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Reliable ion temperature measurements by collective Thomson scattering in fusion plasmas require powerful and long radiation pulses between 300 GHz and 3000 GHz. Gyrotrons with a sufficient power level are still not available in this frequency range whereas they exist at lower frequencies. The rotational level structure of some asymmetric top molecules suggests that frequency tripling by a near resonant 4-photon process is possible. The frequency conversion should be most effective if the resonance occurs at the 2-photon transition. For a proof of principle, a strong pulsed FIR laser is used as a radiation source. Some molecules are selected which have a 2-photon resonance near a powerful laserline. The principle and preliminary results are presented.

Additional information

Authors: NIESWAND S, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, Lausanne (CH)
Bibliographic Reference: Article: Bulletin of the Société Suisse de Physique, Vol. 9 (1992) No. 1, p. 62
Record Number: 199210520 / Last updated on: 1994-12-02
Original language: en
Available languages: en