1. V. Jakovlev, L. Lebedev and L. Solin V.G. Khlopin Radium Institute
Neutron radiation hardness tests of silicon micro-strip detectors for CBM STS at KRI cyclotron
V. Jakovlev, L. Lebedev and L. Solin
V.G. Khlopin Radium Institute

2. 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

3. KRI cyclotron (MGC-20) MGC-20 cyclotrons are manufactured by
the Efremov Electro-Technical Institute.
Beam types (external):
Protons: 8 – 18 MeV,
i < 50 mA;
Deutrons: 4 – 10 MeV,
Helium-3: 10 – 27 MeV,
i < 25 mA;
Helium-4: 10 – 20 MeV,
i < 25 mA.
Geography of MGC-20:
St. Petersburg (Russia) – 3
Turku (Finland)
Debrecen (Hungary)
Cairo (Egypt)
Somewheretown (North Korea).

4. Be-target neutron irradiations
9Be(p,n)9B, Q = MeV, Tp = 2.06 MeV

5. Computer program (example)

6. Cross sections of NAA-reactions to monitor neutron flux

7. Table 3. Discrepancies of neutron flux for different NAA-reactions.
Results
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,a)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

8. Experimental and calculated Be-target neutron spectra
[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]

9. Smoothed ratio of the experimental and calculated neutron spectra

10. Corrected neutron spectra

11. Types of neutron spectra
Four types of neutron spectra:
From 9Be(p,n)9B(g.s.) reaction
From 9Be(p,n)9B* reaction
From accompanying reactions:
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

12. Drosg-2000 and ENDF/B-VII Data

13. Cross sections of the 9Be(p,n)9B* reactions
[ ]

14. D(d,n)3He reaction Q = 3.269 MeV
[ ]

15. D2-gas target 7.75 MeV 3.79 MeV 4.77 MeV D2-gas pressure = 2.4 ÷ 3 atm
Beam current = 8 ÷ 12 mA

16. Neutron spectrum program modified for gas target

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

18. D2-gas density reduction
- - - [S.-J. Heselius, Studies of Density Reduction in Gas Targets, Academic Dissertation, Åbo Akademi, Turku, Finland, 1986]

19. 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.

20. Neutron hardness tests of SMSD
Table. Neutron fluxes for different detectors.
Irradiation
number
Detector number
Exposure, h
49-52
67, 68, 69
31.5 52
60,61-,61+ 18
49-54
64, 65, 66
42.5
52-54
40,41-,41+ 29
52-66
50,51-,51+
150
Difference between Al and Ti NAA-monitors < 5%
Neutron flux error ±10%

21. Thank you for your attention!

22. Neutron spectra calculations

23. Derivative of solid angle with respect to reaction angle for the coaxial disks geometry

24. Noncoaxial geometries

25. Neutron spectra calculations in frame of ISTC-project No 176 (1995-1997)

26. Computer program (example)

27. Comparison with the Monte-Carlo method

28. Background neutrons
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