Study of bubble distributions by high-energy protons in bubble detectors and its hints in neutron detection at

higher altitude and in space

S.-L. GuoChina Institute of Atomic Energy, Beijing, China

T. Doke et al., Waseda University, Tokyo, JapanD.-H. Zhang, Shanxi Normal University, Linfen, China

M. Komiyama, RIKEN, JapanN. Yasuda et al., NIRS, Japan

1. Introduction

Primary Cosmic RaysPrimary Cosmic RaysSecondary Cosmic RaysSecondary Cosmic Rays

n → bubblesn → bubblesp p ??? dose? dose

BD

This work

2. Bubble Detectors and Irradiation

Large size: BD: China Institute of Atomic EnergyLarge size: BD: China Institute of Atomic Energy

trajectorytrack

Stop

23 cm

Irradiation p cyclotron, RIKEN, Japan

Cyclotron Scint. D Stopper BDCyclotron Scint. D Stopper BD

Acrylic AlAl

p

stop

210 MeV 105.5 MeV

Arrangement of irradiationArrangement of irradiation

p + T -14

3. Bubble distribution and categories

Bubble distribution and categories

T-24

high density low density

(1) Random

(2) Abrupt change , density

(3) L = R

(4) ~ fluence, p/cm2

V

N

Fluence8,333 p/cm2

8,3332,083416.783.341.7

p

Bubble categories

(1) Scattering bubbles(1) Scattering bubbles

(2) Recoil bubbles

(3) Intrinsic bubbles

0

50

100

150

200

250

0 50 100 150 200X / mm

N

BD: T-24Fp = 2.083× 103 cm-2Ep = 105.5 MeV

ε = (4.6± 1.5)×10-2 (bobble.cm-3/proton.cm-2)

0

50

100

150

200

250

300

350

0 50 100 150 200

X / mm

N

BD: T-14Fp = 8.33×103 cm-2Ep = 105.5 MeVε =( 0.93±0.27)×10-2 (bobble.cm-3/proton.cm-2)

0

50

100

150

200

250

300

0 50 100 150 200

X / mm

N

BD: T -12Fp = 2.083E3 cm-2Ep = 105.5 MeV

ε = (4.7 ± 1.7)E2 (bobble.cm-3/proton.cm-2)

4. Bubble density distribution

(1) Two terraces

(2) Steep drop

(3) Higher terrace = Recoil bubbles + Scattering bubbles + Intrinsic bubbles

Lower terrace = Scattering bubbles + Intrinsic bubbles

_______________________________________________________________________

Difference = Recoil bubbles

Recoil bubble density ----- unique

T-14 T-24 T-12

5. Results of measurements

Detection efficiency for protons via recoil bubbles

T-14 0.93±0.27×10-2

T-24 4.6 ±1.5 ×10-2

T-12 4.7 ±1.7 ×10-2

pcmbubble

cmproton

cmbubble

3-

2

3

Bubble detector

Energyof

protons

Fluenceof

protons

Visibledepth

Volumeof

measurement

Density ofscattering bubbles

Density of

Recoilbubbles

Detection efficiencyfor

protons

MeV ×103 cm-2 mm cm3 cm-3 cm-3 (bubble/cm3)/(proton/cm2)

T-14 105.5 8,333±0.019 4±1 2.36±0.64 28.0±8.2 77±23 (0.93±0.27)×10-2

T-24 105.5 2.083±0.010 4±1 1.27±0.34 30.4±9.7 95±30 (4.6±1.5)×10-2

T-12 105.5 2.083±0.010 3±1 1.65±0.57 33±12 97±36 (4.7±1.7)×10-2

6. Comparison with detection efficiency for neutrons

T-12 2% R-12

20 keV ~ 19 MeV ε

En

Visible depth: 3 mm

2

2

/

/

cmneutron

cmbubble

2

3

/

/

cmneutron

cmbubble

)(

)(

n

p

ε(n) ≈ 1.5×10-4

ε(n) ≈ 5× 10-4

ε(p) = 4.7±1.7×10-2

≈ 102

2

3

/

/

cmproton

cmbubble

100 times higher for protons

Origin: Rutherford scattering

p + C, F, Cl → Recoil nuclei →bubbles.Cl

F

C

0.3 — 19 MeV

7. Conclusions

(1) 3 types of BD + p

(2) Proton delection efficiencies

(3) Neutron detection efficiency

(4) Rutherford scattering !!!

Cosmic ray protons → forming bubbles !!!

Space neutron dose ←?→ bubble number

Non Simple

bubblesIntrisic

bubblesRecoil

bubbles Scattering

bubbles Random

pcmbubble107.412-Tp,ε

pcmbubble106.424-Tp,ε

pcmbubble1093.014-Tp,ε

3-2

3-2

-32

100

12-Tn,ε

12-Tp,ε

ncmbubble10512-Tn,ε -34

Thanks