Kinetic instability induced fast ion losses in NSTX

1
Fast ion transport in "sea-of-TAE"
College WM Colorado Sch Mines Columbia
U Comp-X General Atomics INEL Johns Hopkins
U LANL LLNL Lodestar MIT Nova Photonics New York
U Old Dominion U ORNL PPPL PSI Princeton
U SNL Think Tank, Inc. UC Davis UC
Irvine UCLA UCSD U Colorado U Maryland U
Rochester U Washington U Wisconsin
E. Fredrickson for the NSTX Team Burning Plasma
Workshop Dec. 7 - 9, 2005 Oak Ridge, Tennessee
Culham Sci Ctr U St. Andrews York U Chubu U Fukui
U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu
Tokai U NIFS Niigata U U Tokyo JAERI Hebrew
U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST
ENEA, Frascati CEA, Cadarache IPP, Jülich IPP,
Garching ASCR, Czech Rep U Quebec
2
ITER will operate with a large, super-Alfvénic,
fast ion population

• ITER in new, small r regime for fast ion
  transport
• "short" wavelength Alfvén modes
• transport from interaction of many modes
• NSTX also routinely operates with super-Alfvénic
  fast ions
• Although r is large, can study multi-mode
  transport

3
Fast Ion Modes dominate NSTX MHD

• Fast ion transport results from interactions of
  many modes
• Modes clearly interact, either directly or
  through fast ion population
• This type of fast ion transport is expected on
  ITER, other fusion reactors

fci3MHz
3
4
EPMs and TAE strongly interact

• Instability of EPM depends on presence of TAE?
• TAE burst also follow EPM
• Neutron drop correlated with EPM burst, not TAE
• Chirping of TAE indicates non-linear event
• Interaction of TAE EPM also non-linear

5
CAE/GAE may also be involved

• Here, strong burst of CAE/GAE precede each EPM.
• No other strong evidence for fast ion losses from
  CAE/GAE, but modes might modify fast io
  distribution.

6
TAE/EPM-induced losses scale with amplitude

• Substantial scatter in data could arise from
  several uncontrolled parameters
• of modes not controlled for
• External measurement of mode structure, not
  internal
• Fast ion losses inferred from neutron rate
  losses of lower energy ions count less

6
7
Larger losses at strong, multi-mode bursts, weak
losses single mode bursts

• Opportunity to examine multi-mode aspect fast ion
  transport

8
Reflectometer shows "sea of TAE" vs. a few
scattered modes

• High n's imply large krfastest ( 2 - 5), but
  for ions with Vbeam  VAlfvén, krbeam  0.5 - 1.5
  (r  0.06)

9
Difference in fast ion losses not due to
different mode structure
9
N. Crocker, S. Kubota, W. Peebles, UCLA
10
Non-linear simulations needed
M3D Nonlinear hybrid simulations of beam-driven
modes in NSTX shows a bursting n2 TAE as the
mode moves out radially
G.Y. Fu et al., IAEA Fusion Energy conference.
2004
10
G.Y. Fu, PPPL
11
Fast ion transport in a jungle of fast ion
instabilities

• NSTX fast ion loss events typically occur with
  multiple modes ("sea of TAE", as predicted for
  ITER)
• Lower frequency, strongly chirping (EPM) modes
  correlated with most fast ion loss events
• TAE/EPM (CAE) interact, perhaps synergistically
• Fast ion losses from EPM/TAE are not serious in
  NSTX, but
• Next step is to document effect on heating
  profile and on beam driven currents