Speaker
Description
The abundance of elements in the Cosmos is currently a topic of active investigation. Since the dawn of nuclear astrophysics, various processes have been identified to explain the synthesis of elements, as the slow (s-) and rapid (r-) neutron capture processes providing 99% of elements beyond the iron peak. Nucleosynthesis models are sensitive to a variety of inputs, such as neutron capture cross sections and β-decay rates. Both theory [1,2] and experiments on fully stripped ions [3] have shown that β-decay lifetimes can change of even orders of magnitude in ionized matter. The PANDORA (Plasmas for Astrophysics, Nuclear Decay Observation and Radiation for Archaeometry) project [4] aims at building a new experimental facility, at INFN-LNS Catania, for probing for the first time the nuclear β-decay rates in hot plasmas. In this facility the plasma will mimic some thermodynamical stellar conditions, especially in terms of temperature. The setup consists of a compact, superconducting B-minimum magnetic trap, where plasmas of various elements can be generated via Electron Cyclotron Resonance and reach densities ne~10^11-10^13 cm^-3, with a “tunable” temperature in the range Te~0.1-30 keV. 14 HpGe detectors will be used for measuring the decay rates, counting the gammas emitted by the de-excitation of the daughter nuclei. The number of decays per time-unit will be monitored simultaneously to the measurement of thermodynamical plasma parameters, achieved by a multi-diagnostic system (RF interferometers and polarimeters, optical and X-ray spectroscopy, X-ray imaging and space resolved spectroscopy). The facility is now under construction, and first plasma is expected in 2026. The setup enables other astrophysically relevant experiments, such as optical opacities determination that are relevant for the r-process nucleosynthesis in a kilonova scenario. Over a list of more than one hundreds potential physics cases, the first measurements will focus on a shortlist consisting in 94Nb (t1/2 ~ 2 x10^4 y), 134Cs (t1/2 ~ 2,5 y), 176Lu (t1/2 ~ 3.76x10^10). Meanwhile the construction is progressing, the collaboration has developed a generalized theory of β-decay in LTE and nLTE plasmas, benchmarking models predictions with 7Be, 140Pr, 163Dy, in H- or He-like configurations which have been measured in Storage Ring experiments at GSI.
[1] K. Takahashi and K. Yokoi, Nuclear β-decays of highly ionized heavy atoms in stellar interiors. Nuclear Physics A 404(3):578-598 · August 1983. DOI: 10.1016/0375-9474(83)90277-4
[2] K. Takahashi and K. Yokoi, Beta-decay rates of highly ionized heavy atoms in stellar interiors, Atomic Data and Nuclear Data Tables. Volume 36, Issue 3, May 1987, Pages 375-409 DOI: https://doi.org/10.1016/0092-640X(87)90010-6
[3] Y. A. Litvinov and F. Bosch, Beta decay of highly charged ions 2011 Rep. Prog. Phys. 74 016301
[4] D. Mascali et al. PANDORA, a new facility for interdisciplinary in-plasma physics. European Physical Journal A 03/2017; 53(7)., DOI:10.1140/epja/i2017-12335-1