Master of Science (MS)


Physics and Astronomy

Document Type



T2K (Tokai to Kamioka) is the first off-axis long baseline neutrino oscillation experiment, and its primary goal is to measure the neutrino mixing parameter θ13. A beam of muon type neutrinos with mean energy 600 MeV will be directed from the proton synchrotron at JPARC toward the Super-Kamiokande detector 295 km away. A near detector will be located 280 m from the proton beam target and instrumented with sub-detectors for measuring neutrino interactions prior to oscillation. One of these sub-detectors, the side muon range detector (SMRD), will help in measuring the neutrino energy spectrum and identifying backgrounds and also will serve as a cosmic ray muon trigger for calibrations of other sub-detectors. The SMRD will consist of approximately 2000 scintillator slabs distributed inside the iron return yokes for the magnetic field which surrounds the other sub-detectors. The scintillators will be read out via Si-based solid state photosensors. A number of relevant parameters for the photosensors have been measured and the results are presented here. The gain and dark rate have been determined as a function of threshold, bias voltage, and operating temperature. The Si-based photosensors are a new technology that has not been used on previous experiments, and their longevity has been in question especially since T2K will run for approximately ten years. So we have also heated the photosensors to 80 °C for a number of months to accelerate their aging and present the long term variation in dark rate and gain. We find no significant degradation over time. The scintillators have also been characterized; we have performed tests using atmospheric muons and radioactive sources to develop a testing procedure to determine scintillator quality and to reject inferior modules prior to installation. The effect on total light yield of fiber alignment, fiber polishing, gluing the fiber into the scintillator, and fiber damage have been measured. We find that triggering on muons under optimal conditions, the light yield is about 40 photoelectrons. We also conclude that major damage will be detectable using gammas from a source although minor damage may be more difficult to detect.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Kutter, Thomas J.