1 CAE stochastic heating

1
1) CAE stochastic heating

• Goal is direct heating of thermal ions with low
  frequency ( 1 MHz) RF system
• Stochastic ion heating with large amplitude
  waves has been demonstrated in small experiment
• Observed CAE/GAE spectrum suggest many modes
  available to couple to, and relatively low power
  threshold to excite measurable modes.
• Estimated power required (a few kW to create
  observed mode amplitude?)
• ?pol/2 over RF antenna from Mirnov array
• Approximately 10 times more power to reach
  stochastic threshold below stochastic threshold,
  damping is primarily on electrons.

• Early theoretical history
• '75 SmithKaufman proposed stochastic ion heating
  by oblique ES wave
• '77 KarneyBers, stochastic ion heating by
  perpendicular ES wave
• '78 Karney, ion heating in lower hybrid wave
• '79 Hsu,Matsuda,ChuJensen, parallel standing
  wave
• '81 DrakeLee, Lower hybrid drift wave and
  multiple waves
• Experimental documentation of stochastic thermal
  ion heating
• '87'91 McChesney,SternBellan, stochastic ion
  heating with drift-Alfvén wave
• '9395 Bailey,BellanStern, thermal-ion
  equilibrium distributions
• '98 Sanders,BellanStern, transport effects on
  distribution function

2
CAE stochastic ion heating

• Experiment goals
• Document coupling of RF antenna strap to
  NBI-excited CAE.
• Measure antenna loading in AE quiescent regime
  (possibly ohmic shot, maybe with AE present)
• Run plan and run time
• Perform antenna modifications for last week of
  operation
• Data on coupling to beam-excited modes will be
  acquired in piggyback fashion
• There should be a spare channel in the HF data
  acquisition system.
• Need to run cable to RF antenna, install voltage
  divider/matching network.
• If things are going well, measure antenna loading
  with low power source?
• Results will help prepare for more extensive
  experiments next year.

3
Excitation of AE by ICRF beat wave excitation

• Feasibility demonstrated on JET by Fasoli, et.
  al. (NF 36 258) with H-minority heating
• Origin of non-linearity could be wave-wave
  physics or antenna-plasma coupling
• Provides direct measure of mode damping rate -
  potentially for CAE/GAE as well as TAE modes.
• Potential piggy-back XP?
• May need high power for non-linear physics.
• Need reference signal, may need ability to scan
  beat frequency?