1. Determining confinement and stability of q(0)>1 regimes produced
by lower hybrid current drive
R. Parker, Alcator C-Mod Group
Motivation:
Temperature and/or density can peak in sawtooth stabilized
LHCD plasmas. But MHD activity can occur as well, limiting T, n
peaking.
Questions to address:
Is the stability consistent with resistive MHD analysis?
What are the knobs for controlling stability?
What are the confinement properties of these plasmas?
Can stabilized H-mode (“Hybrid Mode”) be triggered before
j relaxes ?

2. MHD activity can occur in discharges with strong current drive
n׀׀ = n׀׀ = 1.95
Time (s)
Ip (MA)
Vloop(V)
Ne_bar
X1019m-3
Te0(keV)
PLH(kW)
Trad,R=0.86
(keV)
MHD
Arctan(Bv/Bφ) (degrees)
Time(s)
MSE traces at various major radii for discharge with MHD. Onset of MHD activity modifies MSE profile.
Sawteeth are stabilized in these plasmas.
Toe and/or no peaks when MHD is absent
J. Ko

3. Proposal: Investigate stability and confinement in sawtooth stabilized LHCD plasmas
Plan:
Setup LHCD discharges with q(0) > 1
Measure confinement properties, rotation and jφ profile with/without MHD activity
Evaluate stability – Δ’ or resistive MHD code?
Investigate as function of npar
Can stabilized H-Mode (Hybrid Mode) be triggered before j relaxes?