Guided transmission of Ne 7+ ions through nanocapillaries in polymers: Scaling laws for higher projectile energies

In past few years, the guiding of highly charged ions through capillaries of mesoscopic dimensions has received great attention [1,2]. Various studies of the guiding phenomena have been performed with capillaries in highly insulating polyethylene terephthalate (PET) polymers [3]. For capillaries tilted with respect to the incidentbeam direction, the ion guiding involves the deposition of positive charges at the inner wall of the capillaries in a self-organizing process. The charge deposition in the entrance region continues until the electric field becomes sufficiently large to deflect the ions in the directions of the capillary exit. The fraction f( ) of the guided ions at equilibrium can be quantized by the guiding angle c for which the normalized transmission fraction drops as f( c) f(0) = 1 e. This definition of the guiding angle has been motivated by the observation that the tilt-angle dependence of the transmitted fraction can well be described by a Gaussian function. A similar definition has been introduced for the profile width t, which describes the FWHM of the angular distribution of the ions transmitted through the capillaries. For the characteristic angles c and t similar scaling laws have been established with respect to the chargeto-energy ratio q/Ep of the projectile [3]. In the present work, we study the guiding angle and profile width of the transmitted ions measured for the polymers PET and PC (polycarbonate) at KVI in Groningen (NL) [4]. The primary goal was the verification of the scaling laws for higher Ne energies of up to 50 keV, corresponding to the projectile charge-to-energy ratio down to 0.14 kV . The results are shown in Fig. 1. The characteristic angles of both polymers PET and PC are compared with the previous scaling law, given by the relation 7 . 0 7 . 0