Speaker
Dr
Stefan Simrock
(DESY)
Description
The designer of an RF control system will be aiming for the best possible control
of the cavity fields that is possible. Optimal control deals with the problem of
finding a control law for a given system such that a certain optimality criterion
is achieved. In control theory the control that minimizes a certain cost functional
is called the optimal control. The problem formulation usually also contains
constraints.
For rf control the goal is usually to regulate the accelerating field to the
required stability (or better if possible) with the available rf power. Contraints
usually include robustness against parameter variations, rf power limititations,
minimizing the trip rate (i.e. maximum availability of the accelerator), maximizing
the lifetime of the components, fast recovery from faults, and other operational
aspects.
Important for the quality of field control are also the cavity field detectors, the
beam diagnostics, the actuators available for control, the perturbations to be
controlled and the choice of the controller. The controller usually applies fast
control to the klystron drive (low level rf) and slow and fast control to the
cavity frequency tuners. Design choices for fast rf control include amplitude and
phase versus IQ-control, analog versus digital, self-excited loop versus generator
driven and individual cavity control versus control of the vector-sum. A
combination of feedforward for repetitive errors and feedback for stochastics
errors is used. Slow drifts are often corrected by beam based rf feedback.
The tutorial will present the definition of optimality in control theory and
considerations for optimal control for accelerators. Design choices will be
discussed and compared.
A concept for the optimal controller will be developed.
Author
Dr
Stefan Simrock
(DESY)
