JET PLASMA ELECTRON DENSITY MEASUREMENTS FROM 2 MM WAVE INTERFEROMETRY
A simple, single channel 2 mm microwave interferometer has been developed for plasma electron density measurements on the Joint European Torus experiment. A long (76 m) plasma probing beam path in oversized waveguide enables all sensitive components to be located outside JET's biological shield. A high sensitivity liquid helium cooled detector compensates for the high waveguide attenuation (about 65 dB). The maximum measurable electron density is expected to be limited by refraction to about 8 x 10**19 electrons/m**3 (about 250 fringes in the interferometer). Detection noise limits the minimum resolvable density change to about +- 1.6 x 10**16 e/m**3 (+- 20 millifringe). The system operates routinely and the maximum JET plasma density to date of about 3 x 10**19 e/m**3 has been measured without difficulty. In addition plasma density fluctuations which represent a variation of only 0.1% of the maximum density signal can be studied with the interferometer.
Bibliographic Reference: WRITE TO THE PUBLICATIONS OFFICER, JET JOINT UNDERTAKING, ABINGDON, OXON, OX14 3EA (UK), MENTIONING REPORT JET-P(85)04, 1985
Record Number: 1989124032200 / Last updated on: 1987-01-01
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