Extension of the particle x-ray coincidence technique: The lifetimes and branching ratios apparatus

TL;DR

This paper introduces LIBRA, an advanced apparatus extending the particle x-ray coincidence technique to measure nuclear lifetimes and branching ratios, enabling crucial data collection for astrophysical reaction modeling.

Contribution

The paper presents the design, validation, and application of LIBRA, a novel instrument that enhances PXCT capabilities for studying radioactive decay processes relevant to astrophysics.

Findings

LIBRA successfully measures lifetimes and branching ratios of resonances.

Validation with radioactive sources confirms LIBRA's effectiveness.

Application to $^{60}$Ga decay provides data for nuclear reaction rate calculations.

Abstract

The particle x-ray coincidence technique (PXCT) was originally developed to measure average lifetimes in the $10^{-17}-10^{-15}$~s range for proton-unbound states populated by electron capture (EC). We have designed and built the Lifetimes and Branching Ratios Apparatus (LIBRA) to be used in the stopped-beam area at the Facility for Rare Isotope Beams that extends PXCT to measure lifetimes and decay branching ratios of resonances populated by EC/$\beta^+$ decay. The first application of LIBRA aims to obtain essential nuclear data from $^{60}$Ga EC/$\beta^+$ decay to constrain the thermonuclear rates of the $^{59}$Cu$(p,\gamma)^{60}$Zn and $^{59}$Cu$(p,\alpha)^{56}$Ni reactions, and in turn, the strength of the NiCu nucleosynthesis cycle, which is predicted to significantly impact the modeling of type I x-ray burst light curves and the composition of the burst ashes. Detailed theoretical calculations, Monte Carlo simulations, and performance tests with radioactive sources have been conducted to validate the feasibility of employing LIBRA for the $^{60}$Ga experiment. LIBRA can be utilized to measure most essential ingredients needed for charged-particle reaction rate calculations in a single experiment, in the absence of direct measurements, which are often impractical for radioactive reactants.