TOF spectrometers for measurement of nd/nt ratios

K.Okada, T.Nishitani2, K. Ochiai2, K.Kondo2, M.Sasao, M. Okamoto, K.Shinto, S.Kitajima

Tohoku Univ. 2JAEA

OUTLINE

Concept Neutron Spectrum in a collimator-optimaization with MCNP Time-of-flight (TOF) spectrometer designTime-of-flight (TOF) spectrometer design High-counting-rate TOF electronics POP experiment of High-counting-rate TOF electronics Future work and Summary

2/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

Neutron Spectrum in a collimator - optimaization with MCNP(1)

H areaBlanket

SUS 316LNVacuum vessele

20 deg.

10 m

Collimatorradius:10 cm

Reflection of all particle

First wall

Estimation of scattered/energy-degraded neutrons originated DT neutrons

The fuel ratio in center of plasma

line of sight on center of plasma

3/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

Neutron Spectrum in a collimator - optimaization with MCNP(2)

In a neutronics calculation on the model of ITER, the possibility of separating the DD component from that of the DT reaction was examined. The separation in a neutron spectrum is possible at an appropriate measurement position with a collimator 1–10 cm in diameter.

4/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

Neutron Spectrum in a collimator - optimaization with MCNP(2)

0 1 2 3 4 5 6 7 8 9 10111213141516170.0

5.0x10-13

1.0x10-12

1.5x10-12

2.0x10-12

2.0 2.5 3.0 3.5 4.0 4.50.0

1.0x10-15

2.0x10-15

3.0x10-15

4.0x10-15

5.0x10-15

Energy [MeV]

total DD DT

(distance from center of plasma : 10 m, collimator radius : 10 cm)

Ti=25 keV

0.5 MeV

The energy resolution demanded is below 0.5 MeV grade.

Neu

tron

flu

x

[

/0.1

MeV

/cm

2/s

our

ce] 2.0

1.5

1.0

0.5

5/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

Time-of-flight (TOF) spectrometer designTime-of-flight (TOF) spectrometer design

a

0.000E+005.000E-041.000E-031.500E-032.000E-032.500E-033.000E-033.500E-034.000E-034.500E-035.000E-03

0 0.2 0.4 0.6 0.8 1

Energy resolution [MeV]

neutron flux [/source]

0.2cm0.5 cm1 cm2 cmd2

d1d

L

n

n’

The second detector

R

W

The optimization is on going using MCNP calculationfor both high detection efficiency for interesting events (2-3 MeV) and the energy resolution.

> 35 [deg.]70~ [cm]

5 ×10×~1 [cm]30×60×2 [cm]

scatter angle q distance Ld1 sized2 size

Optimal value

6/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

High-counting-rate TOF electronics(1)

• Number of interesting events is only ~1/1000 of total e

vents.

• Fast rejection of DT neutrons and gamma events in th

e D1 detector is essential.

• The TOF geometry defines the energy loss (pulse heig

ht) of DD neutrons in the D1 detector.

• We propose fast selection of interesting events by puls

e height discrimination.

7/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

DD 65 nsDL1

d1 PMT

HV

LinearFAN-in/out

LinearFAN-in/out

Discri

Discri

Discri

Coin

GDG TAC

Delay

ADC

MCA

Delay TAC

ADC MCA

d2

HV

PMTLinearFAN-in/out

Discri

-2300 V

-1300 V

DT

Anti

65 ns

Gate

start

stop

start

stop

DL2

DL3

Target room

Target room

d1～ DD stop

d1～ DT stop

start

DL5

Control room

High-counting-rate TOF electronics(2) Experiment circuitExperiment circuit

8/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao0 200 400 600 800 10000.00

0.02

0.04

0.06

0.08

0.10

ch

POP experiment of High-counting-rate TOF electronics at FNS, JAEA

DTDD

-ray

Total TOF spectrum

Time (ch)

Using contaminated deuterium in the tritium target, the principle has been tested at FNS.D1 - 0.5 cm t NE102A (active divider had a trouble) , D2-NE201A, 60 cm apart, 0.35 deg.

cps

9/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

POP experiment of High-counting-rate TOF electronics(2)

0 200 400 600 800 10000.00

0.02

0.04

0.06

0.08

0.10

ch0 200 400 600 800 10000.00

0.02

0.04

0.06

0.08

0.10

ch

DTDD

-ray

Total TAC spectrum

DT spectrum

Separation by a circuit

0 20 40 60 80 100 1200.0

5.0x10-7

1.0x10-6

1.5x10-6

2.0x10-6

2.5x10-6

3.0x10-6

3.5x10-6

time [ns]

DT time spectrum

conversionDT spectrum is separated from total spectrum by fast Discri.

10/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

0 200 400 600 800 10000.0

1.0x10-3

2.0x10-3

3.0x10-3

4.0x10-3

5.0x10-3

6.0x10-3

7.0x10-3

ch

DD peak

DT peak

g-ray

12C(n,n’g)12C

16.7 ns44.3 ns

POP experiment of High-counting-rate TOF electronics- DD output of TAC DD output of TAC (3)

0 200 400 600 800 10000.00

0.02

0.04

0.06

0.08

0.10

ch

DTDD

-ray

Total TAC spectrum

DD separation is not perfect due to the active devider trouble, but the DT component is reduced more than factor 10, by fast Discri.

Separation by a circuit

11/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

POP experiment of High-counting-rate TOF electronics(3)

DD energy spectrumDD energy spectrum

0 1 2 3 4 5

1.0x10-6

2.0x10-6

3.0x10-6

4.0x10-6

5.0x10-6

6.0x10-6

Energy [MeV]

DD peak

DD spectrum is separated from total spectrum

12/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

Future work and Summary (1)

• In a neutronics calculation on the model of ITER, the possibility of

separating the DD component from that of the DT reaction was

examined. The separation in a neutron spectrum is possible at an

appropriate measurement position with a collimator 1–10 cm in

diameter and a spectrometer with energy resolution better than 0.5

MeV. • The optimization TOF spectrometer design is on going using MCNP ca

lculationfor both high detection efficiency for interesting events (2-3

MeV) and the energy resolution. High detection capability with 0.5 MeV

energy resolution can be realized with a single D2 detector. • We proposed a high counting rate TOF electronics using fast selectio

n of interesting events by fast pulse height discrimination (<10 ns).• FNS experiment showed the POP of the high counting rate TOF electro

nics.

13/1310th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

Future work and Summary (2)

• After changing the PMT of D1, the experiment will be repeated.

• The experiment with a full size D2 detector is scheduled.

• In order to have larger dynamic range, multi-layer D1 detecors,

and multi D2 detectors are necessary.

• The measurement with present machines is desired.