On comparison of spectroscopically deduced central ion temperatures and plasma rotation at JET

It is shown that a significant increase in the consistency of charge exchange spectroscopy and x‐ray spectroscopy data for central ion temperature and plasma rotation is obtained when allowance is made for the following: (i) The charge exchange cross‐section dependence on the impact energy of the neutral beam atoms in the frame‐of‐reference of the C+6 nuclei. In this paper we have experimentally verified the predicted cross‐section effects on plasma rotation measurements using charge exchange spectroscopy by comparing to passive x‐ray spectroscopy. The effect increases with lighter species. It should be emphasized that this effect is important for the rotation measurements only, while for the ion temperature measurements the effect is small compared to other error sources. (ii) The precise position of the radiating ion shell in line‐of‐sight averaged measurements using x‐ray spectroscopy. For high‐temperature plasmas with broad emission profiles the uncertainty in central ion temperature is reduced from u...