Endcap for indirectly heated cathode of ion source

An ion source for use in an ion implanter, said ion source comprising:

• a) a confinement chamber having chamber walls that bound an ionization region and including an exit opening to allow ions to exit the confinement chamber;
• b) means for delivering an ionizable material into the confinement chamber;
• c) structure for supporting the confinement chamber in a position for forming an ion beam from the confinement chamber;
• d) a cathode positioned with respect to the ionization region of the confinement chamber to emit ionizing electrons into the ionization region of the confinement chamber to produce ions within the ionization region, the cathode including a heat source positioned in an electrically isolated cathode body, the cathode body including a first tube and an endcap supported in a distal end of the first tube adjacent the heating source, the endcap emitting said ionizing electrons into the ionization region of the gas confinement chamber when heated by the heat source;
• and
• e) the endcap including a first end and a second end spaced apart from said first end by a body portion and having a radially projecting support extending outwardly from the body portion which contacts an inner surface of the first tube to support the endcap within the distal end of the first tube, the radially projecting support having a thickness in an axial direction less than a thickness in an axial direction of the body portion.