C-MOD PROGRESS AND PLANS
RELATING TO H-MODE AND
ADVANCED SCENARIOS
G. Wallace on behalf of the C-Mod team
7th meeting of the ITPA IOS Topical GroupKyoto, JapanOctober 18, 2011

Heating and current drive systems
updated during up-to-air
No plasma operation since last meeting, pumping
down for next campaign this week
New LH limiter installed Upgrade to protection system for longer LH pulses
 New rotated 4-strap ICRF antenna installedAnalysis of existing data covered in individual talks
Further analysis of LH density limit data (see talktomorrow on IOS-5.3)
 Further analysis of ramp-up experiments (see talk on
Thursday by C. Kessel)New LH limiter designed to reducereflected powerOld limiter fixed to wall, launcher
moved relative to limiter Could only operate with launcher between.1 and .5 mm behind old limiter

New limiter fixed to launcher (0.2 mmbehind limiter), both move together
 Can be pushed proud of ICRF limiters toreduce deleterious effects on LH wave
coupling (Tore Supra results show thishelps)
 Will be able to move launcher to region
with best density/density gradient forcouplingTransmitter protection system (TPS)
upgrade allows for longer LH pulses
LH pulse length
administrative limit set at
0.5 s during previous
campaigns
 Need longer pulses foradvanced scenarios

New TPS calculates klystroncollector temperature in
real time TPS will shut off highvoltage if temperaturethreshold is exceeded Shakedown of new TPS
scheduled for December
 Will carefully increase
pulse length duringupcoming run campaign


Klystron coolant temperature simulation

New rotated 4-strap ICRF antenna
designed to reduce impurity production
Rotated design results intotal cancellation of parallel
electric field Lower parallel E-fieldshould result in reduced
sheaths, hopefully leading
to fewer high-Z impurities
 Integrated SOL
reflectometer for density
profiles (contribute to IOS5.2)
 Ready to start assessmentwith first plasmas
Fewer high Z impurities will make
ICRF more effective per MW

If new antenna achieves ~10
MW/m2 (present limit), the injected
power will be limited to 2 MW fromrotated antenna due to smaller area
For present J antenna, 3 MW istypical maximum injected power Will need to achieve ~15 MW/m2 toachieve 3 MW

To reduce impurities, present nonfield aligned antennas are operated
in dipole [0, π] phasing rather thanmonopole phasing [0,0]For [0, π, 0, π], estimated sheathfield is reduced ~3-10
For [0,0,0,0], sheath field is
negligible – a surprising prediction
and one we can test

New impurity seeding gas lines
installed in divertor
Existing gas lines atmidplane and verticalports Two new gas lines locatedin divertor 140° aparttoroidally Plan to compare efficacyof puff locations withrespect to core impuritylevels
FY 2012 run campaign begins soon
Planned experiments related to IOS:
 Evaluate rotated ICRF antenna including coupling (IOS-5.2), impurity
production
 Continue impurity seeding studies at ITER q95 and shape with new gas lines
including feedback control (IOS-1.2)
 Assess new LH limiter configuration
 Extend LH pulse length Examine LHCD density limit at higher temperature (IOS-5.3)
 Combine LHCD with ICRF for higher performance non-inductive scenarios,
and assessment of potential hybrid scenarios
 Expand power and density range for I-mode Continued exploitation of the 2.7T, 2nd harmonic proton heating regime, attarget betaN and n/nG with possible extension to He majority plasma (IOS1.1)