Optical Readout Characteristics in a New Gas Scintillation Chamber for Neutron Measurement

A novel neutron diagnostic method is presented based on optical readout from scintillation in gases excited by recoil charged particles for fusion research. According to the method, we have designed a new gas scintillation chamber filled with scintillation gas CF₄ and installed with a multi-wires structure to provide strong electric field. The electric field distributions of cylindrical multi-wire structures with different geometrical parameters are analyzed systematically. By building up an optimal multi-wire structure, the optical readout characteristics are also studied with energetic charged particles. Electron-induced avalanche in the electric field excites gas molecules to emit numerous scintillation photons, which are readout using photomultiplier tubes, and measured using multichannel analysers. The results show that the light signals and charge signals are enhanced simultaneously and the rise time of the light signal hardly changes, approximately 12ns, as the applied voltage increases. More importantly, the typical pulse height spectrum from the light signals is acquired, and the obtained resolution is 8.8% for 6.5MeV protons.