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 ion linacs. 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 with a wire scanner. In Phase I, we performed full electromagnetic design and in-depth analysis of the proposed multi- dimensional bunch shape monitor, which included beam dynamics studies. In the numerical model, we achieved a significant improvement in collection efficiency and linearity of the beam. A prototype of the improved focusing system was fabricated and delivered to the Spallation Neutron Source (SNS), with proof- of-principle tests planned in the near future. We also performed conceptual engineering design of the scanner, including the design of a movable wire system. In the Phase II project, we will develop the next generation bunch shape monitor prototype, taking advantage of all the aforementioned improvements, and test it at SNS. The full system will include the RF cavity, beam formation system, detectors and data acquisition system. The device will be engineered, fabricated and assembled at RadiaBeam, and then delivered to SNS where the commissioning program will include beam tests with a proton source. Success in this project will enable RadiaBeam to deliver a useful instrument 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 industrial and medical accelerators for ion implantation, isotope production, ion therapy, nuclear energy and materials irradiation.