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Image size and pixel size

The IPCS can provide a wide range of different image formats. The choice of format is often difficult, especially since it affects the saturation characteristics of the detector. Potential users should consult the references listed above for a more detailed discussion. Briefly, the image format depends on two factors: Firstly, it is possible to vary the format of the image from the TV camera. Secondly, the signal produced at the TV camera by each photon event is strong enough that it is possible to calculate the centroid of the event to within a fraction of a TV pixel. Thus the pixel size of the final image in the Detector Memory System can be much smaller than the pixel size of the TV image, and the number of pixels can be correspondingly greater.

The readout uses a GEC CCD, and each pixel has a size in both directions corresponding to 84m at the photocathode. These CCD pixels can be subdivided by factors of 1, 2, 4 or 8, producing pixel sizes in X and Y of either 84, 42, 21 or 10.5 microns. A typical setup uses 2560 560 pixels of dimensions 10.5 42 microns, the first figure in each case being in the dispersion direction.

Tue Aug 15 16:42:46 BST 1995