Speaker
Dr
Bernhard Zipfel
(FH-Fulda / GSI)
Description
At GSI a closed loop beam phase control is planned, which will be used to damp
coherent dipole oscillations of particle bunches. The system is based on a DSP
System for high-precision phase and amplitude detection, which was also developed
at GSI based on commercial DSP, ADC and DAC modules and is also applied for cavity
synchronisation.
A special digital filter with variable pass band is used to convert the beam phase
signal to an adequate correction signal for the accelerating RF-voltage. In order
to get a proper correction signal the digital filter eliminates noise but it
amplifies phase oscillation signals in the matched bandwidth of the synchrotron
frequency of the individual accelerated particles. The filter blocks slow
variations of the beam phase to allow changes of the synchronous phase without
fixing it to a predefined value.
Anyhow the implementation of this digital filter seems to be straightforward and
the realisation does not spend much computational power.
Taking into account limited computing power and given signal processing delays as
well as noise on analogue cables the loop stability limit is determined by
simulation. Influence on beam loss and longitudinal phase space plots can be given.
In future the beam phase control will reduce emittance blow up during accelerating
in SIS18/12.
Author
Dr
Bernhard Zipfel
(FH-Fulda / GSI)
