  Scintillators have long been known as radiation detectors and are still used
in various applications. Recently, scintillators containing $^6$Li have been
developed as neutron detectors and have attracted attention. $^6$Li absorbs
thermal neutrons and emits $\alpha$+$^3$H, which is promising as a neutron
detector if it can be separated from background gamma rays. We have been
developing Eu:LiI-CaI$_2$-based scintillators (Eu:LiCaI) for this purpose. In
scintillator detectors, waveform information is generally used to distinguish
particles such as neutrons and gamma rays. We propose a new particle
identification method using emission wavelengths information. In this study,
experiments were conducted using Eu:LiCaI crystals, multi-pixel photon counter
optical sensors, and long-wavelength cut filters to verify the proposed method.
The results of irradiating a $^{252}$Cf neutron source and a $^{60}$Co
gamma-ray source indicate that there is a particle dependence of the output
signal ratio between with and without filters. This means that different types
of radiation particles have different emission wavelengths. This is the first
demonstration of a wavelength-based particle identification method.
