1. AGATA Demonstrator Test With a 252 Cf Source: Neutron-Gamma Discrimination Menekşe ŞENYİĞİT

2. Investigation the possibilities of discriminating neutrons and gamma rays are important ! Methods for neutron-gamma discrimination with tracking: The energy deposited in the first and second interaction points; The difference in incoming direction of the gamma ray ; Selection based on the FM value

3. To check our methods, we consider an experiment with AGATA triple cluster, 252 Cf source and BaF 2 detector. BaF 2 detector is used for timing. Test period is about 3-4 hours. BaF 2 Lead Shield 252 Cf source 60 Co source ( cm 3 ) AGATA single cluster Loss in gammas ~92-99% Loss in neutrons ~47-50%

4. Simulations 1.Simulations Geant4 with AGATA triple cluster Counts Neutron Energy (MeV) 2.Simulated data: About 1 MeV  -rays Neutrons emitted from 252 Cf source with 2.95  Ci (at LNL) 3.Tracking with MGT code

5. Gamma-ray energy spectrum after tracking (mgt) Eγ (keV) counts Neutrons emitted from 252 Cf source with PHDEF Distance between lead shield and AGATA triple cluster is 60 cm Number of events: 35046000 Neutron multiplicity: 4 Run time: 3 hours Tracking efficiency for gammas: 0.97

6. Eγ (keV) counts 834 keV No conditions With conditions Gamma-ray energy spectrum after tracking (mgt) * Neutrons emitted from 252 Cf source with PHDEF and 1 MeV  -rays * Distance between lead shield and AGATA triple cluster is 60 cm 19854357θg – θc or E first or E second or FM 1169262646θg – θc or E first 14531717 E first 1061252543θg - θc 1 MeV gamma bumppeak 834 keV total 834 keV, 72Ge

7. Time of Flight Spectra for 70 cm TOF Counts  -rays Neutrons In this experiment we would also like to use the TOF technique in order to know when a neutron is hitting detectors to check how succesful our methods are. One problem is that one don’t know the time resolution of the AGATA detectors. Without PSA, it may be around 10 ns but this may be reduced very much by the PSA. Time resolution is energy dependent.

8. Time Resolution Counts TOF, Time resolution = 1 ns TOF, Time resolution = 3 ns TOF, Time resolution = 5 ns Since we don’t know what the time resolution will be for AGATA detectors, we made TOF simulations by using different resolution values.  -rays Neutrons  -rays Neutrons  -rays Neutrons

9. Counts TOF, Time resolution = 10 ns TOF, Time resolution = 15 ns Counts  -rays Neutrons  -rays Neutrons

10. Conclusions We developed 3 methods for neutron-gamma discrimination by using tracking. We would like test these methods in a real test experiment where we shall use a 252 Cf neutron source, one triple Agata detector and a BaF 2 detector for timing. We made some simulation in order to check the effect of our methods. We checked the effect of different time resolution.  We are preparing a proposal for this test experiment which can be run just after the summer.