The ITER Thomson scattering core LIDAR diagnostic

The central electron temperature and density of the ITER plasma may be determined by Thomson scattering. A LIDAR topology is proposed in order to minimize the port access required of the ITER vacuum vessel. By using a LIDAR technique, a profile of the electron temperature and density can be determined with a resolution of about 7 cm in the central region of the plasma by using a short pulse laser ( ~ 300 ps). Requirements for advanced plasma control indicate that such measurements should be taken at a rate of 100 Hz during a plasma shot. The limited collection cone angle possible on the ITER reactor implies the use of a high pulse energy laser ( ~ 5 J at 1 μm). The combination of very high average power and peak power required represents a serious challenge for current laser technology. Schemes able to provide this level of laser performance will be presented along with efficient and cost effective methods of maximizing the collected light while minimizing the collection of background light by the use of an axicon element.