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Proceedings Paper

The receiver system of the fast ion and alpha particle diagnostic at JET
Author(s): J. A. Fessey
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Paper Abstract

A 140GHz collective Thomson scattering diagnostic is presently being built to study the distribution of fast ions and alpha- particles within the JET plasma. A technical overviews and description of the mm-wave transmission system2 are presentedin other contributions to this conference. This paper will discuss the design of the multi-channel super heterodyne receiverand dedicated data acquisition system. 140GHz radiation from a gyrotron (250kW average, 5s pulse duration) is injected intothe plasma where it is scattered by the shielding electrons moving with each ion. The receiver is designed to measure thespectral power density of the scattered radiation (10-19- 10-16W/Hz) against an electron cyclotron background emission ofmuch higher magnitude (1 0-16w/He .) This is achieved by amplitude modulating the probing beam and synchronousdetection of the scattered signal. Refraction of the beams within the plasma can be important at high densities and theposition of the scattering volume will therefore change as the plasma evolves. A system of 'slave' receivers is being developedto track this movement and to control the trajectory of the main receiver beam by adjusting the orientation of the antenna.

Paper Details

Date Published: 30 August 1993
PDF: 2 pages
Proc. SPIE 2104, 18th International Conference on Infrared and Millimeter Waves, 21043I (30 August 1993); doi: 10.1117/12.2298558
Show Author Affiliations
J. A. Fessey, JET Joint Undertaking (United Kingdom)


Published in SPIE Proceedings Vol. 2104:
18th International Conference on Infrared and Millimeter Waves
James R. Birch; Terence J. Parker, Editor(s)

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