Speaker
Description
In the framework of developing a high-resolution cavity beam position monitor (cBPM) and data acquisition (DAQ) system for future linear colliders, a re-entrant cBPM designed at CEA Saclay [1] was tested at the end of the LINAC at the Accelerator Test Facility (ATF), KEK. Position and reference signals are extracted from the same BPM and processed identically. The signals at 1.725 GHz (dipole mode) and 1.250 GHz (monopole mode) were down-converted to lower frequencies using an analog down-conversion chain [2], followed by digital signal processing through a digital down-conversion (DDC) algorithm [3].
The tests highlighted the critical role of using a phase-locked local oscillator (LO) in the analog stage to ensure stable and consistent position measurements. Preliminary results just after beam tests show a resolution below 20 μm for a beam intensity of 0.44 nC/bunch. This is expected to improve after algorithm tuning and data preselection.
This contribution will present the results of the measurements carried out at ATF during May and June 2025, as well as the current status of the new high-resolution BPM design for the ILC Main Linac.
[1] SIMON, Claire et al. Performance of a reentrant cavity beam position monitor. Physical Review Special Topics - Accelerators and Beams, 2008, vol. 11, no 8, p. 082802.
[2] ORAN Friar and LYAPIN Alexey, Building, Optimizing and Measuring the Performance of Downconverting Electronics Using X-Microwave Modules. PH4100 Major Project Report, RHUL (2022).
[3] WALSTON, Sean et al. Performance of a high resolution cavity beam position monitor system. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007, vol. 578, no 1, p. 1-22
