of which depart from the prior art to produce a well focused collimated and controllable ion beam these features include ionizing electron beams generated external to the ionization chamber thereby extending the emitter lifetime 90 degree magnetic deflection of electron beams such that no line of sight exists between the emitter and the process gas load and the emitter is protected from bombardment by energetic charged particles two opposed electron beams which can be operated simultaneously or separately and use of a deceleration lens to adjust the final energy of the electron beam substantially without affecting electron beam generation and deflection application_number US 74807803 A description the ion source which forms a part of the ion implantation system in accordance with the present invention is an electron impact ionization source fig1 is a cross sectional schematic diagram of the ion source in accordance with the present invention which illustrates the construction and the functionality of the components which make up the ion source 10 the cross section is cut along a plane which contains the direction of propagation of the ion beam separating the ion source in two halves the ion source 10 includes a vaporizer 28 and a beam forming region 12 joined together by at a mounting flange 36 the ion source 10 is made to interface to an evacuated vacuum chamber of an ion implanter or other process tool by way of the mounting flange 36 thus the portion of the ion source 10 to the right of the flange 36 in fig1 is at high vacuum pressure lt 1 u00d7 10 u2212 4 torr gaseous material is introduced into an ionization chamber 44 where the gas molecules are ionized by electron impact from one or more electron beams.