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Feb 1994

Volume 65, Issue 2, pp. 285-520

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Thermal anemometry, current state, and future directions

L. M. Fingerson

Rev. Sci. Instrum. 65, 285 (1994); http://dx.doi.org/10.1063/1.1145187 (16 pages) | Cited 11 times

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The variation in heat transfer between a fine wire and the surrounding fluid has traditionally been the most accepted method for measuring the detailed movements of a flow fluid. This paper reviews the present understanding of thermal techniques as used in research and recent advancements of the technique. While the basic research sensor is still a fine wire, modern electronics has greatly simplified data analysis as well as established constant temperature operation of the sensor as the control method of choice. Film sensors have extended the use of thermal sensors to new applications. Comparisons with laser Doppler velocimeters help to identify experiments where thermal sensors still represent the best choice. The ability of modern electronics to easily address the typical nonlinear response of thermal sensors has resulted in increased use for commercial applications. While in these applications fast response can be a factor (e.g., fuel flow control in engines), generally only average flows are needed. As a result, calibration shifts due to deposits on the sensor surface when exposed to contaminated fluids can generally be reduced to acceptable levels by using larger sensors.
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07.20.-n Thermal instruments and apparatus
47.80.-v Instrumentation and measurement methods in fluid dynamics

Cryogenic bolometric radiometer and telescope

G. S. Tucker, J. B. Peterson, C. B. Netterfield, E. L. Griffith, and G. S. Griffin

Rev. Sci. Instrum. 65, 301 (1994); http://dx.doi.org/10.1063/1.1145188 (8 pages) | Cited 1 time

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The design and performance of an instrument to measure cosmic microwave background (CMB) anisotropy on angular scales from 10′ to 30′ is reported. The instrument utilizes a single‐mode waveguide bolometer cooled by an adiabatic demagnetization refrigerator. This is the first time a 100 mK bolometer has been used in a CMB experiment. Observations of the CMB were made using this radiometer from the South Pole during the 1991–1992 season and, with minor modifications, during the 1992–1993 season. The radiometer is used with a fully steerable altitude‐azimuth Cassegrain telescope built for this observation, also described here.
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95.55.Jz Radio telescopes and instrumentation; heterodyne receivers
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
98.70.Vc Background radiations

Amplitude stabilization of a multiwavelength laser beam by an acousto‐optic tunable filter

Chieu D. Tran and Ricardo J. Furlan

Rev. Sci. Instrum. 65, 309 (1994); http://dx.doi.org/10.1063/1.1145189 (6 pages) | Cited 3 times

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A novel method has been developed to stabilize the amplitude of a multiwavelength laser beam. The method is based on the use of an acousto‐optic tunable filter to diffracted light which has more than one wavelength. The number of the wavelengths in the diffracted light is controlled by the number of the rf signals which are applied into the filter. Because the intensity of each wavelength in the diffracted beam is dependent on the power of the corresponding applied rf signal, the total amplitude of the multiwavelength diffracted beam can be stabilized, i.e., adjusted at a constant amplitude and maintained at that level, by individually controlling the intensity of each corresponding wavelength by use of an rf driver with a feedback loop for each wavelength. In addition, the method also provides a unique means to amplitude‐modulate one (or more) wavelength(s) of a multiwavelength beam at a specific frequency while keeping the other wavelengths at a constant amplitude level.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.79.Jq Acousto-optical devices

Parametric study of an x‐ray preionizer with plasma cathode

S. Bollanti, P. Di Lazzaro, F. Flora, G. Giordano, T. Letardi, G. Schina, and C. E. Zheng

Rev. Sci. Instrum. 65, 315 (1994); http://dx.doi.org/10.1063/1.1145190 (8 pages) | Cited 4 times

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The construction characteristics and the performances of an x‐ray diode working at 200 Hz are described. The temporal behavior of both the plasma cathode emission and the diode discharge has been studied, including the measurements of vacuum effects on the repetition rate and lifetime capability, preionization versus electrical features, and ionization density versus dosage. This simple and low‐cost x‐ray diode has been used to uniformly preionize a half‐liter XeCl laser, delivering an output laser energy of 800 mJ/shot at a 100 Hz repetition rate.
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07.85.-m X- and γ-ray instruments
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Development of a pulsed power supply for a large‐bore copper vapor laser

H. Seki, T. Oohashi, T. Shirakura, S. Takemori, Y. Midorikawa, H. Kameyama, G. Yamamura, K. Kotani, and H. Sugawara

Rev. Sci. Instrum. 65, 323 (1994); http://dx.doi.org/10.1063/1.1145245 (4 pages) | Cited 2 times

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A pulsed power supply has been developed for exciting a copper vapor laser with a bore diameter of 80 mm and a discharge length of 2890 mm. The pulsed power supply has two thyratrons, an LC‐inversion circuit and a two‐staged magnetic pulse compression circuit. An efficiency of 82% has been obtained which is defined as the ratio of energy stored in the storage capacitor to the output energy of the magnetic pulse compression circuit, with a voltage greater than 40 kV, averaged output power of 24 kW, and voltage rise time of 70 ns. The pulsed power supply was successfully operated for more than 2000 h and an optical output power of 272 W was obtained.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
84.30.Ng Oscillators, pulse generators, and function generators

Design review of an instrument for spectroscopic total integrated light scattering measurements in the visible wavelength region

Daniel Rönnow and Eugen Veszelei

Rev. Sci. Instrum. 65, 327 (1994); http://dx.doi.org/10.1063/1.1145191 (8 pages) | Cited 16 times

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A spectroscopic total integrated scattering instrument, which uses a focusing sphere and a broadband light source, has been constructed. It records total reflectance and transmittance spectroscopically, in the wavelength region 400–1000 nm. Diffuse reflectance and transmittance values below 10−4 can be registered. These measurements require low scattering optical components and low noise electronics. Design details are given about the detection system, particularly the low noise preamplifier. The purpose of the instrument is to measure diffuse reflectance and transmittance spectra of interference coatings. Such spectra can give information about the amplitude of the roughness of the interfaces and reveal if the interfaces are topographically correlated or uncorrelated. Examples of spectra in both reflectance and transmittance mode are given.
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07.60.Rd Visible and ultraviolet spectrometers

High‐pressure quasielastic and static light scattering apparatus

C. J. Richards and M. R. Fisch

Rev. Sci. Instrum. 65, 335 (1994); http://dx.doi.org/10.1063/1.1145192 (4 pages) | Cited 3 times

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We describe an apparatus for multiangle light scattering studies of samples that are under hydrostatic pressures. The mean hydrodynamic radius and mean radius of gyration can be determined using quasielastic and static light scattering at temperatures between 5 and 85 °C and pressures between 0.1 and 100 MPa.  
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07.60.Hv Refractometers and reflectometers

Grazing angle x‐ray photoemission system for depth‐dependent analysis

Terrence Jach, M. J. Chester, and S. M. Thurgate

Rev. Sci. Instrum. 65, 339 (1994); http://dx.doi.org/10.1063/1.1145193 (4 pages) | Cited 11 times

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We have developed an x‐ray photoelectron spectrometer system which combines an adjustable grazing incidence angle source with reflected beam detection. When operated about the critical angle, this combination permits a variation of the x‐ray penetration depth which can be monitored by means of the reflectivity. At angles of incidence less than the critical angle, the sampling depth of the photoemission is diminished, but the photoemission from the surface is enhanced due to the constructive interference of the incident and reflected x‐ray beams. When used with Mg Kα radiation (Eγ=1253.6 eV), the spectrometry system obtains useful distributions of chemical species in surface layers of 10–40 Å thickness. We present data showing the depth dependence obtained with the spectrometer of different oxides in a sulfide‐treated, oxidized GaAs (100) surface.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
79.60.-i Photoemission and photoelectron spectra
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Long‐lifetime high‐intensity GaAs photosource

R. Calabrese, G. Ciullo, V. Guidi, G. Lamanna, P. Lenisa, B. Maciga, L. Tecchio, and B. Yang

Rev. Sci. Instrum. 65, 343 (1994); http://dx.doi.org/10.1063/1.1145194 (6 pages) | Cited 8 times

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We used a GaAs crystal operating in a negative electron affinity mode to produce an intense continuous electron beam by photoemission. The major drawback of photoemission from GaAs, i.e., rapid current decay, was overcome without continuously supplying cesium. After a little initial decay, the current remained constant at 1 mA over a few mm2, with no degradation. Seasoning of the vacuum chamber played a fundamental role in achieving this performance.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
41.75.Fr Electron and positron beams
79.60.Bm Clean metal, semiconductor, and insulator surfaces

A high sensitivity momentum dispersive multichannel electron momentum spectrometer for studies in experimental quantum chemistry

B. R. Todd, N. Lermer, and C. E. Brion

Rev. Sci. Instrum. 65, 349 (1994); http://dx.doi.org/10.1063/1.1145195 (10 pages) | Cited 14 times

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The design and characterization of a high sensitivity multichannel momentum dispersive electron momentum spectrometer is reported. Electron pair coincidences are detected over a ±30° range of azimuthal angle at the exit slit of a cylindrical mirror analyzer configured to measure symmetric (θ=45°) noncoplanar (e,2e) scattering. A position sensitive microchannel plate/resistive anode encoder electron detector and a channeltron electron multiplier are employed in a novel multichannel coincidence detection system based upon detection of ‘‘pile‐up’’ of pairs of timing pulses from the detectors. Proof‐of‐concept results, exhibiting significantly higher coincidence count rates and statistical precision than have been previously observed in electron momentum spectroscopy, are presented for argon.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Multimass thermal desorption spectroscopy as a monitoring device for chemical reaction products

G. Zagatta, H. Müller, N. Böwering, and U. Heinzmann

Rev. Sci. Instrum. 65, 359 (1994); http://dx.doi.org/10.1063/1.1145196 (4 pages) | Cited 5 times

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To observe the products of surface reaction mechanisms we combined a standard quadrupole mass spectrometer featuring high‐speed scanning options with fast data acquisition and a computer‐controlled sample heating system. This combination served to obtain a general view (like a ‘‘fingerprint’’) of the reaction occurring on a Pt(100) crystal upon heating the adsorbate covered surface, as well as to allow for a detailed analysis of the gas compounds leaving the surface within a single measurement. The method is denoted by multimass thermal desorption spectroscopy (MTDS). The MTDS device is capable of recording 850 amu/s providing up to 15 complete mass spectra per second of 50 amu width while heating the surface linearly. The data contain the ion currents of both the reaction products and their fractions (cracking patterns) generated in the spectrometer. Thus it is possible to distinguish between gas species with equal mass numbers by subsequent numerical evaluation.
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07.75.+h Mass spectrometers
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Enhanced‐efficiency spray extractor for sampling volatile organic compounds in aqueous systems

Birgit Nölke and Gökhan Baykut

Rev. Sci. Instrum. 65, 363 (1994); http://dx.doi.org/10.1063/1.1145197 (3 pages) | Cited 2 times

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The spray extractor for sampling volatile organic compounds in water, reported in Rev. Sci. Instrum. 63, 3196 (1992), has been modified and optimized for high extraction efficiencies. A low‐flow spray nozzle is placed in the spray chamber, which produces very small droplets at water flow rates around 80 ml/min. Compounds extracted during a 2 min sampling period are trapped in a sorbent tube and analyzed by gas chromatography/mass spectrometry. With carrier gas (nitrogen) flow rates around 250 ml/min, spray‐and‐trap efficiencies up to 62% (tetrachloroethene) were achieved for various volatile organic compounds.
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82.80.Bg Chromatography

A photon counter and pulse train generator interface for a personal computer in pulse optically detected magnetic resonance

B. E. Granger and A. M. Nishimura

Rev. Sci. Instrum. 65, 366 (1994); http://dx.doi.org/10.1063/1.1145198 (4 pages) | Cited 4 times

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The decay of coherently prepared excited triplet state can be observed by pulse optically detected magnetic resonance (ODMR). Analysis of this data yields important information about the various relaxation pathways open to a molecule in a given environment. Pulse ODMR requires shorter pulses with higher resolution than those used in pulse nuclear magnetic resonance. Programmable pulse train generators are commercially available, but they can be costly. In this article, a fully programmable photon counter‐pulse train generator interface is described which has the required resolution and speed. The interface cards occupy two slots of a personal computer and are based on advanced Shottky transistor–transistor logic series of logic circuits. This inexpensive, yet highly flexible apparatus for use in pulse ODMR, can be adapted for other applications, such as pulse magnetic resonance and photon counting. In addition, the modular design allows easy expansion to multichannel pulse or photon counting and to the generation of even the most imaginative pulse sequences.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
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)
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques

Development of a simple electrolytic jet thinning apparatus for the preparation of thin metal foils for transmission electron microscopy

T. K. Chini, S. R. Bhattacharyya, and D. Basu

Rev. Sci. Instrum. 65, 370 (1994); http://dx.doi.org/10.1063/1.1145141 (4 pages)

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A very simple and inexpensive electrolytic jet thinning apparatus for rapid thinning of metal foils for transmission electron microscopy has been described. Regarding the specimen holder assembly, either a polytetrafluoroethylene (PTFE) holder or a platinum tipped locking tweezer‐type holder, can be attached electrically and mechanically to a micromanipulator to be used in the same jet thinning apparatus. This gives a unique feature to our unit, in which the specimen remains above the electrolyte during the polishing process. Also the constructional simplicity of the unit provides easy drainage of the electrolyte for lengthy polishing and a simple way of stopping the thinning process. Transmission electron micrographs of bombarded and unbombarded specimens electrothinned in the unit are presented herein.
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81.05.Bx Metals, semimetals, and alloys
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

An analytical model for scanning electron microscope Type I magnetic contrast with energy filtering

W. K. Chim

Rev. Sci. Instrum. 65, 374 (1994); http://dx.doi.org/10.1063/1.1145243 (9 pages) | Cited 2 times

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In this article, a theoretical model for type I magnetic contrast calculations in the scanning electron microscope with energy filtering is presented. This model uses an approximate form of the secondary electron (SE) energy distribution by Chung and Everhart [M. S. Chung and T. E. Everhart, J. Appl. Phys. 45, 707 (1974). Closed form analytical expressions for the contrast and quality factors, which take into consideration the work function and field‐distance integral of the material being studied, are obtained. This analytical model is compared with that of a more accurate numerical model. Results showed that the contrast and quality factors for the analytical model differed by not more than 20% from the numerical model, with the actual difference depending on the range of filtered SE energies considered. This model has also been extended to the situation of a two‐detector (i.e., detector A and B) configuration, in which enhanced magnetic contrast and quality factor can be obtained by operating in the ‘‘A–B’’ mode.
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68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Micromagnetic scanning microprobe system

C. A. Thompson, R. W. Cross, and A. B. Kos

Rev. Sci. Instrum. 65, 383 (1994); http://dx.doi.org/10.1063/1.1145142 (7 pages) | Cited 2 times

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We describe the apparatus, instrumentation, and data acquisition techniques which make up the micromagnetic scanning microprobe system (MSMS). This system was developed to study magnetoresistive (MR) thin films used in magnetic recording read heads. It uses a dc, four‐probe resistance measurement coupled with two pairs of orthogonal field sources. Voltage contacts to the thin film are made with microprobe tips 0.1 μm in diameter on local edge and central regions of the film. Horizontal and vertical microscopes are used to verify tip placement. Results from magnetoresistance measurements of the dynamic response of a MR read head film are shown to demonstrate system operation and performance. The bulk and local magnetoresistance of a 10 μm×10 μm NiFe thin film was measured as a function of applied field and angle. Significant variations in MR responses were seen across the width of the device because of local domain formation. The MSMS is an effective tool for characterizing the effects of domain formation on the output of a MR read head.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
07.55.-w Magnetic instruments and components

A combined scanning tunneling, scanning force, frictional force, and attractive force microscope

L. M. Eng, K. D. Jandt, and D. Descouts

Rev. Sci. Instrum. 65, 390 (1994); http://dx.doi.org/10.1063/1.1145143 (4 pages) | Cited 5 times

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We report on the adaptation of a commercially available scanning force microscope (SFM) for the simultaneous measurement of electrical and mechanical surface properties combining the scanning tunneling microscope, the SFM, and the friction force microscope. Furthermore, the microscope may be operated in the noncontact or attractive mode (AC‐SFM) which is specially suited for the nondestructive investigation of soft sample surfaces.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Friction effects in the deflection of atomic force microscope cantilevers

R. J. Warmack, X.‐Y. Zheng, T. Thundat, and D. P. Allison

Rev. Sci. Instrum. 65, 394 (1994); http://dx.doi.org/10.1063/1.1145144 (6 pages) | Cited 48 times

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The conventional deflection‐mode atomic force microscope operates by optically monitoring the slope near the end of a microcantilever in contact with the sample surface. This signal is usually interpreted as a measure of height change. Lateral forces from friction, surface geometry, or inclination of the cantilever to the surface also affect the slope due to cantilever buckling. We calculate the deflection of a hollow triangular model cantilever subject to both lateral and normal forces. The measured response of the servo circuit to an inclined, loaded cantilever is then determined. This shows (1) errors are always present in height measurements of structures on inhomogeneous surfaces; (2) the sensitivity to buckling can be reduced by repositioning the laser; (3) friction measurements can be accurately made by scanning in two directions and applying the proper calibration.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Scanning tunneling microscope for cluster studies

Thomas Poothackanal, P. J. Ouseph, and R. G. Mathur

Rev. Sci. Instrum. 65, 400 (1994); http://dx.doi.org/10.1063/1.1145145 (4 pages) | Cited 5 times

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Details of the construction of a scanning tunneling microscope (STM) are given in this article. This STM enables one to change the atmosphere around the sample easily from air to inert gases or to vacuum. The STM is compatible with a chamber in which metallic clusters are prepared.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Characterization of carbon material as a scanning tunneling microscopy tip for in situ electrochemical studies

T. Ohmori, L. A. Nagahara, K. Hashimoto, and A. Fujishima

Rev. Sci. Instrum. 65, 404 (1994); http://dx.doi.org/10.1063/1.1145146 (3 pages) | Cited 5 times

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We have studied the feasibility of using carbon as a scanning tunneling microscopy tip material for experiments conducted under electrochemical environments. The tips were found to be stable and durable in acidic or alkaline solution for several hours. The fabricated carbon tips were capable of resolving graphite atoms in electrolyte solution under potentiostatic condition as well as in air.
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82.45.-h Electrochemistry and electrophoresis
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

A pulsed supersonic molecular beam with high rotational temperatures

J. Häger, S. Zech, D. Glatzer, M. Fink, and H. Walther

Rev. Sci. Instrum. 65, 407 (1994); http://dx.doi.org/10.1063/1.1145147 (5 pages) | Cited 5 times

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The construction and operation of a novel high temperature pulsed quartz nozzle employed for the generation of rotationally excited supersonic molecular beams are reported herein. At high stagnation pressures (≳ 1 bar) the NO molecules in the beam pulse exhibit a translational and rotational behavior identical to heated continuous nozzles (Trot<50 K; Ekin≊7/2 kTN). At reduced stagnation pressures (10 mbar–1 bar) the rotational temperatures of the beam molecules are increased substantially (up to Trot≊700 K) accompanied by a translational behavior, which can be characterized by a small Mach number. The design has produced the rotationally hottest supersonic beam ever prepared in the pulsed mode.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors

Shear cell for the study of liquid‐solid interfaces by neutron scattering

Shenda M. Baker, Gregory Smith, Roger Pynn, Paul Butler, John Hayter, William Hamilton, and Lee Magid

Rev. Sci. Instrum. 65, 412 (1994); http://dx.doi.org/10.1063/1.1145148 (5 pages) | Cited 14 times

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A cell for examining the density profile of sheared fluids at the solid‐liquid interface by neutron reflectometry is presented. This cell has also proven valuable in examining near‐surface bulk structures in the plane perpendicular to the shear flow using small angle neutron scattering. The shear rates can be controlled by changing the volume flow through the cell over three orders of magnitude. All components of the cell are designed to be chemically inert. A temperature‐controlled environment compatible with neutron studies is also briefly described. Preliminary neutron reflectivity and small angle neutron scattering results using this cell are presented, and potential applications are discussed.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
28.20.Cz Neutron scattering

Negative hydrogen ion production in the hollow cathode Penning surface‐plasma source

Yu. I. Belchenko and A. S. Kupriyanov

Rev. Sci. Instrum. 65, 417 (1994); http://dx.doi.org/10.1063/1.1145149 (9 pages) | Cited 5 times

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A small hollow cathode Penning surface‐plasma source (SPS) was developed and studied. The H− yield was proportional to the emission apertures area and increased over a wide range of discharge current. The H− yield, with an intensity of up to 0.95 A and an emission current density of up to 3.6 A/cm2, was obtained in a pulsed mode. With the discharge current of 20 A and a pulse duration of 60 s, an H− yield with current of 0.1 A was obtained. The H− emission current density had approximately the same value for various diameters (0.5–7 mm) and thicknesses (0.3–4.0 mm) of cylindrical emission holes, if the thickness of hole walls did not exceed the hole diameter. The H− yield extracted through the thick conical emission holes had a value 25% higher than that for a thin cylindrical hole with the same permeable diameter. Dependencies of the H− yield versus magnetic field and hydrogen feed were different from that of the standard Penning SPS. The optimal cesium coverage of the electrodes was stable for both high‐current, long‐pulse and low‐current, dc source operation. Noticeable H− production was realized with a low‐discharge voltage of 15 V. The heavy negative ions fraction was less than 1% of total negative ion yield for long‐pulse operation. The yield of D− ions from deuterium discharge had a value 15% lower than that of H− ions from the hydrogen discharge. Most of the extracted H− ions are produced by conversion of fast and superthermal (E≳1 eV) atoms on the cesiated surfaces of the emission hole cones or they are due to the resonant charge exchange of anode‐produced H− ions in the volume adjacent to the emission apertures.
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52.80.Sm Magnetoactive discharges (e.g., Penning discharges)

Micro‐pellet injection into tokamak plasma by laser acceleration

S. Zoletnik, S. Kálvin, and G. Bürger

Rev. Sci. Instrum. 65, 426 (1994); http://dx.doi.org/10.1063/1.1145150 (4 pages) | Cited 2 times

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Different methods are tested for the injection of small (<100 μm) pellets into tokamak plasmas using laser acceleration. In one type of method the pellets are formed in the random fragmentation process of a foil, while in another series of experiments aluminum granules were accelerated. In the first case pellet velocities up to 4 km/s were achieved, but the reproducibility was found to be poor. In the second case the reproducibility was much better, and pellets with diameters in the ten micron range were accelerated to 200–300 m/s velocity. With some further improvements, this technique may become a simple source of impurities for transport studies in fusion plasmas.  
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52.25.Vy Impurities in plasmas
52.55.Fa Tokamaks, spherical tokamaks

Deuterium pellet injector for speeds up to 3400 m/s

J. P. Perin, G. Claudet, and F. Disdier

Rev. Sci. Instrum. 65, 430 (1994); http://dx.doi.org/10.1063/1.1145151 (3 pages)

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The injection of pellets of frozen deuterium into magnetically confined, hot plasmas is one of the most attractive methods for refueling fusion power reactors. High injection speeds for solid deuterium pellets are necessary for improving the experimental analysis of pellet ablation in a hot plasma and the effects of the pellet on the plasma properties, in particular the confinement parameters. The optimization of a two‐stage light gas gun is being pursued; the search for the cryogenic conditions of freezing deuterium with good mechanical properties is carried out. In particular, the impurities concentration in deuterium during the condensation process has been studied. These developments have allowed one to reach velocities up to 3400 m/s for integer bare deuterium pellets (3 or 4 mm in diameter, 1–3×1021 particles) with a reliability of 80%.
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28.52.Cx Fueling, heating and ignition
52.55.Fa Tokamaks, spherical tokamaks
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