Abstract
Image intensifiers combined with columnar scintillators have found application in x-ray and gamma-ray, biomedical
imaging and other fields. In scintillator imaging, hundreds or thousands of optical photons can illuminate the
faceplate of the image intensifier in a small area, essentially simultaneously. This is a situation not found in the
typical design application for an image intensifier, night vision or low-light-level imaging. Microchannel plates
(MCPs) are known to exhibit gain saturation that could result in non-linear signal response in scintillator imaging,
limiting quantitative measurement capabilities. A calibrated LED photon source was developed that can provide a
known average number of photons per unit area in a small spot size, similar to that seen due to a gamma-ray
interaction in a BazookaSPECT imager. A BazookaSPECT imager is composed of a columnar scintillator and an
image intensifier, with output light optically imaged onto a CCD camera. The calibrated source was used to
investigate gain-saturation effects for two Proxivision, GmbH image intensifiers, a single-stage BV 2583 EZ and a
two stage BV 2583 QZ-V 100N in a BazookaSPECT imaging configuration. No gain saturation was found for the
single-stage image intensifier up to more than 100 optical photons per microchannel, but significant gain-saturation
non-linearities were measured in the two-stage image intensifier at high gains for >12 optical photons per
microchannel. Implications for scintillator imaging using such systems are discussed.
