Neutron production and iodide transmutation studies using intensive beam of Dubna Phasotron Mitja Majerle Nuclear Physics Institute of CAS Řež, Czech republic

Summary Experiment and its main goals Experimental setup Measurement method Simulation and experimental data Conclusion

The experiment Carried out in December 2003 on Phasotron Dubna (protons of energy 660 MeV, protons) Pb target (cylinder - 45 cm, 9.6 cm) Irradiation time 10 minutes Monitor foils were measured in three HPGe detectors Calibration of the detectors Data are still analysed at Řež

Main goals of experiment To identify the products of transmutation of 129 I (~10 7 y) and 127 I in the field of spallation neutrons To determine the cross-section dependency on the energy of neutrons for different reactions (for 129 I and 127 I) To compare experimental data with the simulation To measure the intensity and distribution of the neutron field along the target and to compare it with the simulation To get more accurate results for short-lived iodide isotopes To compare simulated neutron distribution with experimental data at > 30cm

Spallation target Pb cylindrical rod (45 cm, 9.6 cm) 660 MeV protons, irradiation time - 10 minutes The total number of protons and distribution of neutrons were measured with monitor foils (activation method)

Target photo

Iodide samples 4 samples 2 samples of natural 127 I 2 samples of mixture of 85% 129 I and 15% 127 I I in form of NaI in Al shield The samples were put at the distance 9 and 21 cm from the beginning of the target Each sample was measured many times in HPGe detector to determine isotopes with different decay times

Detectors calibration We measured well-defined 152 Eu, 154 Eu, 57 Co, 60 Co, 137 Cs, 88 Y, 228 Th and 133 Ba sources From spectra we calculated detector efficiencies

Number of protons 4 monitor foils (2 Al, 2 natural Cu) in the proton beam Reactions of elements in foil with protons (p,X) produced radioactive isotopes (decay time from minutes to days) HPGe detectors Spectrum analysis

Number of protons Foils were too close to the target - some time was needed before the start of measurement Direct contact between foils (products from reactions with Al were seen on Cu foil) 1,58·10 15 protons passed through foils during 10 minutes of irradiation - accuracy 3% - 20 analyzed isotopes (Na, K, Be, Co, Sc, Fe, Mn, Ni, V, Cr)

Values for the number of protons from one of the Cu foils (Cu201)

Number and distribution of neutrons - experimentally Measured with metal foils (Au, Al, Bi, Pb) along the target Reactions (n,  ) to (n,10n) - different tresholds HPGe detector Spectrum analysis

Number and distribution of neutrons - simulation With MCNPX programs we simulated the experiment The program calculated the number of neutrons and protons that are supposed to pass monitor foils and the number of activated nuclei in these foils

Simulation (produced Au isotopes along the target)

Conclusion So far I have finished the calibration of the detectors and calculations for the number of protons in the beam Currently I am analyzing data from Au foils and comparing them with the simulation First results with iodide should follow in some months Thank you.