Speaker
Description
The CW operation mode of the superconducting linear accelerator ELBE allows
reinterpreting a beam-based feedback control problem as a regulation goal.
By moving the focus of attention to low-frequency RF noise, i.e. the disturbance
that makes a significant contribution to electron beam fluctuations, the necessity
to pursue a bandwidth-demanding bunch-by-bunch control can be avoided.
Simultaneously, the fundamental bandwidth limitation of a superconducting RF
cavity, i.e. the usual actuator in such control schemes, no longer poses a problem.
Furthermore, the benefit of implementing the resulting beam-based feedback regulator
using an FPGA is twofold. Firstly, the low-latency nature of FPGAs allows dealing with
fast processes, such as the regulation of an electron bunch arrival time. Secondly,
the high configurability of FPGAs enables the implementation of sophisticated regulation
algorithms, e.g. an optimal H2 regulator in its state-space representation.
Accordingly, in this report we provide the details of the work that has been done
so far, both in control engineering and digital logic domains. We support our
work by demonstrating the results of the latest machine studies at ELBE.
These results show not only a reduction in the bunch arrival time jitter,
but also a correspondence between a model and a measured data.
