Stark-effect measurement of high FEL (free-electron laser) electric fields in MTX (Microwave Tokamak Experiment) by laser-aided particle-probe spectroscopy

Conference · Fri May 04 00:00:00 EDT 1990

OSTI ID:6824853

Oda, T; Takiyama, K ^[1]; Odajima, K; Ohasa, K; Shiho, M ^[2]; Mizuno, K ^[3]; Foote, J H; Nilson, D G ^[4]

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1. Hiroshima Univ. (Japan)
2. Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan)
3. California Univ., Davis, CA (USA) Sandia National Labs., Livermore, CA (USA)
4. Sandia National Labs., Livermore, CA (USA)

We are constructing a diagnostic system to measure the electric field (>100 kV/cm) of a free-electron laser (FEL) beam when injected into the plasma of the Microwave Tokamak Experiment (MTX). The apparatus allows a crossed-beam measurement, with 2-cm spatial resolution in the plasma, involving the FEL beam (with 140-GHz, {approx}1-GW ECH pulses), a neutral-helium beam, and a dye-laser beam. After the laser beam pumps metastable helium atoms to higher excited states, their decay light is detected by a collimated optical system. Because of the Stark effect due to the FEL electric field ({rvec E}), a forbidden transition can be strongly induced. The intensity of emitted light resulting from the forbidden transition is proportional to E{sup 2}. Because photon counting rates are calculated to be low, extra effort is made to minimize background and noise levels. It is possible that the lower {rvec E} of an MTX gyrotron-produced ECH beam with its longer-duration pulses also can be measured using this method. Other applications may include measurements of ion temperature (using charge-exchange recombination), edge-density fluctuations, and core impurity concentrations. 11 refs., 2 figs., 2 tabs.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6824853
• Report Number(s): UCRL-102939; CONF-900557-5; ON: DE90011911; TRN: 90-016495
• Resource Relation: Conference: 8. topical conference on high-temperature plasma diagnostics, Hyannis, MA (USA), 6-10 May 1990
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
TOKAMAK DEVICES
PLASMA DIAGNOSTICS
DYE LASERS
ELECTRIC FIELDS
ENERGY LEVELS
EXCITATION
EXCITED STATES
FREE ELECTRON LASERS
IMPURITIES
ION TEMPERATURE
LASER SPECTROSCOPY
STARK EFFECT
CLOSED PLASMA DEVICES
ENERGY-LEVEL TRANSITIONS
LASERS
LIQUID LASERS
SPECTROSCOPY
THERMONUCLEAR DEVICES
700102* - Fusion Energy- Plasma Research- Diagnostics