Functional dependence of the lower hybrid power absorption coefficient in JET
The fraction of the coupled Lower Hybrid (LH) power absorbed in the divertor plasmas in the Joint European Torus (JET) has been determined experimentally with a method utilizing the time derivative of the total stored energy (plasma and magnetic). This method can account for the power absorbed inside the normalized flux coordinate (psi is approximately equal to 0.7). The experiment LK absorption coefficient reaches 100% at low plasma densities and decreases to 25%. The LH wave accessibility to the plasma core has been found to play an important role in determining the power absorption and the radial deposition profile. The decreasing absorption is correlated with a gradual shift of the LH power deposition profile, as determined by the hard X-ray profiles, towards the plasma periphery. The frequency spectrum of the LH pump wave, as determined by a probe outside the tokamak vessel, broadens strongly as the wave accessibility is reduced and the absorption drops.
Bibliographic Reference: Report: JET-P(96)55 EN (1996) 13pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (GB)
Record Number: 199710056 / Last updated on: 1997-02-26
Original language: en
Available languages: en