Aging test of resistive Micromegas detectors operated with and without hydrocarbons

Abstract

Abstract A long-term irradiation and longevity test was conducted on two bulk-Micromegas detectors with screen-printed resistive strips, working with Ar:CO2 gas mixture at the CERN GIF++ facility between 2015 and 2018. The results of the test, for a total integrated charge of about 0.3 C/cm2, have been recently published. One of the detectors exposed at GIF++ was then irradiated with X-rays from Cu, this time with an Ar:CO2:iC4H10 mixture to study the effect of hydrocarbons like isobutane to the detector longevity. The resistive Micromegas under test has accumulated a total charge of 1.5 C/cm2. A second detector with identical construction and characteristics, operated at the same voltages and with the same gas but not irradiated, has been used as reference chamber. Charge spectra with an 55Fe source were acquired at regular intervals for both detectors to monitor the evolution of the gain and energy resolution. The accelerated ageing test has been subsequently repeated with the same detector operated with hydrocarbon-free Ar:CO2 mixture. The paper describes the experimental setup and test procedure, and focuses on the main results and their interpretation.