Improved Multi-dimensional Bunch Shape Monitor

Measuring longitudinal beam parameters is important for operation and development of high intensity linear accelerators, but it is notoriously difficult for ion beams at non-relativistic energies. The Bunch Shape Monitor (BSM) is a well-known device used for measuring the longitudinal bunch distribution in a hadron linac. However, the existing BSM models have poor electron collection efficiency from the wire and are limited to one dimensional measurements of the phase coordinate. At the same time, there is a great potential of using BSMs for advanced beam dynamics experiments, but the technical limitations of the existing design make it difficult. In response to this problem, RadiaBeam has designed a BSM with improved performance that incorporates three major innovations. First, the collection efficiency was improved by adding a focusing field between the wire and the entrance slit. Second, an improvement of the measurement speed was achieved by sampling longitudinal profiles of multiple energy slices simultaneously. Finally, the design will be augmented with both a movable wire and a microwave deflecting cavity to add functionality and enable measuring the transverse profile as a wire scanner. To date we have developed and built a focusing system for the existing BSM with a significant improvement in collection efficiency and linearity of the beam. A prototype of the improved focusing system was fabricated and delivered to SNS, with proof-of-principle tests demonstrating a significant improvement of BSM performance. Then, we developed the next generation bunch shape monitor prototype, taking advantage of all the aforementioned improvements, which was fabricated, assembled, tested and shipped to SNS for further evaluation. In the proposed Phase IIB we will develop a new RF cavity with the revised design to achieve fabrication, tuning, and operation simplicity as well as to improve its focusing parameters. Then we will develop an EPICS compatible data acquisition and control system for ease of facility integration. Engineering design will be significantly improved to allow robustness, reliability, and transportability of the cavity. This design revision will also allow us to reduce the number of components to reduce the BSM production costs. Success with this project will enable RadiaBeam to deliver a useful instrument used for measuring the longitudinal bunch distribution at the SNS facility. The proposed instrument can be used not only in numerous scientific proton and ion accelerators across the world but also in the majority of industrial and medical accelerators for ion implantation, PET isotopes production, ion therapy, nuclear energetics and materials irradiation.