Approach to a window coating problem by {ital in situ} transmission monitoring and laser blow-off cleaning developed in the JT-60U Thomson scattering system

Journal Article · Wed Jan 01 04:00:00 EST 1997 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.1147820· OSTI ID:451058

Yoshida, H; Naito, O; Hatae, T; Nagashima, A ^[1]

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1. Japan Atomic Energy Research Institute, Naka-machi, Ibaraki 311-01 (Japan)

For solving a window coating problem, an {ital in situ} window transmission monitoring by inferring it precisely from a known attenuation of the deposited film has been developed in the JT-60U Thomson scattering system. Also the practicability of an {ital in situ} window cleaning based on a laser blow-off technique has been investigated extensively. The coated film composition could be guessed to be a resin such as {ital polyacrylonitrile} with a small amount of metals. The existence of chromatic upper limit has been found in the recovered transmission after the blow-off cleaning, which gives systematic errors only of less than 3% to an apparent measurement of both electron density and temperature at 10 keV or less. The attenuation itself is unchanged before and after the laser blow-off cleaning. A complementary use of both methods will provide the Thomson scattering measurement of high T{sub e} plasmas with durable reliability and sufficient precision in the existing tokamaks and the International Thermonuclear Experimental Reactor. {copyright} {ital 1997 American Institute of Physics.}

• OSTI ID: 451058
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 1 Vol. 68; ISSN RSINAK; ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
APERTURES
ELECTRON DENSITY
ELECTRON TEMPERATURE
JT-60U TOKAMAK
KEV RANGE
LASER RADIATION
LIGHT TRANSMISSION
PLASMA DENSITY
PLASMA DIAGNOSTICS
RESINS
SURFACE CLEANING
SURFACE COATING