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At ASIPP 2014/10/20

At ASIPP 2014/10/20. Effect of Energetic-Ion/Bulk-Plasma-driven MHD Instabilities on Energetic Ion Loss in the Large Helical Device.

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At ASIPP 2014/10/20

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  1. At ASIPP 2014/10/20 Effect of Energetic-Ion/Bulk-Plasma-driven MHD Instabilities on Energetic Ion Loss in the Large Helical Device Kunihiro OGAWA, Mitsutaka ISOBE, Kazuo TOI, Masaki OSAKABE,Fumitake WATANABE, Akihiro SHIMIZU, DonaldA. Spong3, Douglass S Darrow4, Satoshi OHDACHI, Satoru SAKAKIBARA, LHD Group. National Institute for Fusion Science, Nagoya Univ.1, Kyoto Univ.2, ORNL3, PPPL4

  2. Contents of my presentation • Background and purpose • The meaning of study • Experimental setups • scintillator-based lost ion probe • Experimental result • Increase of lost ion flux due to TAE • Calculation setups • DELTA5D code (guiding-centre orbit code) • The result of calculation • Compare with experimental result • Summary

  3. GAE induced loss in TFTR [1] m/n=2/1 NTM induced loss in AUG [2] Fast Ion Loss NTM mode Background • Anomalous loss of fast ion in fusion device • It might cause localized damage of first wall • Understanding of loss process of fast ion is needed • Alfvén eigenmode (AE)-induced loss is observed on many tokamaks • Low frequency MHD modes such as NTM also cause fast-ion losses • Contribution from the 3D plasma is needed to confirm the theory [2] M. Garíca-Muñoz et.al, NF (2007) [1] D.DARROW et al., NF (1997)

  4. Experimental setups

  5. The structure of Helical system Flux surface of EAST Profile of safety factor Flux surface of LHD • plasma shape and magnetic field • Tokamak : poloidal cross sections at any toroidal angle are the same • Magnetic surface is created w/ plasma current. • Helical : poloidal cross section have certain cycle • Magnetic surface exist w/o plasma current. • Safety factor • Increase toward the outside (normally, q = ~1 to ~3) • decrease toward the outside (normally, q = ~3 to ~ 0.6)

  6. Scintillator-Based Lost-Fast Ion Probe (SLIP) • Double aperturestructure allows fast ions having certain velocities to enter • Scintillation points has information of velocity and pitch angle (c) of fast ions • This SLIP has two sets of double apertures :“Bi-directional lost-fast ion probe” • It can be applicable to both cases of CW or CCW direction of Bt • Observation of co-going lost fast ions at relatively low field (Bt < 0.75 T)

  7. Experimental Result

  8. TAE discharge • TAE (m~1/n=1) • f = 40 ~ 80 kHz (TAE1, TAE2) (Amplitude: TAE1 <<TAE2) • RIC (dominant: m/n = 1/1) • Dominant: f = 2 kHz • Excited by bulk plasma <bbulk> ~ 1.5 %<bfast> ~ 1.0 % TAE: toroidal Alfvén eigenmodeRIC: resistive interchange mode

  9. Energy and pitch angle of lost ion due to TAE Image of scintillator plate Time trace of TAE2, RIC and GSLIP(#90091) Mirnov Mirnov SLIP SLIP SLIP • Three domains are observed. (D1 ~ D3) • D1: E~130 keV, χ=35º D2: E~100 keV, χ=40º D3: E~150 keV,χ=55º • D1: mainly RIC loss, D2: mainly TAE loss, D3: mainly collisional loss • Increase of loss flux coming D2 region due to TAE2 are observed

  10. Initial Study on the Effect of TAE on Energetic Particle Confinement

  11. The method to simulate the energetic ion confinement flow of the calculation • VMEC • Reconstruction of equilibrium • HFREYA • birth profile of energetic ion • DELTA5D (guiding centre) • Orbit of energetic ion in plasma region • The model of fluctuation • Follow the orbit to the LCFS • Scattering/collision by bulk plasma is concerned • Lorentz orbit • Orbit of energetic ion outside of the plasma with vacuum field. • follw the orbit to SLIP from LCFS • E = 0 is assumed Beam f of TAE α: f(place, amplitude) Lost Ion

  12. Condition of the Calculation Profiles of Te, ne, Alfvén spectra Eigenfunction of TAE2 • Te and ne are measured with Thomson scattering • Ti = Te, ni = ne is assumed in the calculation • Model of TAE : magnetic fluctuation having m/n=1+2/1 TAE2 structure

  13. Effect of TAE model fluctuation on energetic ion orbit Orbit of energetic ion in presence of TAE model fluctuation. w/o TAE w/ TAE w/ TAE • Normalized amplitude of fluctuation is b/b0 =0, 4.5x10-4, 1.0x10-3 • Energetic ion • E ~ 180 keV, χ~ 15º • Topology of passing orbit drift toward outside is as same as the drift of banana orbit

  14. Effect of TAE model fluctuation on energetic ion loss Effect of TAE on lost ion flux • We follow the energetic ion orbit within 1 ms • TAE exist but profile of energetic ion seems not to be changed. • Energetic ion :E=160 ~ 200 keV • b/b0=1.0x10-3 assumed • Increase of loss in χ~25º , 40º ,50 region is gotten from the calc.. • Three loss region correspond to the D1 ~ D3 region? although there are some degrees difference. • However, only D2 flux increases in the experiment. • Effect of RIC or interaction of TAE and ion should be included? • Amplitude of TAE2 should be measured? #90091 t = 2.82 s Exp. Res. RIC loss TAE loss Collisional loss

  15. Summary • Lost energetic ion due to energetic particle/bulk plasma pressure excite MHD is observed • TAE cause energetic ion loss comes to D2 region. • Calculation of orbit in presence of TAE model fluctuation using DELTA5D was held • three domains of loss are identified though they have some degrees difference. • Loss coming to D1 ~ D3 regions increase due to TAE model fluctuation in calculation • Interaction between TAE and energetic particle and effect of RIC should be included in future calculation.

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