GRANITE: High-Resolution Imaging and Electrical Qualification of Large-Area TPC Electrodes

TL;DR

This paper introduces GRANITE, a high-resolution, non-contact imaging and electrical testing system for large-area TPC electrodes, enabling precise quality assurance for next-generation rare event search detectors.

Contribution

We developed a comprehensive, non-invasive electrode testing setup with a novel wire scanning head, correlating surface features with electrical discharge behavior for high-voltage applications.

Findings

Discharge hotspots are transient and not linked to static surface features.

Artificial surface damage reduces discharge inception voltage.

The system provides a new method for electrode qualification in low-background experiments.

Abstract

Next-generation dual-phase time projection chambers (TPCs) for rare event searches will require large-scale, high-precision electrodes. To meet the stringent requirements for high-voltage performance of such an experiment, we have developed a scanning setup for comprehensive electrode quality assurance. The system is built around the GRANITE (Granular Robotic Assay for Novel Integrated TPC Electrodes) facility: a gantry robot on top of a $2.5\,\text{m}\times1.8\,\text{m}$ granite table, equipped with a suite of non-contact metrology devices. We developed a coaxial wire scanning head to measure and correlate localized high-voltage discharge currents in air with high-resolution surface images. We find that the identified discharge 'hotspots' are transient and show no significant correlation with static visual features. Next, we established a quantitative relationship between artificially induced abrasive surface damage on the wires and a reduction in the discharge inception voltage. This work provides a novel non-invasive tool for qualifying wires dedicated for use in electrodes for future low-background experiments.