The Transmission Of KeV Negative Ions Through The Glass Macro-capillaries

Experiments are performed to study the transmission of 15-keV C~-ions through straight and tapered borosilicate glass capillaries.The results showed that a stable negative ion beam can be achieved when the ions transmitted through the straight and tapered capillaries.In the transmission,the scattering process and charge exchange process played a role.Base on the change of the electrical conductivity of the glass material at different temperatures,how the temperature influences the transmission of negative ions is studied.1.The time evolution of the transmission of 15-keV C~-ions through straight and tapered capillaries was studied.The transmitted particles passing through the straight capillary formed an elliptical spot at 0°tilt angle and the corresponding projection is a single-peak structure.As the measurement time increases,the intensity of the transmitted particles is stable.The particles emitted through the tapered capillary formed two patterns:a concentrated core at the center of the 2D image and a surrounding halo pattern.And an interval between them.With the increase of measurement time,the intensity,peak position and FWHM of the emitted particles are stable.The experimental results show that negative ions can form a stable beam in the glass macro-capillaries.2.The Experiment was carried out to study the transmission of 15-keV C~-ions through straight and tapered capillaries at different tilt angles.The tilt angle is varied within 0°~0.8°.By measuring the 2D images and angular distributions of transmitted particles,when the C~-ions transmit through the straight capillary,a spot was observed and its intensity declined with the increase of the tilt angle.Almost 99%of the transmitted particles in the spot kept their initial charge state.There is no obvious movement of the spot's position.The transmitted particles through the tapered capillary were also formed the two patterns:a core with 0.957 negative ion fraction and 3.7density enhancement,and a surrounding halo.The negative ion fraction of the halo is only 0.425 and the halo keep symmetrical at 0°tilt angle.The intensity of the transmitted particles and its fraction of C~-declined when the tilt angle increased,and the halo was gradually far from symmetric.These results proved that the scattering with a significant charge exchange process played a role in the transmission.3.The experiment was carried out to study the transmission of 15-keV C~-ions through straight and tapered capillaries at different temperatures.By measuring the 2D image and the corresponding projection,the transmitted particles still formed a core and a halo shape.With the temperature increasing,the intensity of the transmitted particles and the FWHM of the corresponding peaks were declined at 0°tilt angle,but the peak positions did not move.The negative ion fraction of the halo was declined with the increasing temperature,which indicated that the high temperature can change the conductivity of the insulating material.Therefore,the charge deposited on the inner wall had a weak influence on the transmitted particles and the transmission followed the geometrical rule.