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High-Voltage Performance Testing in LAr of the PMMA Cathode Connection for the DarkSide-20k Experiment

Ludovico Luzzi

TL;DR

This work validates the DS-20k cathode HV delivery by replicating the detector’s local electric-field conditions in a dedicated UC Davis test setup with a DS-20k HV cable, stress-cone, PMMA window, and an HV-equipped aluminum sphere in liquid argon. The apparatus was cooled and filled under carefully controlled conditions, and HV operation was demonstrated up to $-100$ kV for about 14 days, with currents around $10^2$ nA and no discharges observed. Post-test electrical characteristics remained consistent with pre-test values, supporting the reliability of the HV cable and stress-cone assembly for the DarkSide-20k cathode. The results provide a solid design and operational input for DS-20k, with planned upgrades such as integrating an argon purity monitor for ongoing monitoring.

Abstract

DarkSide--20k (DS--20k) is a next--generation dual--phase liquid argon (LAr) time projection chamber (TPC) devoted to the direct--detection of dark matter. The detector is currently under construction in Hall--C at the Laboratori Nazionali del Gran Sasso, Italy, at a depth of approximately 3500 m water equivalent. The detector will instrument 49.7~t of low--radioactivity underground LAr contained within an acrylic TPC and is designed to reach a WIMP--nucleon spin--independent cross--section sensitivity down to $10^{-48}\,\mathrm{cm}^{2}$ for a WIMP mass of $0.1\,\mathrm{TeV}/c^{2}$ in a 200~tonne--year run. In DS--20k a uniform electric drift field is established in the active volume to transport ionization electrons toward the electroluminescence region, with the required high voltage delivered to the TPC cathode through a custom cable and stress--cone assembly. At the University of California, Davis, a dedicated test setup was developed to reproduce the DS--20k cathode high--voltage connection in LAr, matching the local electric--field conditions. This work summarizes the results of a comprehensive test campaign validating the operation of the DS--20k cathode HV system in LAr up to $-100$~kV.

High-Voltage Performance Testing in LAr of the PMMA Cathode Connection for the DarkSide-20k Experiment

TL;DR

This work validates the DS-20k cathode HV delivery by replicating the detector’s local electric-field conditions in a dedicated UC Davis test setup with a DS-20k HV cable, stress-cone, PMMA window, and an HV-equipped aluminum sphere in liquid argon. The apparatus was cooled and filled under carefully controlled conditions, and HV operation was demonstrated up to kV for about 14 days, with currents around nA and no discharges observed. Post-test electrical characteristics remained consistent with pre-test values, supporting the reliability of the HV cable and stress-cone assembly for the DarkSide-20k cathode. The results provide a solid design and operational input for DS-20k, with planned upgrades such as integrating an argon purity monitor for ongoing monitoring.

Abstract

DarkSide--20k (DS--20k) is a next--generation dual--phase liquid argon (LAr) time projection chamber (TPC) devoted to the direct--detection of dark matter. The detector is currently under construction in Hall--C at the Laboratori Nazionali del Gran Sasso, Italy, at a depth of approximately 3500 m water equivalent. The detector will instrument 49.7~t of low--radioactivity underground LAr contained within an acrylic TPC and is designed to reach a WIMP--nucleon spin--independent cross--section sensitivity down to for a WIMP mass of in a 200~tonne--year run. In DS--20k a uniform electric drift field is established in the active volume to transport ionization electrons toward the electroluminescence region, with the required high voltage delivered to the TPC cathode through a custom cable and stress--cone assembly. At the University of California, Davis, a dedicated test setup was developed to reproduce the DS--20k cathode high--voltage connection in LAr, matching the local electric--field conditions. This work summarizes the results of a comprehensive test campaign validating the operation of the DS--20k cathode HV system in LAr up to ~kV.
Paper Structure (6 sections, 3 figures)

This paper contains 6 sections, 3 figures.

Table of Contents

  1. Introduction
  2. Electric Fields and High--Voltage in DS--20k
  3. Experimental Test Setup at UC Davis
  4. Cool--down and LAr Filling
  5. High--Voltage Operation and Results
  6. Conclusions

Figures (3)

  • Figure 1: Plug of the HV cable to the DS--20k cathode through the dedicated stress--cone assembly. Left: simplified schematic cross--section in the $XZ$ plane. Right: 2D COMSOL simulation with the cathode biased at $-75$ kV.
  • Figure 2: Experimental test setup at UC Davis. Left: photograph of the hardware configuration. Right: 2D COMSOL simulation with the aluminum sphere biased at $-75$ kV.
  • Figure 3: Measured output voltage during HV ramp--up to $-100$ kV at a rate of $5$ V/s and ramp--down to ground at $50$ V/s, as read out by the DAQ system over a $24$--h period.