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

Abstract

Theoretical predictions as well as experiments performed at storage rings have shown that the lifetimes of β-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 β-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 γ-rays emitted by the excited daughter nuclei following the β-decay. An array of 14 HPGe detectors placed around the trap will be used to detect the emitted γ-rays. For the first experimental campaign three isotopes, 176Lu, 134Cs, and 94Nb, 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.

Theoretical Estimate of the Half-life for the Radioactive 134Cs and 135Cs in Astrophysical Scenarios

“…The use of the new rates to s-process computations in AGB stars remarkably reconciles models and observations for both the Sun and the presolar SiC grain isotopic composition by leading to an overall decrease in the 134 Ba/ 136 Ba and 135 Ba/ 136 Ba abundance ratios predictions, and provides realistic inputs and comparisons to the now forthcoming experiments (Mascali et al 2017(Mascali et al , 2022. D.V.…”

“…After decades of experiments on reaction rates for neutron captures and charged-particle processes, our understanding of the above scenario now depends also on improving the knowledge of weak nuclear reactions in hot stellar plasmas. Their accurate assessment still represents a crucial bottleneck, while experiments simulating stellar conditions in terrestrial ionized plasmas to measure decay rates are still in their infancy (Mascali et al 2017(Mascali et al , 2022. In particular, for a better agreement between nucleosynthesis models and observations (Vescovi et al 2019) a great deal of theoretical work to assess stellar reaction rates with increased accuracy is still required (Nomoto et al 2013); in fact, there is a dearth of computations for decay processes in stellar scenarios from first principles (Simonucci et al 2013;Vescovi et al 2019).…”

Trends in particle and nuclei identification techniques in nuclear physics experiments

“…The PANDORA project [120,121] proposes a new approach to measure, for the first time, in-plasma nuclear β-decays of isotopes of astrophysical interest (e.g. relevant for r-and s-process nucleosynthesis chain), covering different plasma densities n e and temperatures T e [122].…”

An Innovative Superconducting Magnetic Trap for Probing β-decay in Plasmas

“…However, the storage ring approach is based on the investigations of a single charge state at a time: while clearly showing the role played by the high ionization state of an atom in the β-decay process, is not able to reproduce stellar-like conditions where, due to the high temperature of the plasma, a Charge State Distribution (CSD) of the ions is established. A totally new and challenging approach, based on the study of decays rates in a plasma whose conditions can mimic the hot stellar environment, has been conceived in the PANDORA (Plasmas for Astrophysics Nuclear Decays Observation and Radiation for Archaeometry) project Mascali et al [1]. The main idea is to build a compact and flexible magnetic plasma trap (where plasma reaches a density n e ~10 11 -10 13 cm −3 , and a temperature kT e ~0.1-30 keV) and use it to measure, for the first time, nuclear β-decay rates in stellar-like conditions.…”