title: First results from EBW emission diagnostics on COMPASS.
abstract: COMPASS tokamak shots at low magnetic field feature overdense plasmas during the extended current flat-top phase. The first harmonic of the electron cyclotron emission is completely cutoff for O and X modes and so the emission caused by electron Bernstein waves (EBWs) propagating obliquely with respect to the magnetic field and undergoing so called EBW-X-O conversion process can be observed. We perform an angular scan of the EBW emission during a set of comparable shots in order to determine the optimum antenna direction. A weak dependence of the radiative temperature on the antenna angles indicates an influence of multiple reflections from the vessel wall. The low temperature at the mode conversion region is responsible for the collisional damping of EBW, which can explain several times lower measured radiative temperature than the electron temperature measured by the Thomson scattering system.
authors.affiliation: Institute of Plasma Physics AS CR, vvi, Association EURATOM∕IPP.CR, Prague, Czech Republic. zajac@ipp.cas.cz
authors.forename: J
authors.initials: J
authors.lastname: Zajac
authors.forename: J
authors.initials: J
authors.lastname: Preinhaelter
authors.forename: J
authors.initials: J
authors.lastname: Urban
authors.forename: M
authors.initials: M
authors.lastname: Aftanas
authors.forename: P
authors.initials: P
authors.lastname: Bílková
authors.forename: P
authors.initials: P
authors.lastname: Böhm
authors.forename: V
authors.initials: V
authors.lastname: Fuchs
authors.forename: S
authors.initials: S
authors.lastname: Nanobashvili
authors.forename: V
authors.initials: V
authors.lastname: Weinzettl
authors.forename: F
authors.initials: F
authors.lastname: Zácek