Enhanced Quadrupole and Octupole Strength in Doubly Magic Sn-132

The first 2(+) and 3(-) states of the doubly magic nucleus Sn-132 are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The Sn-132 ions are accelerated to an energy of 5.49 MeV/nucleon and impinged on a Pb-206 target. Deexciting gamma rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0(g.s)(+) -> 2(1)(+), 0(g.s)(+) -> 3(1)(-), and 2(1)(+) -> 3(1)(-) in Sn-132. The results on these states provide crucial information on cross-shell configurations which are determined within large-scale shell-model and Monte Carlo shell-model calculations as well as from random-phase approximation and relativistic random-phase approximation. The locally enhanced B(E2; 0(g.s)(+) -> 2(1)(+)) strength is consistent with the microscopic description of the structure of the respective states within all theoretical approaches. The presented results of experiment and theory can be considered to be the first direct verification of the sphericity and double magicity of Sn-132.Peer reviewe

Miniball: A Gamma-Ray Spectrometer With Position-Sensitive Ge Detectors For Nuclear Structure Studies At REX-ISOLDE

Miniball is a dedicated Ge detector array which has been developed for the investigation of rare decays at the new radioactive beam facility REX-ISOLDE [1, 2] at CERN. The array is optimised for high full-energy peak efficiency and for high granularity needed to perform Doppler corrections of -rays emitted by fast moving nuclei. Miniball will finally consist of 40 six-fold segmented, encapsulated detectors which are clustered in eight cryostats with three detectors each and four cryostats with four detectors, respectively. It is shown that from an analysis of the pulse shapes and of the amplitudes of the mirror charges in the adjacent segments the effective granularity of Miniball can be enhanced from 240 to 4000. The properties of Miniball are compiled on the basis of experimental data. Examples of the first data measured with Miniball are presented

A Ge detector array for radioactive ion beam

Dedicated Ge-detector arrays are being developed for the investigation of rare gamma decays with low gamma -ray multiplicity at the upcoming radioactive ion beam facilities. These arrays are optimized for the high full-energy peak efficiency and angular resolution of the gamma -ray detection needed for a proper Doppler correction of the gamma -rays emitted by fast recoiling nuclei. MINIBALL will consist of 40 six-fold segmented, encapsulated Ge detectors which are clustered in eight cryostats with three detectors each and four cryostats with Four detectors, respectively. The individual components the six-fold segmented Ge detector, the cryostats, the fast preamplifier, the digital pulse-processing electronics and the mechanical frame - and their properties are described. The results of test measurements with the first MINIBALL cluster detector using a Cs-137 source and the in-beam reaction D(Cl-37, n) Ar-38 are presented. It is shown that from pulse-shape analysis of the events within a detector segment the effective granularity of the MINIBALL array can be enhanced from 240 to similar to 4000. The specifications of MINIBALL are compiled on the basis of experimental data. First results with a 12-fold segmented, encapsulated detector are discussed with respect to the feasibility of future gamma -ray tracking arrays

Miniball: A Gamma-Ray Spectrometer with position-sensitive Ge Detectors for nuclear structure studies ar REX-ISOLDE

Miniball is a dedicated Ge detector array which has been developed for the investigation of rare decays at the new radioactive beam facility REX-ISOLDE [1, 2] at CERN. The array is optimised for high full-energy peak efficiency and for high granularity needed to perform Doppler corrections of gamma -rays emitted by fast moving nuclei. Miniball will finally consist of 40 six-fold segmented, encapsulated detectors which are clustered in eight cryostats with three detectors each and four cryostats with four detectors, respectively. It is shown that from an analysis of the pulse shapes and of the amplitudes of the mirror charges in the adjacent segments the effective granularity of Miniball can be enhanced from 240 to 4000. The properties of Miniball are compiled on the basis of experimental data. Examples of the first data measured with Miniball are presente