The Lund Nuclear Microprobe sub-micron set-up. Part I: Ion optics calculation

✍ Scribed by Asad Shariff; Vaida Auzelyte; Mikael Elfman; Per Kristiansson; Klas Malmqvist; Christer Nilsson; Jan Pallon; Marie Wegdén

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 184 KB
• Volume: 231
• Category: Article
• ISSN: 0168-583X
• DOI: 10.1016/j.nimb.2005.01.026

✦ Synopsis

A new beam line for generating a sub-micron beam spot for high-resolution nuclear microprobe applications has been constructed at the Lund nuclear microprobe facility. In this paper, the first in a series of three, a detailed theoretical investigation of different focusing systems is presented based on calculations performed with the computer programs PRAM and OXTRACE. Comparison is made between a doublet, a triplet, a quadruplet and a split quadruplet (two-stage focusing). For the split quadruplet all four quadrupole magnets were uncoupled.

The conclusion from the calculations was that to obtain the smallest possible beam, the two-stage focusing system should be used. Such a focusing system (a doublet at each stage) has been chosen for the new sub-micron set-up at the Lund NMP laboratory. The first stage focuses the beam in an intermediate chamber, which has a high-resolution optical viewing system facilitating more control over the beam spot. This real image of the first stage is then used as a virtual object for the second stage.