Space- and time-resolved study of impurities by visible spectroscopy in the high-density regime of JIPP T-II tokamak plasma

Abstract

Time-resolved spatial profiles of Zeff in JIPP T-II tokamak plasmas have been determined from the measurement of bremsstrahlung in the visible spectral region. The effective ion charge Zeff increases at the plasma centre and decreases at the plasma periphery in the high-electron-density regime. The emissions from low ionization states of light impurities increase notably in the region of lower electron temperatures in this regime. As a result, impurities accumulate in the plasma centre in the high-density regime. The results obtained with respect to the plasma periphery support the interpretation of the behaviour of the impurities, which is based on VUV spectroscopic studies.

Effect of boronization on ohmic plasmas in NSTX

“…Four analysis sites were spaced 5 mm apart on a line through the center of the coupon and the results are summarized in Table 1. The B+C areal density was 10 18 (B+C) cm -2 corresponding to a film thickness of 100 nm, similar to the 96 nm calculated thickness of 10 g of TMB deposited uniformly over the ≈ 41 m 2 surface area of the vessel. The B/C ratio of 1/3 is consistent with the stoichiometric ratio in TMB (as in TEXTOR (0.38) [2], and -4 -in COMPASS (0.46 on stainless coupons) [7]) while the D/(B+C) ratio was 2/3.…”

Effect of Boronization on Ohmic Plasmas in NSTX

“…The system was absolute intensity calibrated and checked against high density He discharges. Z eff was calculated [18] from the intensity and the electron density and temperature as measured by Thomson scattering and was in the range Z eff ≈ 2 immediately following the first boronization.…”

Multichannel light detector system for visible continuum measurements on Alcator C

“…If, however, the spectrum is relatively free of both recombination and line emission, the analysis becomes much less complicated. This condition is most easily satisfied in the visible, and, as shown by K. Kadota,[ 3 ] et.al.. (1979), Zeff can in this way be measured in tokamak plasmas.…”