Several Techniques for Improving Several Techniques for Improving Neutron-Energy Dependence Neutron-Energy Dependence

of PADC Track Detectorof PADC Track Detector

K. Oda1, D. Hayano1, H. Ohguchi1,2, T. Yamauchi1, T. Yamamoto2

1 Graduate School of Maritime Sciences, Kobe University, Japan

2 Oarai Research Center, Chiyoda Technol, Co., Ltd., Japan(Protection dosimetry service)

Paper ID:185

BackgroundBackgroundBackgroundBackground

A lot of studies for 30 years by many groups- Fabrication of detector material (PADC) sensitivity, transparency, stability, etc.- Sensitization by radiator for higher energies- Automatic counting system

“Personal neutron dosimetry with PNTD”

Practical application (at commercial base)- 30,000 pieces per month (fast processing)- stability, accuracy, fast processing

Present status of CTC servicePresent status of CTC servicePresent status of CTC servicePresent status of CTC service

- PADC fabrication in own laboratory quality control of detector material- Reduction of false pits by pre-soaking- Fast imaging system by HSP-1000

without & with presoakingOhguchi et al., Radiation Measurements, 43[2-6], 2008

energy response

5 15MeV

Purpose of this studyPurpose of this studyPurpose of this studyPurpose of this study

Check of existing techniques for improving sensitivity to 15-MeV neutrons without any modification in detector material & etching conditions

1. Analysis of other parameters (1-a) distribution in etch-pit diameter (1-b) distribution in gray size (1-c) distribution in shape factor

2. Multi-layer radiator (2-a) deuterized radiator (2-b) radiator-degrader technique

ExperimentalsExperimentalsExperimentalsExperimentals

N. Yasuda et al., Radiation Measurements, 40 (2005)

Etch-pit observation - HSP-1000, SEIKO - Auto-focus system - Scan 48 mm2 within 1 min - a few thousand tracks

Neutron irradiation - 0.14, 0.57, 5.0, 15.0 MeV - Van de Graaff, National Institute of Advanced Industrial Scienc

e & Technology, Tsukuba, Japan

Chemical process - fixed by CTC - pre-soaking & etching

(1-a) Distribution in diameter(1-a) Distribution in diameter(1-a) Distribution in diameter(1-a) Distribution in diameter

F. d’Errico et al., Radiation Measurements 28 [1-6], 1997

0

0.005

0.01

0.015

0.02

0.025

0.03

0 5 10 15 20 25 30 35 40

144 keV

565 keV

5 MeV

15 MeV

Nor

mal

ized

Num

ber

of E

tch-

Pits

[m

-1]

Etch-Pit Diameter [m]

0

0.0005

0.001

25 30 35 40

0.14 0.57 5.0 15 MeV1.1% 0.2% 0.7% 5.3%

(1-a) Improvement of response(1-a) Improvement of response(1-a) Improvement of response(1-a) Improvement of response

0.6

0.8

1

1.2

1.4

0 5 10 15 20

Cor

rect

ed S

ensi

tivi

ty [

(pit

s / c

m2 )

/ S

v]

Weighting Coefficient, a

1.5

5 MeV

S = S1 + aS

2

0.5

15 MeV

)26()26( 21 mdaSmdSS error bar (1mSv)

possible, but low statistical precision

(1-b) Distribution in gray level(1-b) Distribution in gray level(1-b) Distribution in gray level(1-b) Distribution in gray level

0

0.01

0.02

0.03

0.04

0.05

0 40 80 120 160

144 keV

565 keV

5 MeV

15 MeV

Nor

mal

ized

Num

ber

of E

tch-

Pits

Gray Level [arb.unit]180

0.14 0.57 5.0 15 MeV15.7% 11.3% 11.4% 28.0%

- reason not clarified yet, but applicable ?

(1-c) Etch-pit shape(1-c) Etch-pit shape(1-c) Etch-pit shape(1-c) Etch-pit shape

0

5

10

15

20

25

0.5 0.6 0.7 0.8 0.9 1 1.1

144 keV565 keV5 MeV15 MeV

Nor

mal

ized

Num

ber

of E

tch-

Pits

Ratio of Minor to Major Radius

No difference !

(2-a) Two-layer radiator(2-a) Two-layer radiator(2-a) Two-layer radiator(2-a) Two-layer radiator

K. Oda et al., Radiation Measurements 40 [2-6], 2005

PNTD CH2CD2CD2 CH2

neutrons

C32D66

too expensive

(2-b) Radiator-degrader(2-b) Radiator-degrader(2-b) Radiator-degrader(2-b) Radiator-degrader

PNTD CH2degrader

Matiullah & S. A. Durrani, Nucl. Instrum. Methods Phys. Res. B28, 1987

Spectrometery by unfolding

K. Oda et al., J. Nucl. Sci. Tenol. 28 [7], 1991

(2-b) Experimental data(2-b) Experimental data(2-b) Experimental data(2-b) Experimental data

0.1

1

10

0.1 1 10

Sen

siti

vity

[(p

its

/ cm

2 / S

v)]

Neutron Energy [MeV]0.5 505

0.5

5

PE (1 mm)

Al (0.4 mm) + PE (1 mm)

(2-b) Calculated radiator effect(2-b) Calculated radiator effect(2-b) Calculated radiator effect(2-b) Calculated radiator effect

0.1

1

10

0.1 1 10

Enh

ance

men

t in

Sen

siti

vity

[(pi

ts /

cm2 )

/ S

v]

Neutron Energy [MeV]50

PE (1 mm)

Al (0.4 mm) + PE (1 mm)

Calculation

0.5 5

0.5

5

PNTD CH2

degraderPNTD CH2

1mm

ConclusionConclusionConclusionConclusion

We checked five techniques as commercially-based routine procedure for improving the sensitivity for high-energy neutrons.

- Etch-pit diameter possible, statistical error- Gray size possible, theoretical consideration needed- Shape factor negative

- Deuterized radiator negative, too expensive- Radiator-degrader promising, optimization of thickness

Thank you for your patience.