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pick-up

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CT01 Measurements with a versatile Test Bench for Commissioning of the new GSI High Current Linac emittance, rfq, ion, diagnostics 45
 
  • P. Forck, P. Strehl
    GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
  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.  
 
CT04 Bunch Length Measurements in LEP synchrotron, impedance, photon, monitoring 59
 
  • A.J. Burns, H. Schmickler
    CERN, Geneva, Switzerland
  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.  
 
PS02 Chromaticity Measurements at HERA-P Using the Head-Tail Technique with Chirp Excitation betatron, synchrotron, proton, kicker 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 emittance, quadrupole, synchrotron, instrumentation 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 ion, heavy-ion, instrumentation, linac 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 lattice, betatron, synchrotron, simulation 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 linac, damping, injection, vacuum 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.  
 
PS12 Performance of the new SPS beam position orbit system (MOPOS) ion, heavy-ion, proton, extraction 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. 		 
 
PS20 A current digitizer for ionisation chambers/SEMS with high resolution and fast resoponse ion, power-supply, electron, 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.  
 
PT09 The closed-orbit measurement system for the CERN antiproton decelerator antiproton, closed-orbit, vacuum, shielding 177
 
  • M. LeGras, L. Søby, D.J. Williams
    CERN, Geneva, Switzerland
  The closed-orbit measurement system for the new Antiproton Decelerator (AD) employs 59 electrostatic pick-ups (PU). The intensity range from 2·1010 down to 107 particles poses challenging demands on the dynamic range and noise of the head amplifier. A low noiseamplifier has been developed, having an equivalent input noise of 0.6nV/√(Hz), allowing beam positions to be measured to ±0.5 mm with 5·106 particles. Two different gains take care of the large dynamic range. After amplification and multiplexing, the PU signals are fed to a network analyser, where each measurement point corresponds to one PU. The network analyser is phase locked to the RF of the AD, thus acting as a “tracking filter” instrument. An orbit measurement takes from 0.2 to 12 s depending on the IF-bandwidth of the network analyser, selected according to the beam intensity, and the precision required. At the end of the network analyser sweep the data are read via a GPIB interface and treated by a real-time task running in a VME based Power PC.  
 
PT11 Dipole modes study by means of HOM couplers at SBTF kicker, dipole, coupling, damping 183
 
  • N. Baboi, M. Dohlus, A. Jöstingmeier, N. Holtkamp, M. Wendt, M. Nagl, J. Boster, H. Hartwig
    DESY, Deutsches Elektronen Synchrotron, Hamburg, Germany
  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.  
 
PT19 A method for measurement of transverse impedance distribution along storage ring impedance, betatron, vacuum, storage-ring 202
 
  • V. Kiselev, V. Smaluk
    BINP, Budker Institute of Nuclear Physics, Novosibirsk, Russia
  A new method for measurement of transverse couple impedance distribution along storage ring is described. The method is based on measuring of a closed orbit deviation caused by local impedance. Transverse impedance acts on the beam as a defocusing quadrupole, strength of which depends on the beam current. If a local bump of closed orbit has been created at the impedance location, then the orbit deviation occurs while varying the beam current. The local impedance can be evaluated using the orbit deviation measured. Measurement technique is described, the method accuracy is evaluated. The method described was successfully used for measurement of the impedance distribution along the VEPP-4M storage ring.