Base for small bell jar.?

ok so i need s base for a small bell jar. I want the jar to be seven inches internal, under eight outside. i have 10 mm mild steel plate. I have edwards pump to use. The base plate is 8*8 inch. The surface is a little warn. What should i place between the jar and plate.. I plan on putting a metal cage round it for safety. The project is a small home fusion reactor. People say they wnt work. But my physics teacher has checked my maths and thinks it could. I will use a high pd to accelerate deuterium towards inner grid. Anyways basically its going to have high vacuum. What is the best way to attach the jar t base plate, would a cushion of silicon sealant do? I will machine holes into base. I plan on having a central inlet for electrode and outer one. As well as a 10mm hole for vacuum outlet. What should i use for the protective mesh around it? thanks.