An investigation was conducted for a very small helicon plasma source of a 2.5 cm i.d. glass tube. Since the operational features of electric propulsion are determined by its plasma density and degree of ionization, the helicon plasma including inductively coupled plasma (ICP) has a niche requirement as high as 10(13) cm(-3) density at the optimized condition of both RF frequency and applied magnetic field. In this paper, by using Ar, the RF frequency was scanned from 27.12 up to 67.80 MHz and the applied magnetic field was moderately varied from 0 to about 0.01 T. The maximum input power was 250 W at this time and 8 X 10(12) cm(-3) was achieved. (c) 2005 Elsevier B.V. All rights reserved.