DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 135: Carbon wall tritium removal using massive hydrogen injection | ||
| Name: | Eric M. Hollmann ( |
Affiliation: | University of California, San Diego |
| Research Area: | Hydrogenic Retention | Presentation time: | Requested | Co-Author(s): | A. Pigarov, D. Rudakov |
| Description: | Injection of massive quantities of H2 into a H-mode discharge is proposed as a possible method of rapidly replacing T bound in soft C layers in the vicinity of the divertor strike points. MGI shutdown/disruption heat loads and wall fluxes are known to be much broader than the normal discharge strike points. Also, massive H2 injection has been shown to cause a very high density plasma (20x density increase), with fairly significant divertor and wall plasma fluxes (thermal quench radiated power loss of ~20% or less). | ||
| Experimental Approach/Plan: | To test the efficiency of divertor isotope replacement during hydrogen injection, MGI of D2 would be performed near or at the end of of H2 run day, with a graphite DiMES sample exposed and saturated with D2. After H2 MGI, the DiMES sample could be retracted and then analyzed for D2 and H2 content. For consistency, the reverse experiment could also be performed (H2 MGI into a D2 saturated DiMES sample). The intial target discharge could be biased downward slightly to ensure that the post-TQ VDE drifted downward and maximized divertor plasma flux. | ||
| Background: | Removal of co-deposited tritium from graphite divertor tiles is a challenging problem for which a wide variety of possible solutions have been proposed. The use of massive gas-injection shutdowns was proposed previously by D. Whyte. The present proposal is new in that instead of injecting a high-Z impurity like Ar and using the resulting radiation flash to thermally desorb T from the walls, H2 is injected and driven into the divertor in the resulting disruption, replacing T bound in the C surface. A preliminary piggyback experiment testing this idea (proposed by A. Pigarov) was performed in 2007, with encouraging initial results. | ||
| Resource Requirements: | A single high power shot during a H2 run day, as well as a single high power shot during a D2 run day. DiMES with graphite sample (and MiMES, if possible). | ||
| Diagnostic Requirements: | MDS and RGA could be used to monitor H/D ratios in subsequent discharges; this could provide some clue as to the global amount of H2/D2 swapped in a single MGI shot. | ||
| Analysis Requirements: | Thermal desorption spectroscopy of DiMES graphite samples can be done at UCSD. | ||
| Other Requirements: | -- | ||
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