2003.10.7 2003 TCM-EP-M.Sasao 1

Overview of Neutron and Escaping Alpha Diagnostics Planned for ITER

M. Sasao1, A. V. Krasilnikov2, T. Nishitani3, P. Batistoni4, V. Zaveriaev5, Yu.A.Kaschuck2, S. Popovichev6, T. Iguchi7, O.N. Jarvis5, J. Kallne8,

C.L. Fiore9, Ray Fisher, L. Roquemore10, W.W. Heidbrink11,

A.J.H. Donné12, A.E. Costley13, C. Walker14

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

2003.10.7 2003 TCM-EP-M.Sasao 2

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

2003.10.7 2003 TCM-EP-M.Sasao 3

Background (1) Alpha Particle Related Physics

1. heating

2. particle diffusivity

3. Alfven Instability

4. particle stabilization of sawtooth oscillation, etc.

5. Localization of Escaping Alpha’s

6. 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)

Alpha particle physics in standard H-mode and in high n mode with ITB should be experimentally studied.

2003.10.7 2003 TCM-EP-M.Sasao 4

Overview of Neutron Diagnostics

Absolute neutron yield and fusion output measurementIn-Vessel and Ex-Vessel flux monitorsNeutron CameraNeutron Activation Systems (foil and water)

Fast Neutron emission rate measurement for Burn control and MHD studyIn-Vessel and Ex-Vessel flux monitors

Ti(r,t) measurementCompact Neutron Spectrometers in Radial Neutron CameraA big Neutron Spectrometer

Neutron /Alpha birth profilesNeutron Camera

Confined Alpha particle distributionsKnock-on Tail Neutron SpectrometersGamma-Ray spectrometers

Lost Alpha particlesLost- Detectors

2003.10.7 2003 TCM-EP-M.Sasao 5

In-Vessel -fission chambersEx-Vessel flux monitors

Fast time-resolved measurement of neutron emission rate

-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 235U and a ”blank” detector are proposed to be installed behind blankets # 11 and # 16.

Number of detectors and locations for other monitors are still under discussion.

2003.10.7 2003 TCM-EP-M.Sasao 6

235U -Counters

(1/v Property) 238U -Counters

(Threshold Property)

ITER requirement is 107 dynamic range

with 1 ms temporal resolution

with 10 % accuracy.

xCounting-mode Current-modeCampbelling mode

In-Vessel flux monitorsEx-Vessel flux monitors

2003.10.7 2003 TCM-EP-M.Sasao 7

10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9

Fusion output (W)

10 12 10 14 10 16 10 18 10 20

Neutron Source (s-1)

Neutron Flux behind blanket (s-1)

In-Vessel -fission chambers

10 3 10 5 10 7 10 9 10 11

Counting rate (s-1)

238U-chamber

235U-chamber

Current/campbelling mode

counting mode

counting mode

DD DTcalibration

10 -3 10 -1 10 1 10 3 10 5

10 0 10 2 10 4 10 6 10 8

Current/campbelling mode

2003.10.7 2003 TCM-EP-M.Sasao 8

In-Vessel -fission chambers

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

The thermalization time is a big concern for 235U. Thermalization is affected by surrounding materials and structures, and those between neutron source and detectors. 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.

2003.10.7 2003 TCM-EP-M.Sasao 9

Neutron /Alpha birth profiles

Radial Neutron Camera has been designed in detail.

A set of 12 viewing chords covers |Z-Z0| < 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.

2003.10.7 2003 TCM-EP-M.Sasao 10

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

0

0.2

0.4

0.6

0.8

1

1 2 3 4 5 6

(1-r/a) 0.5

(1-r/a)

(1-r/a) 2

(1-r/a) 3

(1-x) 2 :x=r 4 /(1+r 4 )

(1-x) 0.5 :x=r 4 /(1+r 4 )

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.

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1r/a

2003.10.7 2003 TCM-EP-M.Sasao 11

Additional viewing chords to Radial Neutron Camera

8 viewing chordsCovers |Z-Z0| > 0.5b

0

0.2

0.4

0.6

0.8

1

2 4 6 8 10

(1-r/a) 0.5

(1-r/a)

(1-r/a) 2

(1-r/a) 3

(1-x) 2 :x=r 4 /(1+r 4 )

(1-x) 0.5 :x=r 4 /(1+r 4 )

ch#

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.

2003.10.7 2003 TCM-EP-M.Sasao 12

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 PhysicsSelective production of trapped particles by ICRF, Selective loss of energetic ions in a 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.

2003.10.7 2003 TCM-EP-M.Sasao 13

Non uniform neutron emission on a magnetic flux surface ?

0

0.5

1

1.5

2

0 90 180 270 360

ε=0.1ε=0.2

ε=0.3ε=0.4

( ,Y sθ)

Poloidal angle

( ,Y s θ)= ( )(1+Y s εcosθ)

Non-uniformity on the MFS, caused by trapped particles, approximated by

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.

Y(s, θ)= ( )(1+Y s εcosθ)

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8 10

ch#

2003.10.7 2003 TCM-EP-M.Sasao 14

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

Non-uniformity on the MFS, caused by trapped particles can be distinguished by 7 additional chords of divertor camera.

Y(s, θ)= ( )(1+Y s εcosθ)

0

0.5

1

1.5

2

2.5

11 12 13 14 15 16 17

ch#

2003.10.7 2003 TCM-EP-M.Sasao 15

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

0

1 10 15

2 10 15

3 10 15

4 10 15

11 12 13 14 15 16 17

45 o bump90 o bump135 o bump

Neutron flux at the detector

ch#

0

1 10 15

2 10 15

3 10 15

4 10 15

-10 -5 0 5 10

45 o bump90 o bump135 o bump

Neutron flux at the detector

ch#0

0.5

1

1.5

2

0 90 180 270 360

Y(s,

θ)

Poloidal angle

Local high emissivity of 40% enhancement in poloidal direction is assumed and tested against 27 viewing chords. It can be resolved with 45o of poloidal angle resolution if the enhancement is higher than 40 %.

2003.10.7 2003 TCM-EP-M.Sasao 16

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.CO2 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

Major concern in red

2003.10.7 2003 TCM-EP-M.Sasao 17

Confined Alpha particle distributions -2

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

Gamma-ray spectroscopy 10B(, p) 13C reaction (V. Kiptily ) radial distribution of Be should be known

Major concern in red

2003.10.7 2003 TCM-EP-M.Sasao 18

Confined Alpha particle distributions -3

Alpha knock-on measurements

d t n

d

+

n

+

+ +d

+ +dt

Neutron high-energy tail

high energy deuteron or triton

2003.10.7 2003 TCM-EP-M.Sasao 19

Alpha knock-on measurements on NPA

Knock-on tritons are neutralized by the 1 MeV D0 beams (R. Fisher et

al.) or by electron capture from intrinsic impurities(Petrov), and analyz

ed by NPA.

Stripping foils can be used to separate energetic D+ from He 2+.

Calculations for ITER show NPA count rates up to 104/sec for deutero

ns of E > 1 MeV.

2003.10.7 2003 TCM-EP-M.Sasao 20

Knock-on Tail Neutron Spectrometers

Alpha knock-on measurements on the neutron high-energy tail

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

2003.10.7 2003 TCM-EP-M.Sasao 21

Lost alpha detectionLocalization (Subtask report by S.V. Konovalov, 2000)

246810R-6-4-20246Z

01000200030004000E (keV)0.00.20.40.60.81.0dN/dE

180200220240260280Θ0510152025HeatLoad(kW/m2)

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

FW region marked by the thick red line undergoes alpha particle bombardment. Analysis of TF Ripple Loss of Energetic Particles

Hea

t L

oad

(k

W/m

2)

2003.10.7 2003 TCM-EP-M.Sasao 22

Camera Viewing line

Candidates of Measurement Tools

Point measurement

( resolved) :

Faraday-cup sc

intillator probes

Loss imaging:

IR camera imaging

camera imaging of

scintillators on the FW

gamma-ray measurement from B

-FW, by 10B(, p) 13C reaction

(V. Kiptily )Probe/FC

Lost alpha detection

2003.10.7 2003 TCM-EP-M.Sasao 23

Neutron induced noise is 1- 4% of the signal level, for the FC and Scintillato

r 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

Summary of lost alpha detection

2003.10.7 2003 TCM-EP-M.Sasao 24

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 45o 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.

Summary

2003.10.7 2003 TCM-EP-M.Sasao 25

Prospect of performance of neutron subsystems :Oct. 2003

Sub systems Pfusion/Yn(t) Yn(r,t) Ti(r,t) f(E) FL(t)

In-Vessel -fission chambers0.1 - 1 MHz

(5%)

Ex-Vessel flux monitors

- 100 kHz (5%)

Radial Neutron Camera t:1-50 ms (5%)

t:1-50 ms (10%)

Vertical Neutron Camera t:1-50 ms (5%)

Neutron Activation System(foil) No time resolution (5%)

Neutron Activation System(water) t-50 ms (10%)

Gamma-Ray spectrometers t:>50 ms t>50 ms

Lost- Detectors 0.1 - 10 0 kHz

Knock-on Tail Neutron -MPR t>10 ms

Knock-on Tail Neutron BD No time resolution

Accuracy is in red

2003.10.7 2003 TCM-EP-M.Sasao 26

Background (1) - ITER

ITERBt (Max.) 5.3 (T)

R 6.2 (m)

a/R 3.1

Ip 15 (MA)

q95 3

N 1.8

Tpulse 300 - 1000 s

Fusion Power ~ 500 MW

Neutron Flux > 0.5 (MW/m2)

Pa ~ 100 MW

Q ~ 20

• To achieve extended burning in inductively driven plasmas at the capital Q larger than 10

• To aim at demonstrating steady -state operation by non-inductive current drive at Q > 5

• To retain the possibility of exploring controlled ignition

The technical requirements of ITER are

2003.10.7 2003 TCM-EP-M.Sasao 27

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 28

Alpha knock-on measurements on NPA

Knock-on tritons are neutralized by the 1 MeV D0 beams (R. Fisher et

al.) or by electron capture from intrinsic impurities(Petrov), and analyz

ed by NPA.

Stripping foils can be used to separate energetic D+ from He 2+.

Calculations for ITER show NPA count rates up to 104/sec for deutero

ns of E > 1 MeV.

2003.10.7 2003 TCM-EP-M.Sasao 29