Neutron radiation hardness tests of silicon micro-strip detectors for CBM STS at KRI cyclotron

V. Jakovlev, L. Lebedev and L. SolinV.G. Khlopin Radium Institute

Plan of the presentation

Be-target neutron irradiations Reasons of replacement Be(p,n)

reaction with D(d,n) one D2-gas target D(d,n) neutron spectra calculations Effect of D2-gas density reduction Neutron hardness tests of SMSD

KRI cyclotron (MGC-20)

MGC-20 cyclotrons are manufactured by

the Efremov Electro-Technical Institute.

Beam types (external):Protons: 8 – 18 MeV, i < 50 A;Deutrons: 4 – 10 MeV, i < 50 A;Helium-3: 10 – 27 MeV, i < 25 A;Helium-4: 10 – 20 MeV,i < 25 A.

Geography of MGC-20:St. Petersburg (Russia) – 3Turku (Finland)Debrecen (Hungary)Cairo (Egypt)Somewheretown (North Korea).

Be-target neutron irradiations

9Be(p,n)9B, Q = -1.85 MeV, Tp = 2.06 MeV

Computer program (example)

Cross sections of NAA-reactions to monitor neutron flux

0 2 4 6 8 10 12 14 16N eutron energy [M eV]

0.00

0.40

0.80

1.20

1.60

2.00A

rbitr

ary

units

N AA Cross sections andN eutron spectrum

Neutron spectrum

Cu63(n,2n)

Ce140(n,2n)

Nd142(n,2n)

Nb93(n,2n)

Au197(n,2n)

A l27(n,a)

U238(n,2n)

A l27(n,p)

Results

.2

,calcn

n

s cm mA

exp .

.100

calcn n

calcn

, %

101.14 10

Table 3. Discrepancies of neutron flux for different NAA-reactions.

Reaction Threshold, MeV

27Al(n,p)27Mg 1.90 124

238U(n,2n)237U 6.18 - “ - 21

27Al(n,)24Na 3.25 - “ - 23

197Au(n,2n)197Au 8.11 - “ - 36

93Nb (n,2n) 92Nb 8.93 - “ - 6

140Ce(n,2n)139Ce 9.27 - “ - -11

142Nd(n,2n)141Nd 9.90 - “ - -21

63Cu (n,2n) 62Cu 11.03 - “ - 10

Experimental and calculated Be-target neutron spectra

0 2 4 6 8 10 12 14 16N eutron energy [M eV]

1.0E+11

1.0E+12

1.0E+13

1.0E+14

1.0E+15

1.0E+16N

eutr

on fl

ux [

]ne

utro

nsM

eV s

r A

s

Ep= 14.8 M eV

Lone et. a l

th ick

1 m m

[Lone et. al: “Thick target neutron yields and spectral distributions from the 7Li(p/d,n) and 9Be(p/d,n) reactions” NIM 143 (1977) 331]

Smoothed ratio of the experimental and calculated

neutron spectra

2 4 6 8 10 12 14N eutron energy, M eV

0

5

10

15

Rat

io(E

xp/T

h)

Corrected neutron spectra

2 4 6 8 10 12 14 16Neutron energy [M eV]

1.0E+8

1.0E+9

1.0E+10

1.0E+11N

eutr

on fl

ux [

]

neut

rons

MeV

cm

2 mA

s

N eutron spectra o f9Be(p,n) reaction

14.2 M eV

15.7 M eV

Types of neutron spectra

Four types of neutron spectra:

1. From 9Be(p,n)9B(g.s.) reaction

2. From 9Be(p,n)9B* reaction

3. From accompanying reactions:

4. Background of neutrons scattered on walls and floor of experimental room

9Be + p 4He + 5Li + n – 3.5 MeV

8Be + p + n – 1.7 MeV

2 4He + p + n – 1.6 MeV

Drosg-2000 and ENDF/B-VII Data

1 10 100Proton energy [M eV]

0

10

20

30

40

Cro

ss s

ectio

n [m

b/sr

]P artia l cross sections

G round state

E = 1 .60 M eV

E = 2 .36 M eV

E = 2 .79 M eV

E = 4 .80 M eV

E = 6 .97 M eV

D rosg-2000

Total

Cross sections of the 9Be(p,n)9B* reactions

[ http://t2.lanl.gov/data/proton7.html ]

D(d,n)3He reaction

Q = 3.269 MeV

thresholdD+d D+p+nE = 4.45 MeV

[ http://t2.lanl.gov/data/deuteron.html ]

D2-gas target

•D2-gas pressure = 2.4 ÷ 3 atm

•Beam current = 8 ÷ 12 A

7.75 MeV

4.77 MeV

3.79 MeV

Neutron spectrum program modified for gas target

Neutron spectra for Be-disk and D2-gas target systems

2 4 6 8 10 12 14N eutron energy [M eV]

0.0E+0

4.0E+9

8.0E+9

1.2E+10

1.6E+10

2.0E+10

Neu

tron

flux

[

]

Cro

ss s

ectio

n [b

]

0.10

0.02

0.04

0.06

0.08

0

0.12

neut

rons

MeV

cm

2 mA

s

27A l(n ,p)27M g

27A l(n , )24N aBe(p,n)

D (d,n)

D2-gas density reduction

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.05

0 5 10 15

i [A]

r/r

- - - [S.-J. Heselius, Studies of Density Reduction in Gas Targets, Academic Dissertation, Åbo Akademi, Turku, Finland, 1986]

Background neutron flux determination

D2 was replaced with H2. Irradiation conditions, Al and Ti samples were the same as in D2-irradiation.

Main part of background neutron flux belongs to natW(d,n) (Q = 2.6 ÷ 3.8 MeV) and 181Ta(d,n) (Q = 4.87 MeV) reactions going in

the window and beam stopper materials. As result activities of samples were about

0.5% from the D2-irradiation respective values.

Neutron hardness tests of SMSD

Table. Neutron fluxes for different detectors.

1MeV2

,n

n

s cm

1MeV

2,n

ndt

cm

81.1 10 131.2 10

81.5 10 131.0 10

81.4 10 132.1 10

81.8 10 131.9 10

81.1 10 136.1 10

Irradiationnumber

Detector number

Exposure, h

49-52 67, 68, 69 31.5

5260,61-,61

+18

49-54 64, 65, 66 42.5

52-5440,41-,41

+29

52-6650,51-,51

+150

•Difference between Al and Ti NAA-monitors < 5%

•Neutron flux error ±10%