DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 51: Runaway electon diagnosis by impurity pellet injection | ||
| Name: | Alex James
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Affiliation: | University of California, San Diego |
| Research Area: | Disruptions | Presentation time: | Requested | Co-Author(s): | E. M. Hollmann, G. R. Tynan, G. Jackson |
| Description: | Study runaway electron generation and transport by injecting impurity pellets into plasmas disrupted by MGI or killer pellet injection, and observing the interaction with runaway electrons using the UCSD fast framing camera and scintillation detectors. Resulting data will reveal clues about runaway electron spatial distributions and energy distributions in mitigated plasmas. Diagnosis of naturally disrupting plasmas may also be possible. Successful experiments will contribute to A. James' advancement to PhD candidacy. | ||
| Experimental Approach/Plan: | H-mode plasma disruption will be initiated with MGI or killer pellets. Theory predicts generation of runaway electrons coincident with the thermal quench, with runaway beam termination indicated by a radiation spike (probably due to photoneutrons) in proximal scintillators ~10ms later. Injecting impurity pellets into the runaway beam for bombardment generates a narrow, strongly directional, cone of radiation which will be observed with a scintillator array. Visible radiation will also be observed by the UCSD fast framing camera. | ||
| Background: | Many disruption mitigation schemes appear to generate the same runaway electron phenomena which they set out to prevent. Observing the radiation emitted by runaway electrons bombarding an impurity pellet will reveal information about the energy distribution of said electrons. Also, theory postulates a braiding like transport phenomena of runaway electrons which will manifest a particular temporal signature in the emitted radiation. While we can study runaway electrons in DIII-D, larger machines such as JET and eventually ITER may suffer critical damage preventing further operations due to runaway electron interaction with wall materials. | ||
| Resource Requirements: | Engineering and technician support will be required for reinstalling the old lithium pellet injector (LPI) hereforth know as the impurity pellet injector (IPI). | ||
| Diagnostic Requirements: | Experiments will require H-mode plasmas terminated by MGI or killer pellets. The disrupting plasmas will then be probed by the impurity pellet injector, which needs to be reinstalled pending bench tests. | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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