CERN, Geneva, Switzerland
Royal Holloway, University of London, Surrey, United Kingdom
CIVIDEC Instrumentation, Wien, Austria
LINAC4 has started its staged commissioning at CERN. After completion it will accelerate high brightness H− beams to 160 MeV. To measure the transverse profile and emittance of the beam, a non-destructive method based on electron photo-detachment is proposed, using a pulsed, fibre-coupled laser to strip electrons from the H− ions. The laser can be focused and scanned through the H− beam, acting like a conventional slit. A downstream dipole separates the neutral H0 beamlet, created by the laser interaction, from the main H− beam, so that it can be measured by a diamond strip-detector. Combining the H0 beamlet profiles with the laser position allows the transverse emittance to be reconstructed. A prototype of this instrument was tested while commissioning the LINAC4 at 3 and 12 MeV. In this paper we shall describe the experimental setup, challenges and results of the measurements, and also address the characteristics and performance of the diamond strip-detector subsystem. In addition, the proposal for a permanent system at 160 MeV, including an electron detector for a direct profile measurement, will be presented.
CERN, Geneva, Switzerland
IOFFE, St. Petersburg, Russia
CIVIDEC Instrumentation, Wien, Austria
EBG MedAustron, Wr. Neustadt, Austria
The Beam Loss Monitoring (BLM) detectors close to the interaction points (IP) of the Large Hadron Collider (LHC) are currently located outside the cryostat, far from the superconducting coils of the magnets. In addition to their sensitivity to lost beam particles, they also detect particles coming from the experimental collisions, which do not contribute significantly to the heat deposition in the superconducting coils. In the future, with beams of higher energy and brightness resulting in higher luminosity, distinguishing between these interaction products and dangerous quench-provoking beam losses from the primary proton beams will be challenging. The system can be optimised by locating beam loss monitors as close as possible to the superconducting coils, inside the cold mass of the magnets in superfluid helium at 1.9 K. The dose then measured by such Cryogenic Beam Loss Monitors (CryoBLMs) would more precisely correspond to the real dose deposited in the coil. The candidates under investigation for such detectors are based on silicon and diamond, several of which have now been installed inside the magnets in the LHC tunnel. This contribution will present the mechanical and electrical designs of these systems, as well as the results of their qualification testing.