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Beam Modulation Effects on Ion Power Balance XP 737

P.W.Ross. Beam Modulation Effects on Ion Power Balance XP 737. Basics of XP 737. The goal of XP 737 is to study the ion power balance and the coupling between the injected beam and the thermal ions

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Beam Modulation Effects on Ion Power Balance XP 737

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  1. P.W.Ross Beam Modulation Effects on Ion Power BalanceXP 737 2007 NSTX Results Review

  2. 2007 NSTX Results Review Basics of XP 737 • The goal of XP 737 is to study the ion power balance and the coupling between the injected beam and the thermal ions • Also goal is to minimize known uncertainties in power balance such as edge charge exchange losses (need edge neutral measurements Experimental technique for fast ion response • Modulate Beam power, modulate 3->2 beams • Evaluate the fast ion response using the NPA, SSNPA, FIDA, and SFLIP diagnostics • Compare diagnostics to TRANSP predictions • Understand any differences

  3. 2007 NSTX Results Review ENDD Profile and image

  4. 2007 NSTX Results Review ENDD shows densities from 1e12-1e14 Preliminary Seperatrix The Edge Neutral Density Diagnostic measures the neutral density in the edge of the plasma. Typical densities range from 1e12 to about 5e13.

  5. 2007 NSTX Results Review Problems with the ENDD Diagnostic • ENDD is heavily dependent on Thomson Scattering. • This is in the region of low temperature (a few eV). Slight variations in the temperature causes significant changes in the calculated Neutral Density • ENDD profiles behave erratically with edge TS (large error bars in the edge). • Possibility of lithium coating. • X-rays can cause spikes in the image which need to be ignored.

  6. NPA signal shows lack at certain pitch angles Rtan=50cm Rtan=80cm Rtan=120cm 2007 NSTX Results Review

  7. 2007 NSTX Results Review Shot 125332 NPA signal dependent on Beam Timing • Shot 125331 These shots were very similar. The beam timing on shot 331 was a mistake, but it showed how the beam timing affects the NPA signal.

  8. 2007 NSTX Results Review TRANSP shows NPA modulations at all pitch angles Rtan 125 TRANSP shows modulations at all tangency radii that match the beam modulations. This is not seen in the measured NPA signal, particularly for Rtan 80, near the magnetic axis. (The measured NPA signal is not shown) Rtan 80 Rtan 50

  9. 2007 NSTX Results Review FIDA shows similar behavior to NPA This is the overlay of 5 shots with identical beam timing and plasma parameters. Individual shots were too noisy to detect a correlation. When several signals are overlaid from repeated shots, a small modulation is seen. A similar effect may be possible with the NPA and other diagnostics Shot 125332 showed no distinct signal on the NPA and shows a similar lack of signal on the FIDA diagnostic with the beam modulation (Neutron signal in red, FIDA in black)

  10. 2007 NSTX Results Review SSNPA and SFLIP Add to the Confusion SFLIP probe shows loss associated with MHD activity, but does not show any activity associated with the beam modulation SSNPA signal at various energies. No obvious signal matches beam modulation

  11. 2007 NSTX Results Review Conclusions and Further Analysis • The ENDD diagnostic has taken data and initial analysis has been performed • Firm estimates will be available about the effect of lithium on the edge neutral density • XP 737 highlighted the lack of understanding of the presence or absence of a strong NPA signal, particularly as related to beam modulations • Shots with 3 beams early have a significantly higher absolute NPA signal, but lack the large modulations that are apparent in shots without 3 beams early • SSNPA, FIDA and SFLIP confirm lack of large modulations in fast ion population, although overlaying several shots/performing a Fourier transform may show low amplitude signals • We would like to have TRANSP simulate other diagnostics, such as the FIDA and SSNPA, which would assist in understanding their signals.

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