Towards the limits of frame transfer CCDs in beam instrumentation

Charge-coupled devices (CCDs) are used for beam position and beam size measurements with screens and synchrotron radiation monitors. They have a large spatial resolution and a high dynamic range which make them interesting for high resolution two-dimensional measurements. In most applications, the video signal is digitised with a frame grabber and then the beam parameters are computed. The results are limited in resolution, usually to 8 bits, and in rate. These restraints were seen as major limitations for fast and precise beam observations with synchrotron light monitors in LEP, where the revolution frequency is 11 kHz. They have been overcome by using the characteristics of frame transfer CCDs. Advantage is taken of the separate image and memory areas on the CCD chip to control independently the integration and digitising periods to achieve a 12-bit amplitude resolution at the individual pixel level. Using the CCD as a buffer memory, together with a pulsed intensifier, it is possible to make 9 to 18 two...