Effect upon the core plasma radiation due to high power laser injection onto C, W and Ta test-limiters in TEXTOR

To investigate the effect due to localized high heat flux pulses onto plasma facing components, light pulses from a ruby laser (15 J in maximum energy, 0.3 ms in duration) were injected onto test-limiter (C, W, and Ta) surfaces immersed in TEXTOR edge plasmas. When the laser pulses irradiated the C limiter surface, the CVI signal from the plasma core increased slightly. In laser injection onto high-Z limiters, the increment of the quasi-continuum around 5 nm of the Ta signal was larger than that of the W signal. With the laser focusing down to 2 mm in diameter, small high-Z particles were found to be ejected from the limiter surfaces which penetrated into the plasma beyond the LCFS. However, the plasma withstood the core cooling due to the radiation loss of high-Z impurity. The amounts of impurities in the core were also estimated by a laser blow-off experiment.