The Importance of Internal Fluctuation

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The Importance of Internal Fluctuation Fast-ion
Profile Measurements
The 1 Question of Non-Specialists is
Where do the fast ions go?
The most interesting aspect of our work to
non-plasma physicists
What are the nonlinear dynamics of a system with
combined kinetic (as in accelerator physics)
fluid (as in neutral fluids) nonlinearities?
The most ambitious goal we can set as a community
is
Can we harness these instabilities for beneficial
purposes?
All require accurate measurements of the wave
fields the fast-ion distribution function.
W. Heidbrink
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Recent Development Internal Fluctuation
Diagnostics
JET data
Interferometer

• New Diagnostics
• Interferometry
• Reflectometry
• Far Infrared Scattering
• Phase Contrast Imaging
• Beam Emission Spect.

Magnetics
Sharapov, PRL 93 (2004) 165001
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• Recent Developments
• New Fast-ion Profile Diagnostics

DIII-D Fast-ion Da Data
JET Gamma-ray Data
Heidbrink, PPCF 46 (2004) 1855

• Collective Thomson Scattering
• Solid state Neutral Particle Analysis
• Neutron Collimators

Kiptily, NF 45 (2005) L21
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2) Fast-ion Transport by TAEs Why cant we
explain the losses?
Similar results for TFTR
Todo, Phys. Pl. 10 (2003) 2888
DIII-D data/analysis

• To approach measured losses,
• simulation needs 10 times larger
• mode amplitude than the
• experimental value!

Mode Amplitude
Carolipio, Phys. Pl. 8 (2001) 3391
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3) Consequences of not solving range from
None (if saturation is benign) Catastrophic (if
alphas burn holes in the vessel)
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4) Issues to be solved in a burning plasma
experiment
Internal fluctuation fast-ion diagnostics will
be even harder in ITER ? Must get most of our
understanding from existing experiments

• Nevertheless, ITER should
• Detect fast-ion driven instabilities
• Detect alpha-particle losses
• Attempt to detect alpha-particle redistribution

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5) The US Program Should (near-term goals)

• Fund further improvements in internal fluctuation
  diagnostics.
• Develop fast-ion profile capabilities on the
  major tokamaks.
• Perform experiments with combined fluctuation
  fast-ion measurements.
• Analyze these data. Does theory agree with
  experiment?
• Develop new codes as needed to obtain agreement.
• Pursue control techniques on (cheaper) smaller
  devices with excellent diagnostics

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6) The BPO should be organized so

• We dont waste time in meetings
• My priorities get funded done!

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Combined wave field fast-ion measurements are
important because
We have to know where the alphas go! This system
is complexwe cant develop control tools without
understanding.
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Da Light from Neutralized Fast Ions

• Like Charge-Exchange
• Recombination Spec-
• troscopy of fast helium
• ions (TFTR, JET)
• Fast ions neutralize
• when they intersect a
• heating beam
• Da is the 3 ?2 transition
• Wavelength determined
• primarily by Doppler shift
• Cross sections known

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Energy resolution of lt 10 keV
Steps in fast-ion distribution from half- and
third-energy beam components are resolved
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Clear Signals for Most Minor Radii
80
40 keV

• Although the fast-ion density
• peaks on axis, the injected
• neutral density is largest at edge
• Strong signals throughout
• outer half of plasma