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Register a new userFundamentals of Gas Micropattern Detectors
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We performed a new series of systematic studies of gain and rate characteristics of several micropattern gaseous detectors. Extending earlier studies, these measurements were done at various pressures, gas mixtures, at a wide range of primary charges and also when the whole area of the detectors was irradiated with a high intensity x-ray beam. Several new effects were discovered, common to all tested detectors, which define fundamental limits of operation. The results of these studies allow us to identify several concrete ways of improving the performance of micropattern detectors and to suggest that in some applications RPCs may constitute a valid alternative. Being protected from damaging discharges by the resistive electrodes, these detectors feature high gain, high rate capability (10^5 Hz/mm^2), good position resolution (better than 30 micrometer) and excellent timing (50 ps sigma).
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Currently a revolution is taking place in the development of gaseous detectors of photons and particles. Parallel plate-type and wire-type detectors which dominated for years in high energy and space flight experiments are now being replaced by recently invented Micropattern gaseous detectors. We will now review the main achievements in this field and discuss the most promising directions in future developments and applications.
The prospect of pileup induced backgrounds at the High Luminosity LHC (HL-LHC) has stimulated intense interest in technology for charged particle timing at high rates. In contrast to the role of timing for particle identification, which has driven incremental improvements in timing, the LHC timing challenge dictates a specific level of timing performance- roughly 20-30 picoseconds. Since the elapsed time for an LHC bunch crossing (with standard design book parameters) has an rms spread of 170 picoseconds, the $sim50-100$ picosecond resolution now commonly achieved in TOF systems would be insufficient to resolve multiple in-time pileup. Here we present a MicroMegas based structure which achieves the required time precision (ie 24 picoseconds for 150 GeV $mu$s) and could potentially offer an inexpensive solution covering large areas with $sim 1$ cm$^2$ pixel size. We present here a proof-of-principle which motivates further work in our group toward realizing a practical design capable of long-term survival in a high rate experiment.
Nowadays RPCs are in a booming phase: they are successfully used in many experiments, including LHC; there are ambitious plans to use them in several upgrade detectors and in some new experiments as well as in various applications. The aim of this paper is to highlight the main challenges which the RPC community may face in the next few years and which were addressed in talks presented at this conference. Examples could be: new and difficult requirements from experiments (and their upgrades) and applications, optimization and improvements of the existing traditional detector designs, improvement of their characteristics (timing /rate performance, aging, dark current and so on), implementation of new more sensitive electronics, investigation of new materials, development of large- area detectors. We will also review the fast and very promising developments of another type of resistive electrode gaseous detector -micropattern detectors having at least one of their electrodes made of resistive materials. These innovative detectors combine in one design the best features of RPC (spark protection) and micropattern detectors (high granularity-high position resolution).
Electroluminescence produced during avalanche development in gaseous avalanche detectors is an useful information for triggering, calorimetry and tracking in gaseous detectors. Noble gases present high electroluminescence yields, emitting mainly in the VUV region. The photons can provide signal readout if appropriate photosensors are used. Micropattern gaseous detectors are good candidates for signal amplification in high background and/or low rate experiments due to their high electroluminescence yields and radiopurity. In this work, the VUV light responses of the Gas Electron Multiplier and of the Micro-Hole Strip Plate, working with pure xenon, are simulated and studied in detail using a new and versatile C++ toolkit. It is shown that the solid angle subtended by a photosensor placed below the microstructures depends on the operating conditions. The obtained absolute EL yields, determined for different gas pressures and as functions of the applied voltage, are compared with those determined experimentally.
The paper summarizes our latest progress in the development of newly introduced micro pattern gaseous detectors with resistive electrodes. These resistive electrodes protect the detector and the front-end electronics in case of occasional discharges and thus make the detectors very robust and reliable in operation. As an example, we describe in greater detail a new recently developed GEM-like detector, fully spark-protected with electrodes made of resistive kapton. We discovered that all resistive layers used in these studies (including kapton), that are coated with photosensitive layers, such as CsI, can be used as efficient photo cathodes for detectors operating in a pulse counting mode. We describe the first applications of such detectors combined with CsI or SbCs photo cathodes for the detection of UV photons at room and cryogenic temperatures.
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