Design and offline testing of a resonant stripline beam position monitor for the IRFEL project at NSRL

A 476 MHz resonant stripline beam position monitor (BPM) is planned to be installed in an infrared free electron laser machine at National Synchrotron Radiation Laboratory. This type of BPM was developed based on a standard stripline BPM by moving the coupling feedthrough closer to the short end downstream, which introduces a resonance and therefore a capability for higher resolution compared with broadband BPMs. The design and offline measurement results of the prototype are shown in this paper. The design goal is the optimization of the central frequencies and corresponding quality factors of the three intrinsic transverse electromagnetic modes to roughly 476 MHz and 30, respectively, the fulfillment of which is demonstrated by a transmission parameter test via a network analyzer. Induced voltage signal modeling and an estimation of the position resolution of the designed BPM are shown in detail. Furthermore, a calibration test of the prototype using the stretched wire method is presented, including a description of the test stand and the evaluation of position sensitivities.