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Effect of Energetic-Ion/Bulk-Plasma- driven MHD Instabilities on Energetic Ion Loss in the Large...
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Transcript of Effect of Energetic-Ion/Bulk-Plasma- driven MHD Instabilities on Energetic Ion Loss in the Large...
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 ASIPP05/14/23
Page 2
Contents of my presentationBackground and purpose
– The meaning of studyExperimental setups
– scintillator-based lost ion probeExperimental result
– Increase of lost ion flux due to TAECalculation setups
– DELTA5D code (guiding-centre orbit code)The result of calculation
– Compare with experimental resultSummary
Page 3
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
[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 LHDProfile 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 dischargeTAE (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 spectra Eigenfunction 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 wit
hin 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 differen
ce. However, only D2 flux increases in t
he experiment.– Effect of RIC or interaction of TAE an
d ion should be included?– Amplitude of TAE2 should be measur
ed?
#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.