plate detector with resistive electrodes and actually was the first prototype of modern ... YangBaJing (ARGOâYBJ), RPCs were standard 2âmm Bakelite devices, ...
Resistive gaseous detectors: designs, performance, and perspectives M. Abbrescia, V. Peskov, P. Fonte
Book content and abstracts
Introduction Chapter 1
“Classical” Gaseous Detectors and Their Limits Summary This chapter reviews some main designs of traditional gaseous detectors that existed before the implementation of resistive electrodes, and the principles they operate upon. Historically, the first gaseous detector used in experimental measurements was ionization chamber. The capability of ionization chambers to detect radiation is determined by the sensitivity of the current meter used to measure the current flowing between the two electrodes. The first gaseous detector able to record individual photons and elementary particles was the avalanche counter. The chapter shows a figure to illustrate typical voltage‐ current characteristics for a single‐wire counter irradiated by photons or charged particles. At low applied voltages, this gaseous detector operates just like a cylindrical ionization chamber. The development of avalanches depends on their size. When this is sufficiently small, it can be safely assumed that the local electric field is almost entirely due to the external electric field.
Chapter 2
Historical Developments Leading to Modern Resistive Gaseous Detectors Summary The first gaseous detectors were based on a cylindrical geometry: the primary electrons created by the crossing ionizing particle were collected at a central wire and the avalanche processes occurred in the region immediately surrounding it. The need for developing gaseous detectors with a time resolution better than the one
provided, for instance, by the Geiger‐Muller detector (the prototype of central wire detectors) or the ones derived from it, was determinant to drive the introduction of planar detectors. The first detectorsof this kind were developed in the 1940s, and this chapter reviews some of the various technological instances of this concept, together with the further developments that lead to the devices used nowadays. The chapter introduces resistive electrodes. The planar detector was the first parallel‐ plate detector with resistive electrodes and actually was the first prototype of modern resistive plate chambers (RPCs).
Chapter 3
Basics of Resistive Plate Chambers Summary This chapter considers the earliest version of the resistive plate chambers (RPCs). It presents the material that constitutes the necessary background for examining and understanding more complicated RPC designs. The charge distribution, efficiency, and time resolution are three fundamental aspects of RPC performance. The chapter focuses on these aspects. The choice of the gas mixture was crucial for a correct operation of the RPC detectors. The chapter discusses main requirements for RPC gas mixtures. It examines which gas mixtures were found to be most suitable for the RPCs, during the process of their development. Most RPCs are exploited in avalanche mode. Operating RPCs in avalanche mode had the advantage of reducing the charge traveling inside thegas gap, which is a direct benefit for increasing the rate capability. When operating RPCs at varying temperatures, one observes changes in the current drawn, counting rate of noise pulses, efficiency, and time resolution.
Chapter 4
Further Developments in Resistive Plate Chambers Summary The single‐gap resistive plate chambers (RPCs) gave rise to a plethora of further developments in this field, using this module as a starting point and changing its geometrical parameters or simply the number of modules used. Multi‐gap RPCs (MRPCs) were first proposed in 1996 in the group led by M.C.S. Williams, and, in a sense, they were the evolution of the double‐gap concept, successfully getting together the advantages of the wide‐gap RPCs with the possibility of obtaining an improved time resolution. The chapter describes the space‐charge effects in RPCs. It summarizes the main characteristics of the front‐end amplifiers and integrated solutions employed for the major RPC applications. When operating RPCs in avalanche mode one has to take care of what is generally called the “streamer probability”, that is, the percentage of times that the number of electrons in an avalanche reaches the Raether limit.
Chapter 5
Resistive Plate Chambers in High Energy Physics Experiments Summary An resistive plate chamber (RPC) system was added to the forward‐backward muon spectrometer of the L3, which was one of four large detectors experiment operating at the large electron positron (LEP) collider at CERN, in order to increase its angular coverage along the beam direction. In BaBar, RPCs were used as active detectors for muon identification and neutral hadron detection; they were positioned inside the gap between the iron plates used to return the magnetic flux of the experiment. In Astrophysical Radiation with Ground‐based Observatory at YangBaJing (ARGO‐YBJ), RPCs were standard 2‐mm Bakelite devices, equipped on one side with copper strips, whose signals were digitally read out and grouped in logical ORs of eight strips each, called “pads”. The largest experiments, A Toroidal LHC ApparatuS (ATLAS) and Compact Muon Solenoid (CMS), were both designed with muon systems including RPCs as trigger.
Chapter 6
Materials and Aging in Resistive Plate Chambers Summary This chapter speaks about two issues which are probably among the less known in the field of resistive gaseous detectors, namely, materials and aging. One of the interesting features of the resistive plate chamber (RPC) systems of the experiments operating at Large Hadron Collider (LHC) is that they use closed‐loop recirculation gas systems. The chemical analysis of the outgoing gas from multi‐ gap resistive plate chambers (MRPCs) during tests mimicking the conditions at LHC and using gas chromatography measured concentration of fluorine under the limit of detection. It has been hypothesized that the reduced charge produced inside MRPCs and the fact that this detector is operated in pure avalanche mode with a very small gap distance leads also to a strong suppression of hydrofluoric acid (HF) production by dissociation of gas molecules.
Chapter 7
Advanced Designs: High‐Rate, High‐Spatial Resolution Resistive Plate Chambers Summary This chapter talks about some issues related to rate capability, which has been one of the hot topics in the resistive plate chambers (RPCs) community, and which needs
to be tackled by a deep understanding of the physics processes involved and specific technological solutions. Some of the principles outlined in the chapter will probably find implementation for the upgrade of the muon systems of the A Toroidal Large Hadron Collider Apparatus (ATLAS) and Compact Muon Solenoid (CMS) experiments at Large Hadron Collider (LHC). This upgrade is necessary by the decision to prolong the operational lifetime of LHC RPCs during the so‐called high luminosity phase of LHC. The chapter reports about studies specifically devoted to develop RPCs able to stand rate capabilities much higher than the ones, on the order of the 1 kHz/cm2, cited up to now in connection with the experiments at LHC.
Chapter 8
New Developments in the Family of Gaseous Detectors: Micropattern Detectors with Resistive Electrodes Summary This chapter talks about gaseous micropattern detectors, whose invention constitutes the third breakthrough (after the invention of multiwire proportional chambers (MWPCs) and resistive plate chambers (RPCs)) in the field of gaseous detectors at the end of the past millennium. A new momentum to the use of these detectors was given when discharge quenching using resistive electrodes was introduced. The chapter also describes these exciting developments. For a long time, gas electron multipliers (GEMs) and MICRO‐MEsh GAseous Structure (MICROMEGAS) were the most popular micropattern detectors. Other types of micropattern detectors were considered to be less reliable for practical applications and, with time, they were almost abandoned. The resistiveelectrode approach is applied practically to all types of micropattern detectors. The chapter then reviews some specific examples. It further discusses the parallel‐plate avalanche counters (PPACs), that is, parallel‐plate detectors operating in avalanche mode.
Chapter 9
Applications beyond High Energy Physics and Current Trends Summary This chapter mainly focuses on some applications of resistive gaseous detectors outside the field of high‐energy physics. Modeling and prototyping efforts were made also in the direction of applying resistive plate chamber (RPC)‐positron emission tomography (PET) to the monitorization of oncological hadron therapy treatments. The detection of thermal neutrons by means of gaseous detectors, and RPCs in particular, is especially relevant because of its possible applications also outside the field of high‐energy physics. The muon
scattering tomography (MST) is presently considered as very promising for applications in the field of homeland security, in particular to address the issue of illicit trafficking of radiological or nuclear material hidden in containers or large trucks. Basically, cosmic ray muon radiography is similar to X‐ray radiography, except that penetrating muons serve in place of X‐rays: the absorption of cosmic muons is a measure of the thickness and density of the material crossed.
Some Guidelines for RPC Fabrication Conclusions and Perspectives Glossary
