1. Several Techniques for Improving Neutron-Energy Dependence of PADC Track Detector K. Oda 1, D. Hayano 1, H. Ohguchi 1,2, T. Yamauchi 1, T. Yamamoto 2 1 Graduate School of Maritime Sciences, Kobe University, Japan 2 Oarai Research Center, Chiyoda Technol, Co., Ltd., Japan (Protection dosimetry service) Paper ID:185

2. BackgroundBackground 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

3. Present 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 presoaking Ohguchi et al., Radiation Measurements, 43[2-6], 2008 energy response 5 15MeV

4. Purpose 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

5. ExperimentalsExperimentals N. Yasuda et al., Radiation Measurements, 40 (2005) Etch-pit observation - HSP-1000, SEIKO - Auto-focus system - Scan 48 mm 2 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 Science & Technology, Tsukuba, Japan Chemical process - fixed by CTC - pre-soaking & etching

6. (1-a) Distribution in diameter F. d’Errico et al., Radiation Measurements 28 [1-6], 1997 0.14 0.57 5.0 15 MeV 1.1% 0.2% 0.7% 5.3%

7. (1-a) Improvement of response error bar (1mSv) possible, but low statistical precision

8. (1-b) Distribution in gray level 0.14 0.57 5.0 15 MeV 15.7% 11.3% 11.4% 28.0% - reason not clarified yet, but applicable ?

9. (1-c) Etch-pit shape No difference !

10. (2-a) Two-layer radiator K. Oda et al., Radiation Measurements 40 [2-6], 2005 PNTDCH 2 CD 2 CH 2 neutrons C 32 D 66 too expensive

11. (2-b) Radiator-degrader PNTDCH 2 degrader 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

12. (2-b) Experimental data

13. (2-b) Calculated radiator effect PNTDCH 2 degrader PNTDCH 2 1mm

14. ConclusionConclusion 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

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