Authors:
Kai Kruppa
1
;
Sven Pfeiffer
2
;
Gerwald Lichtenberg
1
;
Frank Brinker
2
;
Winfried Decking
2
;
Klaus Flöttmann
2
;
Olaf Krebs
2
;
Holger Schlarb
2
and
Siegfried Schreiber
2
Affiliations:
1
Hamburg University of Applied Sciences, Germany
;
2
DESY, Germany
Keyword(s):
Nonlinear Systems, Thermal Modelling, Predictive Control, RF Cavities.
Related
Ontology
Subjects/Areas/Topics:
Case Studies
;
Dynamical Systems Models and Methods
;
Formal Methods
;
Health Engineering and Technology Applications
;
Neural Rehabilitation
;
Neurotechnology, Electronics and Informatics
;
Performance Analysis
;
Simulation and Modeling
;
Simulation Tools and Platforms
Abstract:
High precision temperature control of the RF GUN is necessary to optimally accelerate thousands of electrons
within the injection part of the European X-ray free-electron laser XFEL and the Free Electron Laser FLASH.
A difference of the RF GUN temperature from the reference value of only 0.01 K leads to detuning of the
cavity and thus limits the performance of the whole facility. Especially in steady-state operation there are
some undesired temperature oscillations when using classical standard control techniques like PID control.
That is why a model based approach is applied here to design the RF GUN temperature controller for the
free-electron lasers.
A thermal model of the RF GUN and the cooling facility is derived based on heat balances, considering the
heat dissipation of the Low-Level RF power. This results in a nonlinear model of the plant. The parameters are
identified by fitting the model to data of temperature, pressure and control signal measurements of the FLASH
facility, a pilot test facility for the European XFEL. The derived model is used for controller design. A linear
model predictive controller was implemented in MATLAB/Simulink and tuned to stabilize the temperature of
the RF GUN in steady-state operation. A test of the controller in simulation shows promising results.
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