Synchronous RF-Receivers for Beam Position and Intensity Measurements at the CERN SPS Collider

In view of new modes of operation of the SPS, the old superheterodyne receivers designed for the closed orbit measurements of fixed target beams are being replaced by homodyne 200 MHz receivers with a better time resolution for measuring single bunches. The new receivers have a bandwidth of 4 MHz, a dynamic range of 70dB, and are able to measure the position either of continuous beams with 1012 to 5×1013ppp bunched at 200 MHz CW for fixed target physics, or of single bunches shorter than 5ns with 109 to 2×1011 particles per bunch when the SPS is used as a ppbar collider or as an e+e- injector for LEP. The homodyne receiver has been chosen for its simple layout, linearity, excellent noise inmunity and high accuracy of the beam centre position. The built-in calibration facility using the intensity signal of the beam allows to calibrate all 240 receivers and acquisition systems of the closed orbit measurement for zero offset errors to less than 5×10-3 of the monitor radius and for relative gain errors to less than 4×10-2. The same synchronous receivers, but running at 20 MHz and 50 MHz, are also used for intensity and lifetime measurements of the SPS collider.