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Nov 2000

Volume 71, Issue 11, pp. 3981-4344

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Photodetachment diagnostic techniques for measuring negative ion densities and temperatures in plasmas

M. Bacal

Rev. Sci. Instrum. 71, 3981 (2000); http://dx.doi.org/10.1063/1.1310362 (26 pages) | Cited 73 times

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Photodetachment diagnostic techniques can help determine densities and temperatures of negative ions in a variety of scientific devices in which these ions are one of the major charged particle species. This method has been extensively used in the development of hydrogen negative ion sources as well as other devices. In order to obtain spatial resolution, a photodetachment diagnostic technique is used with an electrostatic probe that detects the currents of photodetached electrons. © 2000 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
32.80.Gc Photodetachment of atomic negative ions
01.30.Rr Surveys and tutorial papers; resource letters
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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

An image plate chamber for x-ray diffraction experiments in Debye–Scherrer geometry

Oliver Stachs, Thomas Gerber, and Valeri Petkov

Rev. Sci. Instrum. 71, 4007 (2000); http://dx.doi.org/10.1063/1.1318915 (3 pages) | Cited 3 times

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A new design for implementation of x-ray diffraction experiments is proposed. The exploitation of the imaging plate technique opens new possibilities to carry out diffraction experiments. The detector chamber in Debye–Scherrer geometry equipped with an image plate takes advantage of this technology such as high resolution, high sensitivity, linearity in intensity, and linearity over the detector area. The proof of this measurement principle is demonstrated by presentation of the x-ray diffraction pattern of corundum (crystalline), nickel (crystalline), and sodium borate (amorphous). © 2000 American Institute of Physics.
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61.05.cp X-ray diffraction
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors

Electrically induced Bragg-diffraction grating composed of periodically inverted domains in lithium niobate crystals and its application devices

Masahiro Yamada

Rev. Sci. Instrum. 71, 4010 (2000); http://dx.doi.org/10.1063/1.1319341 (7 pages) | Cited 19 times

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Bragg diffraction by an electrically induced and controlled grating composed of periodically inverted domains in a lithium niobate crystal is discussed theoretically and experimentally. As the applications of the Bragg-diffraction grating, experimental results of an optical switch with one input port and six output ports and a wide band optical amplitude modulator for a violet-blue light with the wide frequency bandwidth from direct current to 1 GHz are presented. © 2000 American Institute of Physics.
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42.79.Dj Gratings
77.80.Dj Domain structure; hysteresis
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.79.Hp Optical processors, correlators, and modulators
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Erbium/ytterbium fluorescence based fiber optic temperature sensor system

T. Sun, Z. Y. Zhang, and K. T. V. Grattan

Rev. Sci. Instrum. 71, 4017 (2000); http://dx.doi.org/10.1063/1.1289682 (6 pages) | Cited 13 times

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Erbium/ytterbium co-doped fibers have been investigated in this work for the first time to determine their potential in thermometry applications based on the use of fluorescence decay. Several samples have been used and their performance characteristics determined. These have included studies of fiber annealing as well as thermal cycling tests and it was found that unlike other rare-earth ion doped fibers previously studied, such as Nd3+, Er3+, or Tm3+ doped fibers, the Er/Yb co-doped samples used here have shown a much smaller degree of thermal annealing when their thermal characteristics have been evaluated and compared. The response of the thermometer and the error in the measurement was found to be, at <±5 °C, within the stability of the oven used in the tests over a wide temperature range from 0 to 850 °C. © 2000 American Institute of Physics.
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42.81.Pa Sensors, gyros
07.20.Dt Thermometers

A broadly tunable extreme ultraviolet laser source with a 0.008 cm−1 bandwidth

U. Hollenstein, H. Palm, and F. Merkt

Rev. Sci. Instrum. 71, 4023 (2000); http://dx.doi.org/10.1063/1.1310344 (6 pages) | Cited 46 times

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A new coherent narrow bandwidth extreme ultraviolet (XUV) laser source has been developed that is broadly tunable in the range 10–17 eV with a bandwidth of 0.008 cm−1 and intensities of 108 photons/pulse at 20 Hz. The source is based on two-photon resonance-enhanced sum-frequency mixing in rare gases. To demonstrate its properties, high-resolution photoionization and photoelectron spectra of argon have been recorded in the vicinity of the second, spin-orbit excited ionization threshold (Ar+2P1/2). From the analysis of the autoionization line shapes of the ns′[1/2](J = 1) and nd′[3/2](J = 1) resonances, reduced linewidths Γr,l = Γl×n∗3 of 499.3(46) cm−1 and 28.76(89)×103 cm−1 have been determined for the s′ and d′ series, respectively. The results for the ns′[1/2](J = 1) series confirm the conclusion reached by Klar et al. [Z. Phys. D 23, 101 (1992)] that earlier single-photon XUV investigations have overestimated the width of these sharp resonances. The narrow bandwidth of the source is also used to accurately determine the range of principal quantum number of the high Rydberg states that are probed by selected electric field ionization sequences in pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopy. © 2000 American Institute of Physics.
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42.72.Bj Visible and ultraviolet sources
07.81.+a Electron and ion spectrometers
42.60.Fc Modulation, tuning, and mode locking
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Improved external cavity design for cesium D1 (894 nm) diode laser

A. Andalkar, S. K. Lamoreaux, and R. B. Warrington

Rev. Sci. Instrum. 71, 4029 (2000); http://dx.doi.org/10.1063/1.1319860 (3 pages) | Cited 14 times

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We have developed an external cavity diode laser for use near the cesium D1 transition at 894 nm, producing over 20 mW of single-mode power with a continuous tuning range of up to 25 GHz. Our mechanical design allows simple alignment and optimization of the cavity with very good passive stability, as temperature control of the diode is not coupled with changes in cavity length, and it could easily be used with diodes at other wavelengths. We detail the design and construction, and review the performance of the current system, which has been in operation for several years. © 2000 American Institute of Physics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

A sub-Doppler resolution double resonance molecular beam infrared spectrometer operating at chemically relevant energies (∼2 eV)

H. K. Srivastava, A. Conjusteau, H. Mabuchi, A. Callegari, K. K. Lehmann, and G. Scoles

Rev. Sci. Instrum. 71, 4032 (2000); http://dx.doi.org/10.1063/1.1310343 (7 pages)

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A molecular beam spectrometer capable of achieving sub-Doppler resolution at 2 eV (∼18 000 cm−1) of vibrational excitation is described and its performance demonstrated using the CH stretch chromophore of HCN. Two high finesse resonant power-buildup cavities are used to excite the molecules using a sequential double resonance technique. A v = 0→2 transition is first saturated using a 1.5 μm color center laser, whereupon a fraction of the molecules is further excited to the v = 6 level using an amplitude modulated Ti:Al2O3 laser. The energy absorbed by the molecules is detected downstream of both excitation points by a cryogenically cooled bolometer using phase sensitive detection. A resolution of approximately 15 MHz (i.e., three parts in 108) is demonstrated by recording a rotational line in the v = 6 manifold of HCN. Scan speeds of up to several cm−1/h were obtained, with signal-to-noise ratios in excess of 100. The high signal-to-noise ratio and a dynamic range of 6×104 means that future experiments to study statistical intramolecular vibrational energy redistribution in small molecules and unimolecular isomerizations can be attempted. We would also like to point out that, with improved metrology in laser wavelengths, this instrument can also be used to provide improved secondary frequency standards based upon the rovibrational spectra of molecules. © 2000 American Institute of Physics.
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37.20.+j Atomic and molecular beam sources and techniques
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
34.50.Lf Chemical reactions
33.40.+f Multiple resonances (including double and higher-order resonance processes, such as double nuclear magnetic resonance, electron double resonance, and microwave optical double resonance)

A high-power picosecond near-infrared laser transmitter module

Sergey N. Vainshtein, Andrey V. Maslevtsov, Ari J. Kilpelä, and Juha T. Kostamovaara

Rev. Sci. Instrum. 71, 4039 (2000); http://dx.doi.org/10.1063/1.1315353 (6 pages) | Cited 1 time

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A compact laser diode based transmitter was designed and tested for laser radar and various laboratory applications. Single optical pulses with a peak power of up to 200 W, 23–65 ps pulse duration, and a repetition rate of up to 50 kHz were measured. Transient mode spectral filtering suppressed after pulsing modes by a factor of 104–105 with respect to the peak power. A control module was developed which provided a jitter value between electrical triggering and the optical pulses as low as 14 ps. Averaging of 103 events allows 1.5 ps stability between the triggering and the optical pulses to be achieved within a delay range from 5 to 250 ns. © 2000 American Institute of Physics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.72.Ai Infrared sources
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

An externally controlled, nanosecond-pulsed, Xe lamp using a high voltage semiconductor switch

Tetsuo Iwata, Toshiki Tanaka, Toshiyuki Komatsu, and Tsutomu Araki

Rev. Sci. Instrum. 71, 4045 (2000); http://dx.doi.org/10.1063/1.1321299 (5 pages) | Cited 2 times

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We have constructed a nanosecond pulsed Xe lamp which is controllable by a small-sized, high-voltage semiconductor switch that is driven by a transistor-transistor-logic level external signal. The Xe lamp used here is commercially available and it is usually operated in a direct-current (dc) mode. The aim of the external control is to solve a discharge difficulty in a free-running Xe lamp that we have developed previously. The problem is that the free-running discharge Xe lamp suddenly switches in its operation mode from a pulsed spark-discharge mode to an undesirable, weak, dc arc-discharge mode. The pulse width of emitted light from the pulsed Xe lamp was 3.8 ns and the repetition frequency was 0.5–1 kHz with a peak power 100 W. In order to obtain an accurate timing signal required for a fluorescence-lifetime measurement system, a current probe circuit was added in the control circuit. Details of the lamp and the results of fundamental performance tests are shown. © 2000 American Institute of Physics.
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42.72.Bj Visible and ultraviolet sources
52.80.Yr Discharges for spectral sources (including inductively coupled plasma)
07.60.Rd Visible and ultraviolet spectrometers
85.30.-z Semiconductor devices

Picosecond infrared optical parametric amplifier for nonlinear interface spectroscopy

D. Bodlaki and E. Borguet

Rev. Sci. Instrum. 71, 4050 (2000); http://dx.doi.org/10.1063/1.1321302 (7 pages) | Cited 5 times

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A tunable, narrow bandwidth, high peak power picosecond infrared (IR) laser system is described. The pump source is a picosecond Ti:sapphire regenerative amplifier seeded by a picosecond Ti:sapphire oscillator. The pump bandwidth and pulse duration are tunable producing 4–5 ps, 5–4 cm−1 pulses at 1 kHz. IR pulses are produced by optical parametric generation (OPG) followed by optical parametric amplification (OPA). Tuning is possible over the entire 1050–3300 nm region of the IR, with energies in excess of 15 μJ over most of the range. The temporal and spectral characteristics of the IR pulses are reviewed with a particular focus on the sources of bandwidth broadening in the OPG/OPA. Bandwidth optimization of the IR output is discussed. A spectral filtering scheme results in less than 15 cm−1 IR bandwidth, suitable for nonlinear optical spectroscopic applications. © 2000 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.72.Ai Infrared sources
42.60.Fc Modulation, tuning, and mode locking
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources

Design and implementation of a rapid-mixer flow cell for time-resolved infrared microspectroscopy

Nebojsa S. Marinkovic, Aleksandar R. Adzic, Michael Sullivan, Kevin Kovacs, Lisa M. Miller, Denis L. Rousseau, Syun-Ru Yeh, and Mark R. Chance

Rev. Sci. Instrum. 71, 4057 (2000); http://dx.doi.org/10.1063/1.1319342 (4 pages)

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A rapid mixer for the analysis of reactions in the millisecond and submillisecond time domains by Fourier-transform infrared microspectroscopy has been constructed. The cell was tested by examination of cytochrome-c folding kinetics. The device allows collection of full infrared spectral data on millisecond and faster time scales subsequent to chemical jump reaction initiation. The data quality is sufficiently good such that spectral fitting techniques could be applied to analysis of the data. Thus, this method provides an advantage over kinetic measurements at single wavelengths using infrared laser or diode sources, particularly where band overlap exists. © 2000 American Institute of Physics.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.53.-k Femtochemistry
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
87.64.K- Spectroscopy
87.64.M- Optical microscopy

Supercritical-fluid cell with device of variable optical path length giving fringe-free terahertz spectra

Ken-ichi Saitow, Keiko Nishikawa, Hideyuki Ohtake, Nobuhiko Sarukura, Hiroshi Miyagi, Yuji Shimokawa, Hitoshi Matsuo, and Keisuke Tominaga

Rev. Sci. Instrum. 71, 4061 (2000); http://dx.doi.org/10.1063/1.1318923 (4 pages) | Cited 5 times

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An optical cell suitable for supercritical fluids was constructed for measurements of far infrared absorption spectra with terahertz radiation as a light source. It was designed to withstand temperature up to 400 K and pressure up to 15 MPa. The cell has two characteristic devices; one is diamond windows set in the Brewster angle to the incident far infrared light and the other is a variable optical path length from 30 μm to 20 mm under high pressure conditions. Using the cell, fringe-free spectra of CHF3 ranging from low-density gaseous states to high-density supercritical ones were measured in a low-energy region of 10–100 cm−1. © 2000 American Institute of Physics.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

Large area flat crystal x-ray spectrometer with high integrated intensity for an electron beam ion trap

Nobuyuki Nakamura

Rev. Sci. Instrum. 71, 4065 (2000); http://dx.doi.org/10.1063/1.1319978 (5 pages) | Cited 8 times

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A flat crystal x-ray spectrometer has been constructed for spectroscopic studies of highly charged ions with an electron beam ion trap. It consists of a flat crystal and a position sensitive proportional counter. Employment of a flat crystal yields easy alignment, easy processing of the crystal, and high flexibility. The proportional counter has been designed to have a large effective area, which is needed to compensate for weak focusing power of a flat crystal. The utility of the new spectrometer has been demonstrated with the Tokyo electron beam ion trap. © 2000 American Institute of Physics.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
07.85.Nc X-ray and γ-ray spectrometers
29.40.Gx Tracking and position-sensitive detectors
29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche counters
29.30.Kv X- and γ-ray spectroscopy

A triply differentially pumped supersonic beam target for high-resolution collision studies

S. Götte, A. Gopalan, J. Bömmels, M.-W. Ruf, and H. Hotop

Rev. Sci. Instrum. 71, 4070 (2000); http://dx.doi.org/10.1063/1.1319343 (8 pages) | Cited 7 times

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A Campargue-type source of an intense, triply differentially pumped supersonic beam of atoms (He, Ne, Ar) and molecules (N2) for use in high-resolution collision experiments is described. Using stagnation pressures of (1–10) bar, nozzle diameters of (0.05–0.25) mm, and skimmer diameters of (0.5–1.0) mm, the center-line intensity and collimated target density are quantitatively characterized by electron impact ionization in conjunction with total ion collection. Optimum densities in a target plane, located about 160 mm from the nozzle, range from 1012 cm−3 (N2) to 8×1012 cm−3 (He) at background densities which are about 1% of the beam densities. The results are compared with values calculated for ideal supersonic expansions. © 2000 American Institute of Physics.
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37.20.+j Atomic and molecular beam sources and techniques
07.77.Gx Atomic and molecular beam sources and detectors
47.40.Ki Supersonic and hypersonic flows
34.80.-i Electron and positron scattering

Development of a Fourier-transform ion cyclotron resonance mass spectrometer-ion mobility spectrometer

Brian K. Bluhm, Kent J. Gillig, and David H. Russell

Rev. Sci. Instrum. 71, 4078 (2000); http://dx.doi.org/10.1063/1.1288235 (9 pages) | Cited 22 times

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In an effort to incorporate ion-molecule reaction chemistry with ion mobility measurements we designed and constructed a novel instrument that combines a Fourier-transform ion cyclotron resonance (ICR) mass spectrometer with an ion mobility drift cell and a time-of-flight mass spectrometer. Measured mobilities for Ar+ and CO+ in helium are in excellent agreement with accepted literature values demonstrating that there are no adverse effects from the magnetic field on ion mobility measurements. Drift cell pressure, extracted from the measured mobility of Ar+ in helium, indicate that a pressure of ∼0.25 Torr is achieved in the present configuration. There are significant technological challenges associated with combining ICR and ion mobility that occurred during construction of this instrument, such as differential pumping and aperture alignment are presented. © 2000 American Institute of Physics.
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07.75.+h Mass spectrometers
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment

A trochoidal analyzer to measure the electron beam energy distribution in a traveling wave tube

D. Guyomarc’h and F. Doveil

Rev. Sci. Instrum. 71, 4087 (2000); http://dx.doi.org/10.1063/1.1319339 (5 pages) | Cited 12 times

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The trochoidal monochromator is commonly used to produce a monoenergetic electron beam in an axial magnetic field. By adding a retarding electric field system at the entrance and a Faraday cup at the exit of the monochromator, such a dispersive device can be used to measure the energy distribution of an electron beam. This device is used in a traveling wave tube in order to study wave particle interactions. © 2000 American Institute of Physics.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
41.75.Fr Electron and positron beams
41.85.Qg Particle beam analyzers, beam monitors, and Faraday cups
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Fast magnetic fluctuation diagnostics for Alfvén eigenmode and magnetohydrodynamics studies at the Joint European Torus

R. F. Heeter, A. F. Fasoli, S. Ali-Arshad, and J. M. Moret

Rev. Sci. Instrum. 71, 4092 (2000); http://dx.doi.org/10.1063/1.1313797 (15 pages) | Cited 12 times

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Alfvén eigenmodes and other magnetohydrodynamic phenomena have been studied in tokamak plasmas at the Joint European Torus (JET) using a new eight-channel, 4 s, 1 MHz, 12-bit data acquisition system (KC1F) in conjunction with the JET fast Mirnov magnetic fluctuation pickup coils. To this end, the JET magnetic pickup coils were calibrated in the range 30–460 kHz using a new remote calibration technique which accounts for the presence of the first few LRC circuit resonances. Signal processing software has been developed to implement the calibration via digital filtering. A data analysis program has been written which produces spectrograms of fluctuation amplitude and toroidal mode number versus frequency and time, both interactively and for automatic overnight analyses. Modes with amplitudes δB/B ≥ 10−8 and toroidal mode numbers ∣n∣<32 are now routinely detected. Since KC1F data are now available for over 4000 JET discharges, a pulse-characterization database has been developed to help select pulses of interest for detailed analysis. © 2000 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.55.Fa Tokamaks, spherical tokamaks
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
07.05.Hd Data acquisition: hardware and software
52.30.-q Plasma dynamics and flow

Omegatron ion mass spectrometer for the Alcator C-mod tokamak

R. Nachtrieb, B. LaBombard, and E. Thomas

Rev. Sci. Instrum. 71, 4107 (2000); http://dx.doi.org/10.1063/1.1311942 (12 pages) | Cited 10 times

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A new ion mass spectrometry probe that operates at high magnetic field (∼8 T) has been recently commissioned on the Alcator C-Mod tokamak. The probe combines an omegatron E(t)×B ion mass spectrometer and a retarding field energy analyzer. The probe samples the plasma in the far scrape-off layer, on flux surfaces between 25 and 50 millimeters from the separatrix. Radio-frequency (rf) power is used to collect ions with resonant cyclotron frequency on the side walls of an rf cavity. Scanning the frequency results in a spectrum ordered by the ratio of ion mass to charge, M/Z. Resonances are presently resolved for 1 ⩽ M/Z<12 down to signal levels as low as 5×10−4 times that of the bulk plasma species. Well-resolved resonances have widths within a factor of two of theoretical values obtained from particle orbit theory. Absolute impurity fluxes and individual impurity charge state temperatures are quantified by varying the applied rf power and recording the change of the amplitude of the resonant ion current. The design of the hardware and electronics design is described, the principles of operation are discussed, and initial experimental results are presented. Sources of noise which presently limit the sensitivity of the device are also discussed along with techniques to improve the signal–to–noise ratio. © 2000 American Institute of Physics.
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52.70.Nc Particle measurements
07.75.+h Mass spectrometers
52.55.Fa Tokamaks, spherical tokamaks

The “Compact Toroid Injection Experiment” tomographic imaging system

S. D. Terry, D. Q. Hwang, H. S. McLean, R. D. Horton, R. W. Evans, and K. L. Baker

Rev. Sci. Instrum. 71, 4119 (2000); http://dx.doi.org/10.1063/1.1318920 (8 pages)

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The design, construction and operation of a tomographic imaging system on the Compact Toroid Injection Experiment is described. The system measures the total radiated power over energies from visible light up into the extreme ultraviolet. It then reconstructs two dimensional profiles from the data. The reconstruction routine is based on a method known as second order regularization which finds a compromise between smoothness and fit to the data. This method was found to have the best overall fidelity to test images. The hardware and overall reconstruction were calibrated using two different sources. First results from the system under real experimental conditions are presented. © 2000 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks
07.05.Pj Image processing

A source with ion extraction from the plasma volume

B. N. Makov

Rev. Sci. Instrum. 71, 4127 (2000); http://dx.doi.org/10.1063/1.1318916 (4 pages)

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The physical basis of an effective new variant of ion source with extraction of ions from the plasma volume, operating in a longitudinal magnetic field developed at the Kurchatov Institute, is described. A thin layer with an electric field is produced in the plasma column of the source without violation of plasma quasineutrality, in order to transport all types of charged particles across the magnetic field toward the extraction slit. This allows high plasma flows to be transported toward the extraction slit with low potential difference ΔU across the layer, and the ion current density in the extracted ion beam can be increased by up to 10–15 times. The induced plasma flow also increases significantly the content of multicharged ions in the beam. A strong dependence of the ion beam current intensity on the potential across the layer provides a means for pulsed modulating or stabilizing the current intensity at the target by special programming or feedback in an inertia-free manner, without changes in the discharge conditions. The ion source operates with various species—gas or sputter materials. An ion current density of 1.5 A/cm2 was measured in our experiments at ΔU = 10 V. The source can be used for accelerators, in semiconductor technology, and for other applications. © 2000 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
52.50.Dg Plasma sources
41.85.Ar Particle beam extraction, beam injection

Development of a high-speed, reciprocating electrostatic probe system for Hall thruster interrogation

James M. Haas, Alec D. Gallimore, Keith McFall, and Greg Spanjers

Rev. Sci. Instrum. 71, 4131 (2000); http://dx.doi.org/10.1063/1.1318921 (8 pages) | Cited 10 times

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The use of electrostatic probes to measure local plasma parameters inside the discharge chamber of a Hall thruster presents significant difficulties. The high-temperature, dense plasma, and Hall current in the accelerating channel heat the probe rapidly causing ablation of probe material, which perturbs thruster operation and reduces probe lifetime. Results are presented which show the extent of perturbation to discharge current, cathode potential, and thrust for the case where probe material is ablated. A simple thermal model of probe material heating is developed and ablation times for a typical probe configuration are presented. Using the results of the thermal model, a high-speed axial reciprocating probe (HARP) system was developed to enable probe survival and reduce thruster perturbations during interrogation of the discharge chamber of a Hall thruster. Results using the HARP system are presented showing a significant reduction in thruster perturbation. The results also indicate that a mechanism other than material ablation is contributing to perturbation of the thruster. Based on emissive probe data, the tungsten conductor appears to provide a low impedance path between magnetic field lines, enhancing electron transport to the anode. © 2000 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.75.Di Ion and plasma propulsion

Chemical vapor deposition diamond window as vacuum and tritium confinement barrier for fusion application

K. Takahashi, K. Sakamoto, A. Kasugai, T. Imai, J. R. Brandon, and R. S. Sussmann

Rev. Sci. Instrum. 71, 4139 (2000); http://dx.doi.org/10.1063/1.1313799 (5 pages) | Cited 5 times

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A pressure resistant polycrystalline chemical vapor deposition (CVD) diamond disk for a microwave window is used for a vacuum and a tritium confinement boundary in fusion applications. A pressure test of a CVD diamond window disk (2.25 mm in thickness and 100 mm in diameter) was carried out. It was demonstrated that the diamond window tolerated 1.0 MPa (10 atm) in the plenum. The displacement of the window center for both the growth and the nucleation side on the unpressurized side is 40±1 and 41±1 μm, respectively, at the pressure of 1.0 MPa, and these values agree well with those calculated. No damage in the disk and the braze, and no vacuum leakage in the assembly was observed. This result demonstrates that the diamond window assembly could tolerate up to 1.45 MPa. It was experimentally proved that the diamond window satisfied the safety requirement of 0.5 MPa resistance for the vacuum and the tritium confinement boundary of an International Thermonuclear Experimental Reactor. The design prospect for the diamond window of the electron cyclotron heating and current drive system is also discussed, based on the stress analysis using the ABAQUS code. © 2000 American Institute of Physics.
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28.52.Fa Materials
28.52.Nh Safety
52.55.Fa Tokamaks, spherical tokamaks
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
back to top MICROSCOPY and IMAGING

Ultrafast charge division imaging detector

Alan Liu, Brian Woo, and Robert W. Odom

Rev. Sci. Instrum. 71, 4144 (2000); http://dx.doi.org/10.1063/1.1310339 (5 pages) | Cited 1 time

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We have developed position computing electronics having less than 60 ns dead times for resistive anode encoders, a form of charge division imaging detector. These electronics are at least a factor of 5 faster than anything available commercially and are based on using a fast, self-resetting charge integrator and subrange digital division techniques. Our primary application for this detector is secondary ion mass spectrometry (SIMS)/ions imaging and we demonstrate that SIMS imaging applications using these ultrafast electronics can readily be performed at ion intensities above 106 cps. This article discusses the overall electronics design and presents experimental data on dead-time measurements, detector lateral resolution, and SIMS imaging. © 2000 American Institute of Physics.
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29.50.+v Computer interfaces
84.30.Sk Pulse and digital circuits
07.75.+h Mass spectrometers
07.68.+m Photography, photographic instruments; xerography
07.05.Hd Data acquisition: hardware and software

A simple approach for calibrating solid-state imaging systems

Fred W. Leslie, Soyoung S. Cha, and Narayanan Ramachandran

Rev. Sci. Instrum. 71, 4149 (2000); http://dx.doi.org/10.1063/1.1319983 (6 pages)

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Imaging by solid-state array sensors has become an indispensable tool in various modern scientific and engineering applications. In such instrumentation, a linear response of the sensor output to the incident light intensity is often very much desirable. The system linearity can be affected by both the sensing element and electronics. The linearity also needs to be accurately determined in order to assess and correct measurement errors. Some imaging systems, especially those of upper grade with high resolution, allow precise control of exposure time. If so, it is easy to check the linearity in response to the incident energy with changes of exposure time under a constant intensity of illuminating light. For imaging systems without precise time control, especially those of intermediate- or lower-grade, it is highly desirable to have some means for assessing linearity and applying corrections to improve accuracy for photometric uses. Here, we present two simple approaches, one for quickly checking linearity and the other for correcting the response, for those imaging systems without exact exposure-time control. The former allows a quick assessment of the linearity while the latter permits an accurate calibration with minimal hardware preparation. In initial testing, the calibration method works well with an intermediate-grade sensor interfaced to a frame grabber. The nonlinearity of the imaging system tested can be reduced from about 5.1% to much less than 1% in standard deviation. © 2000 American Institute of Physics.
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42.79.Pw Imaging detectors and sensors
85.60.Gz Photodetectors (including infrared and CCD detectors)
06.20.F- Units and standards

Microscopic lock-in thermography investigation of leakage sites in integrated circuits

O. Breitenstein, M. Langenkamp, F. Altmann, D. Katzer, A. Lindner, and H. Eggers

Rev. Sci. Instrum. 71, 4155 (2000); http://dx.doi.org/10.1063/1.1310345 (6 pages) | Cited 20 times

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The detection limit of infrared thermographic investigations can be improved down to 10 μK by using a highly sensitive high-speed infrared camera in an on-line averaging lock-in thermography system. Together with a microscope objective, this allows lock-in thermography to be used as a simple and sensitive technique to localize the sites of leakage currents and other heat sources in electronic components. The practical realization of a novel lock-in thermography system is described and both test measurements and practical applications are introduced. The detection limit for surface-near local heat sources in silicon is a few microwatts with a spatial resolution down to 5 μm. Leakage sites in several microelectronic structures are imaged and assigned to the layout of the integrated circuit by comparing direct images with lock-in ones. The direct comparison of an averaged and background-subtracted stationary thermogram with a lock-in one, both measured under similar conditions at the same sample, clearly demonstrates the gain in information obtained by using lock-in thermography. © 2000 American Institute of Physics.
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85.40.Qx Microcircuit quality, noise, performance, and failure analysis
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Pw Imaging detectors and sensors
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