Incomplete guiding of 300–900 keV O6+ ions through a glass macrocapillary due to saturated charging-up

The transmissions of 300, 600 and 900 keV O6+ ions through a single borosilicate glass macrocapillary with a diameter of 0.6 mm and a length of 31 mm were studied. The ions went out neither along the macrocapillary axis nor along the incident direction, but still kept their initial charge state and energies. The higher the energy, the smaller the deflection angle. With the present conditions, the incident energies exceed the higher energy limit of the self-organizing charge-up mechanism. This incomplete guiding phenomenon is considered to be a consequence of the saturated charge-up at the macrocapillary inner wall, which cannot compensate the transverse momentum of the ions. In the present work, there is a saturated potential difference almost independent of the incident ion energy and current. It implies the existence of an intrinsic limit of the guiding ability of a capillary, depending on its shape, material, boundary conditions and temperature.