Contamination Control and Assay Results for the Majorana Demonstrator Ultra Clean Components

TL;DR

The paper reports on contamination control and assay results for the Majorana Demonstrator, demonstrating how improved cleaning processes reduce surface contamination in ultra-pure detector components for neutrinoless double beta decay experiments.

Contribution

It introduces revised cleaning methods and contamination studies that enhance process control for producing ultra-clean detector components in rare event physics experiments.

Findings

Post-production assays showed increased U and Th contamination in finished parts.

Revised cleaning methods reduced surface contamination levels.

Assay techniques effectively monitor and improve component purity.

Abstract

The MAJORANA DEMONSTRATOR is a neutrinoless double beta decay experiment utilizing enriched Ge-76 detectors in 2 separate modules inside of a common solid shield at the Sanford Underground Research Facility. The DEMONSTRATOR has utilized world leading assay sensitivities to develop clean materials and processes for producing ultra-pure copper and plastic components. This experiment is now operating, and initial data provide new insights into the success of cleaning and processing. Post production copper assays after the completion of Module 1 showed an increase in U and Th contamination in finished parts compared to starting bulk material. A revised cleaning method and additional round of surface contamination studies prior to Module 2 construction have provided evidence that more rigorous process control can reduce surface contamination. This article describes the assay results and discuss further studies to take advantage of assay capabilities for the purpose of maintaining ultra clean fabrication and process design.