The maximum beam particle intensity and minimum emittance that can be injected, accelerated and stored in high-brightness lepton as well as high-energy hadron accelerators is fundamentally limited by self-amplifying beam instabilities, intrinsic to unavoidable imperfections in accelerators. Traditionally, intra-bunch or head-tail particle motion has been measured using optical streak-cameras or 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.
A more holistic approach has been taken to improve upon the limitations that derive from combination of pick-up, signal transportation and signal analysis. Thus this presentation discusses the developments related to the use of fibre-coupled ultra-fast Metal-Semiconductor-Metal Photodetectors (MSM-PD) as an alternative, dependable means to measure signals derived from electro-optical and synchrotron-light based beam diagnostics systems, as well as a complementary novel multiband-instability-monitor (MIM) prototype system developed to exploit the high dynamic range and wide-band nature of the before mentioned pickups.
The prototype pick-up and signal processing systems have been successfully tested at CERN' Super-Proton-Synchrotron (SPS), the Large Hadron Collider (LHC), the 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. Being able to resolve nm-scale particle motion already during the onset of instabilities, this system facilitates a better understanding of beam stability margins and in turn an improved machine performance with high brightness beams.