Development of Burst-Mode Laser based High-speed Thomson Scattering Instruments for Fusion Plasma Devices*

Practical fusion plasma devices at various DOE and international facilities need the state-of-the-art diagnostic tools to understand, predict, and control fusion plasmas. Thomson scattering (TS), as a popular diagnostics technique, has successfully measured electron temperature and density inside the plasma system. However, the traditional TS technique operates only at 10Hz. Since the devices operate at on the order of 10- 100ms, it means only one data point can be obtained for each cycle.

We develop high repetition rate Thomson scattering instruments based on high-speed pulsed burst laser system.  Pulse burst laser was originally developed for supersonic or hypersonic flow diagnostics.  In a typical pulse burst laser, a burst (or train) of high-energy laser pulses is generated at high repetition rates over a period of time (~20 ms). The pulse sequence can reach energies of ~100 mJ per individual pulse up to MHz rates or 1 Joule per individual pulse up to 10 kHz, while maintaining low average power.  Thomson scattering system is being used to obtain electron number density and electron temperature in the plasma.