A fast luminosity monitor system for PEP II

The PEP II fast luminosity system provides a measurement of luminosity to the control system with a time constant of 0.3 s and fluctuations less than 0.1% for this interval, adequate for use in feedback systems. Continuous visual updates of luminosity are provided. The alignment of the positron beam at the collision point can also be monitored, and there is a visual display of the luminosity associated with each bunch pair in the machine, sampled approximately every 2 s.