• F. Becker, C.A. Andre, P. Forck, R. Haseitl, A. Hug, B. Walasek-Höhne
  GSI, Darmstadt
• F.M. Bieniosek, P.N. Ni
  LBNL, Berkeley, California
• D.H.H. Hoffmann
  TU Darmstadt, Darmstadt

As conventional intercepting diagnostics will not withstand high intensity ion beams, Beam Induced Fluorescence (BIF) profile monitors constitute a pre-eminent alternative for online profile measurements. At present two BIF monitors are installed at the GSI UNILAC and several locations are planned for the FAIR high energy beam transport lines. For further optimizations accuracy issues like gas dynamics have to be investigated systematically. Especially the determination of focused beams in front of targets or beam intensities near the space charge limit rely on a careful selection of proper working gas transitions to keep profile distortions as low as possible. With an imaging spectrograph beam induced fluorescence spectra in the range of 300-800 nm were investigated. Wavelength-selective beam profiles were obtained for 5 MeV/u sulphur and tantalum beams in nitrogen, xenon, krypton, argon and helium gas at pressures below 10^-3 mbar. In the calibrated BIF spectra the specific gas transitions were identified. The measurement results are compared with particle tracking simulations and discussed for typical applications at the present setup and the future FAIR facility.

• E. Guetlich, P. Forck, B. Walasek-Höhne
  GSI, Darmstadt
• W. Ensinger
  Technical University Darmstadt, Darmstadt

Optical properties of scintillating screens were studied for various materials and different ion beams at GSI. C²⁺, Ar¹⁰⁺, Ni⁹⁺ and U²⁸⁺-ion beams were applied, in the energy range from 5.5 to 11.4 MeV/u with currents up to some mA, as delivered by the heavy ion LINAC at GSI. Scintillation screens are widely used and are an essential part of a pepper-pot emittance device for which the precise mapping of the beam profile is a critical issue. However, precise measurements of the beam profile yield ambivalent results, especially for high beam currents*,**. The investigations were not only focused on well-known scintillators but also ceramic materials with lower light yield were studied. Their properties (light yield, beam width and higher statistical moments) are compared with different Quartz-glass screens. The recorded beam width shows dependence on the scintillation material and a decrease of the light yield was observed for some materials. Additionally, the light yield and beam width depend significantly on the screen temperature, which is increased by the ion impact. The empirical results are discussed and concepts for further investigations on the materials are presented.

* E. Gütlich, P. Forck et al., GSI-Scientific Report 2007 p.105 and 2008 (to be published).
** E. Gütlich, P. Forck, et al., Proc. Beam Instrum. Workshop BIW, Lake Tahoe (2008).