The polarization sensitivity of GRETINA

Compton polarimeters have played an important role in the study of nuclear structure physics, but have often been limited in their applications because of relatively low γ-ray detection efficiency. With the advent of γ-ray tracking detector arrays, which feature nearly 4π solid angle coverage and the ability to identify the location of Compton-scattering events to within a few millimeters, this limitation can be overcome. Here we present a characterization of the performance of the Gamma Ray Energy Tracking In-beam Nuclear Array (GRETINA) as a Compton polarimeter using the 24Mg(p,p′) reaction at 2.45 MeV proton energy. We also discuss a new capability added to the simulation package UCGretina to simulate the emission of polarized photons, and compare it to the measured data. Finally, we use these simulations to predict the performance of the Gamma Ray Energy Tracking Array (GRETA)

Shapes, softness, and nonyrast collectivity in 186W

Nonyrast, excited states in neutron-rich 186W were populated via inelastic-scattering reactions using beams of 136Xe nuclei accelerated to 725 and 800 MeV. Levels populated in the reactions were investigated via particleγ coincidence techniques using the Gammasphere array of high-purity germanium detectors and the compact heavy-ion counter, CHICO2. The Kπ = 2+ (γ), Kπ = 0+ and Kπ = 2− (octupole) rotational side bands were extended to spins 14¯h,12¯ h, and 13¯h, respectively. A staggering pattern observed in the energies of levels in the Kπ = 2+ band was found to be consistent with a potential that gets softer to vibration in the γ degree of freedom with increasing spin. The odd-even staggering of states in the Kπ = 2− band was found to exhibit a phase opposite to that seen in the γ band; an effect most probably associated with Coriolis coupling to other, unobserved octupole vibrational bands in 186W

Shapes, softness, and nonyrast collectivity in 186W^{186}\mathrm{W}

International audienceNonyrast, excited states in neutron-rich W186 were populated via inelastic-scattering reactions using beams of Xe136 nuclei accelerated to 725 and 800 MeV. Levels populated in the reactions were investigated via particle-γ coincidence techniques using the Gammasphere array of high-purity germanium detectors and the compact heavy-ion counter, CHICO2. The Kπ=2+ (γ), Kπ=0+ and Kπ=2− (octupole) rotational side bands were extended to spins 14ℏ, 12ℏ, and 13ℏ, respectively. A staggering pattern observed in the energies of levels in the Kπ=2+ band was found to be consistent with a potential that gets softer to vibration in the γ degree of freedom with increasing spin. The odd-even staggering of states in the Kπ=2− band was found to exhibit a phase opposite to that seen in the γ band; an effect most probably associated with Coriolis coupling to other, unobserved octupole vibrational bands in W186