1. M. Manolopoulou 1, M. Fragopoulou 1, S. Stoulos 1, E. Vagena 1, W. Westmeier 2, M. Zamani 1 1 School of Physics, Aristotle University of Thessaloniki, Hellas 2 Philipps-Universität, 35032 Marburg, Germany

2.  Operational characteristics of the counter  Energy Calibration  Efficiency Calibration  Simulation with Geant4 and comparison with the experimental results  Neutron spectrum unfolding example 2 RAD2012

3. Fullenergy Full energy peak 3 He(n,p) 3 H Q=764 keV Recoil peak 3 He(n,elastic) 0.75*E n 3 He(n,d) 2 H Q=-3.3 MeV Thermal – epithermal peak (764 keV) 3 RAD2012

4.  Gas Pressure 6 Atm  Gas Mixture 3 He 65% Kr 33% CO 2 2%  Diameter 5 cm  Effect. length 15 cm  Cathode SS304, 0.9 mm  Anode Tungsten, 25 μ m Cd cover 1.2 mm RAD2012

5.  Proton Beam: 2.0 – 5.0 MeV 7 Li(p, n) 7 BeE n = 0.23 – 3.3 MeV  Deuteron Beam: 1.4–7.8 MeV 2 H(d, n) 3 HeE n = 3.7 – 10.7 MeV RAD2012 NIM A 562(2006) 371 “Studies on the response of He-3 and He-4 proportional counters to monoenergetic fast neutrons“ Full energy peak

6. 6 RAD2012

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9. NIM A 618 (2010) 284-293. “Non linearity of recoil pulse height events in He-3 tubes” 9 RAD2012

10. RAD2012

11. RAD2012 565 keV1.2 MeV 2.5 MeV

12. 12 RAD2012

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18.  He-3 proportional counter response can be simulated with Geant4 provided that besides the spectrometry functions, recombination coefficient of 3 He recoiling nucleus will be determined experimentally.  Using the calculated response with Geant4, neutron energy distribution of a neutron field in the MeV energy region can be determined for the energy range ~ 0.2 – 7 MeV.  No prior knowledge of neutron energy distribution is required. Thank you for your attention 18 VARNA 2011