Speaker
Description
Monitoring the longitudinal bunch shape is important for understanding beam dynamics and maintaining beam quality in accelerator facilities. Conventional bunch shape monitors are often interceptive, making continuous measurements difficult during beam operation. Nondestructive approaches based on residual gas have also been developed to reduce beam interaction; however, these systems are generally more complex and require greater effort for installation and maintenance than capacitive pick-up monitors.
We developed a nondestructive Capacitive Pick-Up type Bunch Shape Monitor (CPU-BSM) for nonrelativistic ion beams. The CPU-BSM detects electrical signals induced on a capacitive pick-up electrode without inserting material into the beam path, enabling online bunch-shape monitoring with minimal interaction with the beam and offering advantages in terms of maintenance. For nonrelativistic beams, the longitudinal electric-field spread causes the measured signal to appear broader than the actual bunch. To correct this effect, a reconstruction algorithm was developed to recover the longitudinal bunch profile from the measured signal.
The monitor geometry and signal transmission structure were designed and optimized using electromagnetic simulations. Following fabrication, a dedicated coaxial test bench was developed to reproduce beam-like electric-field signals and verify the response of the fabricated devices before beam installation. The test bench also allows manufacturing and assembly issues in internal structures, which are difficult to inspect after fabrication, to be identified. The performance of the CPU-BSM was subsequently validated with approximately 25 MeV proton beams using a fast Faraday cup as a reference.
This presentation introduces the CPU-BSM and its development process, including electromagnetic design, bench testing, and beam validation.