Abstract
We present the performance of multiplexed XY resistive Micromegas detectors tested in the CERN SPS 100 GeV/c electron beam at intensities up to 3.3×105e−∕(s⋅cm2). So far, all studies with multiplexed Micromegas have only been reported for tests with radioactive sources and cosmic rays. The use of multiplexed modules in high intensity environments was not explored due to the effect of ambiguities in the reconstruction of the hit point caused by the multiplexing feature. For the specific mapping and beam intensities analyzed in this work with a multiplexing factor of five, more than 50% level of ambiguity is introduced due to particle pile-up as well as fake clusters due to the mapping feature. Our results prove that by using the additional information of cluster size and integrated charge from the signal clusters induced on the XY strips, the ambiguities can be reduced to a level below 2%. The tested detectors are used in the CERN NA64 experiment for tracking the incoming particles bending in a magnetic field in order to reconstruct their momentum. The average hit detection efficiency of each module was found to be ∼96% at the highest beam intensities. By using four modules a tracking resolution of 1.1% was obtained with ∼85% combined tracking efficiency.
Highlights
In the past years, a lot of effort has been invested in the development of microstrip gas detectors for particle tracking in various experiments (e.g [1])
The results from the R&D work performed for the ATLAS Muon System upgrade [23] on several 2D Micromegas chambers with spark protection guided our design of the strip widths and pitch for the NA64 modules
The readout strips are multiplexed by a factor 5 and the resistive strips (R strips) of resistance 50 MΩ are placed parallel to the X-strips as shown in the left picture of Fig
Summary
A lot of effort has been invested in the development of microstrip gas detectors for particle tracking in various experiments (e.g [1]). Micromegas (MICRO-MEsh GASeous Structure)[2] have found many applications in particle [3], nuclear [4] and astrophysics [5] for the detection of ionising particles This relatively high-gain (∼ 104) gas detector combines excellent spatial accuracy with a resolution below 100 μm [6], robustness, high rate capabilities, good timing resolution (< 100 ns) and low material budget. In this paper we present the first measurements of resistive XY Micromegas modules multiplexed by a factor of 5 in a high particle flux This test was done using the CERN SPS H4 high intensity secondary beamline in the context of the NA64 experiment [13]. MM3 and MM4 were placed ∼ 2 m from each other (see Fig. 1)
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