LIDAR Thomson scattering diagnostic on JET (invited)

Journal Article · Mon Aug 01 04:00:00 EDT 1988 · Rev. Sci. Instrum.; (United States)

DOI:https://doi.org/10.1063/1.1139686· OSTI ID:6838253

Salzmann, H; Bundgaard, J; Gadd, A; Gowers, C; Hansen, K B; Hirsch, K; Nielsen, P; Reed, K; Schroedter, C; Weisberg, K; others, and

By combining the time-of-flight or LIDAR principle with a Thomson backscatter diagnostic, spatial profiles of the electron temperature and density are measured in a magnetically confined fusion plasma. This technique was realized for the first time on the JET tokamak. A ruby laser (3-J pulse energy, 300-ps pulse duration, 0.5-Hz repetition rate) together with a 700-MHz bandwidth detection and registration system yields a spatial resolution of about 12 cm. A spectrometer with six channels in the wavelength range 400--800 nm gives a dynamic range of the temperature measurements of 0.3--20 keV. The stray light problem in the backscatter geometry is overcome by spectral discrimination and gating of the photomultipliers. A ruby filter in the spectral channel containing the laser wavelength allows calibration of the vignetting along the line of sight by means of Raman scattering, enabling the measurement of density profiles. The low level of background signal due to the short integration time for a single spatial point yields low statistical errors (..delta..T/sub e/ /T/sub e/ approx. =6%, ..delta..n/sub e/ /n/sub e/ approx. =4% at T/sub e/ = 6 keV, n/sub e/ = 3 x 10/sup 19/ m/sup -3/ ). Goodness-of-fit tests indicate that the systematic errors are within the same limits. The system is described and examples of measurements are given.

• Research Organization: JET Joint Undertaking, Abingdon, Oxon OX14 3EA, United Kingdom
• OSTI ID: 6838253
• Journal Information: Rev. Sci. Instrum.; (United States), Journal Name: Rev. Sci. Instrum.; (United States) Vol. 59:8; ISSN RSINA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700102* -- Fusion Energy-- Plasma Research-- Diagnostics
ELECTRON DENSITY
ELECTRON TEMPERATURE
INELASTIC SCATTERING
JET TOKAMAK
LASERS
MEASURING INSTRUMENTS
OPTICAL RADAR
OPTICAL SPECTROMETERS
PLASMA DIAGNOSTICS
RADAR
RANGE FINDERS
RESOLUTION
RUBY LASERS
SCATTERING
SOLID STATE LASERS
SPECTROMETERS
THERMONUCLEAR REACTORS
THOMSON SCATTERING
TOKAMAK TYPE REACTORS