A beam rocking system for the Oxford nuclear microprobe: A new approach to channeling analysis

This paper describes the design and implementation of a beam rocking system for the Oxford nuclear microprobe. This system varies the angle of incidence of a focused MeV ion beam on a sample using two sets of dipole scan coils of equal and opposite fields, allowing the sample to remain fixed while the beam is rocked in angle about a small area. This method of producing angle-resolved channeling images and scans does not require any modifications to existing data-acquisition software nor the use of a high-precision motorized goniometer. Beam optics calculation results are presented for a beam rocking system using three different standard microprobe focusing systems. The maximum angular range of this system is 3.15 degrees. Channeling images and measurements of angular rotation in a strained Si0.90Ge0.10/Si crystal are presented using this technique. (C) 1997 Elsevier Science B.V.