Summer Student Practice, 2007, JINR Dubna 1 Corelative Gamma Spectroscopy of Neutron-Nucleus Interactions Using the COCOS Setup Students: Jan Žemlička, Ondra Šimek, Zlata Mrázová Czech Technical University Prague Supervisors: V.R. Andrianov, A.N. Lihachev FLNP, JINR Dubna

2 Motivation 1980’s – theoretical prediction of parity non-conservation (PNC) effect and its experimental observation in processes of the interaction of slow neutrons with nuclei indirect method of studying through dependence of radiation capture cross-section on neutron energy Breit-Wigner relationship for cross section

3 Targets and reactions PNC effect is the most probable in radiation neutron capture on 204 Pb enriched lead target 204Pb %, 206Pb %, 207Pb -13.2% and 208Pb % cylindrical shape total weight 5,0 g reference target with known 1/E energy dependence of the capture cross section 63 Cu (240 mg)

4 COmbined COrrelative Spectrometer

5 Detection system BGO detection of anihilation photon (511 keV) detection efficiency close to 50 % energy resolution only % on 511 keV HPGe detection of cascade gamma rays of the excited nuclei 205 Pb and 64 Cu in timing windows ( ns) high energy resolution detection efficiency 1-2 %

6 Time of Flight (TOF) spectrum

7 neutrons are divided into 8 groups by their energy for each group HPGe spectrum is obtained single and double escape peaks are identified and their areas are determined for 205 Pb, 208 Pb and 64 Cu energy dependence of area ratios 207 Pb/ 204 Pb and 207 Pb/ 63 Cu is evaluated Spectrum processing

8 HPGe gamma spectrum

9 Energy dependence of area ratios

10 Conclusions COCOS setup decreased observed background, nevertheless, the relative errors reach for % unfortunately, according to this fact the PNC effect cannot be approved further progress could be achieved by greater statistical data set or by more complex geometrical setup

11 Thank you for your attention