Dynamic Resnant Errr Field Crrectin with C-COIL and I-COIL in the DIIID device M. Okabayashi, M.S. Chance, R, Hatcher, J. Manickam P P P L, J. Bialek, A.M. Garfal, G.A. Navratil, H. Reimerdes, C lumbia U., M.S. Chu, G.L. Jacksn, T.H. Jensen, R.J. La Haye, J.T. Scville, E.J. Strait, G A, R.J. Jayakumar, LLNL, D.H. Edgell, FAR -T E C H, Inc "Active C ntrl f MHD S tability: E xtensin t the B urning P lasma R egime " University f Texas-Austin Nvember 3-5,2003
RWM Feedback System Has Been Imprved with New Hardware: :Newly-installed I-cils, New ff midplane Sensrs, SPA upgrade and PCS upgrade Cils being installed in DIII D New I-cil x New Sensrs Existing C-cil
Dynamic Errr Crrectin Prcess Maintains Identical Plasma Rtatin by use f Either C-Cil r I-Cil Ip betan/(2.4li) C-cil cur. (ka) I-cil cur (ka) Plasma Rtatin km/s) Full C-cil crrectin Full I-cil Crrectin
I-cil at Dynamic Resnant Errr field Crrectin is as Effective as C-Cils Maintaining High Plasma Rtatin
Dynamic Errr Field Crrectin with I-Cil Maintains Plasma Rtatin by Requesting Different Level f Current fr Different Cil Cnnectin I-cil current needed fr resnant errr field cmpensatin (amplitude: ka) 5.0 180 cil current limit 240 300 360 420 Disrupted with RWM time cnstant 0.0 Rtatin (km/s) 200 100 DIII D N ATION AL FU S ION FAC ILITY 0.0 100 200 300 400 Upper/Lwer I-cil cnnectin angle
I-cil Feedback Has Opened Higher bn Access Even If the Rtatin is Reduced during Discharge Imprved Time Respnse bserved in the Cntrl n ELM Induced RWM b / n.wall n b n sensr (G) db(g) 1.7 1.0 0.0-20 20 0. ideal wall limit C b 1.0 Gp/Gd=40/20 q=2 MARS predictin Gp/Gd=40/80 Gp/Gd=40/0 Gp/Gd=40/40 I-cil Gp/Gd 114819 40/20 114820 40/40 114821 40/0 114822 40/80 114817 N FB D-alpha ªzer rtatin C-COIL: Gp/Gd=57/0 time rt (km/s) 100 0. n wall limit 0.0 n feedback 0.0 50 Rtatin (km/s) 100 150 data with strng Ip ramp lw-q (q95ª3.0) 2.4li plasma DIII D N ATION AL FU S ION FAC ILITY C b = n.wall (b n - b ) n ( b ideal.wall n.wall - b ) n n
Dynamic Resnant Errr Field Crrectin Prcesss with Feedback High gain limit (K -> ) RESONANT AMPLIFICATION FACTOR <pl Apl K FEEDBACK GAIN Berrr> I_errr Bprepr> I_prepr } -initial guessing - Bfb> I_fb? Estimated Ttal Current fr Errr Cmpensatin = I_fb + I_prepr = -<pl Berrr> <pl Bfb> I_errr + I_prepr * e + 1/(K*Apl) [...] Better cupling between the feedback and plasma -> lwer crrectin current What is pssible cupling mechanism?
Pssible frmulatin fr cuplings : Trque in the tridal directin: Frce in tridal directin F = ( f d j pl x B ext ) f dj pl,n = s db pl. f.- (1/R) f db pl. q dj pl,q = f db pl.n.- (1/R) n db pl. f = - f [ db pl. q B ext.q + db pl. n. B ext.n ] Assumptin: - db pl. f. ª 0: Lcal Trque Integrated ver the surface: Ú F f R ds Vlume integrated trque Phase shift : negative feedback autmatically minimizes the shift
m=2 x r m=1 f m=3 m=5 m=4
dbn n : q= 2-, 2+,3, 4, 5
Mde Structure
Bn Field Pattern n q =3 Surface C-cil -180 0.0-180 plidal directin I-cil Plasma mde 0.0 tridal directin (degrees) 360 * 0 degrees in the uter mid-plane
Lcal Trque Pattern n Surface: C-cil ( t= 2500 ms) I-cil (2600 ms) q=2 + 0. - plidaldirectin q=3 tridal directin tridal directin
Nrmal and plidal field by C-cil Nrmal Field Plidal field C-cil Plasma B*B
Nrmal and plidal field by I-cil(240deg) Nrmal Field Plidal field I-cil Plasma B*B
Trque arund q=3 Surface by I-cil with Actual I-cil Current at t=2600ms Matches with Trque with C-cil by Actual cil current at 2500ms C-cil q=2(-) I-cil q=4 q=2(+) q=5 Full C-cil crrectin Full I-cil Crrectin q=3 Tridal angle relative t the Mde and applied field q=edge Tridal angle relative t the Mde and applied field
Trque by I-cil Matches with C-cil Trque arund qª 3 Surface Trque with I-cil with C-cil Df phase difference (degrees) 40.0 0.0-40.0 1 2 3 4 5 edge Df : Phase Shift between Trque Estimated with C-cil curent at 2500 ms and I-cil current at 2600 ms and I-cil (degrees)
Dynamic Errr Field Crrectin with I-Cil Maintains Plasma Rtatin by Requesting Different Level f Current fr Different Cil Cnnectin I-cil current needed fr resnant errr field cmpensatin (amplitude: ka) 5.0 180 cil current limit 240 300 360 420 Disrupted with RWM time cnstant 0.0 Rtatin (km/s) 200 100 DIII D N ATION AL FU S ION FAC ILITY 0.0 100 200 300 400 Upper/Lwer I-cil cnnectin angle
Effective Averaged Field with Varius Upper / Lwer I-cil Cnnectin Can Be Estimated Using Surface Averaged Trque db eff 1.0 0.0 q-edge q=5 q=4 q=3 q=2 100 200 300 400 Upper/Lwer I-cil cnnectin (degrees) Ú db ext db ds db = n.pl eff db ds n.pl Ú Current fr dynamic crrectin 1 /db eff
I-cil current needed fr resnant errr field cmpensatin (amplitude: ka) Resnant Errr Field Cmpensatin is Mst Effective when I-cil Field Cuples with RWM Structure at q=4 - I-cil pitch was scanned by varying upper/lwer I-cil cnnectin 5.0 180 cil current limit 240 300 360 420 Disrupted with RWM time cnstant Estimate with the cupling at q=4 0.0 Estimated I-cil cupling t RWM Bn (gauss/ka) 1.0 q-edge q=3 q=4 q=5 0.0 100 q=2 200 300 I-cil cnnectin angle 400 DIII D N ATION AL FU S ION FAC ILITY residual errr assumed at 45 deg.
I-cil Feedback Has Opened Higher bn Access Even If the Rtatin is Reduced during Discharge Imprved Time Respnse bserved in the Cntrl n ELM Induced RWM b / n.wall n b n sensr (G) db(g) 1.7 1.0 0.0-20 20 0. ideal wall limit C b 1.0 Gp/Gd=40/20 q=2 MARS predictin Gp/Gd=40/80 Gp/Gd=40/0 Gp/Gd=40/40 I-cil Gp/Gd 114819 40/20 114820 40/40 114821 40/0 114822 40/80 114817 N FB D-alpha ªzer rtatin C-COIL: Gp/Gd=57/0 time rt (km/s) 100 0. n wall limit 0.0 n feedback 0.0 50 Rtatin (km/s) 100 150 data with strng Ip ramp lw-q (q95ª3.0) 2.4li plasma DIII D N ATION AL FU S ION FAC ILITY C b = n.wall (b n - b ) n ( b ideal.wall n.wall - b ) n n
Direct Feedback is Observable n Feedback Respnse t ELM induced RFA_RWM Fast Respnse Cmpnent Amplitude 114819 Impact n after ELMs Feedback n A sensr signal (MPID067U) D-alpha 1200 time (ms) 1600 DIII D N ATION AL FU S ION FAC ILITY
Fast Respnse Cmpnent Amplitude Befre Feedback Feedback n ELMs A sensr signal (MPID067U) D-alpha 1250 time (ms) 1300 1300 time (ms) 1350
Fast Respnse Cmpnent Amplitude Feedback n Feedback n A sensr signal (MPID067U) D-alpha 1300 time (ms) 1400 1400 time (ms) 1450
Fast Respnse Cmpnent Amplitude Feedback n Feedback n A sensr signal (MPID067U) D-alpha 1450 time (ms) 1500 1500 time (ms) 1550
Feedback with I-cil Imprved the Time Respnse up t wt ª 3 w C-Cil I-Cil N Feedback N Feedback Gp/Gd=57/57 FB n 1250 time(ms) 1350 1250 time(ms) 1350 0.3 N feedback Gp/Gd=40/40 FB n db (G) C-cil I-cil 0.0 0.02 0.1 freq(khz) 1.0 196/195/826/820.ai DIII D N ATION AL FU S ION FAC ILITY
SUMMARY Dynamic Resnant Errr Field Crrectin with C-COIl and I-COIL - Identical Impact n Plasma Rtatin - I-cil Cnnectin Flexibility -> Parametric Dependence Lcal Trque Hypthesis Prvides a Cnsistent Interpretatin I-Cil Imprved Time Respnse, better Cntrl n RFA& RWM
I-Cil feedback Imprved the Respnse arund wt = 1-3 - Stable RWM respnse t ELM induced n=1 perturbatin w H-alpha MPID averaged c-cil I-cil 0.02 1.0 freq((khz) 0.02 1.0 freq((khz) C-cil: Gp/Gd=57/114 106197 I-cil : Gp/Gd=40/80 114822 Next Issue: the cntrl at wt = 5-10 regime with feedback ptimizatin and further hardware imprvement w QQ/197/822/cmp/FFT.ai
Fast Respnse f Feedback is Taking Place with I_cil_FB ª 1 ka ( < 1gauss) 4.0 Gp/Gd= 40/40 40/0 40/20 Feedback Requested Current (ka) 2.0 0.0 Cmmn fr varius gain setting Fast Feedback Fine Tuning by Dynamic Errr Field crrectin Ttal errr field Preprgrammed errr field crrectin phase 114820 40/40 114821 40/0 114822 40/80 114819 40/20 1300 time(ms) 1600 ffset-&angle-subtractin/#2.ai DIII D N ATION AL FU S ION FAC ILITY
Direct Feedback Cmpnent is ª 1kA ( 1 gauss n plasma) 1300-1400 ms 1400-1500 ms 1500-1520 ms 1520-1590 ms 1 ka 2 ka DIII D N ATION AL FU S ION FAC ILITY