An actively vetoed Clover gamma-detector for nuclear astrophysics at LUNA

TL;DR

This paper reports on the deployment and characterization of an escape-suppressed Clover gamma-detector at LUNA, demonstrating its suitability for underground nuclear astrophysics and providing improved measurements of a specific resonance in magnesium.

Contribution

The study introduces an escape-suppressed Clover detector for underground use and shows its advantages for precise nuclear astrophysics measurements.

Findings

Underground background levels are significantly reduced compared to overground.

Escape suppression improves detector sensitivity for weak signals.

Precise measurement of the 24Mg(p,gamma)25Al resonance branching ratio.

Abstract

An escape-suppressed, composite high-purity germanium detector of the Clover type has been installed at the Laboratory for Underground Nuclear Astrophysics (LUNA) facility, deep underground in the Gran Sasso Laboratory, Italy. The laboratory gamma-ray background of the Clover detector has been studied underground at LUNA and, for comparison, also in an overground laboratory. Spectra have been recorded both for the single segments and for the virtual detector formed by online addition of all four segments. The effect of the escape-suppression shield has been studied as well. Despite their generally higher intrinsic background, escape-suppressed detectors are found to be well suited for underground nuclear astrophysics studies. As an example for the advantage of using a composite detector deep underground, the weak ground state branching of the Ep = 223 keV resonance in the 24Mg(p,gamma)25Al reaction is determined with improved precision.