Effect of energy dependent cross-section on flow velocity measurements with charge exchange spectroscopy in magnetized plasma

Publication date: Available online 21 January 2019Source: Physics Letters AAuthor(s): J. Chen, K. Ida, M. Yoshinuma, I. Murakami, T. Kobayashi, M.Y. Ye, B. LyuAbstractCharge exchange spectroscopy (CXS) is widely used to measure plasma flow velocity. Accurate measurement is heavily affected by energy dependent cross section between neutral atoms and impurity ions. One symmetric layout of poloidal CXS is applied on Large Helical Device. Correction velocity due to the cross section is exacted from total velocity when actual plasma flow velocity is acquired with the benefit of this layout. A linear relationship between correction velocity and ion temperature is observed. Abundant discharges with wide plasma conditions are investigated and the ratio of correction velocity to ion temperature with the same beam energy shows the normal distribution. The impact of beam energy on the ratio of correction velocity to ion temperature of the carbon system and the hydrogen system is discovered based upon the statistics. Effective emission coefficient (Q) from Atomic Data and Analysis Structure (ADAS) is utilized to study the dependence of correction velocity on Q. The relationship in which the ratio of correction velocity to ion temperature increases linearly with the increasing normalized effective emission coefficient ((1/Q)dQ/dv) is observed. Experimental (1/Q)dQ/dv is obtained according to this observation, and comparison with different fractions of n = 2 excited state is also discu...

Source: Physics Letters A - January 22, 2019 Category: Physics Source Type: research