DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 401: Dedicated Experiments to Check Cross Section Correction forCER Rotation Measurements | ||
| Name: | Keith Burrell ( |
Affiliation: | General Atomics |
| Research Area: | Rotation Physics | Presentation time: | Not requested | Co-Author(s): | W.M. Solomon |
| Description: | Use dedicated scans of plasma temperature and rotation to check the
cross section correction used for CER measurements of plasma rotation. | ||
| Experimental Approach/Plan: | Perform NBI power and torque scans in steady state phase of L-mode
or QH-mode discharges. Goal is to vary Ti and v_phi as much as possible to check cross section correction as a function of these variables. L-mode provides the lowest temperature and rotation points while QH-mode reaches the Ti and v_phi extremes. | ||
| Background: | Because the cross section for charge exchange between beam neutrals
and ion in the plasma depends on energy, ions moving with the beam have typically a lower charge exchange cross section while those moving against the beam have a higher cross section. This results in an apparent shift in the ion velocity when that velocity is measured using the post-charge-exchange spectrum. This correction depends on the ion temperature and toroidal rotation speed of the background plasma. The magnitude of the correction relative to the plasma rotation speed is largest for high temperature, low rotation speed plasmas, such a those created with high power balanced beam injection. Such discharges are becoming increasingly important for the D III-D program. We have an algorithm which we use to correct the C VI rotation speed for the energy dependent cross section. This is fairly complex, since it involves a significant amount of atomic physics. Now that we have CER views of the co and counter neutral beams, we can also directly measure the cross section correction since it has a different sign for the co and counter beams whereas the actual plasma rotation is the same. This experiment would produce high quality CER data to compare the measured and calculated cross section correction. | ||
| Resource Requirements: | NBI modulation with 30LT and 210RT modulated in phase is essential. | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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