The Atomic Beam Laser Cooled Ion Source (ABLIS) is a new source for focused ion beam instruments, which are used in the semiconductor industry, to image and modify structures on the nanometer length scale. The ABLIS employs laser cooling and compression of an atomic beam of rubidium to increase its brightness signicantly. By photo-ionization in an accelerator structure, ions are then created and accelerated immediately. The bottleneck for retaining a high brightness, is disorder-induced heating: ions, created at random initial positions, heat up due to relaxation of the potential energy associated with these positions. This eect is counteracted by the applied electric eld to quickly reduce the ion density. However, since ionization takes place over a nite distance, a larger electric eld implies a larger energy spread of the beam and therefore larger chromatic aberrations of the lens system. Here we report on analytical and numerical investigations of the conditions under which the smallest spot sizes can be reached. With particle tracking simulations, a relation was found between the current and the minimum electric eld needed to suppress disorder-induced heating. This relation was used to account for chromatic aberration of the lens system. An analytical calculation was performed of the possible spot size of the ABLIS setup, including the nite brightness of the beam and spherical and chromatic aberration of a realistic lens system. The results show that sub-nanometer spot sizes are possible for currents up till 10 pA. The calculation was veried with particle tracking simulations of the whole beam line.
|Title of host publication||Proceedings of the 26ste Annual Meeting on Plasma Physics and Radiation Technology CPS/NNV, 11-12 maart 2014, Lunteren. The Netherlands|
|Publication status||Published - 2014|
|Event||26th NNV Symposium on Plasma Physics and Radiation Technology, March 11-12, 2014, Lunteren, The Netherlands - De Werelt, Lunteren, Netherlands|
Duration: 11 Mar 2014 → 12 Mar 2014
|Conference||26th NNV Symposium on Plasma Physics and Radiation Technology, March 11-12, 2014, Lunteren, The Netherlands|
|Period||11/03/14 → 12/03/14|