| Paper |
Title |
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| CT01 |
Measurements with a versatile Test Bench for Commissioning of the new GSI High Current Linac
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45 |
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- P. Forck, P. Strehl
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
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For the commissioning of the new GSI prestripper a conventional
slitdetector system and a single shot pepperpot system has been
installed on a mobile test bench to measure intensity distributions in
the two transverse phase spaces. To determine intensity distributions
in the longitudinal phase space, including beam energy capacitive
pickups and newly developed diamond counters have been installed on the
test bench. The setup of the test bench provides also redundant
information for beam current, beam profile and beam position. The most
important features of all measuring systems including signal processing
and data evaluation are reported. First results from the commissioning
of the upgraded prestripper of the UNILAC at GSI are reported.
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| CT02 |
Determination of Radial Ion Beam Profile from the Energy Spectrum of Residual Gas Ions Accelerated in the Beam Potential
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50 |
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- R. Dölling
IAP, Institut für angewandte Physik der Johann Wolfgang Goethe Universität
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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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| CT03 |
500 fs Streak Camera for UV-Hard X-Rays in 1 kHz Accumulating Mode with Optical 'Jitter Free' Synchronisation
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54 |
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- K. Scheidt, G.A. Naylor
ESRF, The European Synchrotron Radiation Facility, Grenoble, France
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The development at the ESRF of a jitter-free, laser
triggered Streak Camera has now yielded time resolution
results as short as 460 fs while operating in accumulating
mode. The so-called jitter-free synchronisation between
the laser light and the Streak Camera is performed
through a GaAs photo-switch in a simple HV circuit that
connects directly to the Streak tube’s deflection plates.
The novelty of this technique permits to obtain
excellent dynamic range measurements in a shot-to-shot
accumulation of ultra fast (laser stimulated) events at up
to 1kHz without degrading the time resolution.
Important insight was obtained on the quality of this
optical synchronisation and its dependence on the laser
characteristics, the switch circuit, and the structure of the
GaAs switch itself. This permitted to suppress the jitter
causes and today the 500 fs limitation is imposed by the
streak tube’s intrinsic time resolution. This work was
done by measuring (with Au or Pd photo-cathodes) the
3rd harmonic (i.e. 267 nm) of a 100 fs Ti:Saph laser.
Also important progress was made with the reliability
of the photo-switch and problems of HV break-down and
structural degradation have been completely resolved.
Since the principal use of this system at the ESRF is in
ultra-fast X-ray diffraction experiments the
exchangeable photo-cathode structure of this tube covers
the entire UV-to-X-rays spectrum. The QE of various
photo-cathode materials was measured in the 8-30 keV
range.
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| CT04 |
Bunch Length Measurements in LEP
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59 |
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- A.J. Burns, H. Schmickler
CERN, Geneva, Switzerland
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For many years a streak camera has been used for
observing the longitudinal distribution of the particles in
any LEP e+ or e- bunch (5-50 ps r.m.s. length) on a turn
by turn basis, using synchrotron light. In 1996, a
comparison made with the longitudinal vertex
distributions of 3 LEP experiments allowed the
identification and elimination of certain systematic errors
in the streak camera measurements. In 1997, a new bunch
length measurement technique was commissioned that
uses the high frequency slope of the bunch power
spectrum from a button pickup. In 1998, this new method
was confronted with measurements from the streak
camera and the LEP experiments. The measurements
made in 1996 and 1998 are presented, with emphasis on
the calibration of the two instrumental methods and their
respective precision and limitations.
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| CT05 |
Daresbury SRS Positional Feedback Systems
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64 |
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- S.L. Smith, S.F. Hill
CLRC, Daresbury Laboratory, Warrington, UK
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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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| CT06 |
Developments and Plans for Diagnostics on the ISIS Synchrotron
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67 |
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- C.M. Warsop, D.J. Adams, K. Tilley
RAL, Rutherford Appleton Laboratory
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Developments of diagnostics on the 800 MeV High
Intensity Proton Synchrotron of ISIS, the Spallation
Neutron Source at the Rutherford Appleton Laboratory in
the UK, are described. Recent upgrades to instrumentation
and control computers have made much more information
readily available, which is valuable for control of a loss
limited, high intensity machine. Measurements on high
intensity beams have fundamental limitations in terms of
accuracy, detail and interpretation. However, it is found
that use of specially configured low intensity diagnostic
beams can provide much detailed information not
otherwise available, which is extremely valuable after
careful interpretation. The methods and systems being
developed to help trouble shooting, to find optimal
conditions rapidly and systematically, and to improve
understanding of high intensity performance are
described.
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| CT07 |
The ELETTRA Streak Camera: System Set-Up and First Results
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72 |
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- M. Ferianis
ELETTRA, Sincrotrone Trieste, Trieste, Italy
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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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| CT08 |
Adaptive Optics for the LEP 2 Synchrotron Light Monitors
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77 |
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- G. Burtin, R.J. Colchester, G. Ferioli, J.J. Gras, R. Jung, J.M. Vouillot
CERN, Geneva, Switzerland
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The image obtained with the LEP synchrotron
radiation telescopes deteriorates, giving multiple and
deformed images, when the beam energy goes beyond
80 GeV at beam currents above 2 mA. This problem is
due to the deformation of the light extracting beryllium
mirror, by as little as 1 mm, and had been predicted at
the design stage. To overcome this problem, several
changes together with an adaptive optics set-up have
been introduced. These essentially consist of a
cylindrically deformable mirror to compensate the
cylindrical deformation of the beryllium mirror and a
movable detector to compensate the spherical
deformation. Both components are continuously
adjusted as a function of beam current and energy.
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| CT09 |
Luminosity Optimization in DAΦNE
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82 |
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- F. Sannibale
INFN-LNF, Laboratori Nazionali di Frascati dell'INFN, Frascati, Italy
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DAΦNE the Frascati F-factory, started the two beams
commissioning on March 1998. Since then a relevant
amount of experience concerning the techniques and procedures
for optimizing the luminosity has been acquired.
All the schemes used are strongly based on the use of
various diagnostic systems including a dedicated luminosity
monitor, orbit measurement, tune monitor, synchrotron
light monitor and others. A summary of the used
techniques, with accent on the diagnostic aspects, is
presented.
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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
|
87 |
| |
- R. Jones, A. Manarin, G. Pignard, E. Rossa, H. Schmickler, M. Sillanoli, C. Surback
CERN, Geneva, Switzerland
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Fast X-ray detectors based on CdTe photoconductors
have been installed in LEP since the beginning of its
operation in 1989. The angular divergence of the high
energy photons from the synchrotron radiation (x-rays)
and the narrow spacing of the 64 photoconductors of the
detector allow a good measurement of vertical beam
profiles down to an rms beam size of 300 mm.
This paper presents some specific parameters and
experimental results of an upgrade program in which the
local processing power of the front-end electronics has
been increased by a factor 50. Such a powerful tool has
allowed a real time display of the time evolution of the
vertical beam sizes. An online correlation plot between
the electron and positron beam sizes (turn by turn) is
also displayed.
These online video images are available in the LEP
control room and are used in daily operation for
luminosity optimisation.
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| CT11 |
The OTR Screen Betatron Matching Monitor of the CERN SPS
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90 |
| |
- C. Bovet, R.J. Colchester, G. Ferioli, J.J. Gras, R. Jung, J.M. Vouillot
CERN, Geneva, Switzerland
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In order to satisfy the stringent emittance
requirements of LHC, betatron matching monitors,
based on multiturn beam profile measurements, have
been proposed for the SPS and LHC. A test monitor
has been installed for evaluation in the CERN SPS first
in 1996 and improved in 1997. It is based on an OTR
screen and a fast beam profile acquisition system. It
has been used with proton beams to assess the quality
of the betatron matching from the PS to the SPS in
1998. Experience and results are presented.
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| CT12 |
Preliminary Test of a Luminescence Profile Monitor in the CERN SPS
|
95 |
| |
- J. Camas, R.J. Colchester, G. Ferioli, R. Jung, J. Koopman
CERN, Geneva, Switzerland
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In order to satisfy the tight emittance requirements of
LHC, a non-intercepting beam profile monitor is needed
in the SPS to follow the beam emittance evolution during
the acceleration cycle from 26 to 450 GeV. Beyond 300
GeV, the synchrotron light monitor can be used. To cover
the energy range from injection at 26 GeV to 300 GeV, a
monitor based on the luminescence of gas injected in the
vacuum chamber has been tested and has given
interesting results. This monitor could also be used in
LHC, where the same problem arises. Design and results
are presented for the SPS monitor.
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