Paper |
Title |
Other Keywords |
Page |
IT05 |
The Comparison of signal Processing Systems for Beam Position Monitors
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insertion, collider, single-bunch, storage-ring |
12 |
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- G. Vismara
CERN, Geneva, Switzerland
|
At first sight the problem of determining the beam
position from the ratio of the induced charges of the
opposite electrodes of a beam monitor seems trivial, but
up to now no unique solution has been found that fits the
various demands of all particle accelerators.
The purpose of this paper is to help instrumentalist in
choosing the best processing system for their particular
application.
The paper will present the different families in which
the processing systems can be grouped.
A general description of the operating principles with
relative advantages and disadvantages for the most
employed processing systems is also presented.
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IT07 |
Bunch Length Measurements
|
laser, radiation, linac, gun |
19 |
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IT09 |
Diagnostics in Heavy Ion Machines
|
ion, heavy-ion, diagnostics, linac |
28 |
|
- P. Strehl
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
|
An overview of the measurements of most important beam
parameters in heavy ion machines is given. The special
characteristics of heavy ions concerning the great variety
of parameters with respect to the type of accelerator (linac,
circular machine), the species of accelerated ions as well
as their energy, beam intensity, beam emittance and time
structure are considered. The consequences for the design
of beam diagnostic systems are discussed. Typical examples
of measuring systems are given. Experimental results
taken during the long operating time of the GSI facilities,
covering a wide range of parameters, are reported.
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IT12 |
Use of Superimposed Alternating Currents in Quadrupoles to Measure Beam Position with Respect to their Magnetic Centre
|
quadrupole, storage-ring, lattice, radiation |
38 |
|
- N. Marks
CLRC, Daresbury Laboratory, Warrington, UK
|
The positional stability of the electron beam in a modern
state-of-the-art synchrotron radiation source is critical, as
the many experimental users require consistency in the
position and dimensions of the incoming photon beams
which are incident on their experimental samples. At the
Daresbury Synchrotron Radiation Source (SRS),
inaccuracies in the measurements of the positions of both
beam position monitors and the lattice quadrupoles can be
overcome by measuring the position of the electron beam
with respect to the magnetic centres of the quadrupoles.
This was achieved by superimposing an alternating
('ripple') current on the direct current excitation of a
single lattice quadrupole and examining the resulting
beam oscillations at remote positions in the storage ring.
If the electron beam is then subjected to a local distortion
at the position of this quadrupole, the amplitude of the
beam oscillation induced by the superimposed current is
minimised (nominally zero) when the beam is at the
quadrupole's magnetic centre. This paper presents details
of the electrical circuit developed to inject an alternating
current into the coils of individual quadrupoles and gives
details of the results achieved to date.
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CT02 |
Determination of Radial Ion Beam Profile from the Energy Spectrum of Residual Gas Ions Accelerated in the Beam Potential
|
space-charge, ion, emittance, acceleration |
50 |
|
- R. Dölling
IAP, Institut für angewandte Physik der Johann Wolfgang Goethe Universität
|
Residual gas ions (RGI) created from collisions of
positive beam ions (BI) with residual gas atoms are
accelerated out of the ion beam by its space charge
potential. It is demonstrated that with one-dimensional
radial symmetry the radial distributions of BI density and
space charge potential can be determined from the energy
distribution of RGI radially leaving the beam tube. RGI
energy spectra were taken with an electrostatic analyser of
Hughes-Rojansky type on a 10 keV 1.5 mA He+ beam.
For comparison the radial BI density distribution was
determined with a radial wire probe, an electron beam
probe and a beam transport calculation based on an
emittance measurement located downstream.
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CT07 |
The ELETTRA Streak Camera: System Set-Up and First Results
|
synchrotron, single-bunch, storage-ring, cathode |
72 |
|
- M. Ferianis
ELETTRA, Sincrotrone Trieste, Trieste, Italy
|
At ELETTRA, a Streak Camera system has been
installed and tested. The bunch length is a significant
machine parameter to measure, as it allows a direct
derivation of fundamental machine characteristics, like its
broadband impedance. At ELETTRA the Light from a
Storage Ring Dipole is delivered through an optical
system to an Optical Laboratory where it can be observed
and analysed.
The Streak Camera is equipped with different timebases,
allowing both single sweep and dual sweep
operation modes, including the Synchroscan mode. The
Synchroscan frequency equal to 250 MHz, which is half
of the ELETTRA RF frequency, allows the acquisition of
consecutive bunches, 2ns apart. To fully exploit the
performances of the Streak Camera, an optical path has
been arranged which includes a fast opto-electronic
shutter. By doing so, the optical power deposited on the
photo-cathode is reduced in the different ELETTRA
fillings.
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CT10 |
Real Time Display of the Vertical Beam Sizes in LEP Using the BEXE X-Ray Detector and Fast VME Based Computers
|
positron, luminosity, synchrotron, radiation |
87 |
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PS10 |
Ionisation losses and wire scanner heating: evaluation, possible solutions, application to the LHC.
|
proton, lepton, ion, vacuum |
120 |
|
- C. Fischer
CERN, Geneva, Switzerland
|
Harmful heating mechanisms, resulting in wire breakage,
limit the utilisation of wire scanner monitors to below
a given beam intensity. This threshold depends on the
accelerator design parameters. In lepton colliders, the
short beam bunches generate strong wake-fields inside the
vacuum pipe which are sensed by the wire and are the
predominant current limit. These effects can be minimised
by a smooth design of the monitor cross section and by
choosing a wire made of an insulating material.
A second source of energy deposition inside the wire,
also present in hadron machines, and even when the wire
material is insulating, results from collision and ionisation
of the wire material atoms by the incident beam particles.
Calculations are presented to evaluate the efficiency of
this process and a possible solution is suggested which
may reduce this limitation. An example is given for the
case of the LHC.
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PS11 |
Ionisation profile monitor tests in the SPS
|
ion, proton, space-charge, insertion |
123 |
|
- C. Fischer, J. Koopman
CERN, Geneva, Switzerland
|
A beam profile monitor, from DESY, based on the ionisation
of the rest gas, was installed in the SPS in 1997. Horizontal
beam profiles obtained from the extracted positive ions are
presented. It is known that in this case some broadening affects
the signal, which limits the monitor resolution. This broadening
results from the transverse momentum that the ions gain
within the space charge field of the circulating beam.
In order to improve the resolution for LHC applications, the
monitor was modified during the 1998/99 winter stop. A magnetic
focusing was incorporated. The aim is to analyse the signal
provided by collecting the electrons, rather than the ions,
of the ionised rest gas. The details of this new set-up and the
expectations for the resolution limit will be compared to the
measurement results.
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PS14 |
Comparative test results of various beam loss monitors in preparation for LHC
|
proton, ion, beam-losses, simulation |
132 |
|
- J. Bosser, G. Ferioli
CERN, Geneva, Switzerland
|
Beam loss detectors will play an important role in the
protection of the superconducting LHC magnets.
Different types of detectors have been tested in the SPS
ring and secondary beam lines with a view to their
possible use for this application.
This paper describes the measurements made with:
microcalorimeters at cryogenic temperatures, PIN diodes,
ionisation chambers, scintillators, and ACEMs.
Measurements made using proton beams showing their
relative sensitivities, linearities in counting or analog
mode and minimum detection level will be presented.
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PS19 |
Photon counting detectors for fill structure measurements at visible wavelengths
|
photon, storage-ring, single-bunch, diagnostics |
144 |
|
- H.L. Owen
CLRC, Daresbury Laboratory, Warrington, UK
|
When making accurate measurements of the relative
populations of electron bunches in a storage ring, notably
in light sources operating with only a single bunch filled,
the method of time-correlated single photon counting
gives the greatest dynamic range. The timing resolution
and background noise level of the photon detector
employed is critically important in determining the overall
performance of the system; hitherto the best performance
has been obtained detecting X-ray photons using
avalanche photodiodes. On the SRS at Daresbury a visible
light diagnostic station offers greater ease of access to
instrumentation and operational advantages. A review is
given of the detector types which have been employed,
and the performances which can be obtained using visible
light.
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PS20 |
A current digitizer for ionisation chambers/SEMS with high resolution and fast resoponse
|
ion, power-supply, pick-up, monitoring |
147 |
|
- H. Reeg
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
|
A current-to-frequency converter (CFC), recently
developed, exhibits a response time up to the ms region.
The frequency limit is raised beyond 1 MHz, extending
the linear range by a factor of 100. The conversion
factor reaches 10-13 C/pulse. The converter is
employed, combined with ionization chambers (IC) and
secondary electron emission monitors (SEM), to
measure the intensity of the extracted beam in the
transfer lines adjoining GSI's heavy ion synchrotron
(SIS). Fast intensity fluctuations during the particle
spill can be observed.
Reduced hum and noise pickup, better handling and
mounting flexibility as well as reduced costs are
achieved building up the spill monitoring system with
distributed components.
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PT01 |
Closed-orbit correction using the new beam position monitor electronic of Elsa Bonn
|
closed-orbit, quadrupole, resonance, alignment |
153 |
|
- J. Dietrich, I. Mohos, J. Keil
IKP, Forschungszentrum Jülich GmbH, Jülich, Germany
|
RF and digital electronics, developed at the
Forschungszentrum Jülich/IKP were integrated to form
the new beam position monitor (BPM) system at the
Electron Stretcher Accelerator (ELSA) of the University
of Bonn. With this system the preservation of the
polarization level during acceleration was currently
improved by a good correction of the closed-orbit. All
BPM offsets relative to the magnetic quadrupole centers
were determined by the method of beam-based alignment.
The optics functions measured by the BPM system are in
good agreement with theoretical predictions.
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PT12 |
Aspects of bunch shape measurements for low, intense ions beams
|
ion, target, scattering, rfq |
186 |
|
- P. Forck, F. Heymach, U. Meyer, P. Moritz, P. Strehl
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
|
For the characterisation of the ion beam delivered by
the new High Current LINAC at GSI, the time structure
of bunches and the knowledge concerning their intensity
distribution in longitudinal phase space is of great
importance. At least 100ps time resolution and the
capability of measuring long tails in the distribution were
design parameters. Taking advantage of Rutherford-scattering
to reduce the count rate, a direct time of flight
measurement technique using diamond detectors can be
applied. First results are reported. Plans for determine the
energy of individual ions by detecting secondary
electrons emitted from a thin C foil using 1m drift are
discussed.
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PT15 |
High current precision long pulse electron beam position monitor
|
kicker, instrumentation, diagnostics, target |
193 |
|
- S.D. Nelson, Y.J. Chen, T. Fessenden, C. Holmes
LLNL, Lawrence Livermore National Laboratory, Livermore, CA, USA
|
Precision high current long pulse electron beam position
monitoring has typically experienced problems with high
Q sensors, sensors damped to the point of lack of precision,
or sensors that interact substantially with any beam
halo thus obscuring the desired signal. As part of the
effort to develop a multi-axis electron beam transport system
using transverse electromagnetic stripline kicker technology,
it is necessary to precisely determine the
position and extent of long high energy beams for accurate
beam position control (6 - 40 MeV, 1 - 4 kA, 2 μs
beam pulse, sub millimeter beam position accuracy.)
The kicker positioning system utilizes shot-to-shot adjustments
for reduction of relatively slow (< 20 MHz) motion
of the beam centroid. The electron beams passing through
the diagnostic systems have the potential for large halo
effects that tend to corrupt position measurements.
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