Paper |
Title |
Page |
PS02 |
Chromaticity Measurements at HERA-P Using the Head-Tail Technique with Chirp Excitation
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103 |
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- M. Wendt, F. Willeke
DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
- A. Boudsko
TRIUMF, Vancouver, Canada
- O.R. Jones, H. Schmickler
CERN, Geneva, Switzerland
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Experiments have been performed in the HERA proton ring
(HERA-p) to test a quasi non-destructive method of chromaticity
measurements for protons. The method is based
on the detection of the head-tail phase shift of coherend betatron
oscillations using a broadband beam position pickup
and a commercial fast-frame oscilloscope. Previous experiments
have relied on a single kick for transverse excitation,
whereas the results presented here were carried out
using swept frequency chirp excitation. The tests proved
to be successful, and the method seems to be a good candidate
for chromaticity measurement in new large hadron
accelerators, such as LHC.
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PS04 |
Influence of transverse beam dimensions on beam position monitor signals
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106 |
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- A. Jankowiak, T. Weis
DELTA, Institute for Accelerator Physics and Synchrotron Radiation, University of Dortmund, Germany
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In this paper we will evaluate the influence of
transverse beam dimensions on the signal functions of a
beam position monitor (BPM) with capacitive pick-up
electrodes. The error which occurs in the determination of
the beam position when disregarding these effects is
calculated as an example for the DELTA1 BPM.
The possibility to use this effect for the measurement
of the beam size / emittance is discussed.
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PS05 |
Recent Improvements of a Cryogenic Current Comparator for nA Ion Beams with High Intensity Dynamics
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109 |
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- A. Peters, H. Reeg, P. Forck
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
- W. Vodel, R. Neubert
FSU Jena, Institut für Festkörperphysik, Friedrich Schiller Universität, Jena, Germany
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Former measurements of extracted ion beams from the
GSI heavy ion synchrotron SIS showed large current fluctuations
in the microsecond region with a high peak-to-average
ratio. To adapt our Cryogenic Current Comparator
(CCC) to this time structure the detectors electronics have
been carefully modified.
The most important improvement of the new DC
SQUID system affects the enlargement of the bandwidth
and the slew rate of the measuring system. In addition the
existing data acquisition system for e.g. SEMs (Secondary
Emission Monitors) was extended to digitize the CCC signals
simultaneously. Measurements of Argon beams will
be shown to demonstrate the improved capabilities of the
upgraded Cryogenic Current Comparator.
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PS06 |
Turn-By-Turn Phase Space Diagram Construction for Non-Linear Betatron Oscillation
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112 |
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- A. Kalinin, V. Smaluk
BINP, Budker Institute of Nuclear Physics, Novosibirsk, Russia
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The problem of phase space diagram construction for
non-linear betatron oscillation measured by pickup, is
considered. The conventional two-pickup method of
phase trajectory construction was improved. Discrete
Fourier filter applied to data measured yields a large
dividend in accuracy. The result of our investigations is
the method of turn-by-turn phase trajectory construction
using data measured by single pickup. The single-pickup
method developed was tested by computer simulation of
non-linear betatron oscillation in several models of
magnet lattice. Practicality of the method and its accuracy
limitation were studied. The method applying for
experimental study of beam dynamic is discussed.
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PS07 |
Trajectory Measurements in the DAΦNE Transfer Lines
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115 |
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- A. Stella, C. Milardi, M. Serio
INFN-LNL, Laboratori Nazionali di Legnaro, Legnaro, Italy
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An improved beam position monitor system has been
installed in the Transfer Lines (TL) connecting the
DAΦNE Linac to the collider Main Rings through the
Damping Ring, to monitor the beam trajectory and optimize
the transmission efficiency.
Signals from stripline type beam position monitors are
stretched, sampled through Track & Hold circuits and
digitized to 12 bits. The sampling stage is triggered,
according to the timing of the desired beam, to measure
the amplitude of the signals induced on a BPM.
Hardware control, data collection and reconstruction of
the beam position along the Transfer Lines are performed
by the DAΦNE Control System on a VME standard local
processor.
Design issues, implementation and performance of the
system are presented.
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PS09 |
Beam Steering With Image Processing In The Cryring Injection Beamline
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118 |
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- A. Källberg, A. Simonsson
MSI, Manne Siegbahn Laboratory Of Physics, Stockholm, Sweden
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By varying six quadrupoles and observing how the
beam spot moves on three fluorescent screens the beam is
aligned in the injection beamline. The method is now
automated and upgraded by using image processing of the
picture to get the position of the beam.
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PS10 |
Ionisation losses and wire scanner heating: evaluation, possible solutions, application to the LHC.
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120 |
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- C. Fischer
CERN, Geneva, Switzerland
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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
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123 |
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- C. Fischer, J. Koopman
CERN, Geneva, Switzerland
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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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PS12 |
Performance of the new SPS beam position orbit system (MOPOS)
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126 |
|
- C. Boccard, T. Bogey, J. de Vries, S. Jackson, R. Jones, J.P. Papis, W. Rawnsley, K. Rybaltchenko, H. Schmickler
CERN, Geneva, Switzerland
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The orbit and trajectory measurement system COPOS
of the CERN SPS accelerator has been in operation since
the construction of the machine in 1976. Over the years
the system has been slightly modified in order to follow
the evolving demands of the machine, in particular for its
operation as a p-pbar collider and, since 1991, for the
acceleration of heavy ions.
In 1995 the performance of the system was reviewed
and the following shortcomings were identified:
- lack of turn-by-turn position measurements due to the
1ms integration time of the voltage to frequency
converters used for the analogue to digital conversion (to
be compared with a revolution time of 23 ms),
- ageing effects on the 200 MHz resonating input filters,
which had over the years drifted out of tolerance. As a
consequence the signal to noise ratio, the linearity and
the absolute precision were affected.
- the calibration system based on electromechanical relays
had become very unreliable, such that frequent
calibrations were no longer possible,
- a remote diagnostic for the observation of timing
signals relative to the beam signals was missing.
For the above reasons a large-scale upgrade program
was launched, the results of which are described in the
following sections.
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PS13 |
Analysis of the proton beam in the DESY transport lines by video readout
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129 |
|
- F. Solodovnik, T. Limberg, K. Wittenburg
IHEP, Institute for High Energy Physics, Protvino, Russia
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Injection efficiency, beam optic matching and
emittance preservation are very important parameters in
achieving a high luminosity in large proton
accelerators. We improved the analysing system of the
phosphor screen readout of the proton transport lines in
the accelerator chain of HERA with respect to the
parameters above. The screens are read out by simple
CCD video cameras. The signals are stored in local
frame grabbers. An analogue output of the stored image
is multiplexed and read-out by a fast PCI frame grabber
card in a PC. The beam orbit and the beam emittance
can be measured from each screen. A Visual Basic
program is used to displays the trajectory and the
envelope of the beam from a single transfer. The same
program helps to drive bumps to achieve a proper
steering through the line. The beam width can be
measured from selected screens to calculate the
emittance and other beam parameters including their
errors. The read out and analysing system will be
described and measurements will be shown.
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PS14 |
Comparative test results of various beam loss monitors in preparation for LHC
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132 |
|
- J. Bosser, G. Ferioli
CERN, Geneva, Switzerland
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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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PS15 |
Beam profile measurements at 40 MHz in the PS to SPS transfer channel
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135 |
|
- G. Ferioli, J.J. Gras, H. Hiller, R. Jung
CERN, Geneva, Switzerland
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Bunch to bunch beam profile measurements provide a
valuable tool to control the injection lines to the SPS.
A fast profile monitor based on a 2.5μm Mylar coated
with Aluminium Optical Transition Radiation (OTR)
radiator, has been developed, installed and tested in the
transfer line between the PS and SPS.
The OTR beam image is focused onto a fast Linear
Multianode Photo Multiplier Tube and the associated
electronics sample and store profiles every 25ns.
The paper describes the detector design, the electronic
processing, and presents the results of different
measurements made with bunches of 109-1011 protons at 26
GeV, and bunches of 106 Pb82+ ions at 5.11 GeV/u.
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PS16 |
The fast head-tail instability suppression in multibunch mode at VEPP-4M
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138 |
|
- G. Karpov, V. Kiselev, V. Smaluk, N. Zinvich
BINP, Budker Institute of Nuclear Physics, Novosibirsk, Russia
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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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PS17 |
Beam Profile Detectors at the new fermilab injector and associated beamlines
|
141 |
|
- G. Tassotto, J. Zagel
FNAL, Fermi National Accelerator Laboratory, Batavia, IL, USA
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Transition radiation (TR) is nowadays intensively exploited
by a number of techniques to characterize different beam
parameters. These methods are based, sometimes implicitly,
on standard formulae, and used often without paying
due attention to their applicability. In particular, standard
expressions are only first-order asymptotic, i.e., strictly
speaking, valid at infinity. In this paper TR is examined in a
spatial domain where conventional results are no more exact
and variations in radiation properties are observed. Under
certain conditions, for example, at long wavelengths or
very high energies the effect is so considerable that should
be taken into account in accurate beam measurements.
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PS19 |
Photon counting detectors for fill structure measurements at visible wavelengths
|
144 |
|
- H.L. Owen
CLRC, Daresbury Laboratory, Warrington, UK
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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
|
147 |
|
- H. Reeg
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
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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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