ADVANCED TECHNOLOGIES FOR NEXT-GENERATION CCD DETECTORS

R.D. Durst¹ and L. Häming²

¹ Bruker-AXS Inc., 6300 Enterprise Lane, Madison, WI 53719 Email: rdurst@bruker-axs.com
² Bruker-AXS GmbH, Rheinbrückenstr, 76181 Karlsruhe Email: ludger.haeming@bruker-axs.de

A critical component of every CCD-based X-ray imager is the phosphor screen which converts the incident X-ray flux to visible light.

The characteristics of an ideal X-ray phosphor include:

• strong X-ray absorption
• high conversion efficiency
• good spectral matching to the CCD
• good linearity
• fast time response and
• extremely low afterglow levels

The characteristics of commercially available X-ray phosphors are discussed with particular attention given to lanthanide-doped Gd₂O₂S (which has become the de-facto standard for CCD-based X-ray imaging). However, Gd₂O₂S was originally developed as an intensifier for ortho film and hence its time response, spectral output and conversion efficiency are not optimal for CCD imaging.

The need for X-ray phosphors, which are specifically optimised for CCD detectors has been recognised for some time.

Here we report on studies of the underlying physical limits to X-ray phosphor performance and the development of a new class of X-ray phosphors, which exhibit:

• higher conversion efficiency
• better spectral matching
• lower afterglow levels and
• superior linearity compared to the best conventional phosphors.