A 35-cm Input-field Image Intensifier for Scintillation Cameras

Publisher Summary This chapter describes the various aspects of a 35-cm input-field image intensifier for scintillation cameras. A 35-cm input-field image intensifier tube is designed for use in scintillation cameras having high spatial and energy resolutions. The γ-rays travel through a collimator, and then impinge on to a scintillator which is in contact with the input face-plate of a demagnifying high-gain image intensifier. Because of the thickness of the scintillator and of the input face-plate, a diffused spot of light is generated on the photocathode, producing a correspondingly diffuse image on the output screen. The quality of the energy selection depends on the energy resolution of the scintillator. This resolution is defined by the full width at half maximum on the curve of response to mono-energetic radiation. Good energy resolution can only be obtained with highly regular materials such as CsI(Na), CsI(Tl), and NaI(T1) monocrystals. The formation of the output signal is the result of a series of photon-electron stochastic interactions. The chain may be considered as a series of amplifiers with a fluctuating gain. It is found that improvements in performance can be obtained by the use of an internal electron multiplier, without affecting the simplicity of the tube.