Observation of scintillation light from interactions of neutrons in liquid methane chamber

Nuclear reaction data on high-energy neutrons are necessary in such fields of technology as accelerator shielding design and irradiation damage of spaceship microelectronics. Few measurements have been made with high-energy neutrons above 100 MeV to date, and the data accuracy is insufficient for these applications. A time projection chamber (TPC) filled with liquid methane is a promising system for detection of high-energy neutrons with high efficiency. In the liquid methane TPC, the scintillation light produced by incident neutrons works as an internal trigger signal for operation of the TPC. However, no report has shown that scintillation light is emitted outward through the liquid methane. Therefore, we examined whether the scintillation light is absorbed in the liquid methane or can be observed by photomultipliers. We constructed a liquid methane chamber and demonstrated that scintillation light can be measured during neutron incidence on the liquid methane. The light was generated without addition of xenon.