Abstracts Brochure - CERN

THPCH082
THPCH083
THPCH084
29-Jun-06 16:00 - 18:00 THPCH — Poster Session
Broadband Bunch by Bunch Feedback for the ESRF Using a Single High Resolution and
Fast Sampling FPGA DSP
E. Plouviez, P. Arnoux, F. Epaud, J. Jacob, J.M. Koch, N. Michel,
G.A. Naylor, J.-L. Revol, V. Serriere, D. Vial (ESRF)
410
In order to increase the current in the ESRF
storage ring we have developed a set of multibunch
feedback systems aimed at fighting
longitudinal and transverse coupled bunch
instabilities. The longitudinal feedback (LFB) has been the first system installed and tested. It was designed using the
scheme developed at SLAC, ALS and INFN Frascati: bunch by bunch processing of a beam phase error signal and
correction using a low Q kicker driven by a QPSK modulator. However, we took advantage for this development of
the latest available technology for the signal processing electronics with high resolution, high sampling rate ADC and
DAC, and FPGA DSP, as well as for the FPGA programming environment. It allowed us to substantially reduce the
complexity: the algorithm runs on a single processor, the kicker requires only 200W of RF power to control a 6GeV
beam, and the implementation took only about one year. We will describe the main features of our LFB and present
the results already achieved in the damping of instabilities driven by our RF cavity HOM. We will also report on the
status of the transverse feedback, which is being built up using the same FPGA system as the longitudinal one.
A Tune Feedback System for the HERA Proton Storge Ring
S.G. Brinker, S.W. Herb, F.J. Willeke (DESY) Th. Lohse (Humboldt
University Berlin, Institut für Physik)
The transverse tunes of an accelerator or storage
ring are important parameters which
have to be controlled and adjusted continuously
during beam operation in order to
assure good experimental background conditions. For the HERA proton storage ring, persistent current effects of
the superconducting magnets are the main source for the inadequate repeatability of the tunes without a feedback
while the proton beam is accelerated. A tune feedback has been developed, implemented and tested during beam
acceleration and luminosity operation. Considering the different conditions during energy ramps and luminosity
runs two versions of this feedback system have been established based on different correction and peak-finding
algorithms (e.g. wavelet analysis). No additional excitation is needed on top of the standard tune indication system
in HERA. The tunes could be kept constant during beam accceleration with a standard deviation of delta Q = 0.003.
In luminosity runs where the tune control is more critical, first tests resulted in a standard deviation which was a
factor of ten smaller. The feedback system is implemented as a standard tool for beam acceleration.
Control Path of Longitudinal Multibunch-feedback System at HERA-p
F.E. Eints, S. Choroba, M.G. Hoffmann, U. Hurdelbrink, P.M. Morozov,
J. Randhahn, S. Ruzin, S. Simrock (DESY)
A longitudinal broadband damper system to
control coupled bunch instabilities has been
developed and installed in the proton accelerator
HERA-p at the DESY. The control sys-
tem consists of a control path and a Fast Diagnostic System (FDS) for oscillation diagnostic. The control path consists
of FPGA-based digital controller, vector modulator, 1kW power amplifier, kicker-cavity and beam. In the FDS, the
bunch phase signals are sampled by a digital FPGA board with 14Bit ADC (controller) with a sampling frequency
of 10.4MHz. Phase calculation for all bunches and offset correction will be done by FPGA software which includes
a digital filter. The filter has to be able to deal with a slowly changing synchrotron frequency. Here we consider a