JAEA-ResearchJAEA-Research JAEA-Research 2008-116...

JAEA

-Research

JAEA-Research

2008-116

─ ZnSシンチレータ、光リフレクタ、及びデジタル信号処理装置の開発 ─

ENGIN-X型1次元シンチレータ中性子検出器の検出器性能向上に関する技術開発

中村龍也　片桐政樹　美留町厚　海老根守澄筒井　紀彰*　曽山和彦　Erik Schooneveld* Nigel Rhodes*

Tatsuya NAKAMURA, Masaki KATAGIRI, Atsushi BIRUMACHI, Masumi EBINENoriaki TSUTSUI*, Kazuhiko SOYAMA, Erik Schooneveld* and Nigel Rhodes*

J-PARC センター

J-PARC Center

March 2009

Japan Atomic Energy Agency 日本原子力研究開発機構

JAEA

-Research 2008-116　

ENGIN-X

型１次元シンチレータ中性子検出器の検出器性能向上に関する技術開発　─ ZnS

シンチレータ、光リフレクタ、及びデジタル信号処理装置の開発

─

日本原子力研究開発機構

Development for Upgrading Japanese ENGIN-X Type Linear Scintillation

Neutron Detectors

- Development of New ZnS Scintillator, Light Reflector and Digital Signal

Processing Module -

1

JAEA-Research 2008-116

ENGIN-X 1

ZnS

J-PARC

+ + *1

Erik Schooneveld*2 Nigel Rhodes*2

(2008 12 19 )

ENGIN-X 1 ZnS

ZnS

ZnS

ZnS/10B2O3 ISIS

2 ( 1 Å)

Al

------------------------------------------------------------------------------------------------------------------------

J-PARC 319-1195 2-4+

*1 ( )*2 Rutherford Appleton Laboratory

��

JAEA-Research　2008-116

2


Development for Upgrading Japanese ENGIN-X Type Linear Scintillation Neutron Detectors

- Development of New ZnS Scintillator, Light Reflector and Digital Signal Processing Module -

Tatsuya NAKAMURA, Masaki KATAGIRI, Atsushi BIRUMACHI+,

Masumi EBINE+, Noriaki TSUTSUI*1, Kazuhiko SOYAMA,

Erik Schooneveld*2 and Nigel Rhodes*2

Materials and Life Science Division, J-PARC Center

Japan Atomic Energy Agency

Tokai-mura, Naka-gun, Ibaraki-ken

(Received December 19, 2008)

New ZnS scintillator, light reflector and digital signal processing modules were developed

to upgrade the Japanese ENGIN-X type linear scintillation neutron detector. The

developed ZnS:Ag/10B2O3 scintillator improved a detector efficiency by a factor 1.2 for

neutrons with a wavelength of 1 Å compared with the ISIS standard scintillator. The

detector maintained a similar gamma sensitivity and multi-count ratio to the present

scintillator. The new light reflector made of an etched-surface aluminum plate was

developed in replace of a light reflector with an acrylic paint coating. The detector

implemented with this reflector exhibited similar detector performances to that with an

acrylic paint coated reflector, securing long-term stability. The digital signal-processing

module incorporating a photon-counting method was successfully developed. The fully

digitalized photon counting system improved temperature stability of neutron counts

significantly compared with the present analogue system.

Keywords: Neutron Detector, Scintillator, Boron Converter, Light Reflector, Digital Signal

Processing, Temperature Stability

------------------------------------------------------------------------------------------------------------------------ + Engineering Services Department, Nuclear Science Research Centre, Tokai Research and

Development Centre *1 Chichibufuji Co. Ltd. *2 Rutherford Appleton Laboratory

��

JAEA-Research　2008-116


��

3

1. 1

2. ENGIN-X 1 27 ch 1

3. ZnS/6LiF ZnS/10B2O3 2

3.1 2

3.2 3

3.3 4

3.3.1 5

3.3.2 Am-Be 6

3.3.3 6

3.3.4 7

4. 8

5. 10

6. 12

12

12

Contents

1. Introduction 1

2. ENGIN-X type linear scintillation neutron detector (27-ch detector) 1

3. Development of ZnS /6LiF and ZnS/10B2O3 scintillator 2

3.1 Specification of developed scintillator 2

3.2 Scintillation light properties: Light yield and decay time 3

3.3 Evaluation of detector performances 4

3.3.1 Experimental methods 5

3.3.2 Evaluation by using an Am-Be neutron source 6

3.3.3 Detector performances plotted with a gamma sensitivity 6

3.3.4 Dependence on neutron wavelength 7

4. Surface etched aluminum reflector 8

5. Digital signal processing with a photon counting method 10

6. Conclusion 12

Acknowledgements 12

References 12

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This is a blank page


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5

1.

J-PARC ( )1) /

1

2008

ISIS2) 1

ISIS ENGIN-X 3)

1 1

ENGIN-X 4) ISIS

160 kW

J-PARC 1 MW ISIS

ZnS

2. ENGIN-X 1 27 ch

ENGIN-X

27 ch

27 ch ENGIN-X

1/5 27

PMT 8 2 27 ch

(ENGIN-X )

2 ZnS

2 2 ZnS


− � −

6

1 98

2 (PMT)

2Cn 3 PMT

/ /

PMT5

27

197 mm ( ) X 8.9 mm ( ) X 0.4 mm ( )

3 mm

20

3

3. ZnS/6LiF ZnS/10B2O3

ZnS

ZnS/6LiF ZnS/10B2O3 (6Li10B) 10B

10B 6Li 410B 6Li Q

3.1ZnS:Ag ZnS/6LiF

ZnS 6LiF

ZnS/10B2O3 ZnS H310BO3

600 1

(1) (2) Applied Scintillation Technologies (AST)

(1) AST (4:1) ENGIN-X

AST(4:1) ZnS 6LiF 4 : 1

(2) AST(2:1) ZnS 6LiF 2

(3) (6) JAEA


− � −


− � −

7

JAEA 6Li, 10B

ZnS

(3) : 6Li ZnS Cl Al

(4) : 6Li 0.7 mm

(5) : 6Li ZnS:Ag,Cl

0.4 mm ZnS 8 m

(6) : 10B (H310BO3

10B2O3 )

(0.4 mm )

3.2

30 mm ( 2

) PMT PMT

4 1000

ZnS 100 ns

1~10 s ( )

(6) (ZnS:Ag,Cl/10B2O3)

20% 10% 2

100-20% ( (1)) 0.46 s

(6) 0.29 s 4

ZnS:Ag,Cl ZnS 6LiF

(2)(4)(5) 0.5~0.95 s 10B

(6)

ZnS/10B2O310B2O3

ZnS/6LiF

(6) 4

( 2 100-10% )

(3) ZnS:Ag, Al Al

5 ( 1 s)

Multi Channel Analyzer


− � −


− � −

8

1

(1) (2) (5) (6) (1) (2) (5)6Li (1), (2) AST (5) JAEA

JAEA ZnS/6LiF AST

2

( (3)) (3) 1.7

Al

4 3

(4)

0.7 mm ZnS

180 m

ZnS

10B (6) 6Li

(6) 10B6Li

(6) 6Li 0.1

mm

(6) ( 0.3 mm)6LiF 0.4 mm 3

ZnS

5

ZnS

3.31


− � −


− � −

9

3.3.1

Quiet 4

Am-Be (10 Ci)

Am-Be (1200 x 1200 x 1200 mm3)

750 mm 77 1/s/cm2

1

ZnS

( 1 s) (nrawcounts) 20 s

(n20-us counts) n20-us counts

,1

,

2020

20

scountss

countsscountstrue

countstrue

countstruecountsrawcountmulti

nn

n

nnn

R

20-us 20 s n 1

1%

Quiet 10B Quiet ( 300

mm) 27 ch 2 PMT

PMT Quiet

60Co 3.3 Ci 50 mm

Quiet60Co 1.17 1.33 MeV

ZnS Quiet


− � −


− � −

10

Quiet

Quiet ENGIN-X 1

~50%@ 1 Å ~1 x 10-7

1% Quiet 6 x 10-4 1/s/cm2

3.3.2 Am-Be (1) (6) 27 ch

ISIS5

6

63

1 ISIS (1)

(3) (5) JAEA ZnS:Ag/6LiF 2

(4), (6)

ZnS:Ag,Cl/6LiF ZnS:Ag,Cl/10B2O3 (4)

0.7 mm (6) 10B

3 1 2 (2) (AST(2:1))

(2) (4) (6)

3.3.37 (1) (2) (4) (6) Quiet

(2) (6)

1 x 10-7

( 7 (a) ) (6) (ZnS:Ag,Cl /10B2O3) (2)

(AST(2:1) ) (4) (ZnS:Ag,Cl/6LiF 1109) (6)10B

( 5 ) (2) (6)

(1) 20~30%

7(b) 1%


− � −


− � −

11

(6) 0.2 0.2%

ZnS/10B2O3

(4) 2

0.7 mm

( 5 )

Quiet (2) (4)

(6) 3~5 Quiet

Quiet

(6)

3

3.3.4AST(2:1) ZnS:Ag,Cl/10B2O3 ( (2) (6))

ISIS ROTAX

ROTAX

27 ch

1 x 10-7 0.5% AST(4:1)

-220 mV AST(2:1) ZnS:Ag,Cl/10B2O3 -180mV

8 AST(4:1)

0.3~5 Å

1

2 ( 1 Å

)

3

AST(2:1) ZnS:Ag,Cl/10B2O3 9

ZnS:Ag,Cl/10B2O3 AST(2:1) ZnS:Ag,Cl/10B2O3

1 Å AST(2:1) ( 1

) AST(2:1) 1

ZnS:Ag,Cl/10B2O3

AST(2:1)

ZnS:Ag,Cl/10B2O3


− � −


− � −

12

ZnS:Ag,Cl/10B2O310B

6Li ZnS:Ag,Cl/10B2O3 AST(2:1)

ZnS AST(2:1)

AST(4:1) Quiet 1 Å

2 ZnS:Ag,Cl/10B2O3

Quiet

2

ZnS:Ag,Cl/10B2O310B 6Li

ZnS/10B2O3

4.

( 2 )

AST(4:1)

10 ZnS 400~500 nm

450 nm ISIS (white paint )

(No.4)

Al No.1 No.2 No.3

Al

ZnS


− � −


− � −

13

white paint

( 3)27 ch

white paint ch 17 ch 18 (No.3 No.7)

No.7 No.3

11 No.3

No.7

white paint

ISIS

SUS

SUS

12

White paint

-220 mV 0.01

13 AST(4:1) white paint

ISIS white paint

AST(2:1) ZnS:Ag,Cl/10B2O3

14 AST(2:1) ZnS:Ag,Cl/10B2O3 white paint

AST(2:1)

ZnS:Ag,Cl/10B2O3

20% ZnS:Ag,Cl/10B2O3

4

15 16 AST(2:1) ZnS:Ag,Cl/10B2O3 white paint


− � −


− � −

14

AST(2:1)

ZnS:Ag,Cl/B2O3 10~20

ISIS AST(4:1) white paint

AST(2:1) ZnS:Ag,Cl/10B2O3

5.

ENGIN-X 1

PMT

( PMT )

PMT

ISIS

Field Programmable Gate Array

(FPGA) ZnS

FPGA

FPGA

FPGA

FPGA

4 JAEA

PMT PMT


− �0 −


− �� −

15

Low Voltage Differential Signaling (LVDS)

17

20 50

ISIS +0.017 %/deg

1/6 +0.003 %/deg

PMT +0.02 %/deg

FPGA 1

18 27 ch

1~20

FPGA

( )

27 ch 1

2

19 FPGA

1 s

FPGA


− �0 −


− �� −

16

6.

ENGIN-X

ZnS:Ag,Cl/10B2O3 AST(2:1)

2 ( 1 Å)

1 MW

1) J-PARC: available from < http://j-parc.jp/MatLife/ja/index.html >

2) ISIS: available from <http://www.isis.rl.ac.uk/>

3) ISIS ENGIN-X: available from <http://www.isis.rl.ac.uk/Engineering/>

4) E. M. Schooneveld, et al: “A new neutron sensitive scintillation detector for ENGIN-X”,

ICANS-XVI, 16th Meeting of the International Collaboration on Advanced Neutron Sources,

p.455 (2003)

5) T. Nakamura, et al: “Performance test of the Japanese ENGIN-X type linear scintillation

neutron detector”, JAEA-Research 2007-014 (2007).


− �� −


− �� −

17

Fig. 1: An image view of Japanese engineering diffractometer, “Takumi”, in the J-PARC/MLF.

Photo. 1: The ENGIN-X diffractometer at ISIS

South bankdetectors

North bankdetectors

Neutron beam

Sample table

South bankdetectors

North bankdetectors

Neutron beam

Sample table


− �� −


− �� −

18

Photo. 2: A 27-ch fibre-coded detector. An top aluminum foil and detector face

cover were removed for visibility.

81 mm

197

mm

PMTs

Scintillator/reflector grid

81 mm

197

mm

PMTs

Scintillator/reflector grid

Fig. 2: A schematic view of a scintillator / light reflector grid.

Scintillator stripsReflectors




− �� −


− �� −

19

Signal processing, Discrim

inator (G

EM electronics)

Decoder electronics

Data acquisition system

8 PMTs

Scintillator/reflectors grid(27 pixels)


inator (G

EM electronics)


inator (G

EM electronics)

Decoder electronics

Decoder electronics



8 PMTs

Scintillator/reflectors grid(27 pixels)

Fig. 3: A schematic view of a 27-ch linear scintillation detector system.

Table. 1: Specifications of scintillator samples

(1) AST*1 AST(4:1) ZnS:Ag,Cl 6LiF 4 :1 0.4 4~5 (-) flexible, thermoplastic

(2) AST AST(2:1) ZnS:Ag,Cl 6LiF 2 :1 0.4 4~5 (-) flexible, thermoplastic

(3) JAEA Ag,Al 1055 ZnS:Ag,Al 6LiF 2.7 :1 0.45 8~9 (1055)*4 non-annealed after sinter

(4) JAEA Ag,Cl 1109 ZnS:Ag,Cl 6LiF 2.7 :1 0.7 4~5 (1109) non-annealed after sinter


(6) JAEA ZnS/B2O3 ZnS:Ag,Cl 10B2O3 1.5 :1*2 0.3/0.4*3 4~5 (1109) scintillator layer formed ona glass substrate.

*1 : Applied Scintillation Technologies LTD.*2 : ZnS : H310BO3

*3 : 0.3-mm thick scintillator formed on a 0.4-mm glass substrate.*4 : Numbers in parenthesis denote powder number from Nichia Co LTD.

No. Manu- Sample Scintillation Converter ZnS:6LiF Thickness ZnS particle Notesfacturer name material material (by weight) (mm) size (um)

(1) AST*1 AST(4:1) ZnS:Ag,Cl 6LiF 4 :1 0.4 4~5 (-) flexible, thermoplastic

(2) AST AST(2:1) ZnS:Ag,Cl 6LiF 2 :1 0.4 4~5 (-) flexible, thermoplastic

(3) JAEA Ag,Al 1055 ZnS:Ag,Al 6LiF 2.7 :1 0.45 8~9 (1055)*4 non-annealed after sinter



(6) JAEA ZnS/B2O3 ZnS:Ag,Cl 10B2O3 1.5 :1*2 0.3/0.4*3 4~5 (1109) scintillator layer formed ona glass substrate.


*3 : 0.3-mm thick scintillator formed on a 0.4-mm glass substrate.*4 : Numbers in parenthesis denote powder number from Nichia Co LTD.

No. Manu- Sample Scintillation Converter ZnS:6LiF Thickness ZnS particle Notesfacturer name material material (by weight) (mm) size (um)


− �� −


− �� −

20

Fig. 4: Normalized signal shapes measured with various scintillators with a bialkali PMT.

The scintillator strips were installed in a light reflector grid. The averaged signals were

displayed.

Table. 2: Scintillation light properties

(1) AST*1 ZnS:Ag,Cl 6LiF 4 :1 0.46 1.44 1.0

(2) AST ZnS:Ag,Cl 6LiF 2 :1 0.50 1.64 0.88

(3) JAEA ZnS:Ag,Al 6LiF 2.7 :1 1.4 3.0 1.69

(4) JAEA ZnS:Ag,Cl 6LiF 2.7 :1 0.95 2.64 (no clear peak)

(5) JAEA ZnS:Ag,Cl 6LiF 2.7 :1 0.86 2.54 0.85

(6) JAEA ZnS:Ag,Cl 10B2O3 1.5 :1*2 0.29 0.82 1.0


No. Manu- Scintillation Converter ZnS:6LiF Time Time Relative signal heightfacturer material material (by weight) 100-20% (us) 100-10%(us) (relative peak position)

(1) AST*1 ZnS:Ag,Cl 6LiF 4 :1 0.46 1.44 1.0

(2) AST ZnS:Ag,Cl 6LiF 2 :1 0.50 1.64 0.88

(3) JAEA ZnS:Ag,Al 6LiF 2.7 :1 1.4 3.0 1.69


(5) JAEA ZnS:Ag,Cl 6LiF 2.7 :1 0.86 2.54 0.85

(6) JAEA ZnS:Ag,Cl 10B2O3 1.5 :1*2 0.29 0.82 1.0



(1) AST*1 ZnS:Ag,Cl 6LiF 4 :1 0.46 1.44 1.0

(2) AST ZnS:Ag,Cl 6LiF 2 :1 0.50 1.64 0.88

(3) JAEA ZnS:Ag,Al 6LiF 2.7 :1 1.4 3.0 1.69


(5) JAEA ZnS:Ag,Cl 6LiF 2.7 :1 0.86 2.54 0.85

(6) JAEA ZnS:Ag,Cl 10B2O3 1.5 :1*2 0.29 0.82 1.0




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− �� −

21

Fig. 5: Pulse height distributions measured with various scintillators with a bialkali PMT.

Fig. 6: Neutron counts plotted as a function of a multi-count ratio.

1

10

100

1000

10000

0 100 200 300 400Pulse height, ch

Cou

nts

in 5

00 s

(1) AST(4:1)(2) AST(2:1)(3) ZnS:Ag,Al/LiF 1055(4) ZnS:Ag,Cl/LiF 1109

(3)(4)

(1)

(2)

1

10

100

1000

10000

0 100 200 300 400Pulse height, ch

Cou

nts

in 5

00 s

(1) AST(4:1)(5) ZnS:Ag,Cl/LiF 2111(6) ZnS:Ag,Cl/B2O3

(6)(5)

(1)


− �� −


− �� −

22

Fig. 7: Detector performances plotted as a function of a gamma sensitivity. (a) detector

efficiency (neutron counts), (b) multi-count ratio and (c) quiet count rate.

(a) Detector efficiency

100

200

300

400

1.E-08 1.E-06 1.E-04 1.E-02

Gamma sensitivity

Neu

tron

coun

ts, c

ps

(1) AST(4:1)(2) AST(2:1)(4) ZnS:Ag,Cl/LiF 1109(6) ZnS:Ag,Cl/B2O3

(b) Multi-count ratio

0

1

2

3

4

1.E-08 1.E-06 1.E-04 1.E-02

Gamma sensitivityM

ulti-

coun

t rat

io, %


(c) Quiet count rate

1.E-05

1.E-04

1.E-03

1.E-02

1.E-08 1.E-06 1.E-04 1.E-02Gamma sensitivity

quie

t cou

nt ra

te, 1

/s/c

m2



− �� −


− �� −

23

(2) AST(2:1)(3) ZnS/B2O3

Detector efficiency% for 1Å

Gamma sensitivityx 10-7

Multi-count ratio%

Quiet count ratex 10-4 1/s/cm2

56 1 0.9 2 0.5 0.3 2.1 0.5

57 1 1.5 4 0.3 0.3 6.9 1.1

(1) AST(4:1) 46 2 2 1 0.6 0.3 2.1 0.3

Scintillator

(2) AST(2:1)(3) ZnS/B2O3

Detector efficiency% for 1Å

Gamma sensitivityx 10-7

Multi-count ratio%

Quiet count ratex 10-4 1/s/cm2

56 1 0.9 2 0.5 0.3 2.1 0.5

57 1 1.5 4 0.3 0.3 6.9 1.1

(1) AST(4:1) 46 2 2 1 0.6 0.3 2.1 0.3

Scintillator

Table. 3: Scintillator detector performances. The threshold voltages for GEM electronics

were set at -220 mV for AST(4:1) and -180 mV both for AST(2:1) and ZnS/10B2O3

scintillator.

Fig. 8: Count ratios between AST(2:1) and AST(4:1) and between ZnS:Ag,Cl/10B2O3

and AST(4:1) plotted as a function of a neutron wavelength.

0.6

0.8

1

1.2

1.4

1.6

0 1 2 3 4 5 6Wavelength of neutron, Å

Cou

nt ra

tio

AST(2:1) / AST(4:1)ZnS_B2O3 / AST(4:1)


− �� −


− �� −

24

Fig. 9: Count ratios between ZnS:Ag,Cl/10B2O3 and AST(2:1) plotted as a function of a

neutron wavelength.

Fig. 10: Reflectivity of light reflectors. An ISIS standard reflector is denoted as

white paint. An etching rate is increased from reflector No. 1 to 3 in an order.

0.6

0.8

1

1.2

1.4

0 1 2 3 4 5

Wavelength of neutron, Å

Cou

nt ra

tio, Z

nS_B

2O3

/ AS

T(2:

1)

1e-7 (gamma sensitivity)

1e-6

0

0.5

1

1.5

2

2.5

3

3.5

200 300 400 500 600

Chichibu-no1Chichibu-no2Chichibu-no3Chichibu-no4Al-powder-nhgWhite-spray-ISIS

Rat

io

Wavelength, nm

White paint

No. 4 (non etched)

No. 1

No. 2

No. 3

Al powder


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− �� −

25

Photo 3: A white painted reflector grid (ISIS standard, left) and etched aluminum grid

reflectors (No.3 and No.7, right). The reflectors for channel 17 and 18 were replaced

with No.3 and No.7 reflectors for the test.

Fig. 11: Neutron counts measured with surface etched aluminum reflectors. An

AST(4:1) scintillator was installed in the grid.

No. 7 No. 3White painted grid No. 7 No. 3White painted grid No. 7 No. 3White painted grid

0

50

100

150

200

250

100 150 200 250

Thresholdvoltage, mV

Cou

nts

per s

econ

d

w hite paint ref lectoretched Al ref lector (No.3)

etched Al ref lector (No.7)


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− �� −

26

Fig. 12: A count ratio in a neighboring pixel through light leakage.

Fig. 13: Detector efficiency (neutron counts) and a multi-count ratio of AST(4:1)

scintillator as a function of a gamma sensitivity.

-0.2

0.0

0.2

0.4

0.6

0.8

50 100 150 200 250 300 350

Threshold voltage, mV

Cou

nt ra

tio in

nei

ghbo

urin

g pi

xel,

%

white paint reflectoretched Al reflector (No.7)


0

100

200

300

400

1.E-08 1.E-07 1.E-06 1.E-05 1.E-04Gam m a sens itivity

Cou

nts

per s

econ

d

AST(4:1), white paint reflector etched Al reflector


0

1

2

3

1.E-08 1.E-07 1.E-06 1.E-05 1.E-04Gamma sensitivity

Mul

ti-co

unt r

atio

, %



− �� −


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27

Fig. 14: Neutron counts measured with white paint and etched surface reflectors.

Fig. 15: Neutron counts and a multi-count ratio of AST(2:1) scintillator as a function of a

gamma sensitivity.

0

100

200

300

400

50 100 150 200 250 300

Threshold voltage, mV

Cou

nts

in c

ps

AST(2:1), white paint

AST(2:1), etched Al No7

ZnS/B2O3, white paint

ZnS/B2O3, etched Al No7


0

100

200

300

400

1.E-08 1.E-07 1.E-06 1.E-05 1.E-04Gam m a sens itivity

Cou

nts

per s

econ

d



0

1

2

3


Mul

ti-co

unt r

atio

, %



− �� −


− �� −

28

Fig. 16: Neutron counts and a multi-count ratio of ZnS:Ag,Cl/10B2O3 scintillator as a

function of a gamma sensitivity.

Photo 4: A digital signal processing module developed by JAEA.


0

100

200

300

400


Cou

nts

per s

econ

d

ZnS/B2O3, white paint reflector etched Al reflector


0

1

2

3


Mul

ti-co

unt r

atio

, %

ZnS/B2O3, white paint reflector etched Al reflector


− �� −


− �� −

29

Fig. 17: Temperature stability of neutron counts measured with an analogue (a)

and a digital (b) photon counting system.

(a) Analog signal processing (Analogue electronics)

0.990

0.995

1.000

1.005

1.010

0 5 10 15 20 25Time, hr

Nor

mal

ized

cou

nts,

a.u

.

21.4 deg 51 deg

+ 0.017 %/deg

(b) Digital signal processing (FPGA electronics)

0.990

0.995

1.000

1.005

1.010

0 5 10 15 20 25

Time, hr

Nor

mal

ized

cou

nts,

a.u

.

20.6 deg 52.4 deg

+ 0.003 %/deg


− �� −


− �� −

30

Fig. 18: A gamma sensitivity measured with an analogue and a digital photon

counting system.

Fig. 19: Neutron counts measured with a digital photon counting system as a

function of a coincidence time.

100

150

200

250

0 0.5 1 1.5 2 2.5

Coincidence time, s

Neu

tron

coun

ts, c

ps

1.E-08

1.E-07

1.E-06

1.E-05

0 5 10 15 20Threshold level, s ingle photon num ber

within 2- s coincidence tim e

Gam

ma

sens

itivi

ty

Analog s ignal process ingDigital s ignal process ing

Quiet count is not subtracted.


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