A Novel Approach to β-Decay: PANDORA, a New Experimental Setup for Future in-Plasma Measurements

Theoretical predictions as well as experiments performed at storage rings have shown that the lifetimes of beta-radionuclides can change significantly as a function of the ionization state. In this paper we describe an innovative approach, based on the use of a compact plasma trap to emulate selected stellar-like conditions. It has been proposed within the PANDORA project (Plasmas for Astrophysics, Nuclear Decay Observation and Radiation for Archaeometry) with the aim to measure, for the first time in plasma, nuclear beta-decay rates of radionuclides involved in nuclear-astrophysics processes. To achieve this task, a compact magnetic plasma trap has been designed to reach the needed plasma densities, temperatures, and charge-states distributions. A multi-diagnostic setup will monitor, on-line, the plasma parameters, which will be correlated with the decay rate of the radionuclides. The latter will be measured through the detection of the gamma-rays emitted by the excited daughter nuclei following the beta-decay. An array of 14 HPGe detectors placed around the trap will be used to detect the emitted gamma-rays. For the first experimental campaign three isotopes, Lu-176, Cs-134, and Nb-94, were selected as possible physics cases. The newly designed plasma trap will also represent a tool of choice to measure the plasma opacities in a broad spectrum of plasma conditions, experimentally poorly known but that have a great impact on the energy transport and spectroscopic observations of many astrophysical objects. Status and perspectives of the project will be highlighted in the paper.