Vacuum Couplings are used for vacuum down to 1 x 10 -8. These are available in either machine finish or polish finish. These are used for an ion implanter for connecting any two parts of the vacuum chamber. The coupling comprises an inner sleeve of ceramic material and an outer sleeve of a polymer/litharge mixture. The coupling is particularly useful for coupling an ion source to the main housing of the vacuum chamber. These are composed of the brazed body and plunger subassemblies.