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Development and preliminary tests of resistive microdot and microstrip detectors
This content has been downloaded from IOPscience. Please scroll down to see the full text. 2012 JINST 7 P12003 (http://iopscience.iop.org/1748-0221/7/12/P12003) View the table of contents for this issue, or go to the journal homepage for more
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P UBLISHED BY IOP P UBLISHING FOR S ISSA M EDIALAB R ECEIVED: August 19, 2012 ACCEPTED: October 24, 2012 P UBLISHED: December 5, 2012
S PECIAL I SSUE ON R ESISTIVE P LATE C HAMBERS AND R ELATED D ETECTORS RPC2012
P. Fonte,a E. Nappi,b P. Martinengo,c R. Oliveira,c V. Peskov,c,d,1 F. Pietropaoloe and P. Picchi, f a LIP
and ISEC, Coimbra, Portugal Bari, Bari, Italy c CERN, Geneva-23, CH-1211, Switzerland d UNAM, Mexico City, Mexico e INFN Padova, Padova, Italy f INFM Frascati, Frascati, Italy b INFN
E-mail:
[email protected] A BSTRACT: In the last few years our group has focused on developing various designs of sparkprotected micropattern gaseous detectors featuring resistive electrodes instead of traditional metallic ones: resistive microstrip counters, resistive gas electron multiplier, resistive micro mesh gaseous structure. These detectors combine in one design the best features of resistive plate chamber (sparkprotection) and micropattern detectors (a high position resolution). In this paper we report the progress so far made in developing other types of resistive micropattern detectors: a microdot-microhole detector and a microgap-microstrip detector. The former detector is an optimal electron amplifier for some special designs of dual phase noble liquid time projection chambers, for example with a CsI photocathode immersed inside the noble liquid. Preliminary tests of such a detector, for the first time built and investigated, are reported in this paper. The latter detector is mainly orientated towards medical imaging applications such as x-ray scanners. However, we believe that after a proper gas optimization, these detectors could also achieve a high time resolution and could thus be used in applications as time of flight positron emission tomography, detection of charged particles with simultaneously high time and position resolution etc. K EYWORDS : Resistive-plate chambers; Noble-liquid detectors (scintillation, ionization two-phase); Micropattern gaseous detectors (MSGC, GEM, THGEM, RETHGEM, MHSP, MICROPIC, MICROMEGAS, InGrid, etc) 1 Corresponding
author.
c 2012 IOP Publishing Ltd and Sissa Medialab srl
doi:10.1088/1748-0221/7/12/P12003
2012 JINST 7 P12003
Development and preliminary tests of resistive microdot and microstrip detectors
Contents Introduction
1
2
Microdot-Microhole Detector for dual phase noble liquid TPCs 2.1 A prototype of a dual-phase LAr detector with a CsI photocathode 2.2 Preliminary measurements with the PMT 2.3 RMMD for dual phase LAr detector with a CsI photocathode 2.3.1 Manufacturing of RMMD 2.3.2 A simplified experimental setup set up for tests of RMMD 2.3.3 Results
2 2 3 6 6 6 9
3
Microgap-Microstrips-RPC for medical imaging and other applications 3.1 Early developments 3.2 MMRPC manufacturing 3.3 Experimental setup for testing MMRPC 3.4 Results
11 11 11 13 14
4
Discussion and Outlook
17
1
Introduction
Micropattern gaseous detectors — microstrip detectors, Micromesh Gaseous Structure (MICROMEGAS), Gas Electron Multiplier (GEMs) and others — offer an unprecedented two dimensional (2D) position resolution (20–40 µm) making them very attractive for many applications such as: tracking of charged particles, detection and visualization of x-rays and Ultraviolet (UV) photons. However, owing to the fine structure of their electrodes, single stage micropattern sensors can be easily damaged by sparks, which are almost unavoidable under real experimental conditions. The reason for discharges is the high voltage necessary to apply across a very small amplification region if used in a single-stage mode. Sparks appear when the total charge in the avalanche approaches the critical value Qcrit , typically 106 –107 electrons, depending on the specific design of the detector [1]. In some cases, however, at total charge values in the avalanche Qs
