Interaction of charged particles with insulating capillary targets – The guiding effect

The guiding of charged particles through microscopic and, more recently, also macroscopic capillaries is a remarkable effect discovered in 2002 by Stolterfoht and coworkers. After an initial charge-up phase, a beam of charged particles entering an insulating capillary can be effectively steered along the tilted capillary axis. The effect results from self-organized charge-up of the capillary wall which subsequently deflects ions electrostatically thereby inhibiting close collisions with the capillary walls. Indeed, in the case of multiply charged projectile ions the projectiles transmitted through the capillary keep their initial charge state indicating that the ions never touched the inner walls. We will review both the existing experimental data as well as theoretical models for this phenomenon and similar guiding processes for energetic charged particles collected over the past 10 years.