Ion transport through macrocapillaries – Oscillations due to charge patch formation

Abstract

We present results on ion transport through large bore capillaries (macrocapillaries) that probe both the geometric and ion-guided aspects of this ion delivery mechanism. We have demonstrated that guiding in macrocapillaries exhibits position-and angledependent transmission properties which are directly related to the capillary material (either metal or insulator) and geometry. Specifically, we have passed 1 keV Rb + ions through glass and metal macrocapillaries, and have observed oscillations for the transmitted ion current passing through the insulating capillaries. Straightforward calculations show that these oscillations can be attributed to beam deflections from charge patches that form on the interior walls of the capillary. The absence of these oscillations in the metal capillary data serve as further confirmation of the role of charge patch formation.

Probing kinetically excited hot electrons using Schottky diodes

“…Beam transmission through the metal capillary was measured previously and is detailed elsewhere. 10 A Faraday cup in plane with the sample (not shown in the schematic) was used for beam tuning and for measuring ion beam currents pre-and postexposure.…”