High power Ruby and Alexandrite lasers for Lidar-Thomson scattering diagnostics
By combining the time-of-flight or LIDAR principle with a Thomson backscatter diagnostic, spatial profiles of the electron temperature and density can be measured with a single set of detectors for all spatial points. The technique was demonstrated for the first time on the JET tokamak and has been in routine operation since July 1987. Originally a ruby laser (3 J pulse energy, 300 ps pulse duration, 0.5 Hz repetition rate) was used together with a 700 MHz bandwidth detection and registration system which yielded a spatial resolution of about 12 cm. A large filter spectrometer with 6 spectral channels covering the wavelength range 400 - 800 nm gave a dynamic range for the temperature measurements of 0.2-20 keV. The original system is described, examples of measurements are given and compared with the results of other diagnostics. The system is being upgraded to make measurements at 10 Hz and a major component of the new system is an Alexandrite laser (1-2 J pulse energy, 350+/-50 ps pulse duration, 10 Hz repetition rate) which is currently being constructed. The new laser and other technological improvements being incorporated into the upgraded diagnostic are described.
Bibliographic Reference: Report: JET-P(90)09 EN (1990) 12 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199011252 / Last updated on: 1994-12-01
Original language: en
Available languages: en