Present Status of TPE-RX Experiment

Transcription

1 Present Status of TPE-RX Experiment IEA RFP Workshop at Madison 28 Feb. - 1 Mar. 2 Y.Hirano, Y. Yagi, T.Shimada, S. Sekine, H.Sakakita, H.Koguchi, Y.Maejima, S.Kiyama, Y.Sato, K.Hayase

2 Reversed Field Pinch Machine, TPE-RX R / a = m /.45m, Vol. = 7 m 3 Designed Max. Ip = 1MA, t dis = <1 ms Aims of TPE-RX To find a way to improve RFP confinement. Vloop <1V & bp >.1 in the same time => t E = 5-1 ms

3 Recent Activities of TPE-RX Almost two years since experiment start (March 1998). 1. Operation range, Ip <~5kA, duration up to 1ms with ~22kA 2. Temperature Measurement and Estimation of bp, tau-e, etc. High Te ~ 64 ev, medium Ti ~ 32eV with low ne ~ 5E18/m3 bp ~ 6-1%, tau-e ~.5-1ms (will be presented by Dr. Yagi) 3. Analysis of locked mode (will be presented by Dr. Yagi) Magnetic, Spectroscopy, Halo current measurement Comparison of discharges with and without locked mode. 4. Spectroscopy Plasma rotation, Toroidal & poloidal radiation profile. 5. Density Control by Gas Puff 6. Trial of PPCD

4 Typical RFP Plasma in TPE-RX Ip = 26kA, Rp*Ip ~ 15V, duration 9ms Without locking mode, Rp (micro ohm) F, Theta Shot Voh=5/1.4kV, Vtf=4.8//.25kV, p=.4mtorr <Bt> 1 <Ip> <Vloop> 5 Rp (micro ohm) 25 <Rp*Ip> Btwi Btwo t (ms) Theta F 2 4 t (ms) Btwo, Btwi, <Bt> (mt) Vloop, Rp*Ip (volt)

5 The longest discharge Ip-peak ~ 2kA & 1ms duration ka VL RpIp rxiv1346.dat Bt_ave Btw 2 4 t (ms) Ip Theta F t (ms) V, mt

6 Variation of Non-inductive Part of Variation of Vloop with shot mber and Ip RpIp now stays almost constant level, (~1-2V at Ip~25kA) Situation that Vloop increases with Ip does not change. Further wall conditioning (Ti gettering and/or Boronization)?? Rp*Ip (V) 5V Decay phase With DC Ver. 2V 15V 15V 5V 4 shot No. V 12 2kA All shots except Ip<1kA, t=32.5ms 4kA

7 Reduction of RpIp by DC Bv From 17-18V to 13-15V at Ip27kA Ip(kA) RpIp(V) I-DCV Scan. Voh=5/1.4, Vtf=5// V at 9G ms ms Ip (A) Ip (25A) ( G) Ip (3A) ( 11G) Ip (35A) ( 13G) Ip (5A) ( 18G) BDCV 36G/kA

8 Reduction of RpIp in Ip decay phase From 17-18V to 1V at Ip24kA IpRp (V) t (ms) dip/dt Scan. t = 4ms -1 Ip*Rp (volt) 2 1 Idcv= RpIp = 1V Idcv = 25A dip/dt (ka/ms)

9 Discharges without locked mode and with locked mode Marginal conditions at Ip ~ 25kA Duration is longer and SBD is larger without LM. 4 Ip 3 SBD rxiv14695.dat 4 SX 3 4 Ip 3 rxiv14676.dat 4 SX Vloop (V) SBD Vloop (V) t (ms) t (ms)

10 Shortening of discharge duration by the Locked Mode But it shows little effect on RpIp at the time of locking locking in the midle No locking of discharge 1 early locking IV_1213_9_LM 8 Ip RpIp t (ms) IpRp (V) no locking rxiv Theta 2 SBD F Locking from t<~2ms No clear difference before locking Clear difference in SBD but little difference in Ip, RpIp, F after locking except before termination. Theta with locking < that w/o locking

11 Plasma Rotation in TPE-RX Toroidal velocity [km/s] Plasma current [ka] Plasma current direction Net toroidal plasma rotation velocities of C 4+ ions around r/a~.9 as a function of the plasma current. Solid symbols show the locked mode cases. Cross symbol shows an unlocked case. Radial electric field (E r ) [kv/m] ρ L / L H. Sakakita, Y. Yagi et al.; J. Phys. Soc. Jpn. Vol. 69, No. 3 (2).

12 Radial profile of CV (227.1nm) line radiation Fitting function ; y = exp[c2{(r/a) - C1}] - exp[c4{(r/a) - C3] + C5 Intensity(Arb.U.)Intensity(Arb.U.) r (m) Raw data (chord integration) After inversion S.Sekine, T. Osakabe. et.al., Journal of Plasma Fusion Research, Vol.2(1999)192

13 Density Control by the Gas Puff, No fatal effect on discharge Increase of <ne>.4e19 =>.7E19 => 1.5E19 /m 3 at Ip ~ 27kA <ne> E2/m No Gas Puffing nli ~.4 E19/m t (ms).3.25 nli With one medium GAS Puffing.1 ~.7 E19/m <ne> E2/m nli With two strong GAS Puffings.15.1 ~ 1.5 E19/m <Bt> 3 75 Ip 2 Vloop 5 RpIp 1 25 Btw-out Btw-in t (ms) 4 <Bt> Vloop Ip 5 1 RpIp 25 Btw-out Btw-in <Bt> 75 2 Ip 5 Vloop 1 RpIp 25 Btw-out Btw-in Bt (mt), RpIp (V), Vloop (V) Bt (mt), RpIp (V), Vloop (V) Bt (mt), RpIp (V), Vloop (V)

14 Density control with Gas Puff in TPE-RX Gas Puff nls14143, Gas Puff at t=25ms (two puffs) <ne> (E2/m3) time (ms) 2 1 Vloop SX (A.U.) rxiv14143.dat 1 SX.5 Btw (mt) time (ms)

15 DMR (Deep Magnetic field Reversal) Exp. in TPE-RX (Initial PPCD Exp.) Plasma current [ka] PPCD Increase of SX SBD Btw_out time [ms] I P F-Theta curve becomes close to relaxed state in Fast Btw reversal. Both radial magnetic fluctuations and D a intensity at r/a~.9 are suppressed. Toroidal plasma rotation velocity (C 4+ ions) shows no extinct behavior in the present conditions SBD [a. u.] F rxiv1558_96_99_abr1.dat Fast Bt Rev. PPCD t=15-25ms Slow Bt Rev. Medium Bt Rev Theta

16 Summary Almost two years since experiment start 1. Max. Ip ~5kA. Max t-dis ~1ms for Ip ~ 22kA. 2. High Te (<~1eV) is realized with low density (~5E18/m 3 ) Similar to TPE-1RM2 & 1RM15. High I/N ~1-13 A/m 3. RpIp has not been reduced to < 1V, remains at high value ~15V Vloop anomaly is ~ 5% of RpIp (H~1 & Zeff~5 are assumed) 4. Comparison of discharges with and w/o locked mode. LM causes strong PWI; reducing t-dis & limiting high Ip Op. 5. Plasma rotation depends on Ip (5km/s at Ip~2kA, at 37kA) 6. Density control is successfully done. ne can go up to 3E19/m 3 7. PPCD seems to be promising, sharp increase of SX(Te & ne) Further investigation is planned.