SIMULATION OF NEUTRAL EMISSION IN THE ION INTERACTION REGIME DURING AN LH EXPERIMENT IN FT
In many lower hybrid heating experiments a strong interaction with the electrons is observed at low density, while above the so called critical density this interaction is not present any more. In FT this occurs at 5 X 10**13 cm**-3 and has been shown as due to the wave interaction with ions, and mainly with the protons which are present as a minority also in D-2 discharges (n-H/n-D = 0.021) (1). In this density region, during the RF pulse, both H and D perpendicular tails are observed in D-2 discharges, together with a neutron flux enhancement, while no parametric decay instabilities (PDI) are observed. At high densities, above 1.5 X 10**14 cm**-3, a strong PDI activity is observed without neutron enhancement and H tails. The D tails are present up to 1.6 X 10**14 cm**-3. In order to get informations about both the wave propagation into the plasma and the wave ion interaction the ion tails generation profile should be known. To this end radial resolved charge exchange measurements have been performed. Unfortunately the interpretation of the results is very difficult because the perpendicular tails, which are generally ripple trapped, are affected by the vertical drift velocity which makes the ions whose mean free path is long enough to be seen in regions different from the one where they are born. In order to analyse the radial resolved CX measurements during the LHH experiment on FT a simulation code has been produced which, given the ion distribution function, computes the neutral emission from a plasma taking into account the ripple trapped ions. The model has been applied to two different D discharges, the first one in the intermediate regime at density of 10**14 cm**-3, and the other one at n = 1.4 X 10**14 cm**-3 that is in the PDI regime. In both cases a peripherical deposition profile seems to be more consistent with the experimental data.
Bibliographic Reference: 12TH EUROPEAN CONFERENCE ON CONTROLLED FUSION AND PLASMA PHYSICS, BUDAPEST (HUNGARY), SEPT. 2-6, 1985 PP. 43-46 WRITE TO SERVIZIO STUDI E DOCUMENTAZIONE - ENEA, CENTRO RICERCHE ENERGIA FRASCATI, C.P. 65 00044 FRASCATI, ROMA (ITALY), MENTIONING REPORT RT/F
Record Number: 1989125046600 / Last updated on: 1987-07-01
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