The development of Thomson scattering system on HL-2A tokamak

Abstract

A new Thomson scattering diagnostic system is successfully developed to measure core plasma electron temperature (Te) and density (ne) of HL-2A tokamak (major radius R=165 cm, minor radius a=40 cm). In this system, a standard lamp-monochromator combination is utilized for the calibration of spectral responses. By sweeping in the range of 750-1200 nm with a step of 2 nm, the work can be done automatically for one-point calibration and then for other. Electronic gain calibration and gain monitoring are done by pulsed light emitting diode light. By utilizing an intense Nd:YAG laser of pulse energy up to 4 J and employing good quality interference filters in the five-channel filter polychromator to surpress greatly the stray light, the TS system can be routinely used to make measurements with good quality data. After each HL-2A plasma discharge, the measured Te and ne data are transferred to HL-2A database for lookup and analyses.

Investigation of impurity transport using laser blow-off technique in the HL-2A Ohmic and ECRH plasmas

“…[18] The ECE signal amplitude is calibrated with the electron temperature measured with the Thom-065202-2 son scattering diagnostic. [19] If it is necessary, a fast scanning Langmuir probe is also used to measure the n e and T e profiles at the edge from the outer mid-plane of the HL-2A plasma.…”

Design and development of five-channel interference filter polychromator for SST-1 Thomson scattering system

“…However, the losses due to reflection from filters are inevitable. Relay lenses, used in many of the earlier designs [14,15], have not been considered for reducing the reflection losses inside the polychromator. The relay lens with appropriate antireflection coating make a loss of nearly 18% (∼2% per interface, 10 interface) in total transmission, which is avoided in this present configuration.…”

Improvement in data processing of Thomson scattering diagnostic on HL-2A tokamak

“…A new Nd:YAG laser source is utilized in the HL-2A core-TS system, which is Q-switched and works at 30 Hz repetition rate with 4 J laser output at 1064 nm. Its beam quality is mismatched with the old laser working at 10 Hz [6]. The HL-2A tokamak has the closed lower and upper divertors, the throat passage is curved and quite narrow.…”