Pellet Charge Exchange Measurement in LHD

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Pellet Charge Exchange Measurement in LHD ITER
ITPA 2006.9.4-8 Tohoku Univ.
Tetsuo Ozaki, P.Goncharov, E.Veschev1), N.Tamura,
K.Sato, D.Kalinina and S.Sudo National Institute
for Fusion Science 1)Graduate Univ. for Advanced
Studies
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Pellet Charge Exchange Measurement
?Direct measurement of energetic particles in
plasma(proton, alpha etc.) ?Background neutral
for charge exchange is required in passive
measurement Difficult to obtain central
information due to low back ground neutral around
the plasma center.
Double charge exchange is necessary to measure
a-particle Line integration ?Pellet Charge
Exchange (PCX) by combination of TESPEL CNPA
PCX has been tried in TFTR for a-particle
measurement New results can be obtained even in
non-DT plasma device ?Diagnostic
development (1) Establishment of the PCX
technique for proton (1/4 mass of a) (2)Try
helium ion measurement by using PCX (3) PCX in
ITER
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Diagnostic Principle of PCX
By measuring the charge exchange particle just
behind the pellet trajectory, the time trace of
the particle emission can be translated to the
spatial distribution.
dl Dti ?vpel
(Typically 100µs )
vpel 500m/s? 5cm Corresponding to the ablation
diameter
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Experimental Apparatus
CNPA(Compact Neutral Particle Analyzer) Channel
40 Energy resolution Typically
several Energy range 0.8168 keV
Time resolution 100µs
Compact NPA
CNPA Viewing Cone
Pellet Injection Axis
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Experimental Setup
SD-NPA
SD-NPA 25 400keV 2048 ch Pitch Ang.
4590deg 6 cords
CNPANDD
NBI 4
NDD(Natual Diamond)
TESPEL
CNPA
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Typical CNPA results in ICH plasma
NBI1
NBI1
ICH5
ICH5
NBI4
NBI4
Central heating
Standard heating
ICHNBI1(??)?ICHNBI14(?) ?ICHNBI4(??) Clos
ed marks(??) mean the standard heating, open
marks(???) mean the central heating of ICH. The
difference of both cases is remarkable in the
ICHNBI1. Particles from NBI4 is also obviously
observed.
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Difference of the resonance positions in PCX
?Time trace of the charge exchange particle flux
during TESPEL injection. Here the time means the
pellet penetration depth. The pellet reaches
r0.1. Vertical axis shows the particle energy.
ICH 2nd harmonics -1.375T Standard heating -1.25T
Central heating In -1.375T, the flux increase at
r 0.5. However in -1.25T, no enhancement of the
flax appears.
Rax3.6,Bt-1.25T
Rax3.6,Bt-1.375T
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Difference of the resonance positions in
PCX(cont.)
ICH 2nd harmonics Standard heating
ICH 2nd harmonics Central heating
In the standard heating?the flux increases at r
0.5. In the central heating, the flux increase
can not be found because the the pellet
trajectory is not cross the resonance surface.
Standard
Central
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Difference of the ICH power
ICH 2nd harmonics Standard heating Flux
increase is depended on the ICH power.
1.1MW
0.74MW
0.6MW
0.29MW
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NBI4
NBI4 Only
Calculation by T.Watanabe
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SD-NPA scan during ICH long discharge(Vertical
sight lines)
Case1 Similar pitch angles
Vertical
Energy
Flux increase at the resonance surface can be
observed in SD-NPA vertical scan.
Vertical
Time (Position)
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helium detection in CNPA
Detector
Z
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Spot on Detector
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Energy loss in Cloud
(by Sergeev)
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He(?)
Pellet velocity 440m/s At plasma edge(?1), the
helium/hydrogen ratio of 0.085 is measure by
visible spectrometer . We assume that the ratio
is at the energy of 11keV(minimum energy)
H
He
?Scattering of the hydrogen atom
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He3 minority heating experiment
He-3 minority experiment had been tried in LHD
9th experimental campaign. He4 was used as the
majority target gas. Small increase of the
temperature could be obtained because the
hydrogen still remained. We have plan to measure
the He-3 spectrum/profile in the next
experimental campaign.
Ti
ICH
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Problem of PCX in ITER
Fisher,RSI
ITER ne1x1020 (m-3) TeTi19.7(1-(r/a)2)0.3
(keV)
Large pellet with high velocity is required. ?
plasma perturbation Small charge exchange cross
section of D,T ? TECPEL (Tracer EnCapsulated
PELlet) low perturbation good spatial
resolution no special equipment
Fisher,RSI
Li, Be
D,T (fuel)
TECPEL
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Neutron and Gamma ray shielding
Medley,RSI(TFTR)
ITER Neutron, gamma 1013 /cm2s on the wall
Shield requirement TFTR 21016 /s Detector
position 10m 8x108 /cm2s Neutron flux in ITER
104 of TFTR 6-inchs (polyethylene)4-inchs
(lead) neutron reduction 1/100 (TFTR)
?45cm(polyethylene)30 cm(lead )
TFTR neutron shielding
ITER neutron spectrum
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Neutral Particle Analyzer for ITER
EB Detector saturation due to
the strong n, g-ray, high detection
efficiency TOF(Frascati) Time-of-flight for
particle species selection, Low detection
efficiency GEMMA(Ioffe) Exchange to light,
intermediate detection efficiency
Scintillator material (prefer thin film in
order to reduce the radiation noise) ZnS(Ag) low
X-ray detection efficiency long decay time (70
ms) ?CsI(Tl) Deliquescence, but to be
resolved by aluminum coating for light
protection short decay time
GEMMA
Optical fiber
Other improvement Reference detector for noise
reduction Detector is far from the scintillator
by using optical fiber ?Shielding?reduce the
magnetic effect for the photo-multiplier, reduce
the radiation noise
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Summary
?The preliminary demonstration of the alpha
particle diagnostics using PCX and SD-NPA has
been done. ? The high-energy particle flux
enhancement around the resonance surface of ICH
can be observed in the standard heating mode of
ICH 2nd harmonics. ?The helium profile
measurement has been tried by using PCX. ? PCX
in ITER has been presented.
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