Characteristics of the copolymerized CR-39-DAP track detector for the observation of ultra heavy nuclei in galactic cosmic rays

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

S. Kodaira1, N. Yasuda1, N. Hasebe2, T. Doke2, S. Ota2, T. Tsuruta3, H. Hasegawa4, S. Sakai4, T. Nishi4 and K. Ogura5

1) NIRS, 2) Waseda Univ.3) Nihon Univ., 4) Kinki Univ.5) Fukuvi Chemical Industry

Scientific ObjectivesPrecise observation of ultra-heavy nuclei (Z>3Precise observation of ultra-heavy nuclei (Z>3

0) in galactic cosmic rays (GCRs)0) in galactic cosmic rays (GCRs)

Origin:Origin: Primary compositions of elements and isotopes in GCRs. The freshly-synthesized material of R-process is enhanced in GCRs ? 　　　　　　　　　　　　　　　　　　 Injection mechanism:Injection mechanism: FIP or Volatility ? Life-time of GCRs: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 Search for trans-Uranium nuclei predicted theoretically

Propose to UH observation

Super pressure balloon - 100 days and 4~20 m2 detector array - Southern hemisphere/ AntarcticaISS/Satellites - 3 years and 4~20 m2 detector array - Space(Lunar base) (- >100m2) (- Space)

Ⓒ JAXA

Need SSTD with high threshold

30 40 50 60 70 80 90 10010-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Nuclear charge

Rel

ativ

e ab

unda

nce

(Fe

1)

Fe

Binns et al., (1989)Ultra heavy nuclei

HEAO-3-C3

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

CR-39-DAP copolymer can: Decrease track registration

sensitivity Control its response curve and

threshold of Z Extremely rough surface

condition after the etching Broad response of used CR-39

(poor charge resolution)

10 1000.1

1

10

Z*

SV

t Vb 1

DAP 0%DAP 25%DAP 50%

Objectives

252Cf-fission track

DAP50%

Former Work @ 23th ICNTS

0 10 20 30 40 50 60 7010-1

100

101

Z

SV

t Vb 1

BARYOTRAK CR-39 (previous work used)

BARYOTRAK

Kodaira et al., RM, 43 (2008) S52

Improvement of CR-39 Improvement of CR-39 materialmaterial using BARYOTRAK using BARYOTRAK

Verification of the Verification of the performance of BARYOTRAK-performance of BARYOTRAK-DAPDAP

CR-39-DAP copolymer

C

C

O

O

O

O

CH2CH2

CH

CH CH2

CH2

OCH2CH2

CH2CH2

O

O

C

C

O

O

CH2CH2

CH

CH

CH2CH2

O

O

Diallyl Phthalate(DAP) • Sensitive only for ultra h

eavy nuclei such as fission fragment

• (Z/)th~150

Polyallyl Diglycol Carbonate (CR-39) •Sensitive for lower Z/ nuclei (most sensitive SSTD)

•(Z/)th~14 (BARYOTRAK)

~4 (HARZLAS TNF-1)MixMix

Polymerization condition

Copolymer

DAP0%

DAP10%

DAP15%

DAP20%

DAP30%

DAP40%

DAP50%

BARYOTRAK

100 90 75 80 70 60 50

DAP 0 10 15 20 30 40 50

Mixing rates of DAP (Xwt %) with CR-39 (BARYOTRAK)

Variation adding polymerization promoter for DAP10%

0 5 10 15 20 25 300

20

40

60

80

100

Time [hr]

Tem

pera

ture

[°C

]

IPP （ diisopropyl peroxy dicarbonate) 3.3% (standard)

5.0%

7.0%

Polymerization condition (2 types): ① Normal CR-39 cycle ② Normal CR-39 cycle++120C annealing (DAP0, 10, 15, 20% only) Stimulate copolymerization of DAP

Beam exposure & Etching condition

Ion Si, Ar, Fe, Kr, Xe

Energy < 500 MeV/n(19 ≤ Z*/ ≤116)

Solution

7mol/l NaOH

Temp. 70CTime 3~48hr

(< Range of 252Cf fission fragment)

Bulk 252Cf fission fragment method

--- Etching condition ---

-- Exposed heavy ion @ HIMAC---

Surface condition after the etching

DAP0% DAP10% DAP20%

DAP30% DAP40% DAP50%

Track image of 132Xe (189MeV/n)

Response curve for normal CR-39 cycle

1 0 2 0 3 0 4 0 5 0 6 0 7 01 0 - 1

1 0 0

1 0 1

Z *

S Vt V

b 1D A P 0 % ( B A R Y O T R A K )D A P 1 0 %D A P 2 0 %D A P 3 0 %D A P 4 0 %D A P 5 0 %

Response curve for with +120C anneal

0 2 0 4 0 6 0 8 01 0 - 2

1 0 - 1

1 0 0

1 0 1

Z

S=V

t Vb 1

A n e e l i n g p r o c e s s o f 1 2 0 ° C

D A P 0 %D A P 1 0 %D A P 1 5 %D A P 2 0 %

Comparison of response curves

1 5 2 5 3 5 4 5 5 5 6 51 0 - 2

1 0 - 1

1 0 0

1 0 1

S=V

t Vb 1

D A P 0 %

1 5 2 5 3 5 4 5 5 5 6 5

Z

D A P 1 0 %

1 5 2 5 3 5 4 5 5 5 6 5

D A P 2 0 %

N o r m a l+ 1 2 0 ° C a n e e l i n g

3 4 5 6 7

I P P [ % ]

K r 2 3 4K r 3 2 0F e 1 3 5F e 1 7 7F e 2 2 9F e 3 0 4F e 4 1 8S i 1 0 7S i 1 5 5S i 2 4 8S i 4 4 5

1 5 2 5 3 5 4 5 5 5 6 51 0 - 2

1 0 - 1

1 0 0

1 0 1

Z

S=V

t Vb 1

D A P 1 0 %

I P P 3 . 3 %I P P 5 . 0 %I P P 7 . 0 %

Response curve by varying IPP adding

Fabricated BARYOTRAK-DAP copolymer & verified its performance

Summary

[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 ion -Variable and selectable its response curve

[Copolymerization condition] -120C annealing is effective to suppress light ion track -IPP adding of 5% is effective to suppress light ion track

Further study is needed…

20 40 60 80 100 120

10-2

10-1

100

101

Z*

SV

t Vb 1

20 40 60 80 100 12010-2

10-1

100

101

Z*

SV

t Vb 1

DAP0% (7N NaOH)DAP10% (7N NaOH)DAP20% (7N NaOH)DAP30% (7N NaOH)DAP40% (7N NaOH)DAP50% (7N NaOH)DAP0% (PEW-65)DAP10% (PEW-65)DAP20% (PEW-65)DAP30% (PEW-65)DAP40% (PEW-65)DAP50% (PEW-65)

[7N NaOH]

[PEW-65]

(Z*/)th>60

[Preliminary]

Cut-Off Rigidity