Regulation of electron bunch arrival time for a continuous-wave linac: Exploring the application of the H2 mixed-sensitivity problem

Le résumé fourni par la source

Regulating the arrival time of electron bunches is a crucial step to improve the temporal resolution of accelerator-based pump-probe experiments. In this regard, an electron beam regulation method called beam-based feedback, has been shown to work well for stabilizing longitudinal beam properties on pulsed accelerator machines. Essentially, the method resembles a typical design of a proportional regulator, where the plant is represented by an electron beam response matrix, and where the inversion of such matrix produces the regulator. In recent years, however, linear accelerators that operate in a continuous-wave mode have received increasing attention. One of the key features of such machines is the improved statistics of measured data, which enables a high-resolution spectral analysis of the noise acting on the electron beam. This new insight allows us to reinterpret the electron beam regulation as a disturbance rejection goal, where the disturbance is based on measured frequency data. In this work, we show that the proportional beam-based feedback method has a principal performance limitation that becomes apparent by analyzing continuous-wave data. To improve this situation, we propose a regulator design that incorporates a dynamical disturbance model formulated in the context of the so-called ${\mathcal{H}}_{2}$ mixed-sensitivity problem. The designed regulator demonstrated excellent agreement between the model and measurements carried out at the continuous-wave linear accelerator ELBE and showed a potential to improve the proportional regulator approach.

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