Paper | Title | Other Keywords | Page | ||
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IT04 | Fast Positional Global Feedback for Storage Rings | feedback, closed-orbit, power-supply, damping | 7 | ||
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Stability of the closed orbit of a storage ring is limited by
the stability of the components defining this orbit:
magnets position and field values. Measurements of the
variation of the stored beam orbit with respect to a
nominal orbit and application of orbit correction derived
from these measurements can reduce these distortions.
The subject of this talk is the implementation of such
correction at high frequencies (up to about 100 Hz) using
global correction schemes.
The basic theoretical aspects of the problem will be
presented:
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CT05 | Daresbury SRS Positional Feedback Systems | feedback, multipole, wiggler, photon | 64 | ||
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The Daresbury SRS is a second generation synchrotron
radiation source which ramps from its injection energy of
600 MeV to 2.0 GeV. Beam orbit feedback systems have
been in routine operation on the SRS since 1994 and are
now an essential element in delivering stable photon
beams to experimental stations. The most recent
enhancements to these systems have included the
introduction of a ramp servo system to provide the orbit
control demanded by the installation of two new narrow
gap insertion device and development of the vertical orbit
feedback system to cope with an increasing number of
photon beamlines. This paper summaries the current
status of these systems and briefly discusses proposed
developments.
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PS16 | The fast head-tail instability suppression in multibunch mode at VEPP-4M | feedback, injection, kicker, impedance | 138 | ||
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In this paper the bunch-by-bunch transverse feedback
system for suppression fast head-tail as well as coupled
bunch instabilities is described. The experimental results
of the feedback affecting on the current threshold are
presented. The effects of reactive and resistive feedback
on the current threshold are discussed. Two times as large
the bunch current than the threshold current was obtained.
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PT10 | Emittance and dispersion measurements at TTF | emittance, quadrupole, linac, acceleration | 180 | ||
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It is well known that beam dispersion , along with the
Twiss parameters and emittance, contributes to the beam
spot size. So that, in general, anomalous dispersion is an
undesirable event and must be minimized by careful tuning
the machine. If not, when the spot size is used to infer
beam emittances, as it is the case of the "quadrupole
scan" method, basically employed at TTF, the unknown
dispersion can lead to overestimated values for the emittance.
This paper presents the first attempt to determine the
dispersion function at several points of the TTF Linac and
to separate its contribution to the local emittance measurement,
performed by means of the OTR imaging technique.
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PT11 | Dipole modes study by means of HOM couplers at SBTF | kicker, coupling, pick-up, damping | 183 | ||
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High order modes (HOM) are generated by the interaction
of a bunched beam with an accelerator environment. They
may act destructively on following particle bunches, leading
to an increase of the transverse oscillation amplitude
and finally to the deterioration of the emittance. Dipole
modes have been studied at the S-Band Test Facility at
DESY. One accelerating structure, specially designed for
this test linac, is equipped with waveguide pick-ups for
measuring the HOMs. For one part of the experiments, a
modulation of the transverse offset of the bunches at the
structure entrance has been induced using a fast broadband
kicker and the effect was measured with a precise stripline
BPM. No high impedance modes were clearly found in the
structure, which has been detuned and damped by both the
tapered geometry of the structure and an absorbing stainless
steel coating applied on the iris tips.
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