Study on Fluctuations durin the RF Current Rampup Phase in 射频电流斜坡阶段期间波动研究

1、study on fluctuations during the rf current ramp-up phase in the cpd spherical tokamak h. zushi1), t. ryoukai2), k. kikukawa2), t. morisaki3), r. bhattacharyay2), t. yoshinaga1,3), k. hanada1), t.sakimura2), h. idei1), k. dono 2), n. nishino4), h. honma2), s. tashima2), t. mutoh3), s. kubo3), k. nag

2、asaki5), m. sakamoto1), y. nakashima6), y. higashizono1), k. n. sato1), k. nakamura1), m. hasegawa1), s. kawasaki1) h. nakashima1), a. higashijima1)1)riam, kyushu university, kasuga, fukuoka, japan, 816-8580, 2) igses, kyushu university, kasuga, fukuoka, japan, 816-8580, 3) national institute for fu

3、sion science, 4) hiroshima university, 5) kyoto university, 6) university of tsukuba,zushitriam.kyushu-u.ac.jp4th iaea tcm on spherical tori and 14th international workshop on spherical torusenea frascati, october 7-10, 2008 1motivationwhy steady bz is required forthe initial condition ?forrest prl

4、19921. confine the trapped electrons = toroidal precession current2. pressure driven/ uni-directional ps current = seed toroidal currentmotivation (role of bz)slab-annulus plasma is unstable because of bad curvaturequestcpdfast camera image shows vertically moving modesslab plasma in simple torusflu

5、ctuations & conversion efficiency1.00.80.60.40.20.0transimission0.200.150.100.050.00ln(m) pol=2cm 40% 20% 10% 1% f=8.2ghz, fce=4.92ghztox v.s. ln at f=8.2 ghz. fluctuation level= 1% (solid-circle), 10% (dot-dashed), and 20% (dotted), and 40 % (solid-square). lpol =20 mm, and parallel refractive

6、index n|=0.7.according to laqua prl 1997open to closed flux surfaces during the current ramp#507034external bv fieldclosed flux surfaceon the flattopip increases slowly with the slow increase of pinj (60kw for ip 1.7ka).less effective than current jump(pinj 30kw for ip 2ka).center postvertical shift

7、 is suppressedunder bv field with higherdecay index.t = 0.146 syoshinaga icpp2008outline1. diagnostics of fluctuations2. results during the current ramp-up 2-1) fluctuations in slab-annulus plasma role of bz 2-2) fluctuations during the current jump3. summary7mm14mm13赤道面配置(mh381(mm12)(m

8、h2)346.40(mm15)(mm16)(mh4)402.86(mm11)306.41(mm17)(mm18)(mh1)590.00525.00590.00525.00rf antennahx(cdte-pha)vuv spectrometersx arrayvisible monitorli-ccdfast camera(10ms)rotatingpumplimiterpump(tmp,cryo)probe ha filterli-bes(50 pmts)rogowskii coilmedium speed camera(1ms)am-reflectometerstray rf power

9、stray rf powerir-tv camera ir spectroscopyvisible spectroscopy (hyougo univ)ct injector(nifs)(nifs)(nifs)(nifs)(hirosima univ.)(tsukuba univ.)csi. 45 flux loop coils8ex. ex. 2fcefcefceopenclosed+openbt=0.29t, bv=40g, ip3karf 8.2ghz, 60kwi. cpd li-imaging (ccd & lbfs)4 tfcoilscstfccdrz10 x10 fibe

10、r+50pmts50 x50mmli injector-600mmtypical discharge0.220.200.180.160.14rres(m)(a)50403020100bz(g)r=0.25 m(b)2.01.51.00.50.0ip (ka)(c)6040200prf (kw)0.400.300.20(d)-0.2-0.10.00.1vloop (v)r=0.106z=0.325(e)500040003000200010000pstray(a.u.)z=0.225(f)43210lii(a.u.)r=0.182z=0.04(g)0.60.40.20.0h (a.u.)0.400

11、.300.20(h)fluctuations in annulus plasma w/o bz3.0 x10172.01.00.0ne(m-3)240220200180r (mm)507795 z=-80mm0.12412410 xx (a.u.) 610324 61042f (hz)507795 t=0.18-0.2sr=0.2m,z=-0.08m1.00.80.60.40.20.0 2610324 61042f(hz) 2r(z=-0.08m) 2z(r=0.2m) 0.250.200.150.100.050.000.220.200.180.165077951 kwrres=164 mml

12、f mode with long correlation length 1.00.80.60.40.20.0 20.240.220.200.180.16r(m) f=1.1khz(a)1.00.80.60.40.20.0 2-0.10-0.06z(m) 507795_1_1.1khz_175_200ms-0.100-0.090-0.080-0.070z(m)0.220.200.18r (m) f=1.1khz (507795_1_175_25_1.1_cs)1.00.80.60.40.20.0(a) r 5 cm z 2.5 cmbz suppresses density fluctuatio

13、ns600400200lii(a.u.)300250200150r(mm) 1fr_bz=50g 2fr_bz=40g 3fr_bz=32g 4fr_bz=24g 5fr_bz=15g507918z=-50mm0.400.350.300.250.20 ili/-50-40-30-20-100bz(g)bz=0g 507803(11/14)others 507918(11/14)density profile is not significantly affected by bz ( 50g)however, the fluctuation level is much reduced.bt=0.

14、29tbz toroidal precession current2. pressure driven/ uni-directional ps current = seed toroidal currentryoukai, icpp 20083. reduced fluctuations = more efficient conversion1.00.80.60.40.20.0transimission0.200.150.100.050.00ln(m) pol=2cm 40% 20% 10% 1% f=8.2ghz, fce=4.92ghz 2 fluctuations during curr

15、ent jump0.220.200.180.160.14rres(m)(a)50403020100bz(g)r=0.25 m(b)2.01.51.00.50.0ip (ka)(c)6040200prf (kw)0.400.300.20(d)-0.2-0.10.00.1vloop (v)r=0.106z=0.325(e)500040003000200010000pstray(a.u.)z=0.225(f)43210lii(a.u.)r=0.182z=0.04(g)0.60.40.20.0h (a.u.)0.400.300.20(h)burst in lii and f f during ip j

16、ump2.01.51.00.50.0ip (ka)(a)43210lii(a.u.)r=0.182z=0.04(b)-0.15-0.10-0.050.000.05vloop (v)r=0.106z=0.325(c)4 msblue: t=218msgreen:t=220 msred: t=221ms43210lii(a.u.)0.2230.2220.2210.2200.2190.218r=0.182z=0.04contour of lii(r,z) during jumpli_508279_0.218_0.2181_cs(a)li_508279_0.219_0.2191_cs0.50.40.3

17、0.20.1(b)li_508279_0.2195_0.2196_cs(c)li_508279_0.221_0.2211_cs(e)li_508279_0.2215_0.2216_cs(g)li_508279_0.2218_0.2219_cs(h)li_508279_0.222_0.2221_cs(i)li_508279_0.2209_0.221_cs(d)li_508279_0.2212_0.2213_cs(f)vertically aligned contour = horizontally aligned contouropen field = closed field lines 15

18、9 r215 mm 27z 52 mmrres=194mm43210lii(a.u.)0.2230.2220.2210.2200.2190.218r=0.182z=0.040.60.50.40.30.2li (r)0.210.200.190.180.170.16r (m) 0.2206_0.2207 0.2210_0.2211 0.2212_0.2213 0.2215_0.2216 t=0.1msprofile flattening occurs 1ms before the burst coherency of 1khz during jumpcohrz_508279_1_211_2_1.1

19、7_cs (a)cohrz_508279_1_213_2_1.17_cs1.00.80.60.40.20.0 (b)cohrz_508279_1_217_2_1.17_cs (c)cohrz_508279_1_219_2_1.17_cs (d)cohrz_508279_1_221_2_1.17_cs (e)cohrz_508279_1_223_2_1.17_cs (f)43210lii(a.u.)0.2240.2200.2160.212r=0.182z=0.04highly coherent mode at f1 khz dominates the viewing areasummary1.

20、initial bz suppresses the density fluctuations, suggesting that the injected ecw can be converted efficiently to ebw 2. 2d structure of the density fluctuations shows that highly coherent mode at low freq. with very long correlation length grows just before the burst of lii only during the current j

21、ump.2 current jump in cpdnormal x-mode injectionco-directional o-mode injectionthresholdp 20 kwthresholdp 25 kwco-directional o-mode injection seems more efficient for achieving current jump than normal x-mode.the critical parameter for current jump phenomenon should be the value of ip, since ip jus

22、t before and just after current jump are almost identical.the difference of the threshold power on the incident mode may be due to the heating efficiency in each mode. ip itself may be determined from some equilibrium conditions.yoshinaga iaea (2008)for x-mode injection (x-b scenario) (normal to b-f

23、ield) for o-mode injection (o-x-b scenario) (injection angle is adjustable) midplane reflector shaft reflecting mirror microwave (8.2ghz) launching system in cpdlincident wave must be converted into electron bernstein wave (ebw) mode to heat the core plasma region in overdense plasmas.lmicrowave lau

24、nchers from 8 klystrons are separated into normal x-mode injectors and co-directional o-mode injectors to study injection mode dependencies.current jump discharge in cpdcurrent jump3msecr2nd ecrecr2nd ecrexternal bv fieldclosed flux configurationafter current jumpcenter postcenter postt = 0.153 st = 0.157 s#506967vertical shift is observed both in magnetic flux and h image.non-inductive current generation by ech via current jumpcurrent jump occurs under relatively high bv ( 30 g).in this range of bv, ip saturates at 1.8 ka without current jump.this