Supersonic Fe beam source for chromatic aberration-free laser focusing of atoms

Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB  Eindhoven, The Netherlands

Corresponding author: K.A.H.v.Leeuwen@tue.nl

Received: 20 November 2001
Revised: 6 March 2002
Accepted: 26 March 2002
Published online: 6 June 2002

Abstract

A monochromatic Fe beam is generated by heated supersonic expansion of argon seeded with Fe vapor. At a nozzle temperature of 1930 K and 800 torr argon inlet pressure the Fe beam has an axial velocity spread of 8% and intensity of 3 × 10¹⁵ s⁻¹ sr⁻¹, corresponding to a deposition rate of 10 nm/h at 150 mm from the nozzle. The two-chamber alumina crucibles are chemically stable for liquid Fe. With 400 mm³ Fe we have operated for more than 200 hours without reloading. The power consumption at 1930 K is 750 W. Temperature stability at constant power (without feedback) is better than 30 K. The source is intended for deposition of nanostructures by laser focusing of the Fe beam. The small axial velocity spread virtually eliminates the increase in focal spot size due to chromatic aberration.