Optimization of Electrical Conductivity of the Anodic DLC Coating of Charged Particle Detector

Abstract

We consider a mathematical model that predicts the electric conductivity of anodic resistive coatings in a charged particle detector and ensures the removal of electron charge in a time shorter than the electron avalanche period. The model is based on the equations for non-stationary electrical current in solids and implemented in COMSOL Multiphysics finite-element code. The model allowed us to establish a correlation between the duration of the avalanche time τ, the amplitude of the current pulse jmax, and the electrical conductivity σ. The model predicted that for a thick gas elecrton multiplier detector with a standard gain about 104 order and a thickness of coating 100 nm, the conductivity σ should be in the range (2...5)·10 7 S/m in order to ensure that current does not exceed the breakdown value that lies in the range ∼1.5 µA. This allowed us to define the most appropriate regime of charged particle detector functioning that combines a high rate of operation and resistance to coating erosion in a detector. The obtained results will be useful for the improvement of the time resolution of charged particles detection in well-type detectors.