Synchronous Detection of Beam Induced Pulses*

This note describes a type of detector which will be used for measuring the amplitudes of short beam induced pulses such as the ones received from a small pick-up electrode. The circuit is called "synchronous "I because it takes a sample of the quantity to be measured in synchronism with the pulse repetition rate; the data can be averaged over many samples such as is done for the measurement of the beam position, or the detector output can be observed directly, without any filtering, as is the case when bunch oscillations are sought. Emphasis was put on three areas in this design: linearity, large dynamic range and immunity to timing variations, Linearily and absence of "knee", or dead zone near the origin, is important for beam position monitoring since they influence the normalization factor; the inputoutput characteristic of this circuit departs from a straight line by less than 1% of full-scale over four decades of input signal variation. The timing of the detector trigger can change by +_2 nsec without impairing the above specifications.