Collective Thomson Scattering Feasibility Study for the LArge Plasma Device (LAPD)

Collective Thomson Scattering (CTS) is a powerful diagnostic tool that provides information about ion and electron temperatures, flow/drift velocities, and electron density. By utilizing an adequate source, measurements are obtained from the scattered radiation spectrum of electron density fluctuations in the plasma. In HED plasmas, CTS has been used extensively with laser based sources, typically in the visible spectrum. CTS has been implemented in fusion plasmas with RF sources for fast ion distribution and density fluctuation measurements. At the Basic Plasma Science Facility (BaPSF), the diagnostic will be used for ion temperature measurements in hydrogen minority heating experiments, including energetic ion interaction with fast waves. The LAPD, an 18 m long and 1 m diameter cylindrical device, produces a magnetized plasma (n = 10¹¹-10¹³ cm^-3, Te= 0.1-15 eV)¹ that is challenging to diagnose with CTS due to the unconventional source required in the far infrared. This study will evaluate laser and non-laser based sources and their requirements to develop CTS for LAPD, including diagnostic setup and measurement techniques.

¹W. Gekelman, et al., Rev. Sci. Instr., 87, 025105 (2016)