BIF Profile Monitor for the UNILAC - Tests and DAQ Upgrade

The non-intercepting Beam Induced Fluorescence (BIF) monitor for transverse beam profile measurements was successfully tested for different ion species and energies from 5 to 750 MeV/u at the GSI accelerators [1]. Starting from its first implementation [2] we systematically investigated technical aspects such as the proper choice of optics and gain factors, as well as physical aspects like the dependency of beam energy and ion species on signal amplitude and the signal to background ratio. Investigations of the wavelength spectrum have shown that unwanted profile distortions by 2-step excitation processes have negligible contributions to the total photon yield [3]. At the UNILAC X2 experimental area a pressure dependent measurement was performed. With a regulated needle valve we changed the N2 residual gas pressure from 10 to 10 mbar. Assuming constant beam parameters and within 1.6 σ according the fit function, the signal amplitude increases linearly with the gas pressure, while the profile width remains constant, as shown in Figure 1. Therefore the residual gas pressure can be used as a free parameter to match the required signal strength. Latest simulations of N+2 trajectories in the electrical field of the beam show negligible profile distortions, even for highest beam intensities in the upgraded UNILAC. For improved reliability, user-friendly operation and enhancend functional range, the DAQ-system and software are substantially upgraded.