Development of a Laser-based emittance monitor for negative hydrogen beams

Viac o knihe

To maximize the collision rate of CERN's Large Hadron Collider, the new injector LINAC4 has been commissioned to accelerate an H- beam, aiming to double beam brightness. A precise understanding of the beam's transverse characteristics, particularly beam emittance, is crucial. This thesis details the development of a laser-based monitor for non-destructive measurement of LINAC4's beam transverse profile and emittance. It covers the design and testing of various prototypes leading to the final instrument intended for permanent installation. The instrument operates by stripping electrons from negative hydrogen ions; a focused laser beam scans through the H- beam, allowing for profile reconstruction through detected detached electrons, while transverse emittance is derived from monitoring H0 profiles at each laser position. The laser system includes a low-power source and a fiber-optic transfer to the interaction point. A diamond strip-detector monitors the H0 signal. Prototype tests at 3 MeV and 12 MeV H- beams showed agreement within +/- 3% of conventional methods. A second prototype, utilizing a dipole magnet to deflect detached electrons, achieved a profile agreement within +/- 2%. The final design integrates electron and H0 detection, enabling simultaneous emittance and profile measurement with resolutions of < 75 µm and < 100 µrad, facilitating routine automated monitoring of LINAC4's transverse beam parameters.