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Investigation of Ion Transport with Beam Modulation. XP Proposal Patrick Ross OP-XP-737. Motivation. Goal: To investigate ion power balance and the effects of beam modulations on fast and thermal ions

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investigation of ion transport with beam modulation

Investigation of Ion Transport with Beam Modulation

XP Proposal

Patrick Ross

OP-XP-737

Investigation of Ion Transport with Beam Modulation P.Ross

motivation
Motivation
  • Goal: To investigate ion power balance and the effects of beam modulations on fast and thermal ions
    • Fast ion distribution function has been shown to be anomalous during periods free of low amplitude MHD modes. This anomaly may be due to high frequency MHD activity. The amplitude of the high frequency modes can be reduced by decreasing the beam power. This XP will study the effects of beam power modulations on the fast ion population distribution.
      • Beam modulations using NPA at various angles. Necessary to show the redistribution of fast ions.
      • NPA analysis will incorporate Edge Neutral Density Diagnostic. Edge neutral density has been shown to have an effect on NPA and neutron signals in TRANSP.
    • Study effects of altered source term (fast ions) on thermal ion power balance. By modulating the beam at different rates, it may be possible to determine if the fast ions are transferring energy to the thermal ions at an anomalously fast rate, possibly via high frequency modes. Such an interaction could be responsible for Ti>Te.
      • Beam will be modulated at various time steps covering the slowing down time (~30 ms) and the energy confinement time (~80 ms) with a duty cycle of ~50%.

Investigation of Ion Transport with Beam Modulation P.Ross

base shot 120001
Base Shot: 120001

Blue shows q(0) as calculated by TRANSP. Black shows q(0) as measured by MSE. Note that the measured q(0) reaches a steady value (~1.3) around the same time as the MHD activity disappears.

No large amplitude low frequency MHD modes after 550 ms.

Investigation of Ion Transport with Beam Modulation P.Ross

npa shows holes in fast particle distribution and discrepancies with transp
NPA shows holes in Fast Particle Distribution, and discrepancies with TRANSP

Investigation of Ion Transport with Beam Modulation P.Ross

ion temperature anomalously high
Ion Temperature Anomalously High

The ion temperature remains anomalously high, even during periods free from low frequency MHD activity. This high electron temperature can persist for much of the shot, as in the case of shot 120001, when Ti>Te for more than 400 ms. This XP will try to correlate Ti with high frequency MHD and the fast ion distribution.

Investigation of Ion Transport with Beam Modulation P.Ross

proposed shots 27 29
Proposed Shots: 27-29

NPA setup, Modulation times (ms):

Investigation of Ion Transport with Beam Modulation P.Ross