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Determination of Neutron Room Background at the NPI Cyclotron U-120M

Nuclear Physics Institute ASCR Faculty of Nuclear Sciences and Physical Engineering CTU in Prague. Determination of Neutron Room Background at the NPI Cyclotron U-120M. P.  Bém , M. G ötz , M.  Honusek , M.  Majerle , E.  Šimečková , and M. Štefánik.

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Determination of Neutron Room Background at the NPI Cyclotron U-120M

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  1. Nuclear Physics Institute ASCR Faculty of Nuclear Sciences and Physical Engineering CTU in Prague Determination of Neutron Room Background atthe NPI Cyclotron U-120M P. Bém, M.Götz, M. Honusek, M. Majerle, E. Šimečková, and M. Štefánik Meeting energy needs in the period ofraw materials insufficiency during the 21st century Department of Nuclear Reactions NPI ASCR, pri, 250 68 Řež near Prague, Czech Republic E-mail: stefanik@ujf.cas.cz

  2. Content of presentation • Goals of experiments • Experimental equipment • NPI Cyclotron U-120M • Be-target station • Measurement of neutron room background • Specification of experiments, set-up, results • Conclusion Determination of Neutron Room Background at the NPI Cyclotron U-120M

  3. Goals of experiments • Measurement of slow neutronsfromroombackground using multi-foil activation method • Determination of spectral fluxat a specific position in the cyclotron hall except directbeam axis • Get an information about different part of neutron spectrum (low-energyneutronroombackground) Determination of Neutron Room Background at the NPI Cyclotron U-120M

  4. NPI Cyclotron U-120M • NG1 target station • Positive ion mode (H, D, He) • Small dimensions of hall • Neutron room background Experimental hall Cyclotron hall U-120M • NG2 target station • Negative ion mode (H, D) • Up to 20 μA of p-beam • Good beam-current stability • Neutron room background Neutron generator NG-2 Fig. 1: Schematic of cyclotron halls Fig. 2: NPI Cyclotron U-120M Determination of Neutron Room Background at the NPI Cyclotron U-120M

  5. Beryllium target station • Source reaction: p+9Be • 19.08 MeV proton beam (current of 15 μA) • Set-up: • 10 mmthick Be-target • Cooling by ethanol • White neutron spectrum • Spectral yieldof 1.2 1011 n sr-1 in forward direction • Safety function of target cooling system Fig. 3: Be-target station Fig. 4: p+9Beneutron spectra Determination of Neutron Room Background at the NPI Cyclotron U-120M

  6. Measurement of neutron room background#1 • Proton (20 MeV) beam current of 10μAduring 4 hours • 9 types of activation detectors + cadmium cover • Experiments: • 1st run: 3. 12. 2010 • Foils: Sc, Ta, Au – Cd • 2nd run: 25. 2. 2011 • Foils: Mn, Co, Cu, Cd, Mo, In, Ta, Au – Cd Fig. 5: Timerecordof proton-beamcurrent Determination of Neutron Room Background at the NPI Cyclotron U-120M

  7. Holder for foils Measurement of neutron room background #2 P3: 80 cm P2: 50 cm • Positions of foils in the Cyclotron hall 90 cm P1: 2 cm Be-target 40° Fig. 8: Geometry of experiment (sample position) Determination of Neutron Room Background at the NPI Cyclotron U-120M

  8. Measurement of neutron room background#3 • Main energy regions: • Epithermal and super epithermal: In, Ta, Au, Mo • Low and medium resonant: Cd, Cu, Mn, Co • Resonant: Sc • Fastresonant: In Fig. 6: Cumulative distribution of isotopes production Determination of Neutron Room Background at the NPI Cyclotron U-120M

  9. Measurement of neutron room background#4 • Specific irradiation positions • Various cooling times • Three HPGe detectors of 22, 23, and 50 % efficiency • Calculation of reaction rates andspecificactivities • power-change correction, attenuation, background influence, time corrections, decay during measurement, total charge Fig. 7: Semiconductor HPGe detector Determination of Neutron Room Background at the NPI Cyclotron U-120M

  10. Results • Spectrumunfolding by least squares method – specific code in Minuit programmed by M. Majerle • Neutron spectrum (position 1, two energy regions): Pos. 1: A = 1 881, B = 7.89E-11, C = 9.20E-8, D = -0.49, E = 0.98 Fig. 10: Room backg. spectrum Fig. 11: Room backg. spectrum Fig. 9: Simulated spectrum Determination of Neutron Room Background at the NPI Cyclotron U-120M

  11. Conclusion • Low-energy neutron room background has been measured • Course of room background neutron flux is described with an analytical function (reliable for energies LT 0.1 MeV) • Neutron spectrum consists mainly of thermal peak and then evaporation peak Fig. 12: Ratio C/Efor position 1 Fig. 13: Ratio C/Efor position 3 Determination of Neutron Room Background at the NPI Cyclotron U-120M

  12. Thank you for your attention.

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