Introduction

Following the lasting success of the DALI2 and DALI2+, the HYPATIA (HYbrid Photon detector Array To Investigate Atomic nuclei) array is being developed as an upgrade for in-beam γ-ray experiments for slowed down and fast rare isotope beams at the RIBF. HYPATIA will be composed of a combination of HR-GAGG(Ce) and CeBr3 scintillation crystals, which will gradually replace the NaI(Tl) crystals of DALI2+ to allow for a continuous physics program. Completion of the project is anticipated to be in line for the planned RIBF upgrade in 2031.

Concept

The design of the HYPATIA array has taken into account the following iprovements with respect to DALI2+

• Higher efficiency: To reach further into Terra Incognita, reduce the amount of measuring time and imprving the quality of the γ-γ coincidence spectra we aim to increase the efficiency to ~50%.
• Better energy resolution: To resolve transitions close in energy and exploit the lifetime effects in the lineshape we would like to achieve a resolution lower than 5% at 661 keV.
• Improved peak-to-total ratio
• Superior time resolution: To increase the background supression, a time resolution below 1 ns is desirable.
• Flexibility: To be able to move the array to the different spectrometers of the RIBF, and to optimize the configuration depending on the need of each experiment.