High Spin States Level Structure In Spherical⁸⁷Sr

The main content of this thesis could be divided to two sentions as follows：The firstpart introduces the High-spin Level Structure in spherical87Sr; The second part is thepackage and test of BGO scintillator.1. High spin states level structure in spherical87Sr.The excited states of nuclei around the N=50show many interesting characters suchas spherical shape, irregular de-excited energy and single particles excitation。The levelstructure study of87Sr is very interesting because it has38protons at the Z=38semimagicshell closure and a neutron hole at the N=50closed shell as a non-deformed nucleus.Nuclear shell model program was used to can well account level structure in this region.The high-spin states of odd-A nucleus87Sr were populated via the heavy-ion fusion-evaporation reaction82Se（9Be,4n）87Sr by using a beam energy46MeV provided by theBeijing HI-13tandem accelerator at China Institute of Atomic Energy. The target wasmade of0.85mg/cm2of enriched82Se backed with4.45mg/cm2natural gold backing. Theinstantaneous-ray emitted from the compound nuclei were detected by a detector arrayconsisting of9BGO-Compton-suppressed HPGe detectors,2palanar detectors and oneClover detector. Energy and efficiency calibration have been done for the detection arrayby using the standard sources of133Ba and152Eu. A total of1.1×108two folds coincidences were collected in event-by-event mode. The data were sorted offline intoE₇-E₇symmetry matrix and asymmetry DCO matrix. These matrices were analyzed withthe RADWARE program XESCL8R based on a Linux-PC system. According to the coincidences and DCO ratios of transitions, the level scheme of87Sr with32new transitions and18new levels have been established. The positive parity states wasextended to about7.5MeV with spin31/2, the negative parity states was extended toabout7.6MeV with spin29/2. A great number of studies have revealed that the level structure in this region can be well reproduced by the shell model calculation and quasi-particles excitation. In theoretical analysis, nuclear shell model program Nushells was used to calculate the level energies and spins on the interaction jun45. No subshell truncations were applied to this model space. The levels energies of shell model calculation have reasonable agreement with the experiment results, and the corresponding levels configurations can be well described the level structure of87Sr. The low-lying yrast states of the87Sr are well characterized by the configuration with π（f5/2p3/2）-1（p1/2g9/2）1（?）vg-19/2. The structure of the higher spins positive parity states are manily dominated by the configuration π（f5/2p3/2）-2（p1/2g9/2）2（?）vg-19/2.The structure of the higher spins negative parity states are manily dominated by the configurations π（f-15/2p-13/2p11/2g19/2）（?）vg-19/2orπ（f-15/2p-23/2g39/2）（?）vg-19/2.2. The package and test of BGO scintillatorBGO crystal is used as suppression shields for HpGe dectors to suppress the compton scattering photons、background counts and raise peak-to-compton ratios.In order to raise further the suppression capability of Compton-suppressed HPGe detectors and design more and more gamma-ray escape-suppressed spectrometer. We package and test the new BGO crystal.photomultiplier tube and voltage divider circuit was used as the light detector. According to the results of previous data, BGO crystal capsules was designed and manufactured. Finally, the amplitude of signal are about320mv with a small noise. The designed voltage divider circuit was applied to escape-suppressed spectrometer, the escape-suppressed inhibition ratio and the loss of peak area achived our design requirement.