In:
Japanese Journal of Applied Physics, IOP Publishing, Vol. 49, No. 10R ( 2010-10-01), p. 106103-
Abstract:
Visible bremsstrahlung emission profiles have been studied over a wide range of electron densities in H 2 gas puff and solid-H 2 -pellet-fueled discharges of large helical device (LHD). Peaked profiles are observed in high-density discharges ( n e ≥10 14 cm -3 ) with pellet injection, whereas hollow profiles appeared in the normal discharges ( n e ≤10 14 cm -3 ) with gas puffing. The total bremsstrahlung radiation is analyzed from the visible bremsstrahlung profile by integrating the energy and plasma volume. It is found that the total bremsstrahlung radiation rapidly increases with the density in the pellet discharges, of which the increment is scaled by the square of density, while it is roughly constant against the density in the gas puff discharges. The total bremsstrahlung radiation becomes equal to the total radiation loss in the pellet discharges. The ratio of the total bremsstrahlung radiation to the total input power has only a range of 3–10% in the gas puff discharges. In contrast, the ratio increases with the density and reaches 30–40% in the pellet discharges. Flat Z eff profiles are observed not only in the gas puff discharges but also in the pellet discharges. This indicates that no impurity accumulation occurs in the high-density operation with H 2 pellet injection.
Type of Medium:
Online Resource
ISSN:
0021-4922
,
1347-4065
DOI:
10.1143/JJAP.49.106103
Language:
Unknown
Publisher:
IOP Publishing
Publication Date:
2010
detail.hit.zdb_id:
218223-3
detail.hit.zdb_id:
797294-5
detail.hit.zdb_id:
2006801-3
detail.hit.zdb_id:
797295-7
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