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At ASIPP 2014/10/20. Effect of Energetic-Ion/Bulk-Plasma-driven MHD Instabilities on Energetic Ion Loss in the Large Helical Device. - PowerPoint PPT Presentation
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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,Kunihiro OGAWA, Mitsutaka ISOBE, Kazuo TOI, Masaki OSAKABE,Fumitake WATANABE, Akihiro SHIMIZU, Fumitake WATANABE, Akihiro SHIMIZU, DD onaldonald A. SpongA. Spong33, , Douglass S DarrowDouglass S Darrow44
, Satoshi OHDACHI, Satoru SAKAKIBARA, LHD Group. , Satoshi OHDACHI, Satoru SAKAKIBARA, LHD Group.
National Institute for Fusion Science, Nagoya Univ.National Institute for Fusion Science, Nagoya Univ.11, Kyoto Univ., Kyoto Univ.22, ORNL, ORNL33, PPPL, PPPL44
At ASIPP04/20/23
Page 2
Contents of my presentationBackground 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
Page 3
BackgroundAnomalous 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
[1] D.DARROW et al., NF (1997)
GAE induced loss in TFTR [1]
m/n=2/1 NTM induced loss in AUG [2]
Fast Ion Loss NTM mode
[2] M. Garíca-Muñoz et.al, NF (2007)
Experimental setups
Page 5
The structure of Helical system
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)
Flux surface of EAST
Flux surface of LHD
Profile of safety factor
Page 6
Scintillator-Based Lost-Fast Ion Probe (SLIP)
Double aperture structure allows fast ions having certain velocities to enter
Scintillation points has information of velocity and pitch angle () 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)
Experimental Result
Page 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
TAE: toroidal Alfvén eigenmode RIC: resistive interchange mode
<bulk> ~ 1.5 % <fast> ~ 1.0 %
Page 9
Energy and pitch angle of lost ion due to TAE
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
Image of scintillator plate Time trace of TAE2, RIC and SLIP(#90091)
Mirnov
Mirnov
SLIP
SLIP
SLIP
Initial Study on the Effect of TAE on Energetic Particle Confinement
Page 11
The method to simulate the energetic ion confinement 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
b B α: f(place, amplitude)
flow of the calculation
Beam of TAE
Lost Ion
Page 12
Condition of the Calculation
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
Profiles of Te, ne, Alfvén spectraEigenfunction of TAE2
Page 13
Effect of TAE model fluctuation on energetic ion orbit
– 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
Orbit of energetic ion in presence of TAE model fluctuation.
w/o TAE w/ TAE w/ TAE
Page 14
Effect of TAE model fluctuation on energetic ion loss
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 re
gion 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 an
d ion should be included?
– Amplitude of TAE2 should be measured?
#90091 t = 2.82 s
Exp. Res.
RIC loss
TAE loss
Collisional loss
Effect of TAE on lost ion flux
Page 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.