Non-Destructive Technique for Measurement of Electron Bunch Longitudinal Charge Distribution

Measurement of the longitudinal charge distribution of short electron bunches moving with relativistic velocities is among the major challenges in the domain of accelerator diagnostics. The strict control of the longitudinal distribution is critical for the operation of X-ray Free Electron Lasers (FELs) and Energy Recovery Linacs (ERLs). Several techniques are presently employed; however, none of them can offer simultaneously high resolution and low cost while at the same time preserving the quality of the measured bunch. One high resolution technique uses a deflecting cavity to spread the bunch in a perpendicular direction. However, it is very expensive and completely destroys the bunch in the process of measurement. Other techniques rely on remotely sensing the electro-magnetic field of the bunch. These are non-destructive, but are limited in sensitivity and resolution, and need to be placed close to the bunch creating risk of bunch interception and radiation damage to components. Our novel solution is non-destructive, has good resolution and is affordable. AES proposes a novel approach that builds upon one of the existing non-destructive techniques. With the help of a low energy electron beam, we will probe the relativistic bunch electro-magnetic field. Afterward we will use a deflecting cavity to analyze the effect on the probe beam due to the relativistic bunch electro-magnetic field. Since the probe beam will have very low energy compared to the relativistic bunch, the requirements for the deflecting cavity will be much lower resulting in a smaller measurement system with a lower cost. AES will demonstrate that the proposed non-destructive technique for measurement of the longitudinal charge distribution of short bunches is capable of achieving the desired resolution and sensitivity while keeping the costs low. A comprehensive simulation framework will be established to demonstrate the performance and set the requirements for the system, and the conceptual design of the measurement device will be completed. Commercial Applications and Other Benefits: The development of non-destructive technique for longitudinal charge distribution measurements is important for existing and future accelerators such as FELs, ERLs and 3-rd generation light sources. The possibility of applying instantaneous feedback will improve the beam quality delivered by these machines, increase their efficiency and reduce operational costs. In addition, the absence of material components on the path of the relativistic bunch will eliminate component activation and reduce the amount of radiation produced by bremsstrahlung