Development of a high-resolution alpha camera

We have developed and tested a high-resolution alpha camera. The alpha camera consists of a thin CaF₂(Eu) scintillator, a tapered fiber optics plate (tapered fiber), a position-sensitive photomultiplier tube (PSPMT) and a position calculation circuit. Though this configuration was originally planned as a high-resolution beta camera for direct measurement of positron distribution over brain surface of animals, we found that, with some modifications, it could also image alpha particles. The scintillator is covered by a thin aluminized mylar to protect it from light while allowing the transmission of alpha particles. The tapered fiber is a key component of the camera. The alpha-induced scintillation image is magnified by the tapered fiber with little light loss. Resolution of the alpha camera can be improved by approximately the magnification factor of the tapered fiber, though the field of view of the camera is decreased. We developed a 20 mm diameter field of view alpha camera. Energy resolution of the camera was 30% full-width at half-maximum (FWHM) for ²⁴¹Am alpha particles (5.5 MeV). Spatial resolution for ²⁴¹Am alpha particles was better than 0.6 mm. We confirmed that this alpha camera can be used for high-resolution alpha autoradiography or other alpha imaging applications.