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Jan 2005

Volume 76, Issue 1, Articles (01xxxx)

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Experimental apparatus and sample preparation techniques for directional solidification

B. Utter, R. Ragnarsson, and E. Bodenschatz

Rev. Sci. Instrum. 76, 012401 (2005); http://dx.doi.org/10.1063/1.1807592 (9 pages) | Cited 1 time

Online Publication Date: 17 December 2004

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We describe a directional solidification stage which allows the controlled solidification of transparent organic alloys. We present two variations of the experiment. In one, large aspect ratio sample cells can be rotated with respect to the temperature gradient between runs, allowing full 360° control over in-plane sample orientation. In the other, thin-walled capillaries are pulled through an oil-filled channel which is optimized for high speed solidification studies (V ≈ 5 mm/s). The use of large aspect ratio cells ( ≈ 11 cm diameter rotatable) and long capillary cells ( ≈ 38 cm) allows solidification for significant times even at rapid solidification rates. We describe in detail material purification, cell construction, and vacuum filling procedures which allow high quality sample preparation completely under inert atmosphere. Succinonitrile is purified using a sublimation apparatus and samples are filled directly from the sublimation chamber. Vacuum-filling epoxied cells produces long-lasting degassed samples. The techniques presented are also suitable for similar materials such as liquid crystals, CBr4, and pivalic acid. Additional features of the experiment include a linear stepper motor and linear temperature gradient (3–150 K/cm).
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06.60.Ei Sample preparation (including design of sample holders)
81.30.Fb Solidification
81.20.Ym Purification
06.60.Jn High-speed techniques (microsecond to femtosecond)
64.70.D- Solid-liquid transitions
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Thermo reflectance bolometry

S. V. Mitko, A. Yu. Oudalov, Yu. B. Udalov, P. J. M. Peters, and K. J. Boller

Rev. Sci. Instrum. 76, 013101 (2005); http://dx.doi.org/10.1063/1.1823655 (5 pages) | Cited 1 time

Online Publication Date: 17 December 2004

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An approach to bolometry has been developed. It is based on the measurements of optical reflectivity change of a thin metal layer deposited on a transparent substrate. The reflectivity change results from the temperature rise due to absorption of energetic particles or x rays. The sensor of the bolometer has no ohmic contact with the measuring unit, making this method well suited for an environment with strong electromagnetic noise interference. The technique was applied to characterize a method for the generation of intense electron beams in a dense gas. Very high efficiency for the e-beam generation (up to 95%) was measured.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
78.70.Dm X-ray absorption spectra
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Resonant interferometric autocorrelator for estimation of laser pulse duration

John J. McFerran, John Winterflood, Clinton Burton, and Andre N. Luiten

Rev. Sci. Instrum. 76, 013102 (2005); http://dx.doi.org/10.1063/1.1834699 (5 pages)

Online Publication Date: 20 December 2004

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We present a simple design for a Mach–Zehnder interferometric autocorrelator that is aimed at real-time laser pulse diagnostics. The device is based around a symmetric and balanced mechanical oscillator that confers a simple and compact design, while still allowing the measurement of a broad range of pulse durations with high speed and high resolution. The device requires a very low drive level and possesses a very weak mechanical coupling to the environment. The apparatus provides two outputs: one output is proportional to the instantaneous velocity of the interferometer arms, which can be integrated to determine the arm position. This gives the means to calibrate the arm position accurately and thereby account for any nonuniformity of the motion. The second output, from a two-photon photodetector, is used to determine the pulse duration. The present device can measure pulses from the femtosecond through to the picosecond domain.
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42.79.Hp Optical processors, correlators, and modulators
07.60.Ly Interferometers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

320-channel dual phase lock-in optical spectrometer

P. S. Fodor, S. Rothenberger, and J. Jevy

Rev. Sci. Instrum. 76, 013103 (2005); http://dx.doi.org/10.1063/1.1830013 (7 pages) | Cited 2 times

Online Publication Date: 20 December 2004

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The development of a multiple-channel lock-in optical spectrometer (LIOS) is presented, which enables parallel phase-sensitive detection at the output of an optical spectrometer. The light intensity from a spectrally broad source is modulated at the reference frequency, and focused into a high-resolution imaging spectrometer. The height at which the light enters the spectrometer is controlled by an acousto-optic deflector, and the height information is preserved at the output focal plane. A two-dimensional InGaAs focal plane array collects light that has been dispersed in wavelength along the horizontal direction, and in time along the vertical direction. The data is demodulated using a high performance computer-based digital signal processor. This parallel approach greatly enhances (by more than 100x) the speed at which spectrally resolved lock-in data can be acquired. The noise performance of a working system optimized for the 1.3 μm wavelength range is analyzed using a laser diode light source. Time-resolved absorption traces are obtained for InAs quantum dots embedded in a GaAs matrix, and for dispersed films of PbSe nanocrystals.
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07.60.Rd Visible and ultraviolet spectrometers
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
78.47.-p Spectroscopy of solid state dynamics
78.66.Li Other semiconductors
78.67.Hc Quantum dots
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Electrostatic ion beam trap for electron collision studies

O. Heber, P. D. Witte, A. Diner, K. G. Bhushan, D. Strasser, Y. Toker, M. L. Rappaport, I. Ben-Itzhak, N. Altstein, D. Schwalm, A. Wolf, and D. Zajfman

Rev. Sci. Instrum. 76, 013104 (2005); http://dx.doi.org/10.1063/1.1832192 (11 pages) | Cited 13 times

Online Publication Date: 20 December 2004

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We describe a system combining an ion beam trap and a low energy electron target in which the interaction between electrons and vibrationally cold molecular ions and clusters can be studied. The entire system uses only electrostatic fields for both trapping and focusing, thus being able to store particles without a mass limit. Preliminary results for the electron impact neutralization of C2− ions and aluminum clusters are presented.
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07.77.Ka Charged-particle beam sources and detectors
29.27.Eg Beam handling; beam transport
29.27.Bd Beam dynamics; collective effects and instabilities

Optimization of momentum imaging systems using electric and magnetic fields

M. Gisselbrecht, A. Huetz, M. Lavollée, T. J. Reddish, and D. P. Seccombe

Rev. Sci. Instrum. 76, 013105 (2005); http://dx.doi.org/10.1063/1.1832411 (8 pages) | Cited 10 times

Online Publication Date: 20 December 2004

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Time-of-flight (TOF) momentum imaging systems utilize the x, y, t information from charged particles striking a position-sensitive detector to infer the x, y, and z components of the particles’ initial momenta. This measurement capability can lead to the complete experimental determination of multi-ionization/fragmentation dynamics. In the case of electron detection, the addition of a magnetic field leads to a significantly increased operational energy range. This study shows that the TOF system has to be carefully designed in order to optimize the magnetic confinement effect. Expressions for the optimal dimensions of a single electric field TOF system are derived and factors contributing to the resolution are discussed, along with their application to an existing imaging system.
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07.75.+h Mass spectrometers
29.40.Gx Tracking and position-sensitive detectors
85.60.Ha Photomultipliers; phototubes and photocathodes

Alternative calibration techniques for high-speed pyrometers in shock experiments

D. Partouche-Sebban, D. B. Holtkamp, P. Rodriguez, J. B. Stone, S. D. Borror, C. A. Kruschwitz, and J. A. Young

Rev. Sci. Instrum. 76, 013106 (2005); http://dx.doi.org/10.1063/1.1833331 (7 pages) | Cited 1 time

Online Publication Date: 20 December 2004

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Optical pyrometry is widely used in industry and research laboratories to perform surface temperature measurements of sample materials. These shock physics experiments are normally conducted at powder or gas gun facilities or at facilities where high explosives can be used as a shock wave source, and using high-speed pyrometers that are usually calibrated by using a blackbody source. But, electrical power, time, and space can be limiting factors in such facilities, and blackbody calibration can be difficult. Crucial parts of the experimental setup (fibers, lenses, and/or mirrors) are destroyed in such experiments, and the pyrometry system must be recalibrated before each experiment. We have developed a calibration technique using integrating-sphere sources that allows us to calibrate pyrometers more rapidly and easily than with blackbodies. Two different integrating-sphere systems are described to cover the wavelength range generally used in pyrometry studies. The characterization of these systems is fully detailed including measurements of their spectral radiances. A discussion of the advantages and drawbacks of both calibration sources is given.
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07.20.Ka High-temperature instrumentation; pyrometers
42.72.Ai Infrared sources
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
44.40.+a Thermal radiation
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.72.Bj Visible and ultraviolet sources

L-band electron paramagnetic resonance spectrometer for use in vivo and in studies of aqueous biological samples

T. Walczak, P. Leśniewski, I. Salikhov, A. Sucheta, K. Szybiński, and H. M. Swartz

Rev. Sci. Instrum. 76, 013107 (2005); http://dx.doi.org/10.1063/1.1832271 (6 pages) | Cited 6 times

Online Publication Date: 22 December 2004

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The development of L-band ( ∼ 1.2 GHz) frequency EPR spectrometers has made feasible many in vivo studies in laboratory animals and, recently, in human volunteers. The lower dielectric and eddy current losses that occur at L-band balance the lower Zeeman splitting so useful measurements can be made in conductive aqueous samples. We describe typical resonators used in such studies and provide details on the construction of the spectrometer, including the bridge, the automatic frequency control subsystem, the low-noise high-stability tunable L-band frequency source, as well as the low-frequency components—the signal receiver and the modulation unit. The application of EPR spectroscopy to larger subjects requires special care in the design of an appropriate magnet with sufficient homogeneity and stability, yet with dimensions that allow operation with a wide range of subject sizes. We describe our solution, which involves a permanent magnet, air-core scan coils to provide the field sweep and offset, and field stabilization by means of a field-frequency lock. We also describe the magnetic field modulation system, which operates at 25 kHz to avoid distortion in spectra from materials with narrow lines (such as lithium phthalocyanine). We refer to recent reviews to illustrate the range of in vivo studies and the clinical applications of the type of spectrometer described here.
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87.80.-y Biophysical techniques (research methods)
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
87.64.K- Spectroscopy
07.05.Dz Control systems
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Low energy beam line at the AGOR facility

Dragan Toprek, Iwo Formanoy, and Sytze Brandenburg

Rev. Sci. Instrum. 76, 013301 (2005); http://dx.doi.org/10.1063/1.1823653 (4 pages)

Online Publication Date: 17 December 2004

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The origin of the low transmission through the low energy beam line between the electron cyclotron resonance source and the AGOR cyclotron has been investigated. Measurements of beam size and emittance, determined with the “varying quadrupole method,” are compared with calculations including fringe fields up to third order with the code COSY INFINITY. Calculations and measurements qualitatively agree; the calculations exhibit the large beam losses observed. On the basis of the calculations new settings have been determined, resulting in a significant increase of the transmission. To achieve full transmission a complete redesign of the beam line, in particular of the bending magnets, is needed.
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07.77.Ka Charged-particle beam sources and detectors
29.27.Eg Beam handling; beam transport
29.27.Fh Beam characteristics
29.20.dg Cyclotrons
29.25.Bx Electron sources

Modification of cos θ coil shape in superconducting dipole magnets for reducing the coil size

P. R. Sarma, N. Ibomcha, and R. K. Bhandari

Rev. Sci. Instrum. 76, 013302 (2005); http://dx.doi.org/10.1063/1.1823779 (5 pages) | Cited 1 time

Online Publication Date: 17 December 2004

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In coil-dominated superconducting dipole magnets the coil size and hence the cost of the magnet can be reduced by optimizing the shape of the coil. We have used the variational calculus and a random search technique to show that the coil shape markedly deviates from the conventional cos θ design when one reduces the coil size while holding the field and field quality to specified values. A block-coil dipole giving a field of 7.0 T has been designed on the basis of the optimization. With iron yoke this can give a field of 8.4 T.
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84.71.Ba Superconducting magnets; magnetic levitation devices
75.30.Cr Saturation moments and magnetic susceptibilities

Creation of plasma density transitions short compared to the plasma skin depth

M. C. Thompson, J. B. Rosenzweig, and G. Travish

Rev. Sci. Instrum. 76, 013303 (2005); http://dx.doi.org/10.1063/1.1829996 (6 pages) | Cited 1 time

Online Publication Date: 20 December 2004

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A plasma based electron beam source apparatus is described which creates a plasma with two distinct density regions separated by a transition which is shorter than the plasma skin depth kp−1 of either region. This sharp density modulation is achieved by using a perforated stainless steel screen to filter half of a diffusing plasma column. A simple physical model predicts that the length of the plasma density transition will vary with the distance from the screen. For a weakly magnetized plasma, the transition length will be twice the distance, on a line normal to the screen plane, from the screen edge to the location where the transition is measured. The plasma column is generated using an argon discharge plasma source. It has a peak density of approximately 3.5×1013 cm−3 and a full width half maximum width of 5 cm. The discharge source utilizes a 7.5 cm diameter LaB6 disk cathode heated to 1300 °C using a graphite heater. The plasma column is filtered with a 78 μm thick stainless steel sheet with 152 μm holes and 21% open area. Plasma density transitions with lengths between 0.74 and 0.95kp−1 were measured.
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52.75.-d Plasma devices
07.77.Ka Charged-particle beam sources and detectors
52.50.Dg Plasma sources
52.55.-s Magnetic confinement and equilibrium
52.25.Xz Magnetized plasmas
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

Design of a delay-line position-sensitive detector with improved performance

G. Da Costa, F. Vurpillot, A. Bostel, M. Bouet, and B. Deconihout

Rev. Sci. Instrum. 76, 013304 (2005); http://dx.doi.org/10.1063/1.1829975 (8 pages) | Cited 49 times

Online Publication Date: 22 December 2004

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A delay-line position-sensitive detector with improved performance is presented. In this device, timing is carried out by means of fast digitizer boards. The use of dedicated signal processing procedures leads to a timing accuracy of 70 ps and a dead-time below 1.5 ns. As a result, the spatial resolving power of this detector is close to 1 mm leading to a high multihit capability. A temporary detector has been designed in which the delay-line anode is combined with a phosphor screen allowing additional positioning to be made via a charge-coupled device camera. This additional positioning is used to unambiguously quantify performances in terms of spatial resolution and multihit capabilities. A three-dimensional atom probe analysis of a material containing low evaporation field phases is used to demonstrate the capabilities of this detector.
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29.40.Gx Tracking and position-sensitive detectors
07.68.+m Photography, photographic instruments; xerography
29.50.+v Computer interfaces
84.30.Sk Pulse and digital circuits

Ray tracing study for a detuned nondispersed double crystal monochromator

Zhengchi Hou

Rev. Sci. Instrum. 76, 013305 (2005); http://dx.doi.org/10.1063/1.1831251 (4 pages) | Cited 2 times

Online Publication Date: 22 December 2004

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The properties of a detuned nondispersive Si(111) double crystal monochromator were studied by using the ray tracing method. The program used was the PC version of shadow V2.3.3 with gui V1.2. This article concentrates on detuning of the second crystal since detuning of the first crystal causes a larger shift of the energy center of the transmitted beam than detuning of the second one does. The results indicate that for a large detuning angle of the second crystal, the transmitted spectrum splits into two bands with equal bandwidth, which is delayed at a large vertical divergence of the incident beam. With increasing detuning angle of the second crystal, both the fundamental bandwidth (for a well collimated beam) and the harmonic contamination decrease until they reach the minimum at a detuning angle of roughly half the full width at half maximum of the rocking curve, where the left fundamental flux is about 50%. The capability of harmonic suppression by detuning the second crystal is limited, with the harmonic contamination reduced by about two orders of magnitude at most, which implies that other methods, such as double mirror system, must be adopted when smaller harmonic contamination is required.
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07.85.-m X- and γ-ray instruments
41.85.Si Particle beam collimators, monochromators
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Construction of a booster linac for the RIKEN heavy-ion linac

O. Kamigaito, M. Kase, N. Sakamoto, Y. Miyazawa, E. Ikezawa, N. Fukunishi, S. Kohara, M. Fujimaki, M. Hemmi, T. Chiba, Y. Chiba, H. Ryuto, A. Goto, and Y. Yano

Rev. Sci. Instrum. 76, 013306 (2005); http://dx.doi.org/10.1063/1.1834708 (11 pages) | Cited 3 times

Online Publication Date: 22 December 2004

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A linac consisting of six rf cavities has been constructed as an energy booster of the RIKEN heavy-ion linac. Various heavy ion beams have been accelerated to 5.8 MeV/u with intensities of more than 1 pμA (particle microampere) in the continuous-wave mode. The booster cavities are based on a quarter-wavelength resonator of a coaxial structure. The first two cavities are frequency-variable in a range from 36 to 76.4 MHz, whereas the last four are operated at a fixed frequency of 75.5 MHz. The design study started in 1997 and the booster was commissioned in 2001. The total voltage gain of the booster ever achieved is 11 MV, which is 70% of the designed value of 16 MV. The high-intensity beams from the booster have been successfully applied to a systematic study on the synthesis of superheavy elements. The beam energy from the ring cyclotron has also been increased, owing to the additional velocity gain provided by the booster.
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29.20.-c Accelerators
29.20.dg Cyclotrons
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Actively cooled plasma electrode for long pulse operations in a cesium-seeded negative ion source

Yukio Fujiwara, Kazuhiro Watanabe, Yoshikazu Okumura, Rusty Trainham, and Claude Jacquot

Rev. Sci. Instrum. 76, 013501 (2005); http://dx.doi.org/10.1063/1.1823611 (5 pages) | Cited 1 time

Online Publication Date: 20 December 2004

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An actively cooled plasma electrode has been developed for long pulse operation in a cesium-seeded negative ion source. To keep the electrode temperature at about 300 °C, which is the optimum range of temperature to enhance cesium effects, the electrode cooling structure has been designed using three-dimensional numerical simulation assuming that the heat flux from the source plasma was 15 W/cm2. Water cooling tubes were brazed to the plasma electrode substrate with spacers made of stainless steel, which acts as a thermal resistance. The fabricated plasma electrode has been tested in a cesium-seeded volume negative ion source called Kamaboko source. The temperature of the electrode reached 280 °C for the arc power of 41 kW, which is the operating condition required for producing D− beams with current densities exceeding 20 mA/cm2. It was demonstrated that the actively cooled plasma electrode is applicable to long pulse operations, meeting the temperature requirement for optimizing the surface-production process of negative ions in the cesium-seeded ion source.
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52.50.Dg Plasma sources
52.75.-d Plasma devices
52.25.Fi Transport properties
52.65.-y Plasma simulation

Tomographic reconstruction of Hα emissivity profiles in HANBIT magnetic mirror device

Jung-Sik Yoon, Dong-Cheol Seo, and Hoon-Kyun Na

Rev. Sci. Instrum. 76, 013502 (2005); http://dx.doi.org/10.1063/1.1831671 (7 pages)

Online Publication Date: 20 December 2004

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Hydrogen is the main constitute of plasmas in HANBIT magnetic mirror device, therefore, measurement of the emission from excited levels of hydrogen atoms is an important diagnostic tool. From the emissivity of Hα radiation one can derive quantities such as the neutral hydrogen density and the source rate, i.e., the rate at which the plasma protons are replenished by ionization of neutral atoms diffusing into the plasma. The reconstruction of emissivity profiles from Hα radiation measurement is a highly undetermined and ill-posed inversion problem, due to the restricted viewing access, number of chords and the increased noise level. An unbiased and consistent probability theory based approach within the framework of Bayesian inference is provided by the maximum entropy method which is independent of model assumptions, but allows any prior knowledge available to be incorporated. The formalism is applied to the reconstruction of Hα emissivity profiles in HANBIT magnetic mirror device.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Kn Thermodynamics of plasmas
52.75.-d Plasma devices

New technique deducing plasma potential by a capacitive coupling method in spraying dielectric barrier discharge plasmas

Yong-Sup Choi, Kyu-Sun Chung, Yong Ho Jung, Hyun-Jong You, and Myoung-Jae Lee

Rev. Sci. Instrum. 76, 013503 (2005); http://dx.doi.org/10.1063/1.1832172 (5 pages)

Online Publication Date: 20 December 2004

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A new method to measure the plasma potential in an atmospheric dielectric barrier discharge (DBD) plasmas is developed for a new spraying DBD plasma source, which is sustained by electric fields generated by flowing plasmas at the outer region of the electrodes, since conventional electric probe can not be applied due to arcing. The new technique is to measure the spatially averaged plasma potential by using a capacitive coupling method with calculation of collisional sheath thickness.
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52.70.Ds Electric and magnetic measurements
52.30.-q Plasma dynamics and flow
52.25.Mq Dielectric properties
52.25.Fi Transport properties
52.50.Dg Plasma sources
52.40.Kh Plasma sheaths

Two-dimensional diagnostic of edge plasma structure using a lithium beam probe in a compact helical system

K. Nakamura, H. Iguchi, M. Ueda, Z. Narihiro, A. Shimizu, T. Morisaki, M. Isobe, C. Takahashi, S. Nishimura, C. Suzuki, Y. Yoshimura, K. Nagaoka, T. Minami, M. Yoshinuma, K. Ida, et al.

Rev. Sci. Instrum. 76, 013504 (2005); http://dx.doi.org/10.1063/1.1809284 (9 pages) | Cited 9 times

Online Publication Date: 22 December 2004

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A neutral lithium beam probe for two-dimensional diagnosis of edge plasmas has been designed and installed on the compact helical system. A lithium beam with an energy of 15 keV and a current of 0.1 mA is used. The spatial resolution is about 10 mm, and the time response is about 10 ms. The beam penetration depth is expressed in terms of the line integral density 〈nel〉, which is about 2×1018 m−2. The beam injection angle can be varied and the observation point covers the edge and separatrix region of the helical diverter configuration. Two-dimensional electron density profiles for electron cyclotron heating and neutral beam injection (NBI) heated plasmas are obtained near and outside the last closed flux surface (LCFS). Analysis for two-dimensional density profile reconstruction indicates that significant amounts of surface plasma are confined outside the LCFS for NBI plasmas even though the ergodic layer is cut by the vacuum chamber wall (inboard limiter configuration). The usefullness of this new two-dimensional diagnostic in the edge region is demonstrated.
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52.70.Ds Electric and magnetic measurements
52.75.-d Plasma devices
52.55.Jd Magnetic mirrors, gas dynamic traps
52.40.Hf Plasma-material interactions; boundary layer effects
52.50.Gj Plasma heating by particle beams
52.25.-b Plasma properties

A compact and portable PC-based Gundestrup–Langmuir probe diagnostic system

P. Sicard, C. Boucher, A. Litnovsky, and J.-P. St-Germain

Rev. Sci. Instrum. 76, 013505 (2005); http://dx.doi.org/10.1063/1.1834705 (5 pages)

Online Publication Date: 22 December 2004

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A compact Gundestrup–Langmuir probe diagnostics system capable of data acquisition as well as data analysis was conceived at INRS-EMT, Canada, and used at IPP-FZJ, Germany. Data acquisition and analysis can be done with this system using several types of probes (Langmuir, double-Langmuir, Mach, Gundestrup,…). The versatility as to the different types of probe that one can use and the relative small size of the whole system makes it advantageous. Using a laptop computer makes the system small size and highly portable. The system acquires data at 1000 scans/s at 12 bit resolution on two probe systems simultaneously, using a total of 12 input channels. Bias is done by a DAC-ADC card and is amplified to give a ±100 V sweeping range. Measured temperatures ranged from 0.75 eV to 6.0 eV with densities observed as low as 1×1010 cm−3 up to 5×1011 cm−3, which are the range of conditions to be found in our experimental device. This system is also easy to reproduce since the hardware is commercially available and the scripts can be duplicated and modified according to the specifics of the hardware.
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52.70.Ds Electric and magnetic measurements
07.05.Dz Control systems
07.05.Hd Data acquisition: hardware and software
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities
07.05.Kf Data analysis: algorithms and implementation; data management

Time dependent 14 MeV neutrons measurement using a polycrystalline chemical vapor deposited diamond detector at the JET tokamak

M. Angelone, M. Pillon, L. Bertalot, F. Orsitto, M. Marinelli, E. Milani, G. Pucella, A. Tucciarone, G. Verona-Rinati, S. Popovichev, and A. Murari

Rev. Sci. Instrum. 76, 013506 (2005); http://dx.doi.org/10.1063/1.1834691 (6 pages) | Cited 6 times

Online Publication Date: 22 December 2004

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A polycrystalline chemical vapor deposited (CVD) diamond detector was installed on a JET tokamak in order to monitor the time dependent 14 MeV neutron emission produced by D–T plasma pulses during the Trace Tritium Experiment (TTE) performed in October 2003. This was the first tentative ever attempted to use a CVD diamond detector as neutron monitor in a tokamak environment. Despite its small active volume, the detector was able to detect the 14 MeV neutron emission (>1.0×1015 n/shot) with good reliability and stability during the experimental campaign that lasted five weeks. The comparison with standard silicon detectors presently used at JET as 14 MeV neutron monitors is reported, showing excellent correlation between the measurements. The results prove that CVD diamond detectors can be reliably used in a tokamak environment and therefore confirm the potential of this technology for next step machines like ITER.
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28.52.Lf Components and instrumentation
52.55.Fa Tokamaks, spherical tokamaks
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.), fast particle effects
29.40.-n Radiation detectors

Calibration of imaging plate for high energy electron spectrometer

Kazuo A. Tanaka, Toshinori Yabuuchi, Takashi Sato, Ryosuke Kodama, Yoneyoshi Kitagawa, Teruyoshi Takahashi, Toshiji Ikeda, Yoshihide Honda, and Shuuichi Okuda

Rev. Sci. Instrum. 76, 013507 (2005); http://dx.doi.org/10.1063/1.1824371 (5 pages) | Cited 93 times

Online Publication Date: 22 December 2004

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A high energy electron spectrometer has been designed and tested using imaging plate (IP). The measurable energy range extends from 1 to 100 MeV or even higher. The IP response in this energy range is calibrated using electrons from L-band and S-band LINAC accelerator at energies 11.5, 30, and 100 MeV. The calibration has been extended to 0.2 MeV using an existing data and Monte Carlo simulation Electron Gamma Shower code. The calibration results cover the energy from 0.2 to 100 MeV and show almost a constant sensitivity for electrons over 1 MeV energy. The temperature fading of the IP shows a 40% reduction after 80 min of the data taken at 22.5 °C. Since the fading is not significant after this time we set the waiting time to be 80 min. The oblique incidence effect has been studied to show that there is a 1/cos θ relation when the incidence angle is θ.
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06.20.F- Units and standards
07.81.+a Electron and ion spectrometers
07.05.Kf Data analysis: algorithms and implementation; data management

High throughput ultrasoft x-ray polychromator for embedded impurity pellet injection studies

D. Stutman, M. Finkenthal, L. Delgado-Aparicio, K. Tritz, N. Tamura, D. Kalinina, A. Matsubara, K. Sato, and S. Sudo

Rev. Sci. Instrum. 76, 013508 (2005); http://dx.doi.org/10.1063/1.1832191 (3 pages) | Cited 2 times

Online Publication Date: 22 December 2004

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A prototype ultrasoft x-ray polychromator has been developed for local particle transport measurements in magnetic fusion devices using the Hα charge exchange emission from low-Z impurity pellets. High throughput together with few cm radial resolution in the plasma are achieved using a toroidally aligned grid collimator, while a few Å spectral bandpass together with strong background rejection are obtained using planar multilayer mirrors and foil filters. As high sensitivity detectors we use a new type of compact, efficient and high-gain multichannel plates. The prototype instrument has been evaluated in the laboratory and tested on the Large Helical Device in Japan. In addition to transport studies, this type of device is of interest for next step experiments, where high beam energy and strong attenuation will make visible charge exchange recombination spectroscopy difficult.
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52.70.La X-ray and γ-ray measurements
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
28.52.Lf Components and instrumentation
52.55.Jd Magnetic mirrors, gas dynamic traps
52.25.Vy Impurities in plasmas
52.25.Fi Transport properties
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.), fast particle effects
52.58.Lq Z-pinches, plasma focus, and other pinch devices
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Application of a dithered sampling technique to increase the spatial resolution of singlet oxygen images

John W. Snyder, Zhan Gao, and Peter R. Ogilby

Rev. Sci. Instrum. 76, 013701 (2005); http://dx.doi.org/10.1063/1.1823631 (7 pages) | Cited 5 times

Online Publication Date: 17 December 2004

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Singlet molecular oxygen (a1Δg) is an intermediate in many important oxidative reactions in heterogeneous biological and polymeric systems. By using a custom-made microscope to detect the 1270 nm phosphorescence of singlet oxygen (a1Δg→X3Σg−), singlet oxygen images of such systems can be created. The microscope uses an InGaAs linear photodiode array to detect this extremely weak near infrared phosphorescence. In this article, the effects of the microscope’s modulation transfer function and the detector’s spatial sampling frequency on the resolution of the images are examined. It is shown that a dithered sampling technique can increase the accessible resolution. In this approach, data are repeatedly acquired from the sample after it has been systematically moved on the microscope stage.
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85.60.Dw Photodiodes; phototransistors; photoresistors
42.30.Lr Modulation and optical transfer functions
78.55.Hx Other solid inorganic materials
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
07.60.Pb Conventional optical microscopes

Formation of glass fiber tips for scanning near-field optical microscopy by sealed- and open-tube etching

J. Shi and X. R. Qin

Rev. Sci. Instrum. 76, 013702 (2005); http://dx.doi.org/10.1063/1.1823778 (5 pages) | Cited 4 times

Online Publication Date: 17 December 2004

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A method, sealed-tube etching, for fabricating glass fiber tips used in scanning near-field optical microscopy is reported. Two glass tips are formed simultaneously inside the acrylate jacket of an optical fiber that is sealed at the bottom end with plastic prior to etching in hydrofluoric acid. The qualities of the tips generated from this and conventional tube etching methods are compared in terms of their taper length, surface smoothness, as well as time evolution of the tip shapes. Etching mechanisms are proposed for this method, which provides more insight into the conventional tube etching method than previously considered.
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07.79.Fc Near-field scanning optical microscopes
68.37.Uv Near-field scanning microscopy and spectroscopy
81.65.Cf Surface cleaning, etching, patterning

Performance of the infrared microspectroscopy beamline at CAMD

Orhan Kizilkaya, John D. Scott, Eizi Morikawa, James D. Garber, and Richard S. Perkins

Rev. Sci. Instrum. 76, 013703 (2005); http://dx.doi.org/10.1063/1.1832455 (4 pages) | Cited 5 times

Online Publication Date: 20 December 2004

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The first infrared (IR) beamline at the Center for Advanced Microstructures and Devices (CAMD) at Louisiana State University has been successfully constructed and commissioned. The beamline features a simple optical design with a minimal number of optical components. A pair of mirrors, planar and toroidal, is utilized for extracting synchrotron radiation (50 and 15 mrad, in horizontal and vertical directions, respectively) from the bending magnet port to a diamond window located outside of the shielding wall. Synchrotron radiation is then collimated by an off-axis parabolic mirror and fed into a Thermo Nicolet Continuum microscope through a Thermo Nicolet Nexus 670 FT-IR spectrometer. The microscope’s performances with synchrotron-radiation and conventional-thermal sources were compared in the mid-IR spectral range (11 700–400 cm−1). Effective beam spot size at sample position of the microscope was measured to be 35×12 μm2 (FWHM). It was also determined that synchrotron radiation has substantial advantages over the conventional thermal source: ∼ 30 times better intensity and ∼ 100 times better S/N at aperture size of the microscope smaller than 15×15 μm2. This performance allows infrared spectroscopy analysis in a small area with a diffraction-limited spatial resolution.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
41.85.Ar Particle beam extraction, beam injection
41.60.Ap Synchrotron radiation
07.77.Ka Charged-particle beam sources and detectors
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