High Time Resolution Tof Detection Technology

As the development of particle and nuclear physics in the last decades, the nature was more deeper understood. All the particles observed to date have been catalogued in a quantum field theory called the Standard Model, which is often regarded as one of the greatest triumphs of modern physics. The detection technology is a very important factor to the study and measurement of the particles. Accelorator or collider with higher energy and luminosity will be used in future particle physics experiments. Thus higher precision and faster detectors are necessary. TOF (Time of Flight) system usually plays an active actor in these experiments. It can be used in charged particle identification by measuring their flight time difference. Therefore the development of TOF technology is always an important subject. "Now there are two kinds of detectors which are better candidates to TOF, one is scintillator+PMT mode, the other is Multi-gap Resistive Plate Chamber (MRPC). The key to get a better identification ability is to improve the time resolution of TOF, which include the intrinsic time resolution of its detector and the time jitter of the readout electrics. I took part in the research and testing work both on BESIII/TOF (scintillator+PMT) and ALICE/TOF (MRPC). A lot of R&D has been carried out during these periods. In this thesis all the work related is presented.BESIII End-cap TOF (ETOF) consists of 2×48 pieces of trapezoidal scintillators, each coupled with a fast fine-mash photomultiplier tube (PMT) R5924. Its intrinsic time resolution is requested to below 80ps to realize the 2σπ/k separation at momentum up to 1.0GeV/c for the physics aim of BESIII. The properties of photomultiplier tube(R5924) and plastic scintillators (BC404, BC408, EJ204) are studied by both Mont-Carlo simulation and beam (800MeV electron) test, a ETOF module with different wrappings (Aluminium, Tyvek paper, ESR-M204) is also tested. The results show that with a 45°slope cut on the end of scintillator where PMT is fixed, using scintillator BC404 or EJ204 and tyvek paper wrapped, the time resolution of an ETOF module is below 80ps which includes the electronic fluctuation. The ESR wrapping can efficiently enhance the amplitude of the output pulse by 10% comparing with Aluminium wrapping and improve the timing performance of the TOF detector. Furthermore, trying to find rational explanation to the experiment results and possible methods to improve of ETOF, the simulation focused on effects of the light transmission characteristic in scintillator with charged particles hitting different positions are studied. The results can make important reference for the design of ETOF.The high flux of particles produced in the collisions of the future particle experiment requires a high granularity of the detector and a lot of electronics channels. The PMTs can work under the high magnetic field of the detector region are extremely expensive. For a larger area TOF (about 100m~2), the total cost will be extremely high for the large number of detection channels. All these facts indicate that the scintillators + PMT solution is impossible. To fulfill the particle identification requirement, a lot of study has been taken to make a new type of detector with high time resolution at acceptable price. The introduction of gaseous detectors into this area offers a new access to develop such a TOF detector and opens a new area for the use of the gaseous detectors. A new Multi-gap Resistive Plate Chamber (MRPC) with internal plates electrically floating makes it possible to construct such a high time resolution TOF system. The STAR group at BNL plans to construct a TOF detector with about 4000 suchMRPCs, and the cost will be a factor of 5～10 lower than the scintillators + PMT solution with the same characteristic. The ALICE experiment at LHC will also built large area of MRPC TOF to identify particles within 0.5 to2.5GeV/c with coverage of～2 rapidity units.MRPC, as a gaseous detector with parallel plate structure, has several sub-gaps about 200μm-300μm. The reduction of the gas gap size can reduce the time jitter related to the position difference of the primary ionization, thus the time resolution is enhanced. The simulation procedure of the working mechanics of MRPC gives the output charge distribution which fits the experiment data well. It shows that the final output signal is the sum of all charge induced in all sub-gaps. This relaxes the requirement for the threshold of electronics which leds to a better porformance near the boundary of the pickup pad. The efficiency is also enhanced.Some optimizations are taken on the assembly techniques of MRPC: Improving the cleaning method of glass; A coating of Licron spray paint on the outer glass sheets acts as the electrodes to apply the voltage. The surface resistivity of this new coating is about 5-10MΩ/square; Using the zigzag fishing line route staggered in different stack can keep the time resolution and efficiency.The beam test(6GeV,π) for ALICE/MRPC is carried out. New eiectrics-24 channel NINO amplifier/discriminator and HPTDC system are used. A typical test result shows that the NINO card has a 3-6ps jitter. The excellent timing properties of MRPC can be fully exploited. Using the Time-Over-Threshold (TOT) instead the amplitude for the slewing correction, the complexity of the system is simplified and the performances are not changed. The effect of gas mixture is also studied. Finally the time resolution of ALICE/MRPC is 40-60ps. Furthermore, we designed a new 4stacks×6gaps MRPC. Its performance is also tested by Cosmic-Rays. The time resolution is 35-40ps, which is a pretty good result.The new experiment Extreme Energy Events(EEE) to detect extensive air showers through muon detection is starting in Italy. With all the understanding of MRPC, a large area MRPC with six 300μm gas gaps and an active area of 158×82 cm~2 is built. It is read out at each end of 2.5 cm wide copper pickup strips, thus allowing the position of the hit along the strip to be obtained from the time difference. The results of beam test show that single chamber has a time resolution of 70-80ps and a spatial resolution of about 3-6mm along the readout strip. Using three of these chambers we have set up a cosmic tracking system in a similar manner. In addition we discuss the time and position resolution of these MRPCs measured using cosmic rays.