GSI, Darmstadt
LBNL, Berkeley, California
TU Darmstadt, Darmstadt
As conventional intercepting diagnostics will not withstand high intensity ion beams, Beam Induced Fluorescence (BIF) profile monitors constitute a preeminent alternative for non-intercepting profile measurements. This diagnostic technique makes use of optical emission of beam-excited gases. Recently BIF became an important diagnostic technique for beam profile measurement with applicability in beam tuning over a wide range of beams and accelerator conditions. Beam induced fluorescence spectra in the range of 300 - 800 nm were recorded with an imaging spectrograph for 5 MeV/u proton, S(6+) and Ta(24+) beams in nitrogen, Xe, Kr, Ar, Ne and He at 10-3 mbar gas pressure. Optical transitions were identified and associated with corresponding beam profiles. Effective light yields, normalized to the differential energy loss, are presented for all gas-species investigated. Since residual gas ionization is the basic process for BIF-monitors as well as for Ionization Profile Monitors (IPM), BIF-results are compared to IPM measurement data.
DESY, Hamburg
DESY Zeuthen, Zeuthen
The stability of the photo injector is a key issue for the successful operation of linac based free electron lasers. Several types of jitter can impact the stability of a laser driven RF gun. Fluctuations of the RF launch phase and the cathode laser energy have significant influence on the performance of a high brightness electron source. Bunch charge measurements are used to monitor the stability of the rf gun phase and the cathode laser energy. A basic measurement is the so called phase scan: the accelerated charge downstream of the gun is measured as a function of the launch phase, the relative phase of the laser pulses with respect to the RF. We describe a method which provides simultaneous information on rms jitters from phase scans at different cathode laser energies. Fluctuations of the rf gun phase together with cathode laser energy jitter have been measured at the Photo Injector test facility at DESY in Zeuthen (PITZ). Obtained results will be presented in comparison with direct independent measurements of corresponding instability factors. Dedicated beam dynamics simulations have been done in order to optimize the method performance.
