PS  --  Posters Sunday


Paper Title Page
PS02 Chromaticity Measurements at HERA-P Using the Head-Tail Technique with Chirp Excitation 103
 
  • M. Wendt, F. Willeke
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  • A. Boudsko
    TRIUMF, Vancouver, Canada
  • O.R. Jones, H. Schmickler
    CERN, Geneva, Switzerland
 
  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.  
PS04 Influence of transverse beam dimensions on beam position monitor signals 106
 
  • A. Jankowiak, T. Weis
    DELTA, Institute for Accelerator Physics and Synchrotron Radiation, University of Dortmund, Germany
 
  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.  
PS05 Recent Improvements of a Cryogenic Current Comparator for nA Ion Beams with High Intensity Dynamics 109
 
  • 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
 
  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 detector’s 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.  
PS06 Turn-By-Turn Phase Space Diagram Construction for Non-Linear Betatron Oscillation 112
 
  • A. Kalinin, V. Smaluk
    BINP, Budker Institute of Nuclear Physics, Novosibirsk, Russia
 
  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.  
PS07 Trajectory Measurements in the DAΦNE Transfer Lines 115
 
  • A. Stella, C. Milardi, M. Serio
    INFN-LNL, Laboratori Nazionali di Legnaro, Legnaro, Italy
 
  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.  
PS09 Beam Steering With Image Processing In The Cryring Injection Beamline 118
 
  • A. Källberg, A. Simonsson
    MSI, Manne Siegbahn Laboratory Of Physics, Stockholm, Sweden
 
  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.  
PS10 Ionisation losses and wire scanner heating: evaluation, possible solutions, application to the LHC. 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.  
PS11 Ionisation profile monitor tests in the SPS 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.  
PS12 Performance of the new SPS beam position orbit system (MOPOS) 126
 
  • C. Boccard, T. Bogey, J. de Vries, S. Jackson, R. Jones, J.P. Papis, W. Rawnsley, K. Rybaltchenko, H. Schmickler
    CERN, Geneva, Switzerland
 
  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:
  1. 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),
  2. 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.
  3. the calibration system based on electromechanical relays had become very unreliable, such that frequent calibrations were no longer possible,
  4. 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.
 
PS13 Analysis of the proton beam in the DESY transport lines by video readout 129
 
  • F. Solodovnik, T. Limberg, K. Wittenburg
    IHEP, Institute for High Energy Physics, Protvino, Russia
 
  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.  
PS14 Comparative test results of various beam loss monitors in preparation for LHC 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.  
PS15 Beam profile measurements at 40 MHz in the PS to SPS transfer channel 135
 
  • G. Ferioli, J.J. Gras, H. Hiller, R. Jung
    CERN, Geneva, Switzerland
 
  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.  
PS16 The fast head-tail instability suppression in multibunch mode at VEPP-4M 138
 
  • G. Karpov, V. Kiselev, V. Smaluk, N. Zinvich
    BINP, Budker Institute of Nuclear Physics, Novosibirsk, Russia
 
  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.  
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
 
  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.  
PS19 Photon counting detectors for fill structure measurements at visible wavelengths 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.  
PS20 A current digitizer for ionisation chambers/SEMS with high resolution and fast resoponse 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.