1. ITB Control with LH Heating & Current Drive
LH should be very effective in controlling density peaking
Current drive phasing can either increase or decrease Vloop
Increase Vloop with LHCD
Increase Ware Pinch
Trigger ITB at will
Expand ITB foot location
Reduce Vloop with LHCD
Reduce Ware pinch, prove ITB due to Ware pinch
Control density peaking:
Ohmically heated ITB (hi B, low Ip)
ITB with off-axis ICRH in H-mode, use LH instead of on-axis ICRH
Also, following H to L transition
LH heating of electrons should drive Trapped Electron Modes, as in previous on-axis cases, limiting density gradient [IAEA 2006, etc]
Document fluctuations and simulate with GS2/GYRO using synthetic PCI
2000 H-Mode
Off-axis ICRH
Ohmic H-Mode 0.8 MA
Fig. 2-5: J. Liptac, PhD Thesis, MIT (2006).
Balance accessibility (higher n||) against efficiency (~ n||-2)
Have done well with n||=1.6; expect 25% of this efficiency at n||=3.2
n|| upshifts after launch, helping some
Lower density and higher field better
Cryopump and 7.5 – 8 Tesla desirable
Only need to access foot of ITB
D. R. Ernst, R. Parker, L. Lin, M. Porkolab, P. Bonoli, C. Fiore et al.
2007 C-Mod Ideas Forum