Development And Applications Of DLC Resistive Electrodes And ?RWELL Detectors

Micro-Pattern gaseous detectors(MPGDs)have been rapidly developed and widely used in the last three decades due to many advantages they exhibit,for ex-ample,high radiation hardness and rate capability,good spatial and time resolution,cost-effective and ease of large-area manufacturing.MPGDs generally suffer from oc-currence of electrical discharge which can damage their electrodes with fine structures.The damage from the electrical discharge can be mitigated by using resistive electrodes for MPGDs.In recent years,the Diamond-like Carbon(DLC)coating has emerged as a viable approach to producing high-quality resistive electrodes,and has become a new research frontier in the MPGD field owing to the excellent properties of DLC electrodes including strong adhesion,a large range of achievable resistivity,high stability and dis-charge resistance.These properties of the DLC coating have offered many possibilities for development of new MPGD structures and performance improvement of existing MPGDs.This is particularly the case for MPGDs with a single stage amplification where resistive electrodes are critical for spark protection.The Micro-Resistive WELL(?RWELL)detector is a typical example of emerging MPGDs that are heavily profiting from developments of DLC resistive electrodes.The ?RWELL is a single stage ampli-fication MPGD which has great application potential thanks to its good characteristics including compact structure,simple and efficient fabrication process.A resistive layer is a key component in an ?RWELL detector for discharge protection,so the DLC re-sistive coating provides an excellent ground for the development of the ?RWELL tech-nology.However,there are still important issues with DLC resistive electrodes that need to be solved.These include unstable surface resistivity,low yield and long pro-duction cycles.In this thesis,the DLC coating method based on magnetron sputtering is studied and key techniques involved in the coating process are developed to optimize the performance of DLC resistive electrodes for application in MPGDs.Research and development on ?RWELL detectors are conducted based on the optimized DLC resis-tive electrodes.?RWELL prototypes with high position resolution and a technique for enabling extremely high-rate capability for a large area ?RWELL are developed.In collaboration with Lanzhou Institute of Chemical Physics,Chinese Academy of Sciences,we have conducted systematic research on DLC resistive coating on various substrates with magnetron sputtering and performance characterization of DLC resistive electrodes with APICAL substrate.The research has involved in various aspects of the DLC coating including reproducibility,adhesion,resistivity,stability,uniformity and large area production.The reproducibility is ensured by strictly controlling the mag-netron sputtering conditions and critical parameters in the sputtering process.The API-CAL substrate and sputtering parameters were optimized to produce high-quality DLC resistive electrodes with excellent adhesion and low internal stress.DLC resistive elec-trodes with stable surface resistivity in a wide range(M?/??G?/?)were developed by doping the hydrogen element into the DLC coating and tuning the coating thickness.Large-area DLC resistive electrodes were developed by using a large magnetron sput-tering device.The uniformity of the surface resistivity reached 25%for a DLC resistive electrode with an effective area of 1.2 m×0.4 m.A copper-DLC composite resistive electrode was also developed by depositing a copper layer on the surface of a DLC re-sistive electrode.A transition layer was needed between the copper layer and the DLC electrode for good adhesion at the interface.The copper-coated DLC resistive electrode realizes surface metallization of DLC electrodes,"which enables complex and fine pat-terning on DLC electrodes by PCB technology.This opens a new way for developing new detector structures.Based on the DLC research work,systematic studies of ?RWELL detectors with a DLC resistive electrode(DLC-?RWELL)have been conducted.A DLC-?RWELL prototype was fabricated for performance comparison to a ?RWELL with a traditional carbon pasting electrode,and the result shows the superiority of the DLC resistive elec-trode over the traditional one.Targeting the application of ?RWELL detectors as a tracking device,the first ?RWELL prototype with two-dimension strip readout was de-veloped and the layout of the readout strips was optimized for equalizing the response in the two dimensions.The test results of the prototype show that the detection effi-ciency of the ?RWELL is higher than 95%,and the position resolution is better than 70?m in both dimensions.The charges of the signals from the optimized readout strips are very close to each other in the two dimensions.Owing to the good performance of the DLC-?RWELL detector,it has been proposed as one of the candidate detectors for the ATLAS high-? muon tagger upgrade.We have studied the application of the DLC-?RWELL detector to the ATLAS high-? muon tagger upgrade.A stand-alone simulation program based on GEANT4 was developed to study the performance re-quirements of the high-? muon tagger.A conceptual design of the high-? muon tagger with the DLC-?RWELL technology was proposed.Fast-grounding techniques were studied for a ?RWELL detector to achieve the very high rate capability required by the ATLAS high-? muon tagger.A scalable fast-grounding technique was developed that can enable fast grounding in a large area ?RWELL detector.DLC-?RWELL proto-types were developed using the scalable fast-grounding technique.The test results of the prototype show that the rate capability with the fast grounding technique can reach up to 10 MHz/cm2 with a detection efficiency of higher than 95%,which can meet the requirements of the ATLAS high-? muon tagger.The high-quality DLC resistive electrodes developed in this work have been used for various MPGDs,greatly promoting the development of a new generation of MPGDs.Various ?RWELL detector structures have been explored with DLC resistive electrodes and high-performance ?RWELL prototypes have been developed.The ?RWELL R&D work presented in this thesis has significantly boosted the development of ?RWELL detectors and laid the foundation for its application in large-scale and high-rate experi-ments.