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Overview of Neutron and Escaping Alpha Diagnostics Planned for ITER

2003.10.7

M. Sasao 1 , A. V. Krasilnikov 2 , T. Nishitani 3 , P. Batistoni 4 , V. Zaveriaev 5 , Yu.A.Kaschuck

2 , S. Popovichev 6 , T. Iguchi 7 , O.N. Jarvis 5 , J. Kallne 8 , C.L. Fiore 9 , Ray Fisher, L. Roquemore 10 , W.W. Heidbrink 11 , A.J.H. Donné 12 , A.E. Costley 13 , C. Walker 14 1 Tohoku Univ.; 2 TRINITI; 3 JAERI; 4 FERC; 5 Kurchatov Inst.; 6 JET-EFDA/CSU; 7 Nagoya Univ.; 8 Uppsala Univ.; 9 MIT.; 10 PPPL; 11 UC Irvine; 12 FOM-Inst.; 13 ITER IT, Naka; 14 ITER IT, Garching

2003 TCM-EP-M.Sasao

Out lines

1. Background 2. Neutron emission rate (time response) measurement for burn control and MHD study 3. Neutron /Alpha birth profiles 4. Confined Alpha particle distributions 5. Escaping Alpha Diagnostics 6. Summary

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2003 TCM-EP-M.Sasao

Background (1)

Alpha Particle Related Physics



heating



particle diffusivity



Instability Alfven



particle stabilization of sawtooth oscillation, etc.

Localization of Escaping Alpha’s



ash density controle Scenarios: A) Standard ELMy H-mode (300 sec)

n =1.5 - 2 B) Hybrid (1000 sec) :

n > 2 C) Steady-state operation

n > 2 An ITB may be created in a region of low (or reversed) magnetic shear in the vicinity of the rational q surface in scenario B) & C)

2003.10.7

Alpha particle physics in standard H-mode and in high

n mode with ITB should be experimentally studied.

2003 TCM-EP-M.Sasao

Overview of Neutron Diagnostics

Absolute neutron yield and fusion output measurement



In-Vessel and Ex-Vessel



Neutron Camera flux monitors



Neutron Activation Systems (foil and water) Fast Neutron emission rate measurement for Burn control and MHD study



In-Vessel and Ex-Vessel flux monitors T i (r,t) measurement



Compact Neutron Spectrometers in Radial Neutron Camera



A big Neutron Spectrometer Neutron /Alpha birth profiles



Neutron Camera Confined Alpha particle distributions



Knock-on Tail Neutron Spectrometers



Gamma-Ray spectrometers Lost Alpha particles Lost-



Detectors

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2003 TCM-EP-M.Sasao

Fast time-resolved measurement of neutron emission rate



In-Vessel

-fission chambers



Ex-Vessel monitors flux

-fission chambers are pencil size gas counters with fissile material, and have been developed to be installed in the vacuum vessel of ITER.

At present, a combination of blankets # 11 and # 16.

235 U and a ”blank” detector are proposed to be installed behind Number of detectors and locations for other monitors are still under discussion.

2003.10.7

2003 TCM-EP-M.Sasao

In-Vessel Ex-Vessel flux monitors flux monitors

ITER requirement is 10 7 dynamic range with 1 ms temporal resolution with 10 % accuracy.

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235 U -Counters (1/v Property) 238 U -Counters (Threshold Property)

Counting-mode Current-mode Campbelling mode

2003 TCM-EP-M.Sasao

In-Vessel

-fission chambers

10 -3 238 U-chamber 10 -1 235 U-chamber 10 0 10 3 10 2 10 5 10 1 2 calibration 10 0

2003.10.7

10 1 10 1 counting mode 10 4 10 7 Current/campbelling mode counting mode 10 3 Current/campbelling mode 10 5 10 6 8 Counting rate (s -1 ) 9 1 1 Neutron Flux behind blanket (s -1 ) 10 2 10 1 4 10 3 10 4 10 1 6 DD 10 5

2003 TCM-EP-M.Sasao

10 6 10 1 8 DT 10 2 0 Neutron Source (s -1 ) 10 7 10 8 10 9 Fusion output (W)

In-Vessel

-fission chambers

During the full DT operation, counting rates are in the range of 100 MHz for 235 U, and 100 kHz for 238 U. The

thermalization time

is a big concern for Thermalization is affected by surrounding materials and structures, and those between neutron source and detectors. 235 U. The typcical time is to be order of 1

sec. More detail assessment is needed with neutron transport code. The frequency range of high frequency macro instabilities (Fishbones and TAEs) is expected in 30 kHz - 300 kHz.

In-vessel

-fission chambers have capability to cover this range.

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2003 TCM-EP-M.Sasao

Neutron /Alpha birth profiles Radial Neutron Camera has been designed in detail.

A set of 12 viewing chords covers |Z Z 0 | < 0.5b. Only line-integrated neutron emission is measured by each chord. Alpha particle birth profiles can be obtained by assuming a simple analytical form as a function of MFS.

Limited plasma coverage. The fraction of neutrons not seen by camera can be larger than10- 20 % Each chord will be equipped with total flux detectors and compact spectrometers. Combination of different detectors are needed to cover the wide range in the expected level of the flux.

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2003 TCM-EP-M.Sasao

Can the change of alpha birth profiles due to ITB be observed by the Radial Neutron Camera of 12 viewing chords?

0.8

0.6

1 0.5

(1-r/a) (1-r/a) 2 (1-r/a) (1-r/a) (1-x) (1-x) 3 2 :x=r 0.5

4 :x=r /(1+r 4 4 ) /(1+r 4 ) 0.4

0.2

0 1 2 3 4 5 6 ch# Errors might be dominantly from change of back scattered neutrons and gamma’s, and change of detector efficiency. The 2% of maximum flux is assumed for every channels.

Profile parameter and a strong ITB profile can be detected, but a moderate ITB cannot be recognized, with 12 viewing chords.

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1.2

1 0.8

0.6

0.4

0.2

0 0 0.2

0.4

r/a 0.6

0.8

0.6

1 Additional viewing chords to Radial Neutron Camera 0.5

(1-r/a) (1-r/a) 2 (1-r/a) (1-r/a) (1-x) (1-x) 3 2 :x=r 0.5

4 /(1+r :x=r 4 /(1+r 4 ) 4 ) 8 viewing chords Covers |Z-Z 0 | > 0.5b

0.4

0.2

0 2 4 ch# 6 8 10 Addition of 8 chords substantially improves accuracy of the profile parameter and determination of the ITB structure.

However, the analysis is on the assumption of uniform neutron emission on a magnetic flux surface.

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2003 TCM-EP-M.Sasao

Is the neutron emission uniform on a magnetic flux surface ?

Non-uniformity on the MFS, caused by trapped particles, has been observed at JET[1]. Interesting Physics Selective production of trapped particles by ICRF, Selective loss of energetic ions in a

r

space induced by MHD, Redistribution of ions during sawtooth oscillation Can those interesting phenomena be observed ?

JET KN3 profile monitor uses 2D-tomography.

This analysis employs a hybrid pixel/analytic algorithm [8], which involves a poloidal Fourier analysis and a radial Abel inversion, starting from outside and working inward.

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2003 TCM-EP-M.Sasao

Non uniform neutron emission on a magnetic flux surface ?

1.5

2 Y(s ,



)=Y(s)(1+



cos



)

 .1

 .2

 .3

 .4

1.2

0.8

0.6

1 1 0.4

0.5

0.2

0 0 90 180 Poloidal angle 270 360 0 0 2 4 ch# 6 8 10 Non-uniformity on the MFS, caused by trapped particles, approximated by Y(s,



)=Y(s)(1+



cos



) This cannot be distinguished by 20 chords of radial camera.

Mean while, Channels of #-1 ~ #-10 are viewing lower half of the cross section. Up-down asymmetry, and vertical movement can be clearly detected by comparison of those with Channels of #1 ~ #10.

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Additional Viewings (DNC) are proposed by NWG [Krasilnikov et al.] Y(s,



)=Y(s)(1+



cos



) 2.5

2 1.5

1 0.5

0 11 12 13 14 ch# 15 16 17 Non-uniformity on the MFS, caused by trapped particles can be distinguished by 7 additional chords of divertor camera.

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Poloidal resolution of the alpha birth profile by 27 chords, 12 present radial chords, 8 additional, plus 7 additional Divertor chords.

4 10 15 2 1.5

3 10 15 45 o bump 90 o bump 135 o bump 2 10 15 1 1 10 15 0.5

0 0 0 -10 4 10 15 -5 0 ch# 5 10 90 180 Poloidal angle 270 360 3 10 15 Local high emissivity of 40% enhancement in poloidal direction is assumed and tested against 27 viewing chords. It can be resolved with 45 o of poloidal angle resolution if the enhancement is higher than 40 %.

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2 10 15 1 10 15

2003 TCM-EP-M.Sasao

0 11 12 45 o bump 90 o bump 135 o bump 13 14 ch# 15 16 17

Confined Alpha particle distributions -1

Measurement of confined alphas is a big challenge on ITER. Several methods are proposed and feasibilities are studied.



Collective Thomson scattering, several approaches.

CO 2 high power laser (50 J, 10 Hz) with the scattering angle of 0.5 degree (Kondoh) injected from the divertor port. Launching of 50-65GHz radiation from tuneable gyrotron and receiving from the top and bottom of a single equatorial port (H. Bindslev ) Launching 1-2 MW at 170 GHz in the O- mode from an equatorial port and collecting the scattered radiation from the upper port (U. Tartari) Stray beam / operational window changes /ECE background



Charge Exchange Recombination Spectroscopy on the heating beam A signal-to-background-ratio on the DNB Beam attenuation with gas-jet Plasma perturbation

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2003 TCM-EP-M.Sasao

Major concern in red

Confined Alpha particle distributions -2



Charge Exchange Neutralization with high energy neutral beams use a tangential 3 He beam with energy 0.8-1.5 MeV from port 6(Sasao).

accessibility and beam development



Gamma-ray spectroscopy 10 B(



, p

) 13 C reaction (V. Kiptily ) radial distribution of Be should be known

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2003 TCM-EP-M.Sasao

Major concern in red

Confined Alpha particle distributions -3



Alpha knock-on measurements

t 

high energy deuteron or triton

 t

d d

 

Neutron high-energy tail

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Alpha knock-on measurements on NPA

Knock-on tritons are neutralized by the 1 MeV D 0 beams (R. Fisher et al.) or by electron capture from intrinsic impurities(Petrov), and analyzed by NPA.

Stripping foils can be used to separate energetic D + from He 2+ . Calculations for ITER show NPA count rates up to 10 4 /sec for deuterons of E > 1 MeV. 2003 TCM-EP-M.Sasao

Alpha knock-on measurements on the neutron high-energy tail Knock-on Tail Neutron Spectrometers Alpha knock-on neutrons are measured at JET by MPR.

J. Källne, L. Ballabio, J. Frenje, S. Conroy, G. Ericsson, M. Tardocchi, and E. Traneus PHYSICAL REVIEW LETTERS,85,1246(2000) Neutron high-energy tail potentially be measured by Magnetic Proton Recoil (MPR) spectrometer or bubble detectors.

One potential way to install MPR on ITER is along the side the neutron camera.

Separation of other energetic ions, signal to noise ratios Major concern in red

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Lost alpha detection

Localization (Subtask report by S.V. Konovalov, 2000) FW region marked by the thick red line undergoes alpha particle bombardment. Analysis of TF Ripple Loss of Energetic Particles

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2003 TCM-EP-M.Sasao

Poloidal distribution of the heat load. Red histogram corresponds to banana particle loss and blue one shows locally trapped



loss

Lost alpha detection

Candidates of Measurement Tools Point measurement (

r

resolved) : Faraday-cup scintillator probes Loss imaging : IR camera imaging camera imaging of scintillators on the FW gamma-ray measurement from B-FW, by 10 B(



, p

) 13 C reaction (V. Kiptily )

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2003 TCM-EP-M.Sasao

Camera Viewing line Probe/ FC

Summary of lost alpha detection

Neutron induced noise is 1- 4% of the signal level, for the FC and Scintillator probe, when loss is 1% of the maximum level.

IR camera imaging => robust, but no discrimination, slow Camera imaging of scintillators on the FW



robust, discrimination of from other plasma particles should be tested, PM+filter should be tested Faraday-cup detectors, => cables should be tested for nA range measurement Scintillator probes, => Cooling system should be designed

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2003 TCM-EP-M.Sasao

Summary

1. 10 sub-systems are now on the planned for fusion product measurement on ITER. 2.

Neutron emission rate (time response) measurement for burn control and MHD study will have the 100 MHz capability, but the effective time-resolution should be assessed with neutron transport code.

3. Neutron /Alpha birth profile can be obtained on the assumption of uniformity on MFS by the addition of 8 viewing chords. Deviation from the uniformity can be detected with 45 o of the poloidal angle resolution by the addition of 7 viewing chords from the divertor.

4. Measurement of confined alpha particle distributions is still a challenge. Several proposals are now under examination.

5. Escaping Alpha Diagnostics is still a challenge. Several proposals are now under examination.

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2003 TCM-EP-M.Sasao

Prospect of performance of neutron subsystems :Oct. 2003

Sub systems In-Vessel

-fission chambers Ex-Vessel monitors flux Radial Neutron Camera Vertical Neutron Camera Neutron Activation System(foil) Neutron Activation System(water) Gamma-Ray spectrometers Lost-



Detectors Knock-on Tail Neutron -MPR Knock-on Tail Neutron BD

2003.10.7

P fusion /Y n (t) 0.1 - 1 MHz (5%) - 100 kHz (5%) No time resolution (5%)

t-50 ms (10%) Y n

2003 TCM-EP-M.Sasao

(r,t) T i (r,t)

t:1-50 ms (5%)

t:1-50 ms (10%) f



(E) F L



(t)

t:>50 ms

t>50 ms 0.1 - 10 0 kHz

t>10 ms No time resolution Accuracy is in red

Background (1) -

ITER

ITER

• • •

The technical requirements of ITER are To achieve Q larger than 10 extended burning in inductively driven plasmas at the capital To aim at demonstrating steady -state operation by non-inductive current drive at Q > 5 To retain the possibility of exploring controlled ignition

2003.10.7

2003 TCM-EP-M.Sasao

B t (Max.) R a/R I p q 95

N T pulse Fusion Power Neutron Flux P a Q 5.3 (T) 6.2 (m) 3.1

15 (MA) 3 1.8

300 - 1000 s ~ 500 MW > 0.5 (MW/m 2 ) ~ 100 MW ~ 20

Environment and Restriction for FC

Neutron Noise on the FC => less than 2%, for 0.01*max. loss but not negligible Dummy probes are necessary.

RIC, RIEMF might be problems for current measurement of nA range.

( recent study on RIEMF indicates the effect of nuclear transmutation) Twisted cables should be tested.

Discrimination from fast ions might be a problem.

2003.10.7

2003 TCM-EP-M.Sasao

2003.10.7

Alpha knock-on measurements on NPA

Knock-on tritons are neutralized by the 1 MeV D 0 beams (R. Fisher et al.) or by electron capture from intrinsic impurities(Petrov), and analyzed by NPA.

Stripping foils can be used to separate energetic D + from He 2+ . Calculations for ITER show NPA count rates up to 10 4 /sec for deuterons of E > 1 MeV. 2003 TCM-EP-M.Sasao

2003.10.7

2003 TCM-EP-M.Sasao