Divertor erosion in DIII-D

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Net erosion rates of carbon target plates have been measured in situ for the DIII-D lower divertor. The principal method of obtaining this data is the DiMES sample probe. Recent experiments have focused on erosion at the outer strike-point of two divertor plasma conditions: (1) attached (Te > 40 eV) ELMing plasmas and (2) detached (Te < 2 eV) ELMing plasmas. The erosion rates for the attached cases are > 10 cm/year, even with incident heat flux < 1 MW/m{sup 2}. In this case, measurements and modeling agree for both gross and net carbon erosion, showing the near-surface transport and ... continued below

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25 p.

Creation Information

Whyte, D.G.; Bastasz, R.; Wampler, W.R.; Brooks, J.N.; West, W.P. & Wong, C.P.C. May 1, 1998.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM (United States)
    Place of Publication: Albuquerque, New Mexico

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Description

Net erosion rates of carbon target plates have been measured in situ for the DIII-D lower divertor. The principal method of obtaining this data is the DiMES sample probe. Recent experiments have focused on erosion at the outer strike-point of two divertor plasma conditions: (1) attached (Te > 40 eV) ELMing plasmas and (2) detached (Te < 2 eV) ELMing plasmas. The erosion rates for the attached cases are > 10 cm/year, even with incident heat flux < 1 MW/m{sup 2}. In this case, measurements and modeling agree for both gross and net carbon erosion, showing the near-surface transport and redeposition of the carbon is well understood and that effective sputtering yields are > 10%. In ELM-free discharges, this erosion rate can account for the rate of carbon accumulation in the core plasma. Divertor plasma detachment eliminates physical sputtering, while spectroscopically measured chemical erosion yields are also found to be low (Y(C/D{sup +}) {le} 2.0 {times} 10{sup {minus}3}). This leads to suppression of net erosion at the outer strike-point, which becomes a region of net redeposition ({approximately} 4 cm/year). The private flux wall is measured to be a region of net redeposition with dense, high neutral pressure, attached divertor plasmas. Leading edges intercepting parallel heat flux ({approximately} 50 MW/m{sup 2}) have very high net erosion rates ({approximately} 10 {micro}m/s) at the OSP of an attached plasma. Leading edge erosion, and subsequent carbon redeposition, caused by tile gaps can account for half of the deuterium codeposition in the DIII-D divertor.

Physical Description

25 p.

Notes

INIS; OSTI as DE98005507

Source

  • 13. international conference on plasma surface interactions, San Diego, CA (United States), 18-22 May 1998

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  • Other: DE98005507
  • Report No.: SAND--98-1238C
  • Report No.: CONF-980560--
  • Grant Number: AC04-94AL85000
  • DOI: 10.2172/654183 | External Link
  • Office of Scientific & Technical Information Report Number: 654183
  • Archival Resource Key: ark:/67531/metadc704584

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  • May 1, 1998

Added to The UNT Digital Library

  • Sept. 12, 2015, 6:31 a.m.

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  • April 14, 2016, 3:35 p.m.

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Whyte, D.G.; Bastasz, R.; Wampler, W.R.; Brooks, J.N.; West, W.P. & Wong, C.P.C. Divertor erosion in DIII-D, report, May 1, 1998; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc704584/: accessed August 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.