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[24 th ICNTS @ Bologna (Italy) 04/09/2008]

[24 th ICNTS @ Bologna (Italy) 04/09/2008]. Characteristics of the copolymerized CR-39-DAP track detector for the observation of ultra heavy nuclei in galactic cosmic rays.

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[24 th ICNTS @ Bologna (Italy) 04/09/2008]

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  1. [24th ICNTS @ Bologna (Italy) 04/09/2008] Characteristics of the copolymerized CR-39-DAP track detector for the observation of ultra heavy nuclei in galactic cosmic rays • S. Kodaira1, N. Yasuda1, N. Hasebe2, T. Doke2, S. Ota2, T. Tsuruta3, H. Hasegawa4, S. Sakai4, T. Nishi4 and K. Ogura5 • NIRS, 2) Waseda Univ. • Nihon Univ., 4) Kinki Univ. • 5) Fukuvi Chemical Industry

  2. Origin:Primary compositions of elements and isotopes in GCRs. The freshly-synthesized material of R-process is enhanced in GCRs ? • Injection mechanism:FIP or Volatility ? • Life-time of GCRs:Mean-life time, Delay time between nucleosynthesis and acceleration • Search for the nearby source • History of Galactic materials • Study of nucleosynthesis process and its site Scientific Objectives Precise observation of ultra-heavy nuclei (Z>30) in galactic cosmic rays (GCRs) • Search for trans-Uranium nuclei predicted theoretically

  3. Ⓒ JAXA Propose to UH observation Super pressure balloon - 100 days and 4~20 m2 detector array - Southern hemisphere/ Antarctica ISS/Satellites - 3 years and 4~20 m2 detector array - Space (Lunar base) (- >100m2) (- Space)

  4. Need SSTD with high threshold Flux of Z<30 nuclei >>Flux of trans-iron nuclei Using high sensitive SSTD such CR-39 Z<30 nuclei are background tracks for the observation of ultra heavy nuclei Fe Ultra heavy nuclei HEAO-3-C3 Binns et al., (1989)

  5. BARYOTRAK Objectives Former Work @ 23th ICNTS • CR-39-DAP copolymer can: • Decrease track registration sensitivity • Control its response curve and threshold of Z/b •  Extremely rough surface condition after the etching •  Broad response of used CR-39 (poor charge resolution) 252Cf-fission track DAP50% • Improvement of CR-39 material •  using BARYOTRAK • Verification of the performance of BARYOTRAK-DAP Kodaira et al., RM, 43 (2008) S52

  6. CR-39-DAP copolymer Diallyl Phthalate(DAP) • Sensitive only for ultra heavy nuclei such as fission fragment • (Z/b)th~150 Polyallyl Diglycol Carbonate (CR-39) • Sensitive for lower Z/b nuclei (most sensitive SSTD) • (Z/b)th~14 (BARYOTRAK) • ~4 (HARZLAS TNF-1) Mix

  7. Polymerization condition Mixing rates of DAP (Xwt %) with CR-39 (BARYOTRAK) Variation adding polymerization promoter for DAP10% Polymerization condition (2 types): ① Normal CR-39 cycle ② Normal CR-39 cycle+120C annealing (DAP0, 10, 15, 20% only)  Stimulate copolymerization of DAP

  8. Beam exposure & Etching condition -- Exposed heavy ion @ HIMAC--- --- Etching condition ---

  9. Surface condition after the etching Track image of 132Xe (189MeV/n) DAP0% DAP10% DAP20% DAP30% DAP40% DAP50%

  10. Response curve for normal CR-39 cycle

  11. Response curve for with +120C anneal

  12. Comparison of response curves

  13. Response curve by varying IPP adding

  14. Summary Fabricated BARYOTRAK-DAP copolymer & verified its performance [Track response curve] -Improved the surface condition after the etching -Improved the uniformity of track registration sensitivity and the track response curve -Decrease the track registration sensitivity for high Z*/bion -Variable and selectable its responsecurve [Copolymerization condition] -+120C annealing is effective to suppress light ion track -IPP adding of 5% is effective to suppress light ion track Further study is needed…

  15. (Z*/b)th>60 [Preliminary] [7N NaOH] [PEW-65]

  16. Cut-Off Rigidity

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