Multiple scattering is interesting from a fundamental viewpoint because it governs the interaction potential at large interatomic distances while from a practical viewpoint it is important because it limits the ultimate resolution in ion beam imaging and determines the wall shape in proton beam writing.  Previous investigations found that relevant data is rather scarce. The technique is based on characterising the smearing of an initially sharp image I₀(x,y) described by the multiple scattering induced broadening F(x,y),  when the ion beam is spread by a thin film of material placed in front of the object according to:

. In this work direct-Scanning Transmission Ion Microscopy (direct-STIM) measurements were carried out with 1 MeV H⁺ ions using the electrode pattern of the Si –pin detector itself as a sharp object. A Mylar foils of different thicknesses were inserted a defined distance in front of the detector and energy-loss images measured. Using integral transformation the angular broadening could be determined and this showed a close to  proportionality on thickness, t.

1.              H. J. Whitlow, M. Ren, J. A. van Kan T. Osipowicz, F. Watt, Angular and Lateral Spreading of Ion Beams in Biomedical Nuclear Microscopy, Nucl. Instrum. Methods. Nucl. Instrum. Meth. B 267(2009)2153.

2.              S. Gorelick, T. Sajavaara and H.J. Whitlow, Aperture edge scattering in MeV ion beam lithography and nuclear microscopy: an application for the GEANT4 toolkit,  Nucl. Instrum. Methods. 267(2009)2050.

 

Harry James Whitlow*, Department of Physics, University of Jyväskylä, Finland
Minqin Ren, Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore
Jeroen van Kan, Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore
Thomas Osipowicz, Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore
Frank Watt, Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore

*presenting author