Speaker
Description
Resistive Plate Chambers (RPCs), like most gaseous detectors, rely on gas purity to maintain stable performance. Gas degradation can occur due to leaks or permeability within the system, allowing atmospheric gases and/or humidity to enter. Additionally, molecular dissociation products generated during avalanche processes can also contribute to degradation over time. For this reason, permanent and large-scale detectors, in addition to introducing small amounts of fresh gas, use recirculation, purification and cleaning systems to maintain gas purity. These systems add significant complexity and cost to the detector.
The use of HFCs has become a major concern due to their high Global Warming Potential (GWP). This affects the main gas used in RPCs, tetrafluoroethane (C2H2F4). In fact, the European Union (EU) mandated the phase-out of HFCs in 2015. This presents serious challenges for existing RPC systems, and even more so for new systems, which will inevitably require alternative solutions.
A possible solution to the problem, from an environmental perspective is the replacement of these gases with others that have a much lower GWP, the so-called eco-friendly gases, with HFO-1234ze (C3H2F4) being the most promising alternative to tetrafluoroethane. However, using new eco-friendly gas mixtures would not imply a reduction of the complexity of the gas systems to be used.
Another possible solution would be to construct and operate RPCs without any gas supply, i.e. RPCs that contain gas but are hermetically sealed after construction, similar to the Geiger-Müller detectors. These devices were baptized as sealed RPCs (sRPC). It would mitigate the problem of HFCs phase-out by drastically minimizing the amount of gas used, thus reducing its environmental impact to negligible levels. It would also eliminate any dependence on complex gas systems, allowing the expansion of this type of technology towards Cosmic Ray (CR) experiments through the construction of large, high-performance arrays at low cost, which might replace the Cherenkov water tanks in remote and difficult-to-access locations typical of CR experiments.
This work presents a brief review of the initial steps in the development of this technology, highlighting some approaches that proved unsuccessful and others that led to its current state. The main adopted concepts are outlined.
We also review the results achieved so far, including the construction and operation of medium-sized (0.1 m²) and large-area (1 m²) detectors—primarily wide-multigap RPCs—as well as their long-term operation in the laboratory and within the framework of the SND@LHC experiment.
Finally, the next steps in the development of this technology are discussed.