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IT08 Controls and Beam Diagnostics for Therapy-Accelerators diagnostics, controls, light-ion, synchrotron 24
 
  • H. Eickhoff
    GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
  During the last four years GSI has developed a new procedure for cancer treatment by means of the intensity controlled rasterscan-method. This method includes active variations of beam parameters during the treatment session and the integration of 'on-line' PET monitoring. Starting in 1997 several patients have been successfully treated within this GSI experimental cancer treatment program; within this program about 350 patients shall be treated in the next 5 years. The developments and experiences of this program accompanied by intensive discussions with the medical community led to a proposal for a hospital based light ion accelerator facility for the clinic in Heidelberg. An essential part for patients treatments is the measurement of the beam properties within acceptance and constancy tests and especially for the rasterscan method during the treatment sessions. The presented description of the accelerator controls and beam diagnostic devices mainly covers the requests for the active scanning method, which are partly more crucial than for the passive scattering methods.  
 
IT09 Diagnostics in Heavy Ion Machines heavy-ion, diagnostics, electron, 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.  
 
IT11 Beam Diagnostics, Old and New
This is essentially a repeat of 'Beam Diagnostics Revisited', invited talk given at EPAC, Stockholm, June 1998
diagnostics, emittance, linac, injection 33
 
  • H. Koziol
    CERN, Geneva, Switzerland
  The performance of accelerators and storage rings depends critically on the completeness and quality of their beam diagnostic systems. It is essential to equip them from inception with all the instruments providing the information on the properties and the behaviour of the beams, needed during running-in, in operation, and for development of performance towards the design goal and often well beyond. Most of the instruments have proven their worth since decades, but their power has been increased through the modern means of data acquisition and treatment. A few new instruments have made their appearance in recent years, some still under development and scrutiny for their operational value and precision. The multi-accelerator chains of today’s and tomorrow’s big colliders have tight tolerances on beam loss and emittance blow-up. For beam diagnostics this means a great challenge for precision and consistency of measurements all along the chain.  
 
CT01 Measurements with a versatile Test Bench for Commissioning of the new GSI High Current Linac emittance, rfq, pick-up, 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.  
 
CT02 Determination of Radial Ion Beam Profile from the Energy Spectrum of Residual Gas Ions Accelerated in the Beam Potential space-charge, electron, 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.  
 
CT12 Preliminary Test of a Luminescence Profile Monitor in the CERN SPS proton, vacuum, photon, injection 95
 
  • J. Camas, R.J. Colchester, G. Ferioli, R. Jung, J. Koopman
    CERN, Geneva, Switzerland
  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.  
 
PS05 Recent Improvements of a Cryogenic Current Comparator for nA Ion Beams with High Intensity Dynamics pick-up, 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.  
 
PS09 Beam Steering With Image Processing In The Cryring Injection Beamline quadrupole, injection, focusing, synchrotron 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. electron, proton, lepton, 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.  
 
PS11 Ionisation profile monitor tests in the SPS electron, 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.  
 
PS12 Performance of the new SPS beam position orbit system (MOPOS) pick-up, 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.
 
 
PS14 Comparative test results of various beam loss monitors in preparation for LHC proton, beam-losses, simulation, electron 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 injection, proton, radiation, kicker 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.  
 
PS20 A current digitizer for ionisation chambers/SEMS with high resolution and fast resoponse power-supply, electron, 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.  
 
PT07 Emittance measurements at the new UNILAC-pre-stripper using a pepper-pot with a PC-controlled CCD-camera emittance, laser, linac, ion-source 171
 
  • M. Dolinska, M. Domke, P. Forck, T. Hoffmann, D. Liakin, A. Peters, P. Strehl
    GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
  The complex mathematical algorithms and procedures to extract emittance data from intensity distributions measured with a single shot pepper-pot device are described. First results of mathematical evaluation from the commissioning of the new GSI pre-stripper linac structures are presented.  
 
PT12 Aspects of bunch shape measurements for low, intense ions beams target, scattering, rfq, electron 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.