r sartori thank you to the people who contributed
DESCRIPTION
Impact of rotation and momentum input on the L-H transition. R Sartori Thank you to the people who contributed. Outline of the talk L-H threshold and: Changes in rotation by changing NBI torque (DIII-D) Changes in rotation due to changes in SOL flow (Alcator C-Mod) - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/1.jpg)
R Sartori et al, ITPA, Autumn 2009
R SartoriThank you to the people who contributed
Impact of rotation and momentum input on the L-H transition
![Page 2: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/2.jpg)
R Sartori et al, ITPA, Autumn 2009
Outline of the talk
L-H threshold and:
• Changes in rotation by changing NBI torque (DIII-D)• Changes in rotation due to changes in SOL flow (Alcator C-Mod)• Changes in rotation due to TF ripple (JET)• Changes in rotation due to changes in momentum input: NBI vs no momentum input ICH and ECH (Asdex Upgrade and JET)• Changes in rotation due to RMP
![Page 3: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/3.jpg)
R Sartori et al, ITPA, Autumn 2009
• The L-H threshold power is reduced by a factor of 3 going from prevalent co-injection to prevalent counter in USN (ion grad-B drift away from X-point)
• Smaller reduction of PLH in LSN ~80%• No difference between USN and LSN for counter and balanced injection • Reduction in edge toroidal rotation is correlated with the observed
reduction in L-H threshold power
DIII-D: L-H threshold depends on applied beam torque and toroidal rotation
P Gohil, H-mode workshop 2007
![Page 4: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/4.jpg)
R Sartori et al, ITPA, Autumn 2009
DIII-D: L-H threshold depends on applied beam torque and toroidal rotation
The L-H transition can be induced by reduction of applied torque at constant power
![Page 5: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/5.jpg)
R Sartori et al, ITPA, Autumn 2009
The experiment DIII-D: L-H threshold dependence on torque/rotation is independent of ion mass
• The increase of PLH with torque is seen also in Hydrogen plasmas• In Hydrogen a factor of 2 larger threshold observed in the
range of torque explored
P Gohil, NF, to be published
![Page 6: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/6.jpg)
R Sartori et al, ITPA, Autumn 2009
Description of the Experiment
• Correlation between changes in injected torque and poloidal group velocity of turbulence near edge
• Changes in fluctuation level and flow pattern between co-injection and balanced injection
• Turbulence flow reversal in balanced injection poloidal flow shear
• spectra obtained in 100 ms before L-H. Phase shift of poloidally displaced channels Z=1.2cm.
DIII-D: Changes in rotation/torque correlate with edge turbulence dynamics
GR McKee, IAEA 2008
D J Schlossberg, Phys. Of Plasmas, 2009
![Page 7: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/7.jpg)
R Sartori et al, ITPA, Autumn 2009
Description of the Experiment
• Interplay between pressure gradient and v X B terms in Er:
• lower contribution of toroidal rotation term increase in Er shear at the edge de-correlation and suppression of turbulence .
DIII-D: Increased Er shear at lower rotation
![Page 8: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/8.jpg)
R Sartori et al, ITPA, Autumn 2009
• PLH two times higher in USN (ion B drift away from X-point )• Strong parallel flows are driven in the inner SOL, co-current for LSN, counter
current for USN• At the L-H threshold flows and rotation near a constant value, independent of
configuration strong suggestion that SOL flows are causing differences in PLH with configuration
• Changes in core rotation correlated with changes of SOL flows (largest in inner SOL)
Alcator C-Mod: Changes in L-H threshold correlated with changes in SOL flows/rotation
From H Hubbard, EPS 2004
![Page 9: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/9.jpg)
R Sartori et al, ITPA, Autumn 2009
• Lower rotation with increasing ripple. Edge rotation becomes negative at high ripple
• ASCOT calculation that dominant mechanism for reduction of rotation is banana orbit diffusion induces a radial return current JXB torque in counter current direction. For ripple of 0.5% this torque was found to be 20-30% of that supplied by the NB system
Comparison of density and temperature and toroidal rotation profiles
JET: Variation of toroidal rotation due to TF ripple changes
P De Vries et al, NF 48 2008
1.5% ripple: L-modes with low level of beam power
![Page 10: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/10.jpg)
R Sartori et al, ITPA, Autumn 2009
Comparison of power and torque density
JET: L-H threshold is not affected by large variation in toroidal rotation due to TF ripple
• 0.08% ripple v in co-current direction• 1 % ripple v in counter-current direction• Similar Te and Ti the transition• v unaffected by ripple
Y Andrew et al, PPCF 50 2008
![Page 11: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/11.jpg)
R Sartori et al, ITPA, Autumn 2009
Global and pedestal confinement is similar
Asdex Upgrade: L-H threshold is independent of heating method momentum input/rotation
• No difference in L-H power threshold and in the density dependence of PLH between ICH and NBI, for both D and He plasmas
F Ryter et al, NF 49 2009
![Page 12: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/12.jpg)
R Sartori et al, ITPA, Autumn 2009
• JET results shows that L-H access is independent of heating method, as seen previously in JET for all H isotopes
– New data confirms the results and shows typical changes from ~6-8 kHz (NBI+ICH) down to ~2.5KHz (ICH) at 3T with similar threshold
Data from 1MA/1T to 3.8MA/3.8T
LH scaling from Righi et al NF 39, 1999
Andrew et al, PPCF 48 2006
JET: L-H threshold is independent of heating method momentum input/rotation
![Page 13: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/13.jpg)
R Sartori et al, ITPA, Autumn 2009
Effect of RMPs on the L-H transition Summary from Carlos Hidalgo- H-mode workshop talk
DIII-DIn Helium plasmas PL-H increased by >50% in the presence of n=3 RMP perturbations.
JETNo effect observed (2009 experimental campaign)
MASTOn MAST there is observation of the delay of the L-H transition time if the n=1 coils are applied before the L-H transition but not with n=3.
NSTX PL-H increases from ~1.4 to 2.6 MW with higher n=3 current (~65% increase for Pheat/ne)
![Page 14: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/14.jpg)
R Sartori et al, ITPA, Autumn 2009
Summary and future work
• PLH increases from ~1.4 to
2.6 MW with higher n=3 current
• PLH unaffected by application of RMP if effect exists it depends on the strenght of the perturbation
• 30% decrease in rotation
NXTS and JET results on L-H threshold with RMP
![Page 15: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/15.jpg)
R Sartori et al, ITPA, Autumn 2009
Summary
• Evidence from DIII-D of strong effect of beam torque on L-H threshold
– The effect persist when mass (and X-point height) are changed
– For counter-injection, it reduces differences between favourable and unfavourable grad-B direction
• The effect is less strong in favourable grad-B direction (why?), therefore effect on threshold scaling not as large as largest reported variations
• When rotation is changed by changing heating methods and ripple the L-H threshold is unchanged, with RMP it increases or is unvaried suggest weaker link with rotation in DIII-D results
![Page 16: R Sartori Thank you to the people who contributed](https://reader036.vdocuments.mx/reader036/viewer/2022062500/5681593e550346895dc67d7f/html5/thumbnails/16.jpg)
R Sartori et al, ITPA, Autumn 2009
Comparison with same density and total power
JET data : LSN configuration and reversed Bt and Ip
• Reversed Bt direction ion B drift away from X-point and counter injection
• Forward Bt direction ion B drift towards X-point and co injection
• No difference between L-H power threshold with ion B drift direction in the JET data.