ITPA-Moscow 060410

Role of neutron emission spectrometry on ITER and instrumental requirements

 Göran Ericsson

 E.Andersson Sundén, A.Combo2), S.Conroy, N.Cruz2), M.Gatu Johnson, L.Giacomelli,

W.Glasser, G.Gorini1), C.Hellesen, A.Hjalmarsson, J.Källne, R.Pereira2), E.Ronchi, H.Sjöstrand, J.Sousa2), M.Tardocchi1), and M.Weiszflog

Uppsala University [EURATOM-VR], Uppsala Sweden1) Univ. of Milano-Bicocca and Istituto di Fisica del Plasma [EURATOM-ENEA/CNR], Milan, Italy2) Instituto Superior Técnico [EURATOM-IST], Lisboa, Portugal.

1

CONTENTS OF PRESENTATION  

1 Introduction

2 ITER parameters from n spectrometry

3 Examples of n spectrometry results

4 NES capabilities (single sight-line)

5 LOS and interface considerations

6 Conclusion

ITPA-Moscow 060410

1 Neutron diagnostic systems and functions

Neutron diagnostics based on measurement of:

• Neutron inclusive flux: n

• Neutron collimated flux: Fn

- cameras for neutron emission tomography - neutron emission spectrometry

Direct (d) and in-direct (s, scattered) neutron flux components at detector

n= d + s and Fn= Fd + Fs

Neutron diagnostic systems – multi-parameter measurements:

• Fission chambers + activation foils

• Cameras: RNC + VNC

• Cameras + spectrometer

• Systems of spectrometers

Recent progress spectrometers - Europe:

• Two new n spectrometers operating at JET – TOFOR, MPRu (UU/VR)

• Unfolding techniques and detailed calibration of NE213 (ENEA, PTB)

• JET-EP2 – programs on compacts and digital electronics (ENEA, IST)

• “Study of Neutron Spectrometers for ITER”, J.Källne (UU/VR) 2

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2. Potential information in high power DT : neutron emission spectroscopy + camera

_____________________________________________________________________________________

A. Fuel ion kinetics(a) Thermal (T) population

(1) reaction rate (Rt)

(2) density product ndnt

(3) temperature TT*

(b) Population with significant supra-thermal (ST) velocity components; as above but(1) up to 4 ST reaction rate components (RST) besides RT

(2) relative densities of ST velocity components(3) TT and TST temperatures (if Maxwellian, otherwise slowing down)

 B. Confined -particles (1) amplitude of slowing down distribution*(2) pressure

 C. Collective motion of fuel ion populations(1) toroidal rotation*

 D. Fusion parameters(1) power Pf *; will provide values for dd and dt reactions separately

(2) division of Pf into thermal and supra-thermal components

(3) fuel ion densities in the core (nd, nt and nd/nt*)+)

E. Other information(1) the extended spectrum of direct and scattered neutrons from the plasma

_____________________________________________________________________________________* Denotes diagnostic functions listed as essential for measurement on ITER +) Requires simultaneous measurement of 2.5-MeV neutrons from dd and 14-MeV from dt.

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3 Some selected NES results from JET (MPR)

• Ohmic phase – thermal Ti extracted• RF phase – isotropic, anisotropic HE components

• LE component due to scattered n

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Peak (energy) shift shown in pulses with different phasing of RF antenna

Alpha knock-on neutrons

102

103

104

105

0

4

8

(a)

Cn [H

z]

PN

B [MW

]

PNB(D)

PNB(T)

Cn

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

12 13 14 15 16

ST, MPRTRANSP

Spe

ctra

l fra

ctio

n

Time [s]

(b)

Count rate power

Spectral components thermal fraction

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102

103

104

105

0

4

8

(a)

Cn [H

z]

PN

B [MW

]

PNB(D)

PNB(T)

Cn

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

12 13 14 15 16

ST, MPRTRANSP

Spe

ctra

l fra

ctio

n

Time [s]

(b)

Count rate power

Spectral components thermal fraction

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Alpha knock-on neutrons

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Peak (energy) shift shown in pulses with different phasing of RF antenna

Alpha knock-on neutrons

102

103

104

105

0

4

8

(a)

Cn [H

z]

PN

B [MW

]

PNB(D)

PNB(T)

Cn

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

12 13 14 15 16

ST, MPRTRANSP

Spe

ctra

l fra

ctio

n

Time [s]

(b)

Count rate power

Spectral components thermal fraction

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4 NES capabilities (single sight-line)

• Energy calibration: Independent and absolute calibration station For toroidal rotation vtor < 10km/s

E < 3 keV

• Energy resolution (instrumental, derived, …)For temperature Ti = 4 keV

dE/E = 2.5%

• Sensitivity (S:B)For AKN, RF, TBN S:B > 10000

• Time resolution in derived quantities (Ccap, LOS, )For Ti(t) t < 10 msFor Qth/Qtot t < 200 ms

• Separate direct and scattered fluxE range, low-En sensitivity benchmarking of n transp. calc.

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Magnetic proton recoil

• System in operation at JET• Classic nuclear physics instr.• Separate tasks: passive n-to-p, passive E det., active p counting• f(En) from f(xp)• Near-Gaussian response function• Abs. calibration in E and • Flexibility, 1 < En < 18 MeV• Separate Fd and Fs, E bite 20%• dE/E = 2.5%, E < 2 keV (10-4)• S:B > 10000• Ccap > MHz• t < 5 ms (for Ti) @ 1 MHz• Size (>m3), magnetic, efficiency (0.5.10-4 cm2)

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MPR instrumental response function (2.5% FWHM @ 14MeV)

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Magnetic proton recoil

• System in operation at JET• Classic nuclear physics instr.• Separate tasks: passive n-to-p, passive E det., active p counting• f(En) from f(xp)• Near-Gaussian response function• Abs. calibration in E and • Flexibility, 1 < En < 18 MeV• Separate Fd and Fs, E bite 20%• dE/E = 2.5%, E < 2 keV (10-4)• S:B > 10000• Ccap > MHz• t < 5 ms (for Ti) @ 1 MHz• Size (>m3), magnetic, efficiency (0.5.10-4 cm2)

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Neutron detector test and calibration station:• MPRw: A w-detector can be developed to improve the time resolution and

dynamic range of the diagnostic in, e.g., yield measurements.

• MPRx: A test/calibration facility for flux detectors in well-characterized Fn(En)MPR

MPRw/x

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5 LOS considerations

• Ideal case: 3 spectrometer systemco-, counter (NBI) tangential, radial

• Next best: co-tangential and radial• Single instr: TBD• Present ITER design: radial LOS?

• Previous studies:NBI – counter-tangential best, co- OKICRH – radial best, tangential OKAKN – co-tangential viewing best, radial OKQth/Qtot – dual LOS best, radial OKYield – tangential LOS best, radial OK

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MPR needs 1010 n/cm2 on foil for full performance

(n camera?)

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6 Summary and conclusions

• High-performance n spectrometer of MPR type:• State of the fuel ions: Ti, ST comp., AKN, vrot, …• Absolute, independent yield determination, Qth/Qtot

• Absolutely calibrated (E,) n detector test station• Scattered n flux for n transport calc. benchmarking

• Interface issues, magnetics

THANK YOU !

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Summary prel. capabilities and requirements @ 14 MeV

MPR TOF14 NDD NE213 ”Required”

Designed system

Conceptual design

Best achieved

Best achieved

Ccap >MHz 50 kHz > MHz 250 kHz N/A

dE/E 2.5% 2.5% 2% 1-2%* <2.5%

(cm2) 0.5.10-4 1.10-2 1.10-4 0.1 N/A

E < 2keV ? ? ? <3 keV

S:B >10000 100 ? 50 >10000

t (Ti) 5 ms 100 ms 5 ms? 250 ms <100 ms

E range 1-18 MeV >10 MeV? >13 MeV 1-18 MeV§ 1-18 MeV

Separation dir. – scatt.

Yes Yes? No? No? Yes

* Derived from unfolding, not instumental as for others

§ Single peaks, prob. not weak (%) LE components

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TOF-14

• Coincidence measurement, n double scattering• Near-Gaussian resp. fcn• f(En) from f(tn’)• Calibration with gammas, muons, sources• High efficiency, 0.01 cm2 ? (14 MeV) @ dE/E = 2.5%• Ccap = 50 kHz (14 MeV) ?• Signal:accidentals = 100 (sensitivity)• t < 100 ms (for Ti)

• Size (>m3), performance, complicated (100’s detectors)

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Diamonds (NDD, CVD)

• Detector in n ”beam”• Full En deposited: 12C(n,)9Be• Radiation hard, high T oper.• dE/E > 2%• Ccap = MHz• Complicated resp fcn - 9Be*, 12C(n,n), (n,3 n’)• f(En) from f(Q)• Individual detector calibration• Small size, low efficiency • Limited experience base

• Resp.fcn, bandwidth, availability/cost, charge trapping

n

NDD

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Scintillator ”compacts” (NE213)

• Detector in n “beam”• n/ separation (PSD)• Complicated resp fcn – H(n,p) single and multiple, 12C(n,n), inelastic channels• Each detector calibrated at accelerator• f(En) from unfolding• Stability monitoring (Cn, T, t)• P.h. resolution 5-8% • dE/E = 1-2% (unfolded) ?• Sensitivity 2% (unfolded) ?• Ccap > 200 kHz ?• t < 250 ms (for Ti) ?• Calibration, stability, performance

n

NE213

n’