9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba1 Electron Internal Transport barriers by LHCD and ECRH in FTU-high density plasmas E. Barbato Associazione EURATOM-ENEA sulla Fusione, CR Frascati (Roma), Italy

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba2 OUTLINE Experimental results –Electron ITB both on steady state during the current rump Transport analysis by ASTRA –Shear dependent BGB model –LHCD physics by FRTC (ray-tracing + Fokker-Planck) coupled to ASTRA

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba3 ITB at high density (n e_LINE ~ m -3 ) Temporal behavior B T =5.TP LH =1.8 MW I P =350KAP EC =0.77MW n eL = m -3 Main heating phase: –0.6 < t < 0.75 sec T e0 = 6 keV Y N increases a factor 3 T i0 =1.3 keV #21636

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba4 ITB during the current ramp up. Temporal behavior B T =5.5T, I p up to 0.50MA n eline up to m -3 P EC =0.3MW in the preheating phase P LH =1.7 MW T e0 up to12 KeV #20859

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba5 ITB are defined following an R/L T criterion. #19739 #20859 s.s. current ramp R/L T ~ 20 >> R/L T ~ 7 of discharges displaying T e - stiffness TeTe TeTe R/L T r(m) r(m)

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba6 TS data and fit #19739#20859

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba7 Transport analysis by ASTRA code. n e, Z eff from exp. Neoclassical electric conductivity Neoclassical model for ions:  i =   NC –  fixed to give experimental Neutron yield Shear dependent BgB model for electrons  e =D B (  B q 2 f(s) +  gB  *) –ITB onset related to an abrupt inhibition of the Bohm transport in the transition region (between the bad confinement (Bohm dominated) region and the good central one) –  B,  gB adjusted to give good Te(r) simulation during the main heating phase –f(s)= s/(1+s 3 )

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba8 LHCD calculations LHCD by FRTC coupled to ASTRA – fast ray-tracing/1D-Fokker-Planck deposition code Link to the experiment: – V LOOP (t) related to total driven current (Z EFF from exp.) – HXR-measurement, related to J LH ( r) Try to reproduce the experimental V LOOP (t) as far as possible

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba9 Transport simulation. Temporal evolution during the main heating phase n e0 up to m -3 V LOOP well reproduced I CD ~ I P = 0.25 MA I OH ~ 0 P LH ~1.6 MW, P EC =0.8MW P RAD =50% P ei ~ MW #21636

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba10 Transport simulation. Ion behavior T i ( r)calculated by fitting the neutron yield. –  i =  (t) x  iNEO  –Best fit by   (t) ~ 1-2 T i0 ~ 1.3keV ~ 0.5 keV ~ 0.95 keV #21636

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba11 Transport Simulation. Shear dependent electron BgB model #21636 Good simulation by  B = 2.8  B  gB =1.3  gB

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba12 Transport Simulation. Shear dependent electron BGB model #21548 Good simulation by  B = 2.4  B and  gB_m1 = 0.67  gB, in the main heating phase (high Te0)   gB_m2 = 1.3  gB in the low heating phase (low Te0)

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba13 Electron diffusivity.  e reduced at the barrier during the main heating Abrupt  e reduction at the barrier, associated to the s~0 region   e ~ m 2 /sec within the barrier Localized barrier ? #19739

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba14 Electron diffusivity. Barrier radius likely linked to the weak shear region Wide barrier radius  ITB ~ 0.5 a related to broad LH deposition profile in low-q / high density plasmas #19739 B=5T I p =0.4MA

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba15 Electron diffusivity. Similar  e at different densities   e ~ m 2 /sec within the barrier (s~0 region) at different densities. Larger J LHCD profile at higher density #21636

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba16 LHCD physics. Good agreement between calculated J LH and HXR-measurement at high density #19739 #18369 At low density ( m -3 ), spatial diffusion of fast electrons plays a role High density ( m -3 )

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba17 LHCD physics. Wider barrier at lower q a Narrow barrier radius due to narrow LH deposition profile at high q a #19739 B=5T I p =0.25MA B=5T I p =0.4MA

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba18 LHCD physics. ITB expanding in time T e profile (from exp) and modeled q-profile at different times Expansion related to the LH power deposition profile, which broadens in time (due to density rise) #20859

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba19 Global energy confinement time. Comparison with ITER-97_L scaling Ohmic discharges –  E in line with the ITER_L_TH_97 scaling ITB discharges –  E exceeds the ITER_L_TH_97 scaling a factor #19739

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba20 Conclusions Stationary electron ITB, lasting 5-10  E, were obtained in FTU up to n eL = m -3, thus showing that operations close to the ITER density and magnetic field do not prevent ITB to be achieved. At the foot of the barrier 1/L T value in excess of 20 were found The barrier radius is likely linked to the weak shear region.

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba21 Conclusions The ray-tracing Fokker-Planck model appears quite satisfactory in describing the LHCD deposition which, in turn, influences the barrier radius : –different LHCD profiles at different density and q a, –ITB expanding in time associated to LHCD expanding in time The ion diffusivity is close to the neoclassical value

9-12 Sept. 2002E. BARBAT0-ENEA, TTF, Cordoba22 Conclusions The electron shear dependent BGB model accounts for T e (r,t), for T e0 up to 6 keV. At higher T e0  gB (central transport ) needs to be reduced. In Ohmic discharges  E is in line with  E ITER-L_TH In ITB discharges  E exceeds a factor  E ITER- L_TH.