K.. Toi

M. "Osakabe

O." Kanako

S. Yamamoto

Y. Takeiri

National Institute for Fusion Science (NIFS-Repository)

§ 21. Interaction of Toroidicity InducedAlfven Eigenmodes on EnergeticParticles on LH 0Osakabe, M., Yamamoto, S.l, Takeiri, Y., Toi, K.,Kanako, O.locating at the gap for the TAE of n=2 and m=3. Thisshows that the energetic particles are influenced by TAEand those particle would change its orbit to a orbit whichhas the maximum particle presence probability aroundthe TAE-gap location.1Kyoto UniversityDuring the high-beta experiments with the magneticfiled of 75 [T], the fast change of energeticneutral particles being associated with MHD burst signalswere observed on the tangential Neutral Particle Analyzer(NPA). The signals of fast neutral particles of around130-keY were increased when the MHD-bursts wereparticles occurred after the increase of the fast particles.This time delay was coming from the slowing-down timeof the circulating particle whose orbit was changed withthe interaction of MHD-bursts .Figure lea) shows a typical waveform ofMIRNOY-coil signal. The toroidal mode number of thisburst is identified to be n=l or 2. In Fig.l(b), the peakposition of the increased neutral flux are plotted withopen-circles at each energy channel of the NPA. Linesin the figure show the exponential fitted curve of the peakposition, which has a lie-time of about 4.3[ms].Comparing this decay time to the slowing-down time ofparticles whose orbits are tangent to the NPA line of sight,the increased particles are considered to be circulating onthe orbit around p=O.55. For this orbit, the particlepresence probability, which is evaluated fromorbit-following calcuation, is shown in Fig.2(a), where"the particle presence probability" is defined by the ratioof "the time for a particle staying in a particular region ofa plasma" to "the total amount of time being followed" inthe orbit calculation. The shear Alfven-spectra are alsoshown in Fig.2(b). In these figures, it is sohwn that thepeak of the particle presence probability distribution is0.80.6p0.40.2o..... 1 LHD#31221::i a!! 0.5> 00I:"- -0.5:E-1..... 150 b)0..>1/eTime_.....100 =-4.3ms0-C)I:50,,-I:Q)«SI:.cWO00.93 0.935 0.94 0.945 0.95 0.955lime [5]Fig.1 (a) A typical wave form of a MIRNOV burst signalbeing associated with NPA flux increase. (b) the peakposition of increased neutral flux at each energy channel of atangential NPA(open circles). Error-bars indicate thesampling duration time of the measurement. The solid lineshows the exponential fitted curve of the peak positions.Fig.2 (a) Radial Distribution of Particle Presence Probability of theorbit which is circulating around p=O.55. (b) Shear-Alfven Spectrafor n=2 at t=O.94.The signal increase of slower neutralobserved.25

Interaction of Toroidicity Induced Alfve?n Eigenmodes on Energetic Particles on LHD

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