High time resolved electron temperature measurements by using the multi-pass Thomson scattering system in GAMMA 10/PDX

High time resolved electron temperature measurements are useful for fluctuation study. A multi-pass Thomson scattering (MPTS) system is proposed for the improvement of both increasing the TS signal intensity and time resolution. The MPTS system in GAMMA 10/PDX has been constructed for enhancing the Thomson scattered signals for the improvement of measurement accuracy. The MPTS system has a polarization-based configuration with an image relaying system. We optimized the image relaying optics for improving the multi-pass laser confinement and obtaining the stable MPTS signals over ten passing TS signals. The integrated MPTS signals increased about five times larger than that in the single pass system. Finally, time dependent electron temperatures were obtained in MHz sampling

Radial Profile Measurements of Electron Temperature and Density Using the Thomson Scattering System in GAMMA 10/PDX

We developed the YAG Thomson scattering (TS) system for electron temperature and density radial profiles in a single laser shot in the tandem mirror GAMMA 10/PDX. The optical collection system for the TS light is constructed using spherical mirrors and nine bundled optical fibers. The measurable radial positions are 5-cm intervals in a region of ±20 cm due to the fixed position of the bundled optical fibers, which are set on a fixed-height optical platform. We replaced this with a lab jack to make the bundled optical fiber positions movable. Consequently, we can measure the radial profiles of the electron temperature in more detail. Moreover, we added a third spherical light collection mirror at the bottom of the main spherical collection mirror to increase the TS light intensity in the edge plasma region. In this way, we can obtain a slightly larger TS signal intensity than in the case without a third collection mirror. The radial electron temperatures and densities at 15 radial positions in GAMMA 10/PDX are successfully obtained. For the in-situ calibration of the electron density measurements of the TS system, we compare the TS system measurements to the electron line density measured using a microwave interferometer system

Effects from the Target Plate Geometry on Fluctuations of Helium Plasma in the Linear Divertor Simulator Magnum-PSI

With the help of the linear divertor simulation device Magnum-PSI, a fluctuation investigation of the impact of the target plate geometry was conducted. We simultaneously quantify coherent low-frequency fluctuations with a newly built 70-GHz microwave reflectometry system, a reciprocating probe, a light emission detector system, and a fast-framing camera system. The strong low-frequency fluctuations were observed at both the electron density and the plasma radiations by moving the target plate along the magnetic field line. Furthermore, a strong peak in fluctuation intensity and the influence of the target plate tilt angle on the fluctuation intensity were noted