Abstract
Comparisons of helium (He) transport and exhaust in L-mode and in an enhanced confinement regime (H-mode), which is induced by a polarizing electrode, have been made for the TEXTOR tokamak. The results show an increased tendency for He accumulation when bulk plasma energy and particle confinement are improved during the polarization-induced H-mode. Since these results imply that a high He pumping efficency may be necessary for H-mode burning plasmas, we have begun exploring He transport in a divertor H-mode, similar to that proposed for the international thermonuclear experimental reactor (ITER). A collaborative program has been initiated to measure He transport and scaling on DIII-D during L-mode, H-mode, and ELMing H-mode plasma conditions. To simulate the presence of He ash in DIII-D, a 25 ms He puff is injected into a DIII-D plasma, resulting in a He concentration of ≈5%. The time dependence of the He2+ density profiles in the plasma core is measured by charge-exchange recombination spectroscopy at 11 radial locations.
| Original language | English |
|---|---|
| Pages (from-to) | 35-44 |
| Number of pages | 10 |
| Journal | Journal of Nuclear Materials |
| Volume | 196-198 |
| Issue number | C |
| DOIs | |
| State | Published - Dec 1 1992 |
Funding
For future steady-state tokamaks, such as the international thermonuclear experimental reactor (ITER), continuous purging of the helium (He) ash is essential. Estimates [1]s how that newly created He ions must be removed within 7 to 15 energy confinement times to maintain continuous reactor operation (r~e/r E < 7- 15). Recent measurements [2-6] on TEXTOR and other tokamaks demonstrate that He can be readily transported from the plasma core during L-mode plasma discharges. TEXTOR experiments use the advanced limiter test-II (ALT-II) system, a toroidal belt * Research sponsored in part by the Office of Fusion Energy, US Department of Energy, under contract DE-AC06-84OR21400 with Martin Marietta Energy Systems, Inc., and by the US Department of Energy under contract DE-AC03-89ER51114.