The Hard X-ray Radiation during Lower Hybrid Current Drive in the HT-7 tokamak

In many tokamaks, including HT-7, LHCD has been demonstrated an effective non- inductive current drive method and a powerful tool to control plasma current profile. In HT-7 tokamak, improved confinement during LHCD has been observed [1] During lower hybrid current drive in tokamaks, suprathermal electrons are generated that emit hard x-ray bremsstrahlung. A multichannel NaI (Tl) detector array [2] as been installed on the HT-7 tokomak [3] for the measurement of the spectral and spatial distribution of suprathermal electron bremsstrahlung during LHCD. The correlation between the hard x-ray radiation and power deposition of the lower hybrid waves has been studied. The LHW enhanced performance is also seemed have an intrinsic relation with the radial profile of hard x-ray. 2. Experimental setup HT-7 is a superconducting tokamak with a major radius R0=122cm, a minor radius a=30cm and the magnetic field BT ≤ 2.5T. The LHW source of HT-7 consists of 12 klystrons that can deliver 12×100 kW power at a frequency of 2.45 GHz [4]. Figure 1 shows a schematic diagram of th