PANDORA: a new experimental setup for measuring in-plasma nuclear β-decays of astrophysical interest

David Mascali (Istituto Nazionale di Fisica Nucleare – Laboratori Nazionali del Sud, Catania, Italy)

Theoretical predictions [1,2] and some experiments performed on Storage Rings [3] have shown that lifetimes of beta-radionuclides can change dramatically as a function of the ionization state. PANDORA (Plasmas for Astrophysics, Nuclear Decay Observation and Radiation for Archaeometry) [4] aims at measuring, for the first time, nuclear β-decay rates in stellar-like conditions (i.e. in magnetized laboratory plasmas) for those radionuclides involved in nuclear-astrophysics processes (BBN, s-processing, CosmoChronometers, Early Solar System formation). Compact magnetic plasma traps, where plasmas reach density n_e~10¹¹-10¹⁴ cm^-3, and temperatures T_e~0.1-30 keV, are suitable for such studies. The decay rates can be measured as a function of the charge state distribution of the in-plasma ions. The collaboration is now designing the plasma trap able to reach the needed plasma densities, temperatures and charge states distributions, as well as the plasma diagnostics and the HpGe detectors array needed for tagging β-decays by measuring γ-rays emitted from the decayproducts. A first list of radioisotopes, including tens of physics cases of potential interest is now available. Possible physics cases include, among the others, ²⁰⁴Tl, ⁶³Ni, ⁶⁰Co, ¹⁷¹Tm, ¹⁴⁷Pm, ⁸⁵Kr, ¹⁷⁶Lu and the pairs ¹⁸⁷Re-¹⁸⁷Os and ⁸⁷Sr-⁸⁷Rb, which play a crucial role as cosmo-clocks. Physics cases are now under evaluation in terms of lifetime measurements feasibility in a plasma trap, and first measurements will be performed on ¹⁷⁶Lu (is it a cosmo-thermometer or a cosmo-chronometer?), ¹³⁴Cs (relevant for the production of the s-only isotopes ¹³⁴Ba and ¹³⁶Ba) and ⁹⁴Nb (relevant for the abundance of ⁹⁴Mo in single or binary systems of stars).

[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

Practical information:

11h00 GANIL seminar room (105)
Coffee will be served 15mn before