Development and preliminary tests of resistive microdot and microstrip detectors

Abstract

In the last few years our group have focused on developing various designs of spark-protected micropattern gaseous detectors featuring resistive electrodes instead of the traditional metallic ones: resistive microstrip counters, resistive GEM, resistive MICROMEGAS. These detectors combine in one design the best features of RPCs (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 TPCs, 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 Xray 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 TOF-PET, detection of charged particles with simultaneous high time and position resolution etc.

Development of a new generation of micropattern gaseous detectors for high energy physics, astrophysics and environmental applications

“…The voltage applied between the meshes was typically 1.5 kV and the typical voltage applied to the CsI photocathode was -3 kV. As was reported in [9], scintillation light from radioactive sources produces enough primary electrons from the CsI photocathode to be reliably detected. However, the secondary scintillation light, generated between the parallel meshes created undesirable feedback pulses (Fig.…”

“…1 and ( [9] for more details). It was housed in an ultra-high-vacuum cryostat equipped with a continuously working recirculation/purification system, allowing a lifetime of several milliseconds to be achieved for electrons inside LAr.…”

“…To convert the UV scintillation radiation (~128 nm) into visible wavelengths the PMT window was coated with a tetrapheny butadiene light shifting layer. In preliminary tests, described in [9], ionization inside the LAr was produced by a point-like alpha source 241 Am deposited on a needleshaped surface. In the present tests a compact 55 Fe source was used as well.…”

“…5. Its principle of operation is similar to the microstrip-microhole detector with metallic electrodes [14]; its manufacturing procedure is described in [9]. 6 shows the gain of this detector as a function of the overall voltage V ov =V bc +V ca , (where V bc is the voltage applied between the back-plane and the cathode strips and V ca is the voltage applied between the cathode strips and the anode dots), measured in various gases and at various temperatures using 241 Am and 55 Fe sources.…”

“…The first micropattern detector with resistive electrodes was a thick GEM [2], and subsequently this approach has also been applied to other detectors: MICROMEGAS [3] and CAT ("Compteur a Trou" [4]. This concept triggered a sequence of similar developments, which are nowadays being followed not only by our team, but by several other groups in the framework of RD51 collaboration (see [1,[5][6][7][8][9] and references therein).…”