First measurements of the ion energy distribution at the divertor strike point during DIII-D disruptions

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Plasma disruptions are a serious concern in tokamak design because of the high impulsive heat loads which can cause strong erosion of divertor materials due to enhanced sputtering, or melting/ablation in the most severe cases. Predictions of net erosion rates and hence component lifetimes are very difficult and are highly dependent on the plasma conditions over the divertor target. It is therefore necessary to characterize the properties of the scrape-off plasma near the divertor target plate under these special conditions. Here, plasma/wall interaction studies are being carried out using the Divertor Materials Exposure System (DiMES) on DIII-D. The objective of ... continued below

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4 p.

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Parks, P. B.; Brooks, N. H.; West, W. P.; Wong, C. P. C.; Bastasz, R.; Wampler, W. R. et al. March 1996.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM (United States)
    Place of Publication: Albuquerque, New Mexico
  • General Atomic Company
    Publisher Info: General Atomics, San Diego, CA (United States)
    Place of Publication: San Diego, California

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Description

Plasma disruptions are a serious concern in tokamak design because of the high impulsive heat loads which can cause strong erosion of divertor materials due to enhanced sputtering, or melting/ablation in the most severe cases. Predictions of net erosion rates and hence component lifetimes are very difficult and are highly dependent on the plasma conditions over the divertor target. It is therefore necessary to characterize the properties of the scrape-off plasma near the divertor target plate under these special conditions. Here, plasma/wall interaction studies are being carried out using the Divertor Materials Exposure System (DiMES) on DIII-D. The objective of the experiment is to determine the kinetic energy and flux of deuterium ions reaching the divertor target during argon-induced radiative disruptions. The experiment utilizes a special slotted ion analyzer mounted over a Si sample to collect the fast charge-exchange (CX) deuterium neutrals emitted within the recycled cold neutral layer (CNL) which serves as a CX target for the incident ions. A theoretical interpretation of the experiment reveals a strong forward pitch-angle dependence in the approaching ion distribution function. The depth distribution of the trapped D in the Si sample was measured using low-energy direct recoil spectroscopy. Comparison with the TRIM code using monoenergetic ions indicated that the best fit to the data was obtained for an ion energy of 100 eV. An estimate of the CNL thickness {integral}nd{ell} indicates that during disruptions the CNL cushion is thick enough to reduce the local ion heat load by {approximately}30% due to CX refluxing.

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4 p.

Notes

INIS; OSTI as DE96006386

Source

  • 16. symposium on fusion engineering, Champaign, IL (United States), 30 Sep - 5 Oct 1996

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  • Other: DE96006386
  • Report No.: SAND--96-0402C
  • Report No.: CONF-960993--1
  • Grant Number: AC04-94AL85000
  • DOI: 10.2172/266755 | External Link
  • Office of Scientific & Technical Information Report Number: 266755
  • Archival Resource Key: ark:/67531/metadc673353

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  • March 1996

Added to The UNT Digital Library

  • June 29, 2015, 9:42 p.m.

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  • Aug. 1, 2016, 6:52 p.m.

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Parks, P. B.; Brooks, N. H.; West, W. P.; Wong, C. P. C.; Bastasz, R.; Wampler, W. R. et al. First measurements of the ion energy distribution at the divertor strike point during DIII-D disruptions, report, March 1996; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc673353/: accessed November 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.