respectively. Using x rays of 17–18 keV, the undulator source image was investigated at the focal plane. The spherical aberrations and the field distortions were carefully examined by taking the images of a gold mesh. Lens No. 1 had an advantage of high transmissivity in the hard x-ray region (18% at 18 keV) and high tolerance to severe radiation damage, e.g., ∼ 5×1012 photons/s/0.03 mm2 of the 18 keV x rays for an exposure time of 1 h. On the other hand, lens No. 2 had an advantage of a large aperture, 0.8 mm, and a small field distortion, e.g., less than 10% inside a diameter of 300 μm. © 1999 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
41.50.+h X-ray beams and x-ray optics

High-efficiency Bragg–Fresnel lenses with 100 nm outermost zone width

C. David and A. Souvorov

Rev. Sci. Instrum. 70, 4168 (1999); http://dx.doi.org/10.1063/1.1150046 (6 pages) | Cited 13 times

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In this article, we describe the manufacture and characterization of linear silicon Bragg–Fresnel lenses (BFLs) with outermost zone widths of 100 nm. This is, to our knowledge, a factor of 3 smaller than any other device of this kind reported so far. Furthermore, we give the first detailed description of an accurate and robust method to measure the diffraction efficiency of BFLs. The first-order diffraction efficiency of our lenses at 13.25 keV photon energy was 26%±0.5%. The combination of wide aperture angle, high efficiency, and large size of our devices results in a significant gain in achievable x-ray flux. © 1999 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
41.50.+h X-ray beams and x-ray optics

Experimental study of self-injection locking oscillator on copper vapor laser

Akira Ohzu, Masaaki Kato, Yoichiro Maruyama, and Takashi Arisawa

Rev. Sci. Instrum. 70, 4174 (1999); http://dx.doi.org/10.1063/1.1150047 (4 pages)

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As a novel method to obtain a low divergence laser beam, a self-injection locking oscillator system has been developed for a copper vapor laser. The system is made of one laser tube, and uses temporal superposition of two pulsed discharges, predischarge and main discharge. The laser pulse is produced in the main discharge by amplifying a seeded laser pulse produced by the predischarge. By optimizing the discharge conditions including an interval period between the two pulsed discharges, a high quality laser beam containing 80% of the whole laser beam energy in divergence as small as eight times diffraction limited has been obtained. The quality of the laser beam is comparable to that obtained with a conventional injection locking oscillator system consisting of two separate laser tubes. © 1999 American Institute of Physics.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Rn Relaxation oscillations and long pulse operation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Compact optical setup for forward-box degenerate four-wave mixing measurement

Toshio Fukaya, Shinichiro Iwai, and Shigeo Murata

Rev. Sci. Instrum. 70, 4178 (1999); http://dx.doi.org/10.1063/1.1150048 (2 pages)

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We have devised compact optics for the forward-box configuration in degenerate four-wave mixing spectroscopy. The core of the optical setup is the successive use of a pair of polarization-based beam splitters that divide the laser beam into four parallel beams. This setup is compact, easy to assemble, and adaptable for laser light over a wide spectral range. Selection of the combination of beam polarization produces two types of transient grating: either a polarization grating or an intensity grating. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.79.Fm Reflectors, beam splitters, and deflectors
07.60.Rd Visible and ultraviolet spectrometers
42.62.Fi Laser spectroscopy

A charge-coupled device-based laser photofragment fluorescence spectrometer for detection of mercury compounds

Xiaomei Tong, Robert B. Barat, and Arthur T. Poulos

Rev. Sci. Instrum. 70, 4180 (1999); http://dx.doi.org/10.1063/1.1150049 (5 pages) | Cited 2 times

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The use of a charge-coupled device (CCD) camera for the detection of mercuric bromide (HgBr2) vapor at low concentrations by laser photofragment fluorescence (PFF) spectroscopy was investigated. The CCD detection system (camera+monochromator) offers reasonable sensitivity plus spectral information, thus enhancing PFF as a technique for the environmental monitoring of airborne mercury compounds. The experiment used laser radiation at 222 nm to photolyze HgBr2 and produce excited atomic mercury (Hg∗). The PFF was monitored at 253.7 nm. Our unenhanced CCD detection limit was about 30 ppb HgBr2 in the absence of air. The CCD response remained linear up to 20 ppm. Observed nonlinearity of the PFF signal at higher concentrations is discussed. With the same collection optics and under the same experimental conditions, the sensitivity of a photomultiplier tube (PMT) with interference filters (253.7 nm) was also investigated for comparison. The detection limit for our PMT system was 10 ppb without signal averaging, but the linear dynamic range ended at 0.7 ppm. It is expected that the CCD detection system would be more versatile for measuring metal compound species by PFF spectroscopy in any future airborne metals monitor. © 1999 American Institute of Physics.
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07.88.+y Instruments for environmental pollution measurements
07.60.Rd Visible and ultraviolet spectrometers
42.62.Fi Laser spectroscopy
85.60.Gz Photodetectors (including infrared and CCD detectors)
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
42.79.Pw Imaging detectors and sensors

A versatile source to produce high-intensity, pulsed supersonic radical beams for crossed-beam experiments: The cyanogen radical CN(X2Σ+) as a case study

R. I. Kaiser, J. W. Ting, L. C. L. Huang, N. Balucani, O. Asvany, Y. T. Lee, H. Chan, D. Stranges, and D. Gee

Rev. Sci. Instrum. 70, 4185 (1999); http://dx.doi.org/10.1063/1.1150050 (7 pages) | Cited 17 times

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In our laboratory a novel and convenient technique has been developed to generate an intense pulsed cyano radical beam to be employed in crossed molecular beam experiments investigating the chemical dynamics of bimolecular reactions. CN radicals in their ground electronic state 2Σ+ are produced in situ via laser ablation of a graphite rod at 266 nm and 30 mJ output power and subsequent reaction of the ablated species with molecular nitrogen, which acts also as a seeding gas. A chopper wheel located after the ablation source and before the collision center selects a 9 μs segment of the beam. By changing the delay time between the pulsed valve and the choppper wheel, we can select a section of the pulsed CN(X2Σ+) beam choosing different velocities in the range of 900–1920 ms−1 with speed ratios from 4 to 8. A high-stability analog oscillator drives the motor of the chopper wheel (deviations less than 100 ppm of the period), and a high-precision reversible motor driver is interfaced to the rotating carbon rod. Both units are essential to ensure a stable cyanogen radical beam with velocity fluctuations of less than 3%. The high intensity of the pulsed supersonic CN beam of about 2–3×1011 cm−3 is three orders of magnitude higher than supersonic cyano radical beams employed in previous crossed molecular beams experiments. This data together with the tunable velocity range clearly demonstrate the unique power of our newly developed in situ production of a supersonic CN radical beam. This versatile concept is extendible to generate other intense, pulsed supersonic beams of highly unstable diatomic radicals, among them BC, BN, BO, BS, CS, SiC, SiN, SiO, and SiS, which are expected to play a crucial role in interstellar chemistry, chemistry in the solar system, and/or combustion processes. © 1999 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
41.75.Ak Positive-ion beams

Photo-induced dissociation of electrospray generated ions in an ion trap/time-of-flight mass spectrometer

Wojciech Gabryelski and Liang Li

Rev. Sci. Instrum. 70, 4192 (1999); http://dx.doi.org/10.1063/1.1150051 (8 pages) | Cited 18 times

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Laser photo-induced dissociation (PID) is an attractive alternative to collision-induced dissociation (CID) in probing structural features of biomolecules, such as peptides, by mass spectrometry. We report a new experimental setup for PID studies of biomolecules. It involves the use of an ion trap/time-of-flight mass spectrometer for the detection of PID products. The intact molecular ions are produced by electrospray ionization and introduced into a quadrupole ion trap. The ions stored in the trap are then dissociated by using a 266 nm laser beam from a pulsed Nd:yttrium–aluminium–garnet laser. After a short delay, all the fragment ions are extracted out of the trap and mass analyzed by a linear time-of-flight (TOF) mass spectrometer. The applications of this instrument for the PID studies of several peptides are demonstrated. The PID spectra are compared to those obtained by CID in the same instrument. It is shown that the amount of photoenergy deposited for fragmentation can be controlled by laser absorption property of the ions, laser power, number of laser pulses, and ion trap buffer gas pressure. Energetically optimal PID process results in spectra providing structural information similar to that obtained from CID. An excessive amount of photoenergy deposited to the fragmenting ions favors the formation of deep fragmentation products at the cost of sequence related ions. It is demonstrated that in some cases the PID technique has the potential in probing structural features of peptides that cannot be fragmented in ion trap CID. Finally, it is shown that the combination of the ion trap with the TOF detector provides a unique capability for fast detection of ions formed via PID. The PID products generated after a time delay from 1.5 μs to several milliseconds following the dissociation laser pulse can be characterized. © 1999 American Institute of Physics.
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87.64.-t Spectroscopic and microscopic techniques in biophysics and medical physics
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
07.75.+h Mass spectrometers
37.20.+j Atomic and molecular beam sources and techniques
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Design and testing of a new magnetorheometer

Aric B. Shorey, William I. Kordonski, Sergei R. Gorodkin, Stephen D. Jacobs, Roger F. Gans, Kevin M. Kwong, and Caleb H. Farny

Rev. Sci. Instrum. 70, 4200 (1999); http://dx.doi.org/10.1063/1.1150052 (7 pages) | Cited 10 times

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A new, commercially available polishing process called magnetorheological fininshing is used to polish and figure precision optics. To understand and model this process correctly it is important to determine the mechanical properties of the fluid under the influence of the magnetic field. Magnetorheotogical (MR) fluids are commonly modeled as Bingham fluids, so one of the essential properties to measure is the yield stress. Since MR fluids are inherently anisotropic, the yield stress will depend on the mutual orientation of the magnetic field and the direction of deformation. The relative orientation of the field and deformation in polishing does not coincide with common rheological setups, so a new rheometer has been designed and tested. This new magnetorheometer design has been shown to give correct stresses during calibration experiments using Newtonian fluids with a known viscosity. The measured stress has also been shown to have a magnitude consistent with published finite element approximations for magnetic fluids. The design of the instrument was complicated because of the requirements imposed upon the magnetic field, and the difficulty in satisfying the no slip boundary condition. Our results show the importance of having a homogeneous field in the test region during measurements. The solutions to these problems and discussion of the measurements on nonmagnetic and magnetic fluids are given. © 1999 American Institute of Physics.
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83.85.Cg Rheological measurements—rheometry
83.80.Gv Electro- and magnetorheological fluids
back to top CHARGED PARTICLE SOURCES, OPTICS and ACCELERATION

Emission optics of the Steigerwald-type electron gun

Chong-Yu Ruan and Manfred Fink

Rev. Sci. Instrum. 70, 4207 (1999); http://dx.doi.org/10.1063/1.1150053 (6 pages) | Cited 2 times

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The emission properties of a Steigerwald-type electron gun are reexamined. Several optical parameters were experimentally determined, and they indicate that the original telefocus mechanism proposed by Steigerwald in 1949 needs to be revised. “Remote focusing” is found to be nonexistent in most of the telefocus electron guns deployed in high-energy electron scattering experiments. Instead, almost parallel beams with variable beam diameters were found. The physical mechanism responsible for producing a very narrow, monochromatic, and highly collimated beam without limiting apertures is explained in this article with supporting evidences from measurements. We think the new emission model proposed here can help new types of electron or ion gun designs and applications using electron gun in electron optical systems. © 1999 American Institute of Physics.
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41.85.-p Beam optics

Optimization of spherical deflecting analyzer with finite-size effects

Chong-Yu Ruan, Scott Nguyen, and Manfred Fink

Rev. Sci. Instrum. 70, 4213 (1999); http://dx.doi.org/10.1063/1.1150054 (8 pages) | Cited 1 time

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Spherical analyzers have been widely used in electron spectroscopy due to their high energy resolution. In this article, we present a way of optimizing the performance of a 90° spherical deflecting analyzer (SDA-90) considering finite-source effects, using an imaging matrix formalism. Results are shown for both symmetrically and asymmetrically charged cases. The asymmetrical case is found to be superior both in transmission and resolution. This unexpected advantage can be explained by the rotation of the image caused by the broken symmetry along the principle trajectory in the analyzer using an asymmetrical potential configuration. The net effect is equivalent to a reduction in the lateral magnification and a gain in energy dispersion. Both factors improve the performance of the analyzer. The fringe fields, carefully controlled by two Herzog lenses, are very important in the optimization. A telefocus electron gun is used to check the numerical result, and to investigate the transverse focusing behavior. © 1999 American Institute of Physics.  
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41.85.Qg Particle beam analyzers, beam monitors, and Faraday cups
07.77.Ka Charged-particle beam sources and detectors

Generation and characterization of high intensity electron beams generated from rough photocathodes

V. Nassisi and M. R. Perrone

Rev. Sci. Instrum. 70, 4221 (1999); http://dx.doi.org/10.1063/1.1150055 (4 pages) | Cited 1 time

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In this work, the generation and the characterization of high current electron beams from rough photocathodes induced by an ultraviolet excimer laser are reported. The cathodes were rough Cu disks. In order to study the influence of the cathode surface, the electron emission from different surface roughnesses was investigated. To establish the electromagnetic and geometric parameters a Rogowski coil and a new slit–slit emittance meter were used. The laser beam utilized was obtained by a mixture of Kr and Cl which generated coherent light at 222 nm. Fixing the laser energy at 0.5 mJ and the laser spot into 4 mm2, the maximum current as well as the maximum emittance value were obtained with the cathode that had the highest surface roughness which resulted in 1 A and 46 π mm mrad, respectively. A low current and a low emittance were obtained with the cathode that had the lowest roughness, namely, 410 mA and 19 π mm mrad, respectively. A quantum efficiency value of 1.2×10−4 was reached with the cathode with the highest amount of roughness. © 1999 American Institute of Physics.
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85.60.Ha Photomultipliers; phototubes and photocathodes
41.75.Fr Electron and positron beams

High-efficiency spin-resolved and spin-integrated electron detection: Parallel mounting on a hemispherical analyzer

G. Ghiringhelli, K. Larsson, and N. B. Brookes

Rev. Sci. Instrum. 70, 4225 (1999); http://dx.doi.org/10.1063/1.1150056 (6 pages) | Cited 19 times

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We have mounted a compact 25 kV mini-Mott spin polarimeter on a commercial high-throughput hemispherical electron analyzer with a double purpose: to maximize the polarization detection and to preserve the original efficiency of the spectrometer in the spin-integrated measurements. We have thus replaced the 16-anode microchannel-plate detector with a 12-anode microsphere-plate detector in parallel with a Rice University retarding Mott spin polarimeter. Passing from one detection mode to the other is quick and easy. The transfer optics from the analyzer exit slit to the scattering target of the polarimeter allows the full potential of both the electron analyzer and the spin detector to be exploited. The expected effective Sherman function (Seff = 0.17) and figure of merit (η0 ≅ 1.4×10−4) are found in the spin-resolved mode, and only 25% of the original efficiency is lost in the spin-integrated acquisitions. © 1999 American Institute of Physics.
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07.81.+a Electron and ion spectrometers
29.30.Aj Charged-particle spectrometers: electric and magnetic
29.30.Ep Charged-particle spectroscopy
07.77.Ka Charged-particle beam sources and detectors

Variable geometry two mode levitation trap

D. Babič and A. Čadež

Rev. Sci. Instrum. 70, 4231 (1999); http://dx.doi.org/10.1063/1.1150057 (3 pages) | Cited 1 time

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Construction and operation of the electrodynamic levitation trap which can be operated in a passive and an active mode is described. This combination together with variable electrode geometry simplifies the trap’s design and simultaneously gives more flexibility with respect to different kinds of measurements. Sample measurements of mechanocaloric effect caused by nonuniform heating of a single levitated particle are presented and discussed. © 1999 American Institute of Physics.
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37.20.+j Atomic and molecular beam sources and techniques
41.20.-q Applied classical electromagnetism

Correlation between the hot-electron dynamics and the afterglow currents in electron cyclotron resonance ion sources

Masanori Kidera, Michele Lamoureux, Vladimir Mironov, Takahide Nakagawa, and Grigori Shirkov

Rev. Sci. Instrum. 70, 4234 (1999); http://dx.doi.org/10.1063/1.1150058 (4 pages) | Cited 2 times

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Time-resolved x-ray spectra were recorded at the RIKEN 18 GHz electron cyclotron resonance ion source (ECRIS) run in a pulsed mode, in order to understand why the best operating conditions are different in continuous and afterglow modes. The production of the largest afterglow currents of highly charged ions appears to be correlated with the building up of an important hot-electron component during the heating stage. The sudden drop of the corresponding hard x-ray emission at the microwave power turn-off is also studied. These observations support the view that the boosting afterglow effect is due to a fast modulation of the ECRIS plasma potential. © 1999 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
29.25.Ni Ion sources: positive and negative
29.25.Lg Ion sources: polarized
52.50.Gj Plasma heating by particle beams

Absolute detection efficiency of a microchannel plate detector for kilo-electron volt energy ions

H. C. Straub, M. A. Mangan, B. G. Lindsay, K. A. Smith, and R. F. Stebbings

Rev. Sci. Instrum. 70, 4238 (1999); http://dx.doi.org/10.1063/1.1150059 (3 pages) | Cited 42 times

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Measurements of the absolute detection efficiency of a commercial microchannel plate detector for kilo-electron volt energy ions are presented. The detector comprises two microchannel plates mounted in front of a resistive anode. It is found that when the detector is appropriately biased, and the ion impact energy is sufficiently high, ions with masses up to 131 amu are detected with equal efficiency and that this efficiency may remain constant over a period of years. © 1999 American Institute of Physics.
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29.40.Gx Tracking and position-sensitive detectors
85.60.Ha Photomultipliers; phototubes and photocathodes
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

The polarizer-analyzer correction problem in neutron polarization analysis experiments

A. R. Wildes

Rev. Sci. Instrum. 70, 4241 (1999); http://dx.doi.org/10.1063/1.1150060 (5 pages) | Cited 6 times

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The equations for correcting the instrumental depolarization effects in neutron polarization analysis experiments are presented in matrix form. It is proved that, when no approximations are made, it is always possible to solve for individual flipper efficiencies but is only sometimes possible to solve for polarizer and analyzer efficiencies. For certain experiments it is necessary to know these quantities to correctly analyze data. This is not a serious problem when the elements are very efficient, but has important ramifications when the efficiency is poor and/or time dependent, as is often the case with the helium-3 neutron polarizing method. Methods of solving for the polarizer and analyzer efficiencies are presented. © 1999 American Institute of Physics.
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07.90.+c Other topics in instruments, apparatus, and components common to several branches of physics and astronomy (restricted to new topics in section 07)

Core correlation reflectometer at the JT-60U tokamak

K. Shinohara, R. Nazikian, T. Fujita, and R. Yoshino

Rev. Sci. Instrum. 70, 4246 (1999); http://dx.doi.org/10.1063/1.1150061 (5 pages) | Cited 18 times

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Core correlation reflectometer has been newly installed on the JT-60U tokamak. The target of this reflectometer is to measure the fluctuation of the electron density and its correlation in the core region, especially in the internal transport barrier, region of high-performance-reversed shear plasma. The reflectometer consists of four channels, two of which operate in fixed frequency and the other two channels are tunable. The tunable channels can step through five frequencies in each 60 ms. The fluctuation correlation is determined from the correlation between fixed and variable frequency channels and the radial profile of the correlations can be measured every 60 ms in a discharge. The polarization of the launched wave is the extraordinary mode, X mode, in order to obtain a high space resolution and to access the high-field side of the magnetic axis. © 1999 American Institute of Physics.
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52.70.Gw Radio-frequency and microwave measurements
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
52.25.-b Plasma properties
52.55.Fa Tokamaks, spherical tokamaks

Fast two-dimensional potential measurement at the thermal barrier region of the tandem mirror Gamma 10

N. Kikuno, K. Ishii, N. Ishibashi, M. Nagasaki, Y. Katsuki, T. Goto, Y. Goi, Y. Ono, M. Yamanashi, A. Nagao, T. Saito, Y. Tatematsu, A. Suzuki, A. Itakura, T. Tamano, et al.

Rev. Sci. Instrum. 70, 4251 (1999); http://dx.doi.org/10.1063/1.1150062 (9 pages) | Cited 5 times

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A gold neutral beam probe system was improved by adopting a multichannel ion detector and adding sweeping functions of beam energy, deflector voltage, and electrode voltage of the analyzer to the system to measure the fluctuations and time evolution of the two-dimensional space potentials with fast resolving time during one shot. Positions of the beam spot on the multichannel detector corresponding to the ionizing points of the beam in the plasma were simulated precisely as a function of the beam energy and the injection angle. A potential derivation formula was determined taking into consideration both the numerical and experimental results, and the reproducibility of the potential profile was checked. Two-dimensional potential profiles were measured in the optimization experiment of the microwave injection angles for formation of the plug potential. © 1999 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium
52.25.Gj Fluctuation and chaos phenomena

Initial long-pulse plasma heating at reduced power with negative-ion-based neutral beam injector in large helical device

Y. Takeiri, N. Noda, Y. Nakamura, Y. Oka, M. Osakabe, K. Kawahata, O. Kaneko, K. Tsumori, M. Sato, T. Mutoh, M. Goto, K. Ida, S. Inagaki, S. Kado, S. Masuzaki, et al.

Rev. Sci. Instrum. 70, 4260 (1999); http://dx.doi.org/10.1063/1.1150063 (6 pages) | Cited 12 times

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We have achieved long-pulse plasma heating using a negative-ion-based neutral beam injector (NBI) in the large helical device (LHD), where the confinement magnetic field is generated by only external superconducting coils. In the initial long-pulse experiments at lower power than that in short-pulse experiments, 80 keV–1.1 MW NBI heating lasted for 10 s with a little increase in the plasma density at the pulse end. Almost steady-state plasma heating was achieved for 21 s with 66 keV–0.6 MW NB injection. Plasma relaxation oscillation phenomena at a period of 1–2 s were also observed for 20 s. Above 1 keV plasma was easily sustained with a long-pulse NBI heating in LHD, without the current drive nor the disruption in tokamaks. Negative ion source operation was stable and the cooling water temperature rise of beam accelerator grids was nearly saturated with a temperature rise below 10 °C. For a higher power injection, the pulse duration is determined by the beam blocking, where the reionization loss is exponentially increased together with an increase in outgas in the injection port. The port conditioning by a careful repetition of injection is effective to the extension of the injection duration and the plasma maintenance duration. The initial long-pulse NBI heating at the reduced power has demonstrated an ability of steady-state operation in superconducting LHD. © 1999 American Institute of Physics.
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52.55.Jd Magnetic mirrors, gas dynamic traps
52.50.Gj Plasma heating by particle beams

An electrostatic probe with end plugs for measurements in a magnetized plasma

V. I. Demidov, S. V. Ratynskaia, and K. Rypdal

Rev. Sci. Instrum. 70, 4266 (1999); http://dx.doi.org/10.1063/1.1150064 (4 pages) | Cited 10 times

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An electrostatic probe for measurements in a magnetized plasma is proposed. It consists of a cylindrical rod with insulating end plugs, and is operated by obtaining the current-voltage characteristic and its first derivative for different orientations of the rod with respect to the magnetic field. The probe provides a simple estimate of ion temperature and ion density and an improved measurement of the electron energy distribution function. © 1999 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements

Estimation method for electron-hole pair density in plasma columns

I. Kanno

Rev. Sci. Instrum. 70, 4270 (1999); http://dx.doi.org/10.1063/1.1150065 (5 pages)

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A simple method to estimate the electron-hole pair density in plasma columns created by heavy ions is described. The volume of plasma column is described in a ratio to the one of cone with the same range and bottom radius of the plasma column. The volume ratio is expressed by second polynomials of the energy per unit mass of the heavy ion. With three parameters of the second polynomials, the range and the bottom radius of the cone, the volume of the corresponding plasma column, and consequently, the electron-hole pair density inside it are easily estimated. © 1999 American Institute of Physics.
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29.40.Wk Solid-state detectors
61.80.Jh Ion radiation effects
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
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Optical detection of ultrasound with a phase-modulated Michelson interferometer

Hidetoshi Nakano, Youichi Matsuda, and Satoshi Nagai

Rev. Sci. Instrum. 70, 4275 (1999); http://dx.doi.org/10.1063/1.1150066 (4 pages) | Cited 1 time

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A phase-modulated Michelson interferometer for optical detection for ultrasound is described. The operating point of the interferometer is kept to the minimum intensity of the interference pattern. This scheme allows the use of a high power laser to improve the sensitivity without a photodiode saturation. Ultrasonic displacement amplitudes as small as 10 pm can be detected when the maximum intensity on the photodiode is 100 mW. The detected root-mean-square noise is twice as much as the theoretical prediction of 3×10−16 m/math. The ultrasonic wave forms excited with a transducer and a pulsed laser in a Si sample are presented. © 1999 American Institute of Physics.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
07.60.Ly Interferometers
42.79.Hp Optical processors, correlators, and modulators

Nd3+-doped optical fiber temperature sensor using the fluorescence intensity ratio technique

S. A. Wade, J. C. Muscat, S. F. Collins, and G. W. Baxter

Rev. Sci. Instrum. 70, 4279 (1999); http://dx.doi.org/10.1063/1.1150067 (4 pages) | Cited 13 times

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An optical fiber temperature sensor employing the fluorescence intensity ratio using Nd3+-doped silica fiber and exhibiting high sensitivity is presented. The development and construction of the sensor, which requires relatively simple electronics and data analysis, is described together with its calibration over the −50 to +500 °C temperature range. © 1999 American Institute of Physics.  
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42.81.Pa Sensors, gyros
07.20.Dt Thermometers
07.60.Vg Fiber-optic instruments
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