8th IAEA Technical Meeting on Energetic Particles

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8th IAEA Technical Meeting on Energetic Particles
in Magnetic Confinement Systems Summary of
Experimental Papers
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Alpha Particles Source of instabilities. Energy
source of self-sustainable burning
plasma Supra-thermal, run away electrons Source
of dangers on disruption
Source of dangers Should be
understood and controlled Energy source
Should be utilized most effectively
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• -- 28 Experimental Papers --
• 11 Tokamak papers
• 8 Helical
• 1 Linear
• 7 Diagnostics
• 1 energetic electrons

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use a energy
understand
understand
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• Understad Instabilities---Tokamak
• Testa JET/ITER Active excitation/passive
  excitation
• Damping Rate Study extended
• PNBI Threshold for Excitation of n5-8 TAEs
  Increases with Edge Magnetic Shear
• Mode Splitting and Lower Damping Rate for n1
  TAEs at PNBIgt3MW , in Low magnetic shear.
• nonlinear coupling of EPMs with MeV ions in
  advanced scenarios .
• Error Field Affects Radial Profile of fFAST(E,r)
• error field locks to q2 surface distorting the
  magnetic topology
• q2 TAEs disappear completely
• q3 EAEs only marginally affected
• fast ions scattering possible method to control
  peaking of ?bFAST(r)?

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Damping Rate of n0/1/2 AEs Increases with Edge
Elongation and Triangularity
conventional tokamak scenario monotonic
q-profile agreement with theory role of edge
magnetic shear
Nucl. Fusion 41 (2001), 809
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• Understad Instabilities---Tokamak
• Testa JET/ITER Active excitation/passive
  excitation
• PNBI Threshold for Excitation of n5-8 TAEs
  Increases with Edge Magnetic Shear
• Mode Splitting and Lower Damping Rate for n1
  TAEs at PNBIgt3MW , in Low magnetic shear.
• nonlinear coupling of EPMs with MeV ions in
  advanced scenarios .
• Error Field Affects Radial Profile of fFAST(E,r)
• error field locks to q2 surface distorting the
  magnetic topology
• q2 TAEs disappear completely
• q3 EAEs only marginally affected
• fast ions scattering possible method to control
  peaking of ?bFAST(r)?

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A.Fasoli A new antenna system has been designed
and is being constructed to excite MHD modes in
the Alfvén range of frequencies, in the range
n5-15, which can be driven unstable by fusion
generated alphas or other fast particles in
large machines.
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Alfvén Eigen Modes Stability---Tokamak Sharapov
JET Alfvén Cascades modes associated with qmin
excited by fast ions. Used successfully for
monitoring the qmin(t) evolution The temporal
correlation between Alfvén grand-Cascades, ITB
triggering events and integer values of qmin has
been established for a wide range of plasma
conditions and pre-heating scenarios on JET
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Alfvén Eigen Modes Stability---Tokamak Sharapov
JET A technique for obtaining ITBs in shear
reversed plasmas by applying the main
heating shortly before the AC time has been
established on JET A new way of detecting Alfvén
Cascades with interferometry has been
found. These measurements give a high-accuracy
monitoring of qmi (t) and may lead to a
systematic diagnosis of the transport properties
of the layer surrounding qmi
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Alfvén Eigen Modes Stability---Tokamak Snipes
C-Mod Active and Passive Study has been carried
out with a pair of active MHD antennas. Stable
TAE resonances at q1.5 are actively excited with
a single high n antenna in both limited and
diverted discharges in the range of toroidal
fields and densities expected in ITER . Software
synchronous detection provides good fits to the
stable TAE resonances on multiple pick-up coil
signals with 0.5 lt ?/?lt 4 Diverted discharges
require an outer gap lt 1 cm to see the
resonance Alfvén Cascades are observed in the
current rise at low density with strong ICRF
heating indicating slightly reversed shear with
qmin 3 Results agree well with MISHKA modeling
of the Alfvén Cascades ?Modes are also observed
in the EAE frequency range 1 MHz in relatively
low density EDA H-modes rotating in the electron
direction
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Alfvén Cascades in the Current Rise

• Rapidly chirping Alfvén Cascades in the current
  rise with strong ICRF heating at low density
  indicate a reversed shear q profile and
  determine the minimum q value at the minimum
  mode frequency

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Alfvén Eigen Modes Stability---Tokamak Shinohara
JT-60U/JFT2M Reversed-Shear-induced Alfvén
Eigenmode (RSAE)
To investigate dependence of mode amplitude on
q-profile, NNB was injected into RS plasmas with
various qmin n1 mode amplitude has its
maximum around qmin 2.4 - 2.7
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A gap is formed due to the reversed shear
q-profile at the zero magnetic shear location and
is not induced by toroidal coupling AE was
found around the upper and the lower boundary of
the gap using the calculation of TASK/WK code
RSAE and its transition to TAE is consistent with
the observed upward and downward frequency
sweeping and subsequent frequency saturation.
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Alfvén Eigen Modes Stability---Tokamak Shinohara
JT-60U/JFT2M Escaping ion measurement in
JFT-2M Heat flux in Complex magnetic field
produced by ferritic inserts
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Alfvén Eigen Modes -- SphericalTokamaks Fredrick
son NSTX Neutral beam injection into the
National Spherical Torus Experiment (NSTX)
results in a broad spectrum of instabilities
. The lowest frequency energetic ion driven modes
have a bursting character with strong frequency
chirpingas "fishbones". Mode activity in the
frequency range of 80 to 150 kHz are classified
as Toroidal Alfvén Eigenmodes (TAE). When the TAE
exhibit bursting, they can cause substantial fast
ion losses. In the frequency range from 0.5 MHz
to over 3 MHz for CAE and in ST geometry Belova
NSTX Numerical Study on Compressional Alfvén
Eigenmodes (CAEs) and Global Alfvén Eigenmodes
(GAEs), which are driven unstable through the
Doppler shifted cyclotron resonance with the beam
ions 2. The strong anisotropy in the fast-ion
pitch-angle distribution provides the energy
source for the instabilities.
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TAE bursts responsible for most of fast ion loss
here

• Neutron drops 10-15 .
• Period is again 10 ms.
• In steady-state, predicted reduction in fast ion
  beta of 40 .
• TAE have strong bursting character with multiple
  modes present.

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Alfvén Eigen Modes -- SphericalTokamaks Fredrick
son NSTX In the frequency range from 0.5 MHz
to over 3 MHz for CAE and in ST geometry Belova
NSTX Numerical Study on Compressional Alfvén
Eigenmodes (CAEs) and Global Alfvén Eigenmodes
(GAEs), which are driven unstable through the
Doppler shifted cyclotron resonance with the beam
ions 2. The strong anisotropy in the fast-ion
pitch-angle distribution provides the energy
source for the instabilities.
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Alfvén Eigen Modes -- SphericalTokamaks Darrow
NSTX loss of 80 keV D beam ions . Comparison of
the measurements and modeling. A detailed
model is being developed which compute the loss
to a specified detector location, incorporating
the measured plasma magnetic equilibrium,
inferred beam deposition profile, and the range
of orbits which enter the detector. Medley
NSTX Horizontally scanning Neutral Particle
Analyzer(NPA) whose sightline views across the
three co-injected neutral beams. For example,
onset of an n 2 mode leads to relatively slow
decay of the energetic ion population (E 5 -
100 keV) and consequently the neutron yield. The
effect of reconnection events, sawteeth and
bounce fishbones differs from that observed for
MHD modes.
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Illustration of MHD-induced Ion Loss during
H-mode BT 4.8 kG, IP 0.8 MA, Source A B _at_
90 keV, Low MCP Bias
Following H-Mode onset at 230 ms, the NPA
spectra show significant loss of energetic ions
only for EgtEb/2.


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Alfvén Eigen Modes Stability---Tokamak Gryaznevi
ch MAST / START Experimental study of Alfvénic
instabilities in STs provides an opportunity to
test theoretical models, which could then be
applied to alpha-particle physics predictions in
ITER and beyond. Several types of high frequency
MHD activity that may be associated with toroidal
Alfvén eigenmodes and energetic particle modes
have been observed on START, MAST and NSTX in
neutral beam heated discharges. Chirping down
modes in STs were first observed on START. In
contrast to START, chirping modes on MAST often
exhibit a symmetric chirp up and down in
frequency simultaneously. This behaviour can be
described by the hole-clump model. MAST exhibits
post-sawtooth humpbacked fishbones as well as
conventional ones. EPD modes on MAST can trigger
long-lasting tearing modes with NTM features.
Results of the modelling (MISHKA and HAGIS codes)
of the mode structure and frequency sweeping show
good agreement with the experimental data and
with theoretical predictions.
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Impact of EPD MHD on START and MAST plasmas
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• Heidbrink NSTX/DIII-D
• The major radius dependence of Alfvén Eigen Modes
  stability is studeid by creating plasmas with
  similar minor radius, shape , magnetic field,
  density, Te, and beam population ( near
  tangential 80 keV deuterium injection) on both
  NSTX and DIIID. The major radius of NSTX is half
  of that of DIID.
• The stability threshed for the TAW is similar in
  the devices.
• The most unstable toroidal mode number n is
  larger in DIIID.

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K. ToiEnergetic-Ion Driven Alfvén Eigenmodes in
Large Helical Device Plasmas with
Three-Dimensional Structure and Their Impact on
Energetic Ion Transport

• 3D-configuration Non uniformity of the field
  strength on the magnetic surface in both poloidal
  toroidal diections.

• q-profile Negative shear configuration in the
  edge, and change to positive shear in the core
  with the increase in the toroidal beta.

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Eigenmode transition from TAE to GAE during time
evolution of i-profile

• When the minimum i(0) goes through 0.4, m2,3/n1
  TAE is converted to m3/n1 GAE and m2/n1 mode.
• m2/n1 mode will suffer from strong continuum
  damping, and it is consistent with exp. Results.
• This phenomenon is similar to RS-TAEs in a
  RS-plasma of JT-60U.

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Observation of new AEs in 3D-configuration(Helici
ty-Induced Alfven Eigenmodes)

• At low Btlt0.7T, coherent magnetic fluctuations
  less than 500 kHz in LHD are observed. Its
  frequency is about 8 times higher than TAE gap
  frequency.
• They will be Helicity induced Alfven Eigenmode
  (HAE) whose frequency is by about Nq-times higher
  than TAE-frequency.

S. Yamaoto et al., to be publshed in PRL (2003)
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MHD induced loss of energetic particles are also
observed in Helical Systems Osakabe LHD Increase
and/or decrease of fast neutral flux being
associated with the MHD-bursts were observed for
low magnetic field (Bt0.51.2T) LHD standard
configuration (Rax3.6m and 3.75m), for
co.-going particles, with dominant components of
the MHD burst being assigned as TAE of
n2/m34. Isobe CHS Escaping fast ion probe is
installed and observation shows that MHD activity
induces beam ion loss toward small R side.
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Evidence for the influence of fast ions on plasma
rotation(L.-G. Eriksson)

• The absorption by fast resonating ions of
  toroidal momentum carried by directed ICRF waves,
  and its subsequent transfer to the bulk thermal
  plasma, is found to influence the toroidal plasma
  rotation
• Discharges with co (90O antenna phasing) and
  counter (-90O) current propagating waves have
  been compared.
• A reference discharge with about 30 of 90o
  ICRF power exchanged for LH power was also
  performed, giving a lower stored energy and ion
  pressure.

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Carbon rotation profiles measured with the charge
exchange recombination spectroscopy using NBI
blips (method described in Noterdaeme et al.1)

• The 90o discharge rotates more strongly in the
  centre than 90o, consistent with fast ion
  absorption of wave momentum.

t51 s
(co-current wave momentum)
With LH

• LH discharge shows the difference is not due to
  modified WDIAor ion pressure.

1J.M. Noterdaeme et al, Nuclear Fusion 2003
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Orbit Topology/alpha channeling/Momentum
injection/Diffusion

• Wong DIII-D
• Alpha channelling is demonstrated by experimental
  data from the DIII-D tokamak.
• 1. It is shown that spontaneous redistribution of
  energetic ions by the excited Alfven eigenmodes
  can reduce the central magnetic shear and produce
  velocity shear at the same time - the two
  ingredients needed for ITB.
• 2. Quasi-steady-state ITB can be sustained in
  DIII-D when Alfven modes are excited. This
  experimental result demonstrates that the process
  envisioned in (1) can indeed occur.
• 3. This mechanism offers the possibility of
  having an ITB as a natural steady state of a
  burning plasma.
• 4. There may not be enough energetic alpha
  particles in the present ITER design to form an
  ITB, but it may be possible in a different
  design.
• 5. Partial effects, i.e., stabilization of part
  of the ITG turbulence, may be possible in ITER,
  and it can still be beneficial to plasma
  confinement.

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Orbit Topology/Ripples/Diffusion in Helical
Systems The ripple trapped energetic particle is
one of important issues in the development of a
reactor based on the helical system.
toroidal angle
Bcnst.
transition
Toroidalprojection(Boozer co.)
helically trapped
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Murakami LHD Radial transport of energetic
particles due to the ripple trapped
particle. Complex behavior and radial transport
of energetic ions during NBI and ICRF heating
using a global transport simulation code
(GNET) Ozaki LHD Charge Exchange Neutral
Particle Flux during Fueling Pellet Injection.
The decay times depend on the particle energy.The
radial information of the diffusion coefficient
obtained Saida LHD Effect of helical magnetic
field ripples on energetic particle confinement
was investigate. Matching of drift surfaces for
trapped particles and Magnetic flux surfaces is
important. Matsushita CHS DNB is scanned to see
the confinement of energetic partilces. Notake
LHD Electric Field effect on partilce orbit is
studied. Resonant Loss-cone, cancellation of ExB
drift and grad-B drift
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Zhao LAPD Liner basic plasma physics machine, 500
eV ions source. Plan for study of wave-particle
resonance between a helium beam and Alfven waves.
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• Diagnostics
• M. Sasao
• Overview of Fusion Products Measurements of ITER
• 10 sub-systems are now on the planned for fusion
  product measurement on ITER.
• Neutron emission rate (time response)
  measurement for burn control and MHD study will
  have the 1 MHz capability.
• Neutron /Alpha birth profile can be obtained by
  20 viewing chords and 7 viewing chords from the
  divertor. Deviation from the uniformity can be
  detected
• Measurement of confined alpha particle
  distributions is a challenge. Several proposals
  are now under examination.
• Escaping Alpha Diagnostics is a challenge.
  Several proposals are now under examination.

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Darrow JET/ITER Design of two lost alpha
particle diagnostics for JET They consist of a
poloidal array of five sets of thin foil Faraday
collectors, with good time resolution (1 kHz) A
scintillator based probe located slightly below
the midplane, the energy and pitch angle
distribution resolution The two candidate
scintillator materials, Y3Al5O12Tb (P53) and
Y2O3Eu (P56), both are luminous to at least 400
C, Experience in operating both diagnostics in a
high temperature and high radiation environment
will be valuable in preparation for the design of
similar diagnostics for ITER.

• Gyromotion of fast ions
• Particle selection by slits
• Light emission by scintillator

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Thin foil Faraday cups allow some energy
resolution

• Detector composed of multiple thin metal foils
• Ion energy determines deposition depth
• Ion current measured for each foil individually
• Current vs depth gives energy distribution
  (DE3050)

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Cecil JET/ NSTX / DIII-D A new lost ion
diagnostic on DIII-D and a redesigned probe on
NSTX. The Faraday foil collectors New Results
are shown. RoquemoreNSTX The neutron emission is
seen to be very sensitive to fast-ion related
phenomena such as MHD and internal reconnection
events. A study presented being performed to
evaluate the feasibility of installing a neutron
profile monitor on NSTX to spatially resolve the
fluctuations in the neutronsignal as well as
provide information on fast ion transport and
confinement. It is important to minimize
Backscattering Lu DIII-D Measurement of
re-neutralized beam ions for beam ion
profile. Gontcharov LHD The multidirectional
passive neutral particle analyzer has been
applied to investigate the behavior of
anisotropic distributions of suprathermal
protons Local measurements of the plasma ion
distribution function by detecting charge
exchange neutrals from an impurity pellet
ablation cloud. Osakabe LHD BLIP experiment was
performed with NPA to see the confinement of
energetic partilces. New technics based on the
Maximum Entropy and Maximum Likelihood
Method(MEMLM).
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V.V. Plyusnin Super-thermal and runaway electrons
at reconnection events during JET disruptions.
Study on major disruptions in JET spontaneous
and intentional has been carried out to further
understanding of the trends of disruption induced
runaway process. Runaway electron parameters
have been measured using the hard X-ray and
neutron diagnostics. Soft X-ray inverse
reconstruction and ECE measurements of the
electron temperature profile have been used in
order to investigate the effect of the magnetic
field re-arrangement at disruptions on the
runaway process. Soft X-ray inverse
reconstruction of the magnetic field evolution at
a reconnection event has shown that an
axis-symmetric confining configuration has been
created again in a very short time-scale (200
microseconds) after reconnection providing
confinement of the super-thermal or low energy
runaway electrons generated at this event.
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• Interaction between energetic ions and MHD
  perturbations are studied in major tokamaks,
  spherical tokamaks and LHD.
• Progress in understanding and development of
  tools for understanding (codes, diagnostic) will
  be made by collaboration between different
  configurations.