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radiation

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IT09 Smith-Purcell Radiation in View of Particle Beam Diagnostics diagnostics, instrumentation, monitoring 40
 
  • G. Kube
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  • H. Backe, W. Lauth, H. Schöpe
    IKP, Institut für Kernphysik, Mainz, Germany
  The development of the next generation high quality electron beams which are necessary for future high luminosity linear colliders and short wavelengths free electron lasers requires sensitive and non-destructive beam diagnostic techniques. In this context Smith-Purcell radiation which is generated when a charged particle beam passes close to the surface of a periodic structure (diffraction grating) is under discussion as a compact and inexpensive beam profile monitor. In order to study the basic emission process of Smith-Purcell radiation also in view of possible applications for particle beam diagnostics, experimental studies were performed at the Mainz Microtron MAMI in the visible spectral region with a microfocused 855 MeV electron beam. The radiation was separated from background components, as diffracted synchrotron radiation and transition radiation generated by electrons scratching the grating surface, by exploiting their specific emission characteristics. These are
  1. the narrow emission cone in the direction perpendicular to the grating surface,
  2. the dispersion relation |n| λ = D (1 / β - cos θ) with n the diffraction order, β the reduced electron velocity, and θ the angle of observation, and
  3. the charcteristic intensity scaling as a function of the distance between beam axis and grating surface.
Based on the experimental results the use of Smith-Purcell radiation as a longitudinal and transversal beam profile monitor will be discussed. 		 
 
CT05 Beam Loss Detection at Radiation Source ELBE diagnostics, instrumentation, linac, electron, beam-losses, beam-transport 65
 
  • P. Michel, J. Teichert, R. Schurig, H. Langenhagen
    FZR, Forschungszentrum Rossendorf, Dresden, Germany
  The Rossendorf superconducting Electron Linac of high Brilliance and low Emittance (ELBE) delivers an 40 MeV, 1 mA cw-beam for different applications such as bremsstrahlung production, electron channelling, free-electron lasers or secondary particle beam generation. In this energy region in case of collisions of the electron beam with the pipe nearly all beam power will be deposited into the pipe material. Therefore a reliable beam loss monitoring is essential for machine protection at ELBE. Different systems basing on photo multipliers, compton diodes and long ionization chambers were studied. The pros and cons of the different systems will be discussed. Ionization chambers based on air-isolated RF cables installed some cm away parallel to the beam line turned out to be the optimal solution. The beam shut-off threshold was adjusted to 1 μC integral charge loss during a 100 ms time interval. Due to the favourable geometry the monitor sensitivity varies less than ±50% along the beam line (different shielding conditions).  
 
PT30 Ionisation Chambers for the LHC Beam Loss Detection beam-losses, instrumentation 245
 
  • E. Gschwendtner, R. Assmann, B. Dehning, G. Ferioli, V. Kain
    CERN, Geneva, Switzerland
  At the Large Hadron Collider (LHC) a beam loss system will be used to prevent and protect superconducting magnets against coil quenches and coil damages. Since the stored particle beam intensity is 8 orders of magnitude larger than the lowest quench level value particular attention is paid to the design of the secondary particle shower detectors. The foreseen ionisation chambers are optimised in geometry simulating the probable loss distribution along the magnets and convoluting the loss distribution with the secondary particle shower distributions. To reach the appropriate coverage of a particle loss and to determine the quench levels with a relative accuracy of 2 the number of the detectors and their lengths is weighted against the particle intensity density variation. In addition attention is paid to the electrical ionisation chamber signal to minimise the ion tail extension. This optimisation is based on time resolved test measurements in the PS booster. A proposal for a new ionisation chamber will be presented.