| 研究実績の概要 |
The research in FY2014 focused on the design and testing of components for a non-destructive proton beam monitor that uses the scintillation of gas in the beam pipe. The areas of research are: testing of the photon detection system, design of the optical system to transport and focus the light, and design of the gas injection system. Multi-pixel photon counters (MPPCs) were operated in the T2K proton beam line during beam operation to test their susceptibility to beam induced noise and radiation damage. It was found that the MPPC operation at 1-2 meters from the beam line leads to degradation due to radiation damage. The MPPCs were then operated in a sub-tunnel located 30 meters from the beam line and the radiation damage and beam induced noise were found to be at an acceptable level. Based on these studies, the MPPCs have been identified as an acceptable photo-detector if light transport over 30 meters can be achieved. Hence, the investigation into optical fiber performance in the beam line has begun. Preliminary designs of the optical system using parabolic mirrors or plano-convex/convex lens systems have been carried out using ray tracing simulation tools. Based on these designs, the construction of scaled prototype systems is now starting. In collaboration with colleagues from KEK, a steady state simulation of the gas injection system has been achieved and confirmed with hand calculations. These preliminary results suggest that a pulsed injection system will be required to achieve the vacuum requirements, and work on the simulation of this will soon start.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
The goals for FY2014 were to study the operation of photo-detectors in the T2K beam line and to achieve simulations of the optical and gas injection systems for the beam monitor. The study of the photo-detectors was a necessary first step to setting the required parameters for the optical system. I have carried out an extensive program of testing MPPCs in the T2K beam line. Acceptable operation has been achieved when the MPPCs were situated 30 meters from the beam line in an accessible sub-tunnel. The beam induced noise, MPPC dark noise and MPPC gain have all been measured at this location and found to be within the requirements of the beam monitor. This testing has informed the design of the optical focusing/transport system which is being designed as a two stage system of focusing elements and optical fibers for light transport to the MPPCs. Preliminary simulations of the optical system with parabolic mirrors and plano-convex/convex lenses have been achieved and the results are being used to build the first scaled prototype system using parabolic mirrors. In collaboration with colleagues from KEK, a simulation of the gas injection system has also been developed and steady state gas injection and pumping configurations have been run. Based on these results, preliminary assessments of the pumping performance have been made and a pulsed gas injection system is now being investigated.
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| 今後の研究の推進方策 |
The research in FY2015 will focus on three major areas: continued testing of photodetectors and optical elements such as optical fibers in the T2K beam line, refinement and prototyping of the optical system design, and refinement and prototyping of the gas injection system. 150,000 JPY has been allocated for travel to J-PARC and KEK for testing of components in the T2K beam line and collaboration with KEK colleagues on the gas injection system design and prototyping. Concerning the photo-detector investigation, 120,000 JPY has been allocated for a multichannel readout board to test larger arrays of MPPCs, while 90,000 JPY has been allocated to purchase and test a PMT as an alternative to the MPPCs for photo-detection. An additional 70,000 JPY has been allocated for cables and electronic parts needed for the photo-detector testing. For the optical system and photo-detection prototyping, 555,000 JPY has been allocated for the purchase of parts including a digital attenuator, fibers, a light tight box, lenses and parabolic mirrors and an optical table. Part of the funds allocated for optical fiber purchases will also be used to test optical fibers for light transport in the T2K beam line. To continue the optimization of the optical system design, 75,000 JPY has been allocated for the purchase of ray tracing software. 20,000 JPY has been allocated for wavelength shifting plastics, which will be used to test the time dependent event reconstruction using the optical and photo-detection prototype systems.
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