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

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. Plan of the presentation. Be-target neutron irradiations Reasons of replacement Be(p,n) reaction with D(d,n) one

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

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  1. 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-targetneutron 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, i < 50 mA; • 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 = -1.85 MeV, Tp = 2.06 MeV

  5. Computer program (example)

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

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

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

  14. D(d,n)3He reaction Q = 3.269 MeV [ http://t2.lanl.gov/data/deuteron.html ]

  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. • Difference between Al and Ti NAA-monitors < 5% • Neutron flux error ±10%

  21. Thank you for your attention!

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