Accelerating field stabilization in IOT powered E-XFEL cryomodule operating with high loaded Q

Upgrade of the pulsed E-XFEL, which is the largest free electron laser
in the world, to continuous wave (CW) operation require usage of the RF
power source alternative to klystron such as Inductive Output Tube (IOT).
In addition operation with high loaded quality
factor (QL) is required for a maximum power efficiency. However, high
QL values in order of 2e7 decreases the bandwidth of the cavities to
the range of tens of Hz. Such system is then highly susceptible to
both microphonics and Lorentz force detuning (LFD).

In this contribution control system stabilizing the accelerating gradient
under such conditions is evaluated. The system is equipped with a RF
feedback loop accompanied with a piezo based cavity detuning
controller both realized using the MicroTCA.4 technology.