Real-time determination of suprathermal electron local emission profile from hard X-ray measurements on Tore Supra

The Tore Supra tokamak is well adapted to sustain long-duration noninductive discharges using the lower hybrid (LH) heating and current drive as the main power source. In these conditions, the LH power deposition profile is strongly linked to the current density profile and can be deduced from the hard X-rays (HXRs) measurements which are produced by the suprathermal electrons generated by the absorption of the LH wave. The powerful HXR diagnostics that is present on Tore Supra has been recently connected to the real-time data network. The availability of the HXR measurements in real-time has allowed the development of an ad hoc algorithm for the real-time computation of the suprathermal electron local emission profile. Since the suprathermal electron local emission profile is well representative of the LH power deposition profile, this can be controlled in feedback (and thereby the current density profile as well). This paper illustrates the main features and real-time connections of the code developed to compute the suprathermal electron local emission profile, together with an explanation of the underlying physics and a description of the HXR diagnostics.