HHFWEBW ET Research Plans

1
HHFW/EBW ET Research Plans

• Speakers Bernabei, Biewer, Bonoli, Carter, Mau,
  Pinsker, Ram, Taylor
• 3 presentations on EBW
• 6 presentations on HHFW
• Other participants M. Bell, Kessel, Peng,
  Phillips, Ryan, Schilling, Synakowski, Wilgen,
  Wilson
• Contributors Batchelor, Bigelow, Efthimion,
  Harvey, Hosea, Jaeger, LeBlanc, Rasmussen, Swain,
  Wright

2
Goal Establish basis for viable 28 GHz EBW
scenarioEmission Experiments

• measure X-Mode emission with local gas feed to
  insure overdense plasma near antenna (XP 404)
• previous attempts found low emission and
  underdense plasma in front of antenna
• measure 20-40 GHz O-Mode EBW emission with new
  obliquely viewing antenna installed at Bay G
  (extensive rewrite of XP 405)
• fast frequency-scanning, dual channel 20-40 GHz
  radiometers will simultaneously measure
  orthogonal polarizations
• incorporate quarter-wave plate for polarization
  measurements 28 GHz
• use fast MHz video amps 500 kHz digitizers to
  study fast emission fluctuations

3
Goal Establish basis for viable 28 GHz EBW
scenarioDirect Launch Experiments

• Low power (15 kW) test of 18 GHz EBW launch
• relatively inexpensive modification to existing
  systems to provide O-mode launch
• modulation may allow power to be detected with 15
  kW source
• determine edge fluctuation effects on
  polarization settings
• verify launch angle and spot size requirements
• address possible parasitic absorption issues
• neutral collisions in the edge
• scattering because of finite beam width
• parametric decay

4
Goal Establish basis for viable 28 GHz EBW
scenarioCollaborations and Design Efforts

• MAST collaborations
• 60 GHz EBW heating during Ip flat top
• 28/60 GHz EBW startup assist
• Develop conceptual EBW launcher design for
  proof-of-principleEBW system

5
Goal Establish basis for viable 28 GHz EBW
scenarioTheory and Modeling

• GENRAY - include fully relativistic dispersion
  ( from R2D2 - MIT)
• CQL3D - include electron transport
• - study bootstrap synergy
• - benchmark comparison with BANDIT (Culham)
• GENRAY/CQL3D - integrate into TRANSP
• - realistic antenna coupling to EBW
• GLOSI/AORSA-1D - EBW coupling above EC
  fundamental
• - realistic antenna/plasma modeling
• DKE - incorporate fully relativistic DQLin Drift
  Kinetic Fokker-Planck code
• - identify regimes for optimum EBW-CD in various
  parts of plasma

6
Goal Establish minimal conditions for successful
heating during start-up and Ip ramp-upExperimenta
l Scoping Studies

• Evaluate HHFW heating and CD characteristics in
  typical start-up and ramp-up parameter regimes
• Measure dependence of heating / CD efficiency as
  a function of density, plasma current and B field
  for range of antenna phasings
• Examine role of possible early H-mode transitions
• Identify any correlations between edge conditions
  and heating / CD efficiency

7
Goal Establish minimal conditions for successful
heating / CD during start-up / ramp-upTheory and
Modeling

• Ray tracing / full wave modeling to evaluate
  single pass absorption rates with start-up /
  ramp-up parameters
• Evaluate effects of edge losses in low single
  pass regimes by including ad-hoc absorber
  boundary condition in AORSA-2D
• Complete coupling of ray codes and full wave
  codes to CQL3D for accurate CD modeling
• Complete installation and benchmarking of CURRAY
  and TORIC4 in TRANSP for data analysis and
  time-dependent simulations of ramp-up scenarios

8
Goal Understand HHFW coupling to core
plasmaEffects of Edge Interactions on Coupling

• Use ORNL reflectometer to detect 30 MHz waves in
  surface
• Use ORNL reflectometer to measure parametric
  decay waves
• Use passive plate Rogowski loops to detect
  rf-driven sheaths for various antenna phasings
  and equilibrium configurations
• Use probes to detect surface waves and/or sheaths
• Use ? to search for evidence of wave scattering
  in edge as function of phase
• Use Frascati soft x-ray camera and PBX parallel
  x-ray camera to look for asymmetries in electron
  distribution functions (can be done piggyback)

9
Goal Understand HHFW coupling to core
plasmaTheory and Modeling

• Develop better models for parametric decay
• Improve plasma-antenna coupling codes, including
  sheath b.c.
• Modify edge conditions in AORSA-2D and TORIC4 to
  evaluate potential for sheath formation in edge
  regions
• Include effects of density fluctuations in CURRAY
  and AORSA to investigate scattering of HHFW by
  edge turbulence

10
Goal Understand HHFW coupling to core
plasmaConfiguration Effects on Coupling

• Measure heating efficiency and antenna loading
  for different equilibrium B field structure in
  front of antenna
• reverse BT only
• reverse Ip (Bp) only
• reverse BT and Ip(Bp) together
• Compare heating efficiency and loading from upper
  single null to lower single null configurations

11
Goal Understand HHFW coupling to core
plasmaTheory and Modeling

• Use AORSA-1D / RANT3D to evaluate effects of
  linear IBW mode conversion with shear and
  collisional edge damping on HHFW power coupling
  to plasma
• Use AORSA-2D to evaluate possible parasitic wave
  absorption in divertor regions
• Study coupling physics of HHFW with low density
  plasma in close proximity to antenna current
  strap
• usual treatment in full wave codes assumes
  current strap is in vacuum.

12
Goal Understand HHFW coupling to core
plasmaComplete Power Modulation XP

• Complete measurements of heating efficiency and
  antenna loading for range of various parameters,
  including Prf, Ip, BT, ne, k, phase, etc
• previous data incomplete and often not clean,
  especially in D plasmas
• Vary shape of power modulation waveform

13
Goal Understand HHFW coupling to core
plasmaUnderstand Results of HHFW NBI XPs

• To accurately model the interaction of HHFW and
  NBI
• requires an accurate closed loop computation
  between full-wave (or ray tracing) module and
  Fokker Planck code
• requires modification of dielectric response to
  include non-Maxwellian ions
• Modification done in AORSA-2D underway in TORIC4
• requires implementation of coupled models in
  TRANSP to evaluate effects on transport
• CURRAY / TRANSP being tested and TORIC4
  installation nearly done, but CQL3D installation
  just beginning
• requires comparison to data (including CX data
  for fast ions)!

14
Goal Understand HHFW coupling to core
plasmaCollaboration with DIII-D

• Ion damping scaling experiments between DIII-D
  and NSTX
• Match ratio of thermal ion velocity to Alfven
  velocity in NSTX to ratio of effective beam ion
  thermal velocity to Alfven velocity in DIII-D
• Compare scans of density, toroidal field, phasing
  at reasonable rf power level
• need to find ways to minimize NBI power yet
  retain reasonably high Ti