Abstract
Resistive micromegas is proposed as an active element for sampling calorimetry. Future linear collider experiments or the HL-LHC experiments can profit from those developments for Particle Flow Calorimetry. Micromegas possesses remarkable properties concerning gain stability, reduced ion feedback, response linearity, adaptable sensitive element granularity, fast response and high rate capability. Recent developments on Micromegas with a protective resistive layer present excellent results, resolving the problem of discharges caused by local high charge deposition, thanks to its RC-slowed charge evacuation. Higher resistivity though, may cause loss of the response linearity at high rates. We have scanned a wide range of resistivities and performed laboratory tests with X-rays that demonstrate excellent response linearity up to rates of (a few) times 10MHz/cm2, with simultaneous mitigation of discharges. Beam test studies at SPS/CERN with hadrons have also shown a remarkable stability of the resistive Micromegas and low currents for rates up to 15MHz/cm2. We present results from the aforementioned studies confronted with MC simulation
Highlights
Resistive Micromegas was proposed [1] for the ATLAS muon detector upgrade for the HL-LHC, in order to cope with the high particle fluxes of times 10kHz/cm2 of minimum ionising particles (MIPs) and mitigate the problem of discharges at high flux radiation environments
The anode pads in resistive micromegas are covered with dielectric material on top of which a resistive layer is overlaid
The semi-static charge, accumulated on the resistive layer, deforms the electric field, lowering the gain and quenching the sparks. The parameters controlling this effect are the capacitance between the resistive layer and the anode pad and the resistance to ground
Summary
Resistive Micromegas was proposed [1] for the ATLAS muon detector upgrade for the HL-LHC, in order to cope with the high particle fluxes of (a few) times 10kHz/cm of minimum ionising particles (MIPs) and mitigate the problem of discharges at high flux radiation environments. The goal of our research program is to develop micromegas detectors with resistive pads suitable for use in Particle Flow (PF) calorimetry at high rates. The expected rates are of the order of 1MHz/cm2 - (a few) times 10MHz/cm MIPs at high pseudorapidity regions. The discharge rate diminishes as the resistivity increases at the cost of loss of linearity at high rates. We have scanned five order of magnitude in resistivities, in order to optimise for these counter acting effects
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