Validation of a narrowband signal processing system for beam position monitoring purposes in linear accelerators

A new RF frontend for a beam position monitoring system for electron linear accelerators (Linacs) is discussed. The frontend applies a waveguide based input filter section for processing the pulse train, generated by non-interceptive pickups and selection of the desired beam harmonic. Due to increased accuracy, narrowband signal processing was chosen for further signal treatment. Therefore, a two-channel downconverter was designed incorporating two single-balanced diode mixer stages optimized for processing frequencies around 6 GHz, the second beam harmonic in S-Band Linacs. Device characteristics and component validation in a demonstrator with electro-magnetic excitation, simulating beam-induced fields are presented.