Dependence of deuterium line-shape on the insertion depth of BN and C limiters in the TPE-1RM20 reversed field pinch plasma

Boron nitride (BN) and graphite limiters were placed in the edge region of deuterium plasma of the reversed-field-pinch machine TPE-1RM20, The limiter s were attached on a linear motion feedthrough and were inserted into the e dge plasma up to 40 mm beyond the plasma boundary defined by fixed limiters . The emission spectrum of deuterium atoms was measured in the vicinity of the limiters. The spectral line profile was analyzed by changing the insert ion depth of the limiter. When the limiter was inserted a certain depth for the first time, the emission of hydrogen atoms was observed for both BN an d carbon materials and the release of retained hydrogen was evident. The em ission intensity of hydrogen was suddenly decreased within 3-5 shots for th e case of BN limiter, and then, the peak was buried under noise. The broade ned spectrum of deuterium was observed when the BN limiter was inserted up to approximately 30 mm. The amount of released hydrogen from the graphite l imiter was 2-3 times larger than that from BN limiter and the release conti nued for 5-10 shots. The profile of deuterium line was changed with shot by shot compared to the BN limiter experiments. A broadened profile was obser ved when the insertion depth exceeded 30 mm. (C) 1999 Elsevier Science B.V. All rights reserved.