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May 2000

Volume 71, Issue 5, pp. 1929-2249

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back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Low cost high resolution thermoluminescence spectrometer

M. W. Rhodes, S. Wanwilairat, T. Vilaithong, and W. Hoffmann

Rev. Sci. Instrum. 71, 2053 (2000); http://dx.doi.org/10.1063/1.1150577 (5 pages) | Cited 5 times

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A high-resolution thermoluminescence dosimetry (TLD) spectroscopy reader has been developed in order to perform detailed quantitative studies of the kinetics of TLD materials. The key features of this system are high wavelength resolution (1.3 nm), low cost, and compact size. In addition, the spectrometer is fiber optic coupled to the sample material isolating the system from thermal influences and electrical noise generated by the heating system. Temperature rate control can be computer set with a heat rate accuracy of better than 0.12% and a temperature readout accuracy of 1 °C or better. Analysis of all three parameters: temperature, wavelength, and intensity, is easily visualized with integrated 2D/3D analysis software. Preliminary analysis on TLD300 samples irradiated with 60Co from 5 to 60 Gy show temperature peaks and wavelength locations consistent with other published measurements. Details of the hardware system and software are discussed along with sample results. © 2000 American Institute of Physics.
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07.60.Rd Visible and ultraviolet spectrometers
78.60.Kn Thermoluminescence
07.05.Dz Control systems
87.50.wj Dosimetry/exposure assessment

A fast-scanning heterodyne radiometer for electron cyclotron emission measurements in HT-7 superconducting tokamak

S. Y. Zhang, V. I. Poznyak, G. Ploskirev, D. Kalupin, Y. X. Wan, J. K. Xie, and J. R. Luo

Rev. Sci. Instrum. 71, 2058 (2000); http://dx.doi.org/10.1063/1.1150578 (4 pages) | Cited 3 times

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A fast-scanning heterodyne radiometer employing a backward-wave oscillator (BWO) in 78–118 GHz was developed and installed for electron cyclotron emission (ECE) measurements in HT-7 superconducting tokamak. The radiometer measures 16 ECE frequency points with a scanning time period of 0.65 ms, each of the frequency points can be preset by the program to meet specific interests in physics. The high scanning speed is achieved by carefully choosing a BWO, very finely adjusting the radiometer over the full waveband, and by eliminating some elements that are routinely included in a fast-scanning radiometer system. A horizontal view of the ECE optics was installed to measure electron temperature profiles. The spatial resolution is about 1 cm (Bt = 2 T) in the center of the HT-7 minor cross section, determined by the intermediate frequency of 0.1–0.5 GHz in the radiometer. Vertically viewing optics along a perpendicular chord was also installed to study nonthermal ECE spectra. Preliminary measurement results in pellet injection plasma and lower-hybrid current drive plasma were presented. © 2000 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Gw Radio-frequency and microwave measurements

A physical model of the beam impedance method within ideal nested magnetic surfaces

Takateru Hamada, Tokuhiro Obiki, Tohru Mizuuchi, Fumimichi Sano, and Masahiko Nakasuga

Rev. Sci. Instrum. 71, 2062 (2000); http://dx.doi.org/10.1063/1.1150579 (6 pages)

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The beam impedance method is used to measure the vacuum magnetic structure of heliotron/torsatron systems. It measures the current that flows from an electron gun inserted into the vacuum chamber to the chamber wall. To interpret experimental results, we have been developing a physical model of the method and a numerical code based on the model. For simplicity, we have focused on a limited model in which only ideal nested magnetic surfaces exist. As a new approach to reproduce the real physical condition, we treat the current that flows across magnetic surfaces and that which is emitted from the electron gun separately. Radial electron distribution forms for the two currents to match each other. The characteristic of electron emission from the gun is obtained experimentally and included in the code. The diffusion process is assumed to obey the neoclassical diffusion theory. The numerically obtained current profile agrees well with the measurement if the suppression of diffusion due to a radial electric field is taken into account. © 2000 American Institute of Physics.
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52.55.Jd Magnetic mirrors, gas dynamic traps
52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
52.65.-y Plasma simulation

Space-time resolving vacuum ultraviolet spectrometer based on a rotating polyhedral mirror

Xiaodong Lin and Jikang Xie

Rev. Sci. Instrum. 71, 2068 (2000); http://dx.doi.org/10.1063/1.1150580 (3 pages)

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Using a rotating polyhedral mirror and a vacuum ultraviolet (VUV) monochromater, a space-time resolving VUV diagnostic system is developed. Measurement of the O VI (103.2 nm) radiation on the HT-6M tokamak shows that the time resolution of the system is better than 4 ms and the space resolution is better than 2 cm. Compared with traditional instruments, this system has improved measurement efficiency, and error from shot-to-shot discharge variations is avoided. © 2000 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.60.Rd Visible and ultraviolet spectrometers
42.79.Bh Lenses, prisms and mirrors
52.55.Fa Tokamaks, spherical tokamaks
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Fast reciprocating probe assembly for the Hanbit magnetic mirror device

J. G. Bak, S. G. Lee, S. M. Hwang, Y. S. Choi, and K. S. Chung

Rev. Sci. Instrum. 71, 2071 (2000); http://dx.doi.org/10.1063/1.1150581 (6 pages) | Cited 4 times

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A fast reciprocating probe assembly (RPA), which can scan a long length up to 100 cm (with maximum velocity of 136 cm/s), is fabricated to measure basic plasma parameters during a plasma discharge time (∼500 ms) in the Hanbit magnetic mirror device. The probe driving mechanism consists of two steps of movements; first a slow movement to set the probe at a standby position, and then a fast one to measure plasma parameters within an adjustable time interval. Both movements are driven by only a pneumatic system. This is a distinctive feature of the probe drive system that has advantages of a simple driving mechanism and an easy adjustment of the fast stroke length for the wide range. The probe head is fabricated as a modular type for easy replacement. Performance test results and initial measurements from the fabricated RPA will be discussed. © 2000 American Institute of Physics.  
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52.70.Ds Electric and magnetic measurements
28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium
07.07.Tw Servo and control equipment; robots
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