Scintillator crystal radiation detector

DETAILED DESCRIPTION The present invention overcomes the problems associated with prior art invisible radiation detectors by providing simple and efficient means for detecting invisible radiation, converting it to light photons, and then to electrical signals in an efficient manner.
According to the invention, the detector comprises a scintillator crystal and a semiconductor P-N junction photodiode.
The crystal has its surfaces provided with diffusing or reflection-enhancing means except for one optically prepared end surface which thus becomes a window.
When one of the diffused surfaces is impinged by an x-ray beam, the beam will penetrate into the interior of the crystal and will cause light photons to be generated within the crystal by absorption of the radiation energy.
These photons are scattered off the diffused surfaces and eventually pass out the end window of the crystal.
The crystal is affixed by its end window to the surface of the photodiode by an optical coupler and when the photons pass to the photodiode this will cause charge carriers to flow across the P-N junction in the normal manner of a photodiode.
This creates an electrical signal which may be directed into the system, which signal corresponds to the intensity or flux of the initial radiation beam.
The crystal is sufficiently thick to absorb a substantial amount of the energy in the beam, and is shaped so that the end window sees all of the other light-scattering surfaces, providing optimum performance since the light flux collected by the photodiode is essentially a function of the relationship of window area to scintillator volume.
The scintillator area "seen" by the incident radiation beam may be the size of a picture element or pixel.
The crystal can be made relatively small to conform to the size or shape of a beam, thus enabling a plurality of the crystals to be grouped in an array for efficient scanning.
Furthermore, such detectors can be provided with shields to prevent portions from becoming undesirably irradiated, thus permitting only the scintillator crystal or crystals to be subjected to the radiation and preventing damage to the photodiode and optical coupler