Forck, P.

Hoffmann, D. H. H.

Lavrik, V.

Shutko, Y.

Sieber, T.

Udrea, S.

GSI Repository

Beam induced fluorescence monitor development:  Comparison of image intensified CCD and electron multiplying CCD cameras* Y. Shutko1#, D.H.H. Hoffmann1, P. Forck2,3 , T. Sieber2, S. Udrea3, V. Lavrik3 1TUD, Darmstadt, Germany, 2GSI, Darmstadt, Germany; 3Goethe-Universität, Frankfurt am Main, Germany.  Beam Induced Fluorescence (BIF) monitors offer the possibility for non-interceptive beam profile diagnostics and are therefore highly relevant for the future FAIR fa-cility. Several BIF monitors are already in operation at the UNILAC accelerator [1] and are based on Image Intensi-fied CCD (ICCD) cameras. However, recent technologi-cal developments of electron multiplying CCD (emCCD) cameras offer an alternative to the ICCD. During the GSI beam time in 2014 profile measurements have been performed both with an ICCD (Proxivison/Basler) [2] and an emCCD (Princeton Instruments ProEM512B) camera [3]. These two cameras have different working principles: the ICCD camera uses  electron multiplication within a microchannel plate (MCP) due to the high voltage applied between photocathode and phosphor screen. The emCCD camera achieves signal amplification by avalanche diode-like electronics in the extended portion of the serial readout register [3]. The goal of the experiments was to compare the perfor-mance of the two cameras under similar conditions. A typical experimental set-up is shown in Figure 1.  Figure 1: Typical set-up of a BIF profile monitor [2].   The measurements have been performed with 300 MeV/u 238U ion beams in slow extraction mode, pulse duration 500 ms, beam widths 7.2 and 10.7 mm for ICCD and emCCD measurements, respectively. Nitrogen has been used as working gas at pressures of 5·10-3, 10-2, 2·10-2 (ICCD) and 3.5·10-2(emCCD) mbar. To increase the S/N ratio, averages over a few hundred acquisitions have been computed both for background and beam im-ages. Figure 2 and Figure 3 show the transverse profiles obtained with the ICCD and emCCD cameras and also for comparison the profiles from a scintillating screen placed 1 m downstream of the BIF diagnostic chamber. The magnitude of the ICCD profiles is basically pro-portional to the N2 pressure (p). This is not the case for the emCCD. The profile taken at 3.5·10-2 mbar shows a not expectable stronger increase in magnitude than at 5·10-3 and 10-2 mbar. The proportionality of the intensity of the N2 emission at 337 nm to p2 may cause this behav-iour. 0 20 40 60 80 100 120 1400.00.20.40.60.81.0Normalized grey value, arb. un.Position, mm 5e-3 mbar 1e-2 mbar 2e-2 mbar Scintillating screen0.00 0.01 0.02 0.03050100150200Intensity, arb. un.Pressure, mbar Figure 2: ICCD transverse profiles at different pres-sures. 0 20 40 60 80 100 120 1400.00.20.40.60.81.0Normalized Grey Value, arb. un.Poisition, mm  5-3 mbar  1e-2 mbar 3.5 e-2 mbar Scintillating screen0.00 0.01 0.02 0.03050100150200Intensity, arb. un.Pressure, mbarFigure 3: emCCD transverse profiles at different pres-sures.   The central part of the emCCD low pressure profiles is comparable to the one from the scintillating screen, while the ICCD profiles are systematically broadened. This be-haviour can be explained by the fact that single photons produce wide spots in the ICCD acquired image. The ef-fect can be mitigated by proper image processing. The tails of the BIF profiles and the strongly increased width at 3.5·10-2 mbar are most probably due to the N2 emission at 337 nm, known to give rise to wide profiles, which also are pressure dependent [4]. Filtering this line out should help to improve the profile width accuracy. References [1] C.A. Andre et al., DIPAC2011 proc., p.185 [2] P. Forck et al., HB2010 proc., p. 497 [3] David Dussault, Paul Hoess, Proceedings of SPIE Vol. 5563, pp.195-204 (2004) [4] P. Forck et al., OPAC Workshop 2014  ___________________________________________  * Work supported by BMBF project No. 05P12RDRBN and Graduate School of Excellence ESE TU Darmstadt. #y.shutko@gsi.de GSI SCIENTIFIC REPORT 2014 FG-GENERAL-45DOI:10.15120/GR-2015-1-FG-GENERAL-45 463

Beam induced fluorescence monitor development: Comparison of image intensified CCD and electron multiplying CCD cameras

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Beam induced fluorescence monitor development: Comparison of image intensified CCD and electron multiplying CCD cameras

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