Design of Thomson scattering diagnostic system on linear magnetized plasma device

Abstract

In addition to the magnetic confinement fusion plasma, Thomson scattering (TS) has been applied to measure electron density and temperature of low-temperature plasmas. Based on Linear Magnetized Plasma (LMP) device, a set of incoherent Thomson scattering diagnostic system is designed to diagnose the plasma with ne=1018~1019m-3 and Te=2~5eV. Due to low plasma temperature and density, this diagnostic system needs high spectral resolution and collection efficiency to meet the requirements of electron velocity distribution function (EVDF) measurements. Through the bench test, the spectral resolution is confirmed to reach 0.01 nm, and theoretical collection efficiency is high enough to obtain Thomson scattering spectrum by 1000 accumulations.

Stray light suppression for Thomson scattering diagnostic on linear magnetized plasma device

“…A Thomson scattering diagnostic system [6] has been installed on the LMP device [9,10]. The incident source is a pulsed Nd-YAG laser operating at the second harmonic (532 nm, 0.6 J, 30 Hz)…”

“…Although only a few (less than 4) photons can be obtained in a single laser pulse, the TS spectra is obtained via multiple accumulations benefited from the good discharge repeatability of LMP device. In our previous work [6], the primary concern was to confirm the signal of Thomson scattering. Without special consideration of stray light suppression, the accumulative number was up to 600 in order to get a TS spectrum.…”

“…Moreover the EAST device [4] utilized a dump made of multi-layer graphite plates. The TS diagnostic technique is also applied to low temperature plasma devices [5,6] where the lower electron temperature and plasma density result in less scattering photons and narrower spectrum broadening. These factors increase the difficulty of the accurate measurement of the electron velocity distribution function and density.…”