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Feb 1995

Volume 66, Issue 2, pp. 955-2385

Page 2 of 18 Pages Previous Page Next Page | Jump to Page

Laboratory‐scale setup for anionic polymerization under inert atmosphere

Sokol Ndoni, Christine M. Papadakis, Frank S. Bates, and Kristoffer Almdal

Rev. Sci. Instrum. 66, 1090 (1995); http://dx.doi.org/10.1063/1.1146052 (6 pages) | Cited 47 times

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‘‘Living’’ anionic polymerization offers a readily feasible preparation of very well‐controlled homo‐ or copolymers in a wide range of molar masses and chemical structures. Such samples are vital in experimental polymer physics and the technique presented here offers self‐sufficiency with such samples. The technique of anionic polymerization performed under inert atmosphere is presented here. The components of the setup are described in detail. Purification procedures for glassware and chemicals for specific polymerizations are given. Illustrative examples and results are presented. © 1995 American Institute of Physics.
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82.35.-x Polymers: properties; reactions; polymerization
06.60.-c Laboratory procedures

A catalytic flow reactor for kinetic studies of multicomponent reacting mixtures on supported catalysts

A. L. Boehman and S. Niksa

Rev. Sci. Instrum. 66, 1096 (1995); http://dx.doi.org/10.1063/1.1146053 (9 pages)

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Our catalytic flow reactor presents several advantages for kinetic studies of heterogeneous chemistry on supported catalysts. This experimental facility enables determinations of the reaction rates of individual species at high conversion levels under isothermal conditions with multicomponent mixtures. Reaction rates are determined simultaneously for any number of species at points along supported catalysts under typical exhaust conditions, allowing detailed characterization of selectivities and inhibition effects. Tight thermal control permits the observation of species with widely varying reactivities, a situation that is typical in exhaust aftertreatment applications. The reactor is ideally suited to studying reaction kinetics under either reducing or oxidizing conditions, as demonstrated by reactant profile data measured with both lean and rich hydrocarbon exhaust streams. © 1995 American Institute of Physics.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.20.Pm Rate constants, reaction cross sections, and activation energies

Preparation of high‐purity, high vapor pressure, complex intermetallic compounds

J. McDonough and A. Huxley

Rev. Sci. Instrum. 66, 1105 (1995); http://dx.doi.org/10.1063/1.1146054 (3 pages) | Cited 2 times

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Until recently, techniques for growing intermetallic compounds with high vapor pressures at their melting points have only produced relatively low quality crystals. A new technique for growing ultra‐high‐purity crystals of such compounds has been developed. The sample is held in a water‐cooled copper boat under 10 atm of one part per billion impurity argon while being heated by rf induction. Using this system high‐purity crystals of CePb3 are grown and their resistivity compared to ones grown by a standard arc furnace technique. © 1995 American Institute of Physics.
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81.10.Fq Growth from melts; zone melting and refining

Characterization, modeling, and design of an electrostatic chuck with improved wafer temperature uniformity

Kurt A. Olson, David E. Kotecki, Anthony J. Ricci, Stephan E. Lassig, and Anwar Husain

Rev. Sci. Instrum. 66, 1108 (1995); http://dx.doi.org/10.1063/1.1145988 (7 pages)

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The resulting temperature distribution of a silicon wafer held by an electrostatic chuck (ESC) in an electron‐cyclotron‐resonance chemical vapor deposition (ECR‐CVD) reactor is characterized and modeled. The effects of the clamping voltage VESC, pressure between the ESC and wafer PHe, and the surface finish and pattern on the ESC are investigated. Heat transfer coefficients between the wafer and various ESCs are determined experimentally. A model is developed to predict the temperature distribution at the surface of the wafer, and used to explain the experimentally observed temperature variations both within wafer and between different chucks. The model is then used to aid in the design of an ESC which provides improved temperature uniformity at the wafer surface. The results of this study indicate: (a) the thermal resistances across the interface between the wafer and ESC control both the absolute wafer temperature and the wafer temperature uniformity; (b) the surface roughness of the ESC and the size of the ‘‘contact’’ regions are major design factors controlling the absolute temperature of the wafer—the temperature can be adjusted by varying the value of VESC and fine tuned by adjusting the value of PHe; (c) the nonuniform temperature distribution across the wafer surface is dictated by the surface pattern on the ESC, the variation in surface roughness, and the size of the ESC relative to the wafer; (d) wafer temperature variations from chuck to chuck are reduced by controlling the surface finish of the ESC and by ensuring that PHe is a dominant heat transfer mechanism; and (e) maximum uniformity in the temperature of the wafer is obtained when the radius of the ESC is matched as closely as possible to that of the wafer. We have shown that numerical heat transfer models can be used to optimize the geometry of the ESC to provide a uniform distribution of temperature across the surface of the wafer. © 1995 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
06.60.Ei Sample preparation (including design of sample holders)

Thermal conductivity and diffusivity of free‐standing silicon nitride thin films

Xiang Zhang and Costas P. Grigoropoulos

Rev. Sci. Instrum. 66, 1115 (1995); http://dx.doi.org/10.1063/1.1145989 (6 pages) | Cited 39 times

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The thermal conductivity and diffusivity of free‐standing silicon nitride (Si‐N) films of 0.6 and 1.4 μm in thickness are measured. A new experimental technique, the amplitude method, is proposed and applied to measurement of the thin‐film thermal diffusivity. The thermal diffusivity is determined by three independent experimental approaches: the phase‐shift method, the amplitude method, and the heat‐pulse method. Good agreement among the measured thermal diffusivities obtained by the three methods indicates the validity of the amplitude method. High‐resolution electron microscopy studies show a large quantity of voids in the 1.4 μm Si‐N films. In contrast, very few voids are found in the 0.6 μm films. This difference may be responsible for the measured lower conductivity of the 1.4 μm Si‐N films as compared to the 0.6 μm thin films. © 1995 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Design of a monochromatic ellipsometer for studies at the solid–liquid interface

R. S. Pai‐Panandiker and J. R. Dorgan

Rev. Sci. Instrum. 66, 1121 (1995); http://dx.doi.org/10.1063/1.1145990 (7 pages)

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A new design for a monochromatic ellipsometer used for studies at the solid–liquid interface is described. The design of the ellipsometer incorporates two novel features—a special optical glass cell and a thermally controlled sample oven. The ellipsometer design allows for in situ kinetic studies through use of the optical glass cell. Furthermore, the apparatus is modified to allow thermal equilibration over a range of temperatures. The temperature response of the cell assembly is presented and the response time is seen to be approximately 1 h. Data on the adsorption of a diblock copolymer [poly(ethylene oxide)–block–polystyrene] are presented; the analyzed data agree with previous studies on the same system. © 1995 American Institute of Physics.
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07.60.Fs Polarimeters and ellipsometers
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Optical windows for a flow cell to contain aqueous solutions at high pressure and temperature

W. J. Bowers, V. E. Bean, and W. S. Hurst

Rev. Sci. Instrum. 66, 1128 (1995); http://dx.doi.org/10.1063/1.1145991 (3 pages) | Cited 7 times

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A flow cell to contain aqueous solutions at pressures up to 40 MPa and temperatures up to 600 °C that is equipped with sapphire windows for the transmission of visible light is described. There are four windows, two for the entrance and exit of a laser beam, and two located at 90° that feature f/1 (53° included angle) collection apertures with a 9 mm diameter unobstructed view for Raman spectroscopy, absorption measurements, or studies using full‐field back illumination. The window‐to‐metal seals are gold o‐rings; the metal‐to‐metal seals are gaskets prepared by pressing a gold o‐ring onto a gold foil washer. This cell has been used for two years for Raman studies of aqueous solutions at high pressures and temperatures both below and above the supercritical point of water. © 1995 American Institute of Physics.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
06.60.Ei Sample preparation (including design of sample holders)

Phase‐frequency relationships in oscillating quartz microbalance electrodes: Determination of an optimal operating frequency for solution‐phase microgravimetry

Glenn C. Komplin and William J. Pietro

Rev. Sci. Instrum. 66, 1131 (1995); http://dx.doi.org/10.1063/1.1145992 (5 pages) | Cited 2 times

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A systematic study of the effects of overtone harmonic, operating frequency, and electrode surface area on mass sensitivity of liquid‐phase quartz‐crystal microbalance (QCM) operation is presented. Although the Sauerbrey equation implies that sensitivity should increase as the square of the operating frequency, the effects of mechanical damping induced by operating the crystal under liquid media causes a loss of phase/mass sensitivity at higher nominal frequencies. The competing effects provide a optimum frequency at which to operate the crystal for maximum mass sensitivity under liquids. In the case of water, this optimum frequency is 12.4 MHz. As the phase of the complex impedance is used by most series resonance crystal maintaining circuits as an error signal in stabilizing frequency, progressively higher operating frequencies are not desirable for QCM operation under liquids. © 1995 American Institute of Physics.
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82.80.-d Chemical analysis and related physical methods of analysis
06.30.Dr Mass and density
07.10.Lw Balance systems, tensile machines, etc.

Local sensitivity of an electrochemical quartz crystal microbalance: Spatial localization of the low frequency mode

R. Oltra and I. O. Efimov

Rev. Sci. Instrum. 66, 1136 (1995); http://dx.doi.org/10.1063/1.1145993 (6 pages) | Cited 3 times

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The frequency response of 5 and 6 MHz AT‐cut electrochemical quartz‐crystal microbalances to the highly nonuniform distribution of mass loading appearing in localized corrosion or local deposition was investigated. It was shown that the evolution of the frequency deviates from the theoretical one calculated using the conventional sensitivity. This behavior is described in terms of localization of resonance modes under the heavy loaded part of crystal. Mass‐dependent corrections to the conventional sensitivity were calculated. © 1995 American Institute of Physics.
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06.30.Dr Mass and density
07.10.Cm Micromechanical devices and systems
82.45.-h Electrochemistry and electrophoresis

A voltage‐controlled resistor for the remote control of monostable multivibrators

Michael J. Chudobiak

Rev. Sci. Instrum. 66, 1142 (1995); http://dx.doi.org/10.1063/1.1145994 (4 pages)

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A new method is introduced for generating a precise large‐signal voltage‐controlled resistance for the purpose of remotely controlling monostable multivibrators (one‐shots). The circuit presented offers linear control of the resistance with ten to one resistance variation and infinite resolution, and a usable resistance range of approximately 100 Ω–500 kΩ. The full‐scale resistance can be arbitrarily set within this range. The circuit has a bandwidth of 10 MHz, and the voltage across the resistance can be as large as ±12 V. The voltage‐controlled resistance is generated by using an analog voltage‐controlled current source. © 1995 American Institute of Physics.
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84.30.Sk Pulse and digital circuits
84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Movable ultra‐high‐vacuum sample mount: Heating, cooling, and temperature measurement capabilities

L. A. Jones, F.‐X. Wei, and D. F. Thomas

Rev. Sci. Instrum. 66, 1146 (1995); http://dx.doi.org/10.1063/1.1146473 (5 pages) | Cited 2 times

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A sample mount which can be moved throughout an ultra‐high‐vacuum environment and through a load‐lock to atmosphere is described. A sample mount holder station is also shown whereby the sample temperature can be monitored and controlled from 80 K to the sample melting point. A unique feature is that the temperature is measured with a thermocouple cemented to the sample, but the sample remains transportable. Contacts to electrically isolated side arms on the sample mount provide the correct electrical connections. © 1995 American Institute of Physics.  
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
06.60.Ei Sample preparation (including design of sample holders)

Inexpensive digital image acquisition for scanning electron microscopes

W. M. Ang, Terry McMahon, Don Schulte, and Leon Ungier

Rev. Sci. Instrum. 66, 1151 (1995); http://dx.doi.org/10.1063/1.1145995 (3 pages) | Cited 1 time

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An inexpensive acquisition system for high‐quality digital images from electron microscopes using standard PC and off‐the‐shelf components is presented. The major limitation of DOS‐based PCs, the inability to access large array of memory at sufficiently high speed, has been overcome by taking advantage of 386 microprocessor protected mode of operation. © 1995 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
07.05.Pj Image processing

A two color mm‐wave interferometer for the JET divertora)

R. Prentice, T. Edlington, R. T. C. Smith, D. L. Trotman, R. J. Wylde, and P. Zimmermann

Rev. Sci. Instrum. 66, 1154 (1995); http://dx.doi.org/10.1063/1.1145996 (5 pages) | Cited 12 times

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An interferometer with compensation for vibration and large scale mechanical movements has been designed and built to measure the line integral electron density along three different lines of sight through the JET divertor plasma. Overcoming the effects of a long transmission path, having an estimated 65 dB loss, requires oversized waveguide transmission lines, sensitive heterodyne detection, low loss quasioptical circuits, and highly stable sources. The sources are frequency doubled, phase‐locked, Gunn oscillators producing 15 mW at 130 GHz and 10 mW at 200 GHz. Waveguide Schottky mixer diodes generate reference and output signals at an IF of 10.7 MHz and the LO Gunn diodes are phase locked to the reference IF. Corrugated feedhorns and ellipsoidal mirrors are used for beam control and polarizing wire grids for beam splitting and recombination. To minimize unwanted, direct coupling of source power into the signal detectors, Brewster angle beam dumps and Faraday rotation isolators are used in the transmit and receive QO circuits, which in turn are separated, on opposite faces of a vertical plate. Martin–Pupplet polarizing interferometers are used to multiplex the two colors into a single coaligned, copolar output beam and to demultiplex the return beam. Constant fraction discriminators are used to optimize the accuracy of the phase detectors, which have sampling and recording rates of 1 MHz and a resolution of ∼7° (0.02 fringe). © 1995 American Institute of Physics.
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52.70.Gw Radio-frequency and microwave measurements
52.55.Fa Tokamaks, spherical tokamaks

Antenna decoupling requirements in a gyrotron collective Thomson scattering diagnostic (CTS)a)

F. Orsitto and U. Tartari

Rev. Sci. Instrum. 66, 1159 (1995); http://dx.doi.org/10.1063/1.1145997 (4 pages)

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The required rejection ratio of the stray light in a CTS, respect to the launching power is investigated, for obtaining useful signal‐to‐noise ratio. This problem is faced considering the central gyrotron frequency f0, as well as the in‐band stray light raising from the spurious mode of the gyrotron and amplified cyclotron emission (the so‐called gyrotron noise), falling into the scattered light spectrum. The statistical nature of the gyrotron noise in the scattering band is important because the required decoupling is obtained using the S/N formula where the fluctuation of the plasma radiation and the gyrotron noise fluctuation appears. It turns out that the total decoupling required at f0 is of the order of or greater than 80 dB, while in the scattering band could be less than 40 dB. © 1995 American Institute of Physics.
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52.70.Gw Radio-frequency and microwave measurements

Magnetic field mapping system on the H‐1 heliaca)

M. G. Shats, D. L. Rudakov, B. D. Blackwell, L. E. Sharp, and O. I. Fedyanin

Rev. Sci. Instrum. 66, 1163 (1995); http://dx.doi.org/10.1063/1.1145998 (4 pages) | Cited 4 times

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The H‐1 heliac recently brought into operation is a medium‐sized 3‐field‐period heliac with major radius R0=1 m, plasma mean minor radius 〈a〉≤0.2 m and a wide range of rotational transforms 0.6≤ι–(0)≤2.0. Electron beam mapping of the vacuum magnetic field was performed using new type of a fluorescent target (movable fluorescent rod array having a transparency about 98%). Up to 150–200 toroidal transits were observed at each electron gun position. The spatial resolution of the system was about 3 mm. Electron collector probes were used for monitoring the positions of the magnetic surfaces in different toroidal field periods. Visible paths of the electron beam due to the excitation of the background gas (p∼10−4 Torr) were used for identification of the toroidal transit numbers. This newly developed method gives an accuracy in measurement of the rotational transform of about 1.5%. Experimental surfaces and measured ι profiles show very good agreement with the computer model results. © 1995 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.55.Jd Magnetic mirrors, gas dynamic traps

Thomson scattering system on FTU tokamak: Calibration, operation, resultsa)

F. Orsitto, A. Brusadin, E. Giovannozzi, D. Santi, R. Bartiromo, and P. Pizzolati

Rev. Sci. Instrum. 66, 1167 (1995); http://dx.doi.org/10.1063/1.1145999 (4 pages) | Cited 2 times

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The Frascati tokamak upgrade (FTU) Thomson scattering system is employed for the measurement of the electron temperature and density spatial profiles along the vertical torus diameter in 19 spatial points up to ten times in a single plasma discharge with a spatial resolution ranging from 2 cm in the central region to 4 cm in the plasma edge. The radiation source is a Nd:YLF laser at 1053 nm. The scattered radiation is collected by two objectives: the first looks at the plasma center, the second at the plasma edge. Bundles of optical fibers in the focal plane of the objectives carry the scattered light from the tokamak hall to a set of 19 interference filter polychromators, whose transmission is 70% and the rejection of the stray light at the laser wavelength is 1/107. The detectors are avalanche photodiodes with a NEP of the order of 10−13 W/(Hz)1/2 at 1053 nm. The absolute calibration for the electron density measurement has been carried out by Raman scattering on hydrogen and deuterium. Examples of temporal evolution of Te and ne spatial profiles are presented for ohmic plasma heating, lower hybrid current drive, and pellet injection experiment. A comparison between scattering data with interferometer for the density measurement, and ECE for the electron temperature shows agreement between the diagnostics. The system is controlled by two computers: a real‐time computer for the laser settings, while the detection system parameters and data acquisition are managed using CAMAC by the data acquisition system (DAS) of FTU. © 1995 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks

Digital interface for quadrature demodulation of interferometer signalsa)

J. Waller, X. H. Shi, N. C. Altoveros, J. Howard, B. D. Blackwell, and G. B. Warr

Rev. Sci. Instrum. 66, 1171 (1995); http://dx.doi.org/10.1063/1.1146000 (4 pages)

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We describe a digital interface for processing signals produced by a scanning multichannel far‐infrared interferometer/polarimeter for plasma density measurements. The interface samples the interferometer signals in quadrature before digital filtering, demodulation and downloading to a transputer array for real‐time tomographic inversion and display. © 1995 American Institute of Physics.  
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Jd Magnetic mirrors, gas dynamic traps
07.05.Hd Data acquisition: hardware and software

Two‐axis goniometer for reflectivity measurements of x‐ray diffractors used in fusion researcha)

N. J. Peacock, R. Barnsley, A. Patel, M. O’Mullane, M. Singleton, and J. Ashall

Rev. Sci. Instrum. 66, 1175 (1995); http://dx.doi.org/10.1063/1.1146001 (5 pages) | Cited 3 times

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Quantitative measurements of the line and continua emissivities and the analyses of spectral line profiles are essential steps in the interpretation of the x‐ray emission from high‐temperature fusion plasmas. One method of placing the emissivities on an absolute basis is to use an absolutely calibrated spectrometer to record the data. The overall sensitivity of the spectrometer can be constructed in terms of the efficiencies of its separate components, the most intractable being Rc, the reflection integral of the diffractor. To this end, a new, compact, two‐axis diffractometer, incorporating modern robotic technology, such as direct‐drive servomotors with closed‐loop operation from built‐in arcsec optical encoders, has been constructed. Improved features of this double‐axis goniometer include the use of fixed line‐of‐sight x‐ray sources with the capability of operation in the (1,−1) parallel, nondispersive mode or the antiparallel, (1,+1), dispersive mode. The diffractometer is now being used to calibrate x‐ray diffractors, filters, mirrors, and detectors associated with x‐ray spectroscopy of fusion plasmas. At certain wavelengths, where line branching ratios involving visible transitions are available, the fusion plasma may itself be used as a transfer standard of x‐ray luminosity, allowing an independent check on the diffractometer values of Rc. Applications to the analyses of impurity concentrations in tokamaks are described while future applications of the diffractometer to radiation damage studies of x‐ray and optical components [Hill et al., Rev. Sci. Instrum. 63, 5032 (1992)] used in D‐T burning plasma experiments are envisaged. © 1995 American Institute of Physics.
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52.70.La X-ray and γ-ray measurements
52.25.Vy Impurities in plasmas
07.85.Jy Diffractometers
52.55.Fa Tokamaks, spherical tokamaks

Linear systems description of the CO2 laser‐based tangential imaging systema)

E. Lo, J. Wright, and R. Nazikian

Rev. Sci. Instrum. 66, 1180 (1995); http://dx.doi.org/10.1063/1.1146002 (4 pages) | Cited 2 times

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It is demonstrated that the phase variation produced by the projection of the density fluctuations onto a laser beam that is aligned tangent to the magnetic field lines in a toroidal plasma is, in fact, a convolution of the density fluctuation profile in the tangency plane with a shift‐invariant point spread function. Thus a spatial filter can be used to invert the corresponding transfer function to produce an undistorted image of the plasma density fluctuations at the tangency plane. Numerical simulations demonstrate that a spatial filter consisting of a simple and versatile step‐function form of a Zernike phase mirror will recover a reasonably accurate image of the fluctuations [Lo et al., Buld. APS 38, 2005 (1993)]. © 1995 American Institute of Physics.  
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Gj Fluctuation and chaos phenomena
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

A multichord spectrometer using an 8×8 anode photomultipliera)

P. G. Carolan and R. O’Connell

Rev. Sci. Instrum. 66, 1184 (1995); http://dx.doi.org/10.1063/1.1146003 (5 pages)

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A multianode photomultiplier (8×8 anodes of 2.5×2.5 mm2) is used to detect a collection of spectra in a high dispersion echelle spectrometer. A cylindrical lens is placed at the output slit to increase the dispersion at the photomultiplier. The cross talk between adjacent spectra is non‐negligible (although <5%), resulting in some interspectral distortion. This is removed by solving a system of simultaneous equations, one for each channel, obtained from the measured cross‐talk coefficients. The spectrometer has been used on the COMPASS‐D tokamak to measure ion temperatures and fluid velocities. © 1995 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks
52.25.Kn Thermodynamics of plasmas

Zeeman absorption measurements of two‐dimensional magnetic field structuresa)

G. G. Spanjers, E. J. Yadlowsky, R. C. Hazelton, J. J. Moschella, and T. B. Settersten

Rev. Sci. Instrum. 66, 1189 (1995); http://dx.doi.org/10.1063/1.1146004 (4 pages) | Cited 1 time

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A diagnostic technique is presented where polarization measurements of transmitted resonant laser light are used to determine the two‐dimensional magnetic field profiles in a plasma. The diagnostic laser is propagated parallel to the magnetic field direction and resonant with circularly polarized transitions. Tuning the laser slightly off‐resonance results in differing absorption coefficients for right and left circularly polarized light. Analysis of the transmitted light, combined with independent measurements of the resonant line profile, results in a measurement of the magnetic field. Spectral analysis of the Zeeman splitting has been commonly used to measure plasma magnetic fields, both in emission and absorption. The intensity comparison of the right and left circular components to measure relatively small magnetic fields has its origins in the astrophysics community. Here, the intensity comparison technique is used in conjunction with resonant absorption, and the information is stored using a high‐speed framing camera. This results in a measurement of relatively small magnetic fields, with a high signal‐to‐noise ratio and two‐dimensional spatial resolution. © 1995 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements

Improvements in the CHERS system for DT experiments on TFTR

C. E. Bush, R. E. Bell, and E. J. Synakowski

Rev. Sci. Instrum. 66, 1193 (1995); http://dx.doi.org/10.1063/1.1146422 (4 pages) | Cited 2 times

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Improvements in the charge exchange recombination spectroscopy (CHERS) system have resulted in accurate measurements of Ti and Vϕ profiles during DT experiments. These include moving the spectrometer detector array and electronics farther away from the tokamak to a low neutron flux location. This relocation has also improved access to all components of the system. Also, a nonplasma‐viewing calibration fiber system was added to monitor the change in fiber transmission due to the high flux DT neutrons. Narrow band filtered light transmitted through the calibration fiber is now used as a reference for the Vϕ measurement. At a high neutron flux of ∼2.5×1018 neutrons/s (peak fusion power∼6.2 MW) with total yield of 1.3×1018 neutrons a modest 5% decrease in fiber transmission was observed. Corrections for transmission loss are made and Ti(r,t) and Vϕ(r,t) profiles are automatically calculated within four minutes of every shot. © 1995 American Institute of Physics.
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52.70.Nc Particle measurements
52.55.Fa Tokamaks, spherical tokamaks

The transient internal probe: A novel method for measuring internal magnetic field profilesa)

M. A. Bohnet, J. P. Galambos, T. R. Jarboe, A. T. Mattick, and G. G. Spanjers

Rev. Sci. Instrum. 66, 1197 (1995); http://dx.doi.org/10.1063/1.1146005 (4 pages) | Cited 4 times

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The transient internal probe (TIP) diagnostic is designed to permit internal magnetic field measurements in hot, high density plasmas. A small probe is fired through the plasma at high velocities and magnetic field measurements are accomplished using Faraday rotation within the Verdet glass probe. Magnetic field resolution of ±40 G and spatial resolution of 5 mm have been achieved. System frequency response is 10 MHz. Ablative effects are avoided by minimizing both the probe size and the time the probe spends in the plasma. A two‐stage light‐gas gun is used to accelerate the probe (held by a sabot) to 2.2 km/s. The sabot is removed using gas dynamic forces and a gas interface system prevents the helium muzzle gas from entering the plasma chamber. Work is underway to integrate the TIP diagnostic with laboratory plasma experiments. © 1995 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements

2D tomography with bolometry in DIII‐Da)

A. W. Leonard, W. H. Meyer, B. Geer, D. M. Behne, and D. N. Hill

Rev. Sci. Instrum. 66, 1201 (1995); http://dx.doi.org/10.1063/1.1146006 (4 pages) | Cited 34 times

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A 48‐channel platinum‐foil bolometer system on DIII‐D was installed to achieve better spatial and temporal resolution of the radiated power in diverted discharges. Two 24‐channel arrays provide complete plasma coverage with optimized views of the divertor. The divertor radiation profile was measured for a series of radiative divertor and power balance experiments. A significant change in the magnitude and distribution of divertor radiation with heavy gas puffing was observed. Unfolding the radiation profile with only two views requires one to treat the core and divertor radiation separately. The core radiation is fitted to a function of magnetic flux and is then subtracted from the divertor viewing chords. The divertor profile is then fit to a 2D spline as a function of magnetic flux and distance from divertor floor. © 1995 American Institute of Physics.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.55.Fa Tokamaks, spherical tokamaks

Neutron penumbral imaging of inertial confinement fusion targets at Phébusa)

O. Delage, J.‐P. Garconnet, D. Schirmann, and A. Rouyer

Rev. Sci. Instrum. 66, 1205 (1995); http://dx.doi.org/10.1063/1.1146007 (5 pages) | Cited 11 times

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First 14 MeV neutron images of imploded microballoons have been obtained at the Phébus laser facility at CEL‐V in 1992 [Garconnet et al. Laser Part Beams 11, 3 (1994)]. The sizes of the neutron source have been measured by using a coded‐aperture imaging system and a scintillator array as a detector. The threshold of the experimental setup was typically 2×1010 neutrons/shot. 600–800 μm source sizes in direct drive experiments have been measured with a 130 μm two‐point resolution. In 1993 we improved the sensitivity of the camera by increasing the light collection efficiency. It can now work at a neutron yield as small as a few 108. Thanks to this improvement some images in indirect drive experiments have been recorded in the range 3×108–5×109 with a 56 μm two‐point resolution. Wiener filter, homomorphic Wiener filter, and Nugent’s ‘‘comb filter’’ methods have been used and compared to deconvolve the penumbral images. Design of the camera and numerical method performances will be discussed. © 1995 American Institute of Physics.
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52.70.Nc Particle measurements
52.57.-z Laser inertial confinement
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