Electron temperature measurements by the use of multi-pass Thomson scattering system in GAMMA 10/PDX

Abstract

A multi-pass (MP) Thomson scattering (TS) system modeled on the GAMMA 10/PDX TS system was constructed for enhancing the Thomson scattered signals. The MPTS system has a polarization-based configuration with an image relaying system. The former MPTS system in GAMMA 10/PDX can measure only four passing signals. We changed the larger aperture polarization control device for improving the MP laser confinement and obtaining the over four passing MPTS signals. The integrated MPTS signals increased about 1.2 times larger than that in the former system.

Development of a laser amplification system for the multi-pass Thomson scattering system for GAMMA 10/PDX

“…16 By adding a polarization control device, a polarizer, and a high-reflection mirror to the double-pass TS system, we previously successfully constructed over three passing MPTS systems. [17][18][19] We achieved approximately 3.6 times increased TS signals by the first to the sixth passing probing lasers through the plasma in a single laser shot. 17 Moreover, the time-dependent electron temperature measurement every 65 ns was successfully obtained.…”

“…[17][18][19] We achieved approximately 3.6 times increased TS signals by the first to the sixth passing probing lasers through the plasma in a single laser shot. 17 Moreover, the time-dependent electron temperature measurement every 65 ns was successfully obtained. 18,19 However, in the normal MPTS system, the MPTS signal intensities decrease with the pass number because of the laser power damping due to the optical components.…”

“…[9][10][11][12][13] In GAMMA 10/PDX (Potential-control and Divertor-simulator eXperiments), the MPTS system of the polarization-based system with imagerelaying optics has been developed. [14][15][16][17][18][19] GAMMA 10/PDX is an effectively axisymmetric minimum-B anchored tandem mirror with a thermal barrier at both end mirrors. 20 The plasma is created by plasma guns, and it is then heated and sustained using ion cyclotron heating (ICH) systems.…”

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

“…16 By adding a polarization control device, a polarizer, and a high-reflection mirror to the double-pass TS system, we have successfully constructed over three passing MPTS systems. [17][18][19][20] We successfully obtained about 3.6 times increased TS signals by first to sixth passing probing lasers through the plasma in a single laser shot. 20 Moreover, the time dependent electron temperature measurement every 65 ns was successfully obtained.…”

Analysis method for Thomson scattering diagnostics in GAMMA 10/PDX

“…3,16,17 We have previously developed an MPTS system with polarization control and image relaying optical systems. 18 In this study, we developed a TS analysis method with a fitting technique to reduce the error in the electron temperature measurement for raw TS signals. The MPTS system enables high-time-resolution measurements of the electron temperature with calculation of the electron temperature in every pass.…”