Speaker
Description
Cavity Beam Position Monitors (cBPMs) are critical components in the diagnostic systems of next-generation particle colliders. They provide precise beam position measurements, with nanometer-level resolution, essential for guiding and stabilizing high-energy beams to maximize luminosity at the collision point. These resonant BPMs operate by detecting specific electromagnetic modes excited when a beam passes off-center through a cavity. The TM010 monopole mode is always excited by the passing bunch and it is used for normalization, as it depends on the bunch charge. The TM110 dipole mode, with an amplitude proportional to the beam offset on the transverse plane, provides the position measurement.
A new cryogenic setup is under development to house both a reentrant cBPM and a superconducting (SC) quadrupole for use in the ILC Main Linac. The BPM prototype must measure the beam position on a bunch-by-bunch basis, achieving temporal and spatial resolutions of less than 369 ns and 1 μm, respectively. This work focuses on the development of a high-resolution cBPM with the mechanical specifications required for cryostat integration.
The optimization of an already existing cBPM design developed by CEA Saclay is performed by means of commercial software CST Studio Suite, where electromagnetic simulations are used to evaluate the cBPM’s performance. Estimating the cavity RF characteristics allows determination of the output power at the BPM ports, while monitoring the S-parameters helps to prevent the phenomenon known as cross-talk.
Additionally, selecting suitable readout electronics is essential to effectively down-convert the high-frequency, fast-decaying cBPM signals while maintaining the required spatial resolution. After digitizing the signals, a digital down-conversion (DDC) algorithm retrieves the signal information from monopole and dipole modes for accurate beam position measurements.
The designed cBPM and its associated electronics readout system will be tested at ATF under ambient conditions at KEK, Japan.
This presentation will detail the operating principles of the cBPM and provide an overview of the developed design and electronics, demonstrating the high-resolution beam position measurements achieved.
