10 kHz repetitive high-resolution TV Thomson scattering on TEXTOR: Design and performance (invited)

In late 2003 a 10 kHz multiposition Thomson scattering diagnostic with high spatial resolution became operational on the TEXTOR tokamak. In the initial phase of operation, one burst of 18 pulses of 12 J each with a repetition rate of 5 kHz could be extracted from the laser system. The installation of a low-dope ruby rod (spring 2005) resulted in a system, which can deliver higher pulse energy and moreover a divergence of better than 0.7 mrad , leading to a big improvement in the detection of Thomson scattering photons. Furthermore, the number of laser pulses in one burst could be extended to even more than 30. The achieved laser energy of more than 15 J ∕ pulse makes it possible to measure electron temperature and density profiles with an observational error of 8% on the electron temperature ( T e ) and 4% on the electron density ( n e ) at n e = 2.5 × 10 19 m − 3 , per spatial element of 7.5 mm . The viewing optics enables sampling of either the full plasma diameter of 900 mm with 120 spatial channels of 7.5 mm each or a 160 mm long edge chord with 98 spatial channels of 1.7 mm each. The system, which has recently become available for physics exploration, has already been used to study the structure of m = 2 magnetic islands and the response of the plasma to off-axis electron cyclotron resonance heating.