Characterisation of the charging up effect in resistive Micromegas detectors

J Samarati,J Wotschack,G Sekhniaidze,L Longo,O Sidiropoulou,P Iengo

doi:10.1088/1742-6596/1498/1/012030

Abstract

During the last decade, a major improvement in the field of the Micro-Pattern Gaseous Detectors has been reached by adding a layer of resistive strips above the readout strips to reduce drastically the effect of discharges. The resistive strips are separated from the readout strips by a thin layer of insulator. When the detector is operated some gain reduction is observed over the first seconds or minutes after switch-on, stabilising after some time. Is this related to the presence of the insulator or are there other mechanisms at work? We report here the results of a detailed study of this effect and compare resistive-strip and Diamond Like Carbon (DLC) Micromegas detectors. We will present and quantify the main characteristics of this effect, i.e, the relative gain drop and the time to reach a stable regime, as a function of the detector configuration and rate. In addition we studied the influence of the pillars that support the mesh on the behaviour of bulk and non-bulk Micromegas detectors.

Highlights

Charging up is a well known effect in gaseous detectors [1] that contain dielectric materials
One with screen-printed resistive strips1, the other using a layer of Diamond Like Carbon (DLC) sputtered on the Kapton foil above the readout strips
Results for the DLC Micromegas We have repeated the same series of measurements as described in Section 2.1 with the DLC chamber

Summary

Introduction

Charging up is a well known effect in gaseous detectors [1] that contain dielectric materials. A typical example of charging up for a resistive-strip Micromegas detector (Fig. 1) exposed to a flux of particles (8 keV Cu X-rays) is shown in Fig. 2 at a relatively low rate of 175 Hz over an area of 1–2 mm2.

Results

Conclusion