STATUS OF AND FUTURE PLANS FOR THE CERN LINAC4 EMITTANCE METER BASED ON LASER ELECTRON-DETACHMENT AND A DIAMOND STRIP-DETECTOR

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 stripdetector. 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.