High voltage stability and cleaning of 2 m$^2$ resistive strip micromegas detectors (SM2) for the upgrade of the forward muon spectrometer of the ATLAS experiment

For the upgrade of the innermost station of the forward muon spectrometer of the ATLAS experiment large Micromegas (MM) detectors of 2 and 3 m$^2$ with 4 active layers each are foreseen. Four types of MM chambers are produced among four sites. Each sites has to deliver 32 quadruplets or 128 active planes. The tiny 120μm distance between the 600 V resistive strip anodes and the ground micro-meshes for these large areas require adequate and well adapted cleaning procedures to guarantee high voltage stability. This is particularly critical for strip shaped surfaces made from resistive material where remnants from the lithographic production processes must be completely removed. The procedure foreseen a visual inspections to be carried on during cleaning and assembly procedures; a wet cleaning procedure to remove dust and possible ionic components of salts from the anode surfaces; a dry cleaning procedure to remove dust; HV tests to be done to validate the cleaning. The cleaning procedure will be illustrated for a New Small Wheel (NSW) Outer Small Module (SM2) of 2 m$^2$.