DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 367: Deuterium retention in tungsten | ||
| Name: | William R. Wampler ( |
Affiliation: | Sandia National Laboratories |
| Research Area: | Hydrogenic Retention | Presentation time: | Requested | Co-Author(s): | Dmitry Rudakov
Clement Wong |
| Description: | Retention of tritium in tungsten plasma-facing components might constrain operation of ITER. Although some studies of deuterium retention in tungsten exposed to plasmas have been done, the possibility of enhanced tritium retention due to trapping at lattice defects from neutron irradiation remains an open issue. It is known that energetic neutron irradiation creates lattice vacancies, and that vacancies in metals trap hydrogen isotopes. In tungsten vacancies are stable below 300 C whereas hydrogen diffuses at room temperature and above. Thus hydrogen isotopes injected from a plasma may diffuse to the vacancies and become trappped. The issue for ITER is how much tritium will become trapped. This depends on the concentration of trapped hydrogen, the depth it extends into the material, and how strongly the hydrogen is bound to the traps. The purpose of the proposed experiments is to answer these questions by measuring the retention of deuterium in tungsten samples exposed to DIII-D plasmas. Some of the samples would be pre-irradiated with energetic ions to produce atomic displacements similar to that resulting from fusion neutron irradiation. The experiments would look for a difference in deuterium content of damaged versus undamaged samples after exposure to divertor plasma in DIII-D. | ||
| Experimental Approach/Plan: | Tungsten samples would be irradiated with energetic ions at Sandia National Laboratories to produce displacement damage up to one displacement per atom (dpa) to depths of a few microns. These samples would be exposed to divertor plasma in DIII-D, along with similar undamaged samples using DiMES. After plasma exposure, the deuterium concentration versus depth would be measured using nuclear reaction analysis at Sandia. Increased deuterium retention in the irradiated samples would be evidence of enhanced retention due to trapping at displacement damage. | ||
| Background: | -- | ||
| Resource Requirements: | One DIII-D run day for setup and exposure of samples to lower single null attached divertor plasma. | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | DiMES probe would be used to expose samples. | ||
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