Large Area Photo-Detection System Using 3-inch PMTs for the Hyper-Kamiokande Outer Detector

Abstract

Hyper-Kamiokande, scheduled to begin construction as soon as 2020, is a next generation underground water Cherenkov detector, based on the highly successful Super-Kamiokande experiment. It will serve as a far detector, 295 km away, of a long baseline neutrino experiment for the upgraded J-PARC beam in Japan. It will also be a detector capable of observingfar beyond the sensitivity of the Super-Kamiokande detector -proton decay, atmospheric neutrinos, and neutrinos from astronomical sources. An Outer Detector (OD) consisting of PMTs mounted behind the inner detector PMTs and facing outwards to view the outer shell of the cylindrical tank, would provide topological information to identify interactions originating from particles outside the inner detector. Any optimization would lead to a significant improvement for the physics goals of the experiment, which are the measurement of the CP leptonic phase and the determination of the neutrino mass hierarchy. An original setup using small 3 PMTs is being designed for the Hyper-Kamiokande OD. They would give better redundancy, spatial, and angular resolution, as they would be twice or three times more photosensors that the original 8 design proposal of the experiment, and for a reduce cost. Several 3 PMTs candidates considered for the Hyper-Kamiokande OD have been characterized at Queen Mary University London. They all show a very low dark counts and good collection efficiency, which makes them excellent choice to be used in the experiment.

Theia: an advanced optical neutrino detector

“…Another advancement in photon detection is the development of multi-PMT modules and mixed PMT coverage schemes. IceCube, KM3Net, and Hyper-Kamiokande are developing digital optical modules (DOMs) [50][51][52] in place of conventional large area photomultipliers. These transparent modules each contain an array of smaller PMTs along with the readout electronics.…”

A New Optical Model for Photomultiplier Tubes

“…Also, the contributions from other positions rely on the AOI of the incident photons, and different external media result in different AOIs on the photocathode. In addition, it is not realistic to perform all required evaluations for each PMT in some applications, which use a large number of PMTs, even up to a few thousand, such as JUNO (∼20,000 20" PMTs and ∼25,000 3" PMTs) [22,23] and Hyper-K (∼40,000 20" PMTs and ∼13,300 3" PMTs) [24,25]. A PMT optical model is an ideal and effective approach to manage all of the aforementioned optical processes and precisely predict the PDE response of PMTs.…”

Sensitivity of Next-Generation Neutrino Detectors to the Observation of Earth Matter Effects on Supernova Neutrinos in the Framework of Invisible Neutrino Decay

“…The detector consist of one cylindrical tank with 71 m height, 68 m in diameter and 40% photo-coverage [206]. It is optically separated into an outer detector with a width of 2 m at the top and bottom or 1 m at the sides, whose objective is to help distinguish the neutrino signal from the background due mainly to cosmic muons [207], and a 217 kton cylindrical inner detector. Hyper-K is designed to employ the new 50 cm PMTs which have a better timing resolution of 2.6 ns and twice the photon detection efficiency than Super-Kamiokande (Super-K) PMTs.…”