Well, this job was easier then I thought since the 'delicate' section had not failed in any manner (vacuum wise.) So I really got rough with it by removing piping (which stress's the assembly when the couplings are undone) and installing an auxiliary vacuum fitting attachment coupling and redid all the pumping (leak valve assembly) so it is almost all SS now (more fittings but only one teflon tube now;) the Deuterium tank can be filled without removal, if desired. More to the point, all the volume of the gun assembly (piping, valve, and even the D2 mini-tank when open) can be evacuated independent of the main accelerator tube. This will help prevent residue gas contamination of the D2 supply for fills and make pump down of the entire accelerator system much faster. The gun's only connection to the main accelerator tube is thru a long, very fine needle (about 150 microns) which makes pumping through that orifice very slow after back filling the system for any maintenance.
In tests, the whole accelerator assembly with the D2 tank open, bottomed out at 1.1 x 10^-6 torr so apparently everything is still leak tight. The new gas line assembly for the gun is how supported by posts (all mounted in a SS hemisphere that will be charged by (hopefully) my new VdG) to reduce any stress on the weakest section; and hopefully, avoid any vacuum failure at the gun/D2 feed line/pipe coupling. While this, as noted, wasn't essential it makes sense to improve a possible trouble source while I have time to use waiting for the weather to change to low humidity.
For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.