Author: Steinhagen, R.J.
Paper Title Page
MOPC20 Application of Metal-Semiconductor-Metal (MSM) Photodetectors for Transverse and Longitudinal Intra-Bunch Beam Diagnostics 97
  • R.J. Steinhagen
    CERN, Geneva, Switzerland
  • M.J. Boland
    SLSA, Clayton, Australia
  • T.G. Lucas, R.P. Rassool
    The University of Melbourne, Melbourne, Australia
  • T.M. Mitsuhashi
    KEK, Ibaraki, Japan
  The performance reach of modern accelerators is often governed by the ability to reliably measure and control the beam stability. In high-brightness lepton and high-energy hadron accelerators the use of optical diagnostic techniques for this purpose is becoming more widespread as the required bandwidth, resolution and high RF beam power level involved limit the use of traditional electro-magnetic RF pick-up based methods. This contribution discusses the use of fibre-coupled ultra-fast Metal-Semiconductor-Metal Photodetectors (MSM-PD) as an alternative, dependable means to measure signals deriving from electro-optical and synchrotron-light based diagnostics systems. It describes the beam studies performed at CERN's CLIC Test Facility (CTF3) and the Australian Synchrotron to assess the feasibility of this technology as a robust, wide-band and sensitive technique for measuring transverse intra-bunch and bunch-by-bunch beam oscillations, longitudinal beam profiles, un-bunched beam population and beam-halo profiles. The used amplification schemes, achieved sensitivities, linearity, and dynamic range of the detector setup are presented.  
poster icon Poster MOPC20 [3.065 MB]  
TUBL3 A Multiband-Instability-Monitor for High-Frequency Intra-Bunch Beam Diagnostics 327
  • R.J. Steinhagen
    CERN, Geneva, Switzerland
  • M.J. Boland, T.G. Lucas
    The University of Melbourne, Melbourne, Australia
  To provide the best possible luminosity, even higher beam intensities are needed in the Large Hadron Collider (LHC) and in its injector chain. This is fundamentally limited by self-amplifying beam instabilities, intrinsic to unavoidable imperfections in accelerators. Traditionally, intra-bunch or head-tail particle motion is measured using fast digitizers, which even using state-of-the-art technology are limited in their effective intra-bunch position resolution to few tens of um in the multi-GHz regime. Oscillations at this scale cause partial or total loss of the beam due to the tight transverse constraints imposed by the LHC collimation system. To improve on the present signal processing, a prototype system has been designed, constructed and tested at the CERN Super-Proton-Synchrotron (SPS) and later on LHC. The system splits the signal into multiple equally-spaced narrow frequency bands that are processed and analysed in parallel. Working with narrow-band signals in frequency-domain permits the use of much higher resolution analogue-to-digital-converters that can be used to resolve nm-scale particle motion already during the onset of instabilities.  
slides icon Slides TUBL3 [3.165 MB]  
WEPC12 Evaluation of Strip-line Pick-up System for the SPS Wideband Transverse Feedback System 690
  • G. Kotzian, W. Höfle, R.J. Steinhagen, D. Valuch, U. Wehrle
    CERN, Geneva, Switzerland
  The proposed SPS Wideband Transverse Feedback system requires a wide-band pick-up system to be able to detect intra-bunch motion within the SPS proton bunches, captured and accelerated in a 200 MHz bucket. We present the electro-magnetic design of transverse beam position pick-up options optimised for installation in the SPS and evaluate their performance reach with respect to direct time domain sampling of the intra-bunch motion. The analysis also discusses the achieved subsystem responses of the associated cabling with new low dispersion smooth wall cables, wide-band generation of intensity and position signals by means of 180 degree RF hybrids as well as passive techniques to electronically suppress the beam offset signal, needed to optimise the dynamic range and position resolution of the planned digital intra-bunch feedback system.