TY - JOUR
T1 - Probe measurements of impurities in the plasma boundary of PLT
AU - Wampler, W. R.
AU - Picraux, S. T.
AU - Cohen, S. A.
AU - Dylla, H. F.
AU - Rossnagel, S. M.
AU - McCracken, G. M.
N1 - Funding Information:
l This work was supported by the US Dept. of Energy, DOE, under contracts DE-ACM-76DPW789 and DE-ACKQ-76-CHO3073.
PY - 1980
Y1 - 1980
N2 - Carbon probes were exposed to the plasma edge in PLT at various distances from the plasma and to different numbers [1–3, 6, 12] of overlayed discharges. The type and areal density of impurities retained were determined using ion backscattering. The principal impurities were found to be O, Fe, Cr, Ti, and Cu which had fluxes of 14, 2.8, 0.8, 0.6 and 0.2 × 1015/cm2 (±25%), respectively, near the radius of the wall. At the same position the deuterium flux was 2.2 ± 0.5 × 1017 D/cm2 s. Lateral spreading of the impurity deposition profile behind the probe slit allowed a lower limit to be placed on the impurity mean ion energy. Between the wall and radius of the ring limiter the impurity fluxes increased by a factor of ~2 compared to an increase in the D flux by a factor of ~5. The observed nonlinear impurity retention versus the number of discharges is consistent with the values determined for the impurity and D fluxes and the expected effects of sputtering. The observed large flux of iron at the radius of the ring limiter suggests that this may be a primary source of metal impurities in PLT.
AB - Carbon probes were exposed to the plasma edge in PLT at various distances from the plasma and to different numbers [1–3, 6, 12] of overlayed discharges. The type and areal density of impurities retained were determined using ion backscattering. The principal impurities were found to be O, Fe, Cr, Ti, and Cu which had fluxes of 14, 2.8, 0.8, 0.6 and 0.2 × 1015/cm2 (±25%), respectively, near the radius of the wall. At the same position the deuterium flux was 2.2 ± 0.5 × 1017 D/cm2 s. Lateral spreading of the impurity deposition profile behind the probe slit allowed a lower limit to be placed on the impurity mean ion energy. Between the wall and radius of the ring limiter the impurity fluxes increased by a factor of ~2 compared to an increase in the D flux by a factor of ~5. The observed nonlinear impurity retention versus the number of discharges is consistent with the values determined for the impurity and D fluxes and the expected effects of sputtering. The observed large flux of iron at the radius of the ring limiter suggests that this may be a primary source of metal impurities in PLT.
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U2 - 10.1016/0022-3115(80)90312-8
DO - 10.1016/0022-3115(80)90312-8
M3 - Article
AN - SCOPUS:0019245809
SN - 0022-3115
VL - 93-94
SP - 139
EP - 145
JO - Journal of Nuclear Materials
JF - Journal of Nuclear Materials
ER -