Bench test of interferometer measurement for the Keda Reconnection eXperiment device (KRX)

Abstract

Motivated by the need of the electron density measurement for the Keda Reconnection eXperiment (KRX) facility which is under development, an interferometer system has been is used to fulfill the high phase difference measurement in such low temperature device. The results of the bench test show that the phase difference is accurately measured. In contrast to tens of degrees of phase shift expected to be measured on the KRX, the system noise (~1o) is low enough for the KRX diagnostics. In order to optimize the system for better performance, we utilize the Terasense Sub-THz imaging system to adjust alignment. The interferometer system has also been calibrated via changing of the optical path length controlled by the piezo inertial motor. Simultaneously, high density polyethylene (HDPE) thin film is introduced successfully to change a tiny phase difference and test the sensitivity of the interferometer system.

Electron density measurement by the three boundary channels of HCOOH laser interferometer on the HL-3 tokamak

“…Electron density is one of the most important parameters in the magnetically confined fusion plasmas. Measurement of the refractive index (N) of plasma by using the electromagnetic wave is a well-established tool for measuring the electron density for many decades [1][2][3][4][5][6]. Far-infrared (FIR) laser interferometer detects the line-integrated electron density through launching a beam of FIR laser into the plasma.…”