Thomson scattering on COMPASS — commissioning and first data

Abstract

High-resolution edge and core Thomson scattering systems have been designed with the main aim to investigate electron density and temperature profiles on the COMPASS tokamak (R = 0.56 m, a = 0.18 m, B T max = 2.1 T). The spatial resolution is optimized namely for the pedestal studies (radial spatial resolution ∼ a/100). Currently, the core Thomson scattering system is commissioned, calibrated and tested in tokamak discharges. This contribution describes particular steps of optical alignment and calibrations. Moreover, we show control tools developed for electronic settings, calibrating procedures and laser beam position measurement. Both the calibration data, i.e. Raman scattering obtained in the N 2 at pressures up to 200 mbar, and the first Thomson scattering data measured by the system in the H discharges are presented.

High resolution Thomson scattering on the COMPASS tokamak—extending edge plasma view and increasing repetition rate

“…The TS system for the COMPASS tokamak was designed and built in 2008-2010 years during the tokamak installation [7] and started its operation in 2011 [8]. Since the beginning, it was designed to have two separate collection optics (both sharing one laser beam); one observing the edge plasma -1 - region with high resolution (~a/100), the second extending the measured profiles to the middle of the plasma.…”

High-resolution Thomson scattering system on the COMPASS tokamak: Evaluation of plasma parameters and error analysis

“…These particles do not contribute to the plasma current. 9 Neoclassical resistivity can be calculated as: 2 . Unknown effective charge number Z eff can be estimated from comparison with fundamental equations for mean resistivity, η = (U loop π a 2 )/(2π RI plasma ), where R = 0.56 m is major radius and a = 0.20 m is minor radius of COMPASS tokamak, U loop is loop voltage, and I plasma is plasma current.…”

“…The Thomson scattering (TS) system for the core plasma on the COMPASS tokamak 1 has been commissioned and is routinely used for measurement of profiles of both electron density n e and electron temperature T e . 2 In this paper we present profiles of T e and n e for ohmically heated plasmas with a circular cross sections including error bars. We compare the TS data with the data obtained by a single-chord lineintegrated electron as density measured by a microwave interferometer.…”

Progress in diagnostics of the COMPASS tokamak

“…The dominant role among optical diagnostics on COMPASS belongs to the Thomson scattering (TS) diagnostic, which routinely provides both electron density and temperature profiles with a spatial resolution of about a/30 in the core and up to a/100 at the edge [32,33]. The core and edge TS systems have separate collection optics, located in separate tokamak ports, sharing the same laser beams (Nd:YAG at 1064 nm).…”