Diamond-like carbon coatings for cryogenic operation of particle detectors

TL;DR

This paper investigates the electrical properties of diamond-like carbon (DLC) coatings at cryogenic temperatures and demonstrates their suitability for particle detectors operating near liquid argon temperatures.

Contribution

It provides the first characterization of DLC coatings' electrical behavior at cryogenic temperatures and applies this to a resistive-protected WELL detector near liquid argon conditions.

Findings

DLC coatings maintain stable electrical properties at 77 K

Surface conductivity follows 2D variable-range electron hopping

Successful operation of a DLC-based WELL detector at cryogenic temperatures

Abstract

Characterization of diamond-like carbon (DLC) coatings at cryogenic temperatures (down to 77 K) is presented, covering the electrical resistivity range of practical interest to gaseous and liquid particle instrumentation: 10^-1-10^5 Mohm/sq. The good behaviour observed in terms of linearity, surface uniformity and stability with time and transported charge add to other well-known characteristics like low chemical reactivity and tolerance to radiation. The observed temperature dependence and stability of electrical properties with transported charge is consistent with a conductivity mechanism based on 2-dimensional variable-range electron hopping, as expected for the surface conductivity of thin films made from amorphous carbon. First results from a resistive-protected WELL detector ('RWELL') built with DLC and operated close to the liquid-vapor coexistence point of argon (87.5 K at 1 bar) are presented.