Production, characterization and operation of $^{76}$Ge enriched BEGe detectors in GERDA

TL;DR

This paper details the production, characterization, and deployment of enriched BEGe detectors in GERDA, highlighting advancements in manufacturing and performance for neutrinoless double beta decay searches.

Contribution

It presents the complete production process and performance evaluation of new $^{76}$Ge enriched BEGe detectors for GERDA Phase II.

Findings

Detectors meet performance requirements for GERDA Phase II

Optimized production minimizes cosmic exposure of enriched germanium

Characterization shows stable long-term operation in liquid argon

Abstract

The GERmanium Detector Array (GERDA) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double beta decay (0{\nu}{\beta}{\beta}) of $^{76}$Ge. Germanium detectors made of material with an enriched $^{76}$Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of the experiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new $^{76}$Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in GERDA during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the $^{76}$Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of GERDA Phase~II.