DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 492: Particle balance in hybrid plasmas over a full day of operations with no helium glow conditioning | ||
| Name: | Phil West ( |
Affiliation: | General Atomics |
| Research Area: | Hydrogenic Retention | Presentation time: | Not requested | Co-Author(s): | Tom Petrie, Steve Allen, Mathias Groth, Neil Brooks, |
| Description: | Establish a baseline H retention in strongly-pumped, high-performance hybrid operation with no between shot helium glow cleaning. Use the hybrid scenario previously found to have no (or even negative) H retention over a single shot. | ||
| Experimental Approach/Plan: | Run a standard hybrid, USN, normal Bt at a Greenwald fraction of ~0.4 all day long with no between shot helium glow. Use all diagnostics related to particle balance, extending vessel pressure measurements to 8 minutes after t=0. Regenerate crypumps between each shot to measure accumulated D2. Step 2: repeat experiment using gas puff feedback to control Greenwald fraction at 0.6 | ||
| Background: | Wall retention of H isotopes is found to be excessive in many devices that operate with strong particle exhaust. This has lead to a serious worry for the ITER team, who have used extrapolations of these results to predict that in vessel T inventory would build up rapidly. The rate of buildup could be high enough to require frequent (e.g. daily) mitigation. Yet DIII-D has observed zero net wall retention in strongly-pumped hybrid discharges, and in some cases net removal of wall inventory has been documented. A clear demonstration of zero wall retention over a full day of operation (roughly 180 plasma seconds) might bring some optimism into the ITER first wall planning process. | ||
| Resource Requirements: | USN Hybrid
Bt direction TBD, but probably normal 6 beams, 7 better Cryopumping, all pumps | ||
| Diagnostic Requirements: | All the usual suspects
ASDEX gauges Capacitance manometers. RGA | ||
| Analysis Requirements: | Good particle balance, work on decreasing error in net particle balance. | ||
| Other Requirements: | -- | ||
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