Low-energy neutral particle analysis by a time-of-flight method on JFT-2M

Journal Article · Thu Nov 01 00:00:00 EST 1990 · Review of Scientific Instruments; (USA)

DOI:https://doi.org/10.1063/1.1141574· OSTI ID:6225233

Miura, Y; Okano, F ^[1]

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

A time-of-flight method is used to measure the energy spectrum of charge exchange atoms emitted from the JFT-2M plasma in the energy range below 1000 eV/amu. The neutral flux is chopped in bunches of about 0.8 {mu}s by a slotted cylinder. The rotating cylinder is driven by a turbomolecular pump. After the flight of 1.5 m the particles are detected by a secondary particle detector. This is an electron multiplier modified from a photomultiplier which can be gated for an intense photon. The signal from the electron multiplier is digitized at a sampling time of 0.2 {mu}s. To get good statistics of the arrival time distribution (ATD), eight or nine ATDs are averaged. Then the energy spectrum of charge exchange neutrals is measured by a 2 ms interval. The fast change ({le}2--6 ms) of energy spectra at the {ital L}/{ital H} and {ital H}/{ital L} transition is also reported. The average energy defined by {integral}{ital E}({ital d}{Gamma}/{ital dE}){ital dE}/{integral}({ital d}{Gamma}/{ital dE}){ital dE} increases by about 100 eV at the {ital H} transition like the increase of the ECE electron temperature at the edge. The neutral flux defined by {integral}({ital d}{Gamma}/{ital dE}){ital dE} decreases like the divertor {ital H}{sub {alpha}}/{ital D}{sub {alpha}} signal. In the energy distribution of the flux, the number of particles whose energy less than about 400 eV decrease by the {ital H} transition but those greater than 500 eV do not change or increase. The flux at 200 eV in the {ital H} phase is two times lower than that in the {ital L} phase.

• OSTI ID: 6225233
• Journal Information: Review of Scientific Instruments; (USA), Vol. 61:11; ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ENERGY SPECTRA
TIME-OF-FLIGHT METHOD
JFT-2M TOKAMAK
PLASMA DIAGNOSTICS
CHARGE EXCHANGE
ELECTRON MULTIPLIER DETECTORS
EV RANGE
NEUTRAL PARTICLES
TURBOMOLECULAR PUMPS
CLOSED PLASMA DEVICES
ENERGY RANGE
EQUIPMENT
LABORATORY EQUIPMENT
MEASURING INSTRUMENTS
PARTICLES
PUMPS
RADIATION DETECTORS
SPECTRA
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
VACUUM PUMPS
700102* - Fusion Energy- Plasma Research- Diagnostics