Imaging properties of scintillator coated silicon CCDs

Silicon CCDs are widely used for X-ray imaging in dentistry. Due to the low absorption coefficients for X-rays in silicon the CCD is generally coated with a scintillating layer. In this work we have measured the X-ray response from a number of different scintillators on a typical silicon CCD. The response has been characterized in terms of generated signal per amount of incident X-ray energy, spatial resolution and signal to noise ratio. The measured values have been compared with simulation data and the results have been used to estimate the performance of some of the new infrared emitting scintillating materials recently reported as well as commonly used scintillators on CMOS pixel sensors. This work confirms that the highest image quality is obtained by using scintillators with high X-ray absorption and high light output into the sensor. The signal from direct absorption of X-rays in the silicon should be minimized.