FTU Activity A. A. Tuccillo on behalf of FTU Team

1. Since last ITPA in Culham Main Experimental Programme ended in May due to: Explosion of two secondary breakers (20kV) on LH Failure of McPherson UV spectrometer 150kV failure? Short circuit on Electro-Optic Probe (dust detection) Experimental Programme continued till July, to: Commissioning new front mirrors RT steerable ECRH Launcher Some ECRH and OH exps on density limit (recycling, Li/B/Mo) Some diagnostic commissioning Summer Shutdown: ECRH antenna inspected, refurbished and reinstalled LH fully refurbished, new 12 arm power divider commissioning McPherson 2 Heads repaired, under calibration (by Oct on FTU) Electro-Optic Probe refurbished and reinstalled FTU pumping down started lst week Friday 14th: FTU ActivityA. A. Tuccillo on behalf of FTU Team

2. RT EC Antenna:Test of Poloidal Movement /1 #34888 αPol 28°14°, βTor=0° Poloidal Max δα= -0.305° Max δβ= 0.056° Max Va= -45.7°/s Max Vβ= 8.5°/s Deg Deg/s Toroidal Deg Deg/s Δα (Deg) Time (s) Acceptable low error on poloidal angle: accounting for beam waist Time (s)

3. RT EC Antenna:Test of Poloidal Movement /2 • Summary of progress • New ECRH launcher for ST/(N)TM real time control installed in FTU in spring 2011 • 2 steerable mirrors symmetric to eq. plane: αPol=±25°(ρ=±0.7)/βTor=±40° • steering velocity: 1° (1cm)/10ms • Technical test w and w/o plasma • completed: • characterization of launched beam in vessel • with low power (mW) source • validation of power handling • EC power deposition location • RT control sys. under development    pre-prog sweeping α=-28°  α=-14°  • completed: • preliminary version of RT DAS: • 8 diagnostics chs + 2 ECRH, 20 kHz) • real time data elaboration: • ECE/ECRH/Mirnov cross correlation  • power deposition location  

4. ITPA: EC Assisted Breakdown on FTU IP (kA) li Resonance scan evidence and perspectives: Reduced flux consumption Faster current ramp (outer localization) Control of plasma starting point Te (keV) R (m) G. Granucci et al. Nucl. Fusion 51 (2011) 073042

5. Next planned experiments • FTU can reproduce same Vloopevolution foreseen in ITER, this will be exploited in: • studying the O1 vs X2 • exploring minimum electric field in both scenarios • Steering beam to study the effect of EC deposition vs. null position • Upper or equatorial injection with/without toroidal angle . Exploiting the new fast steerable launcher • Exploitation of new fast visible camera for plasma evolution measurement (formation, drift, extension)

6. ST destabilization by modulated ECH/ECCD /1 Aim: • pulsed ECH used as trigger of ST crashes to test conditions for a-priori constant ST in view of the real time control of ST period Experiment: • 3 constant ECH modulations (for 500ms): • 20Hz (20% and 80% duty), 125Hz (50%) • target plasma: • Ip=500kA, 5.1T<Bt<5.9T, ne=0.6 1020m-3 • EC rdep moves from inside to outside q=1 • ECE 12-channels polychromator for Te profiles, ST crashes and q=1 position (inversion radius) Btor scan #33257 Te 10ms on/ 40ms off #34286 Te 40ms on/ 10ms off #34285 Te 4ms on/ 4ms off • First Answers: • 0.8 MW of EC power (Pohm=0.5MW) inside q=1shortens ohmicST = 6.4ms up to ~ 35% (ECH only) and ~ 45% (coECCD) • magnetic shear s1 at q=1 increasesup to 0.3 at ST crash where s1 > scr • ST amplitude exhibits a maximum ~ 1.7 its ohmic value inside q=1 outside

7. ST (de)stabilization by modulated ECH/ECCD /2 20Hz @ 80% 125Hz @ 50% 20Hz @ 20% q=1 q=1 q=1 inside q=1 inside q=1 ohmic stab. ST * * ohmic ohmic * inside q=1 outside q=1 outside q=1 outside q=1 Pure EC heating coECCD • The observed stabilizing effect of fast EC modulation in central region inside q=1 with phase on > ohmicsuggests to use faster modulation (1KHz/500Hz @50%) to reduce ST • Transport calculations are in progress to simulate and predict this behaviour • New real time ECRH launcher will allow soon to keep constant ST by proper EC beam steering (0.3 < rdep / r1< 0.6) and compare results with those • of other machines (TCV, ASDEX, TS… ?)

8. Looking for Densitylimiton Toroidalfield in FTU IP: 900 kA, 700 kA, 500 kAdischarges with increasingdensity up to disruption • Hugill plots of the FTU discharges: • Central line averagedensities (r/a = 0) • External line averagedensities (r/a = 3/4) • Open symbols: Onset of the MARFE • Solid symbols: Disruption for densitylimit • The central and the external line averagedensitiescorresponding to the onset of the MARFE are linear functions of the average plasma currentdensity. • The maximum achievablecentral line averagedensityisnotscalinglinearly with the average plasma currentdensity: the Greenwaldlimitisexceeded for qcyl > 4 (q > 5), whileitisnotreached for qcyl < 4. • The external line averagedensityat the disruption for densitylimitresults to scale as a fraction of the Greenwaldlimit.

9. Looking for Densitylimiton Toroidalfieldin FTU /2 • After the onset of the MARFE, with increasingdensitythereis a strong peaking of the densityprofileswhich. • The reduced temperature at the edgemake the plasma more transparent to the neutrals and determine an increase of the particle source inside r/a = 3/4. • The dependence of the densitypeaking on the edgesafetyfactor play a crucialrole on the determination of a densityscaling law when the central line averagedensityisconsidered. • The combination of the external Greenwald limit and the q-dependent density peaking results in a more then linear dependence of the maximum achievable central line average density on the toroidal magnetic field and a substantial independence on the average plasma current density.

10. Fast Camera In the frame of EFDA MHD Tasks on Disruption characterisation and dust dynamics a fast camera has been commissioned on FTU at the end of 2010 3600 frames/s at full resolution Up to 500000 frames/sec at reduced resolution Collection optics through fiber bundle

11. Fast Camera Dust MARFE oscillation

12. GEM detector in front of the neutron D-D target Collaboration ENEA-INFN-CEA (EFDA WP10-DIA-04-03) Gas Electron Multiplier “GEM”:Evaluation of Immunity to Neutron Irradiation Neutrons and γ contribution to the Experimental set up 9000 counts Read out pads (pixel size 6×12 mm2) 9000 counts 2000 counts Frascati Neutron Generator deuterated target 2.5MeV 10cm 16 pixels 8 pixels Only X-rays (Fe55) X-rays and neutron • Neutrons contribution is spatially uniform • Fe55 signal has a well-defined spatial shape • Background Correction will be active based on pulse shape 10cm 9000 counts 7500 counts 2000 counts NeutronFlux=2.1 106n/s

13. Collaboration ENEA-INFN-CEA (EFDA WP10-DIA-04-03) Preliminary tests on polycapillaries as SXR lenses for MCF diagnostics Full lens • Full lens: produces a divergent beam, with an image magnification, and spot broadening is linear with the distance (also much larger than the focal distance) • Half lens: is an excellent light collector, very low divergence (quasi-parallel output beam even at large distance) • Imaging: the geometry of the sample is perfectly reproduced without any distortion 9000 counts 7500 counts Half lens 9000 counts SXR radiography of the mesh (holes 400 mm) SXR image of the mesh with full lens (magnification ~6 )

14. Experimental Campaigns in 2011: March 14th – July 1st Successful Plasma Restart March 15th – March 27th Programme Ops started April 5th November 2nd – December 10th Experimental Campaigns in 2012: January 31st– March 30th May - June (to be decided) All systems operative, but: ECRH 3 gyrotrons available, but 2 magnets being fixed in November, 4thgyrotron back from Russia end of November ECRH Power switchable between two antennas: Old and RT, LHCD 5 lines available FTU programme 2011-12

15. Responsible for the programme till next IAEA FEC P. Buratti Tearing mode control Sawtooth control Disruption avoidance (LH fast e-) with new RT EC Antenna Assisted breakdown (Fast Camera) OXB heating LHCD at high plasma density (complete scan at higher Power (IOS 5.3) control externaTeby ECRH) Control of metallic impurities (W-Mo) by impurity seeding Study low W ionisation states High power operation with Liquid-Lithium-Limiter 2011-12 FTU programme