Abstract: A vacuum chamber 2 has walls having an inner layer 20 of a gas impermeable electrically non-conductive material and an outer layer 22 of a different electrically non-conducting material. The inner layer 20 is a polymeric film layer of Kapton® polyimide. The outer layer 22 is a composite material which includes reinforcing carbon or glass fibers bound in a matrix of epoxy resin. The vacuum chamber has end flanges for attaching it to adjacent parts of a vacuum system. The vacuum chamber is made by placing a sheet of Kapton® material around a mould and sealing its ends together. The composite material is then wound onto the inner layer in its wet form to provide the outer layer. The outer layer material is then cured to dry the epoxy resin, binding the layer to the inner layer, and the multi-layer structure removed from the mould. The vacuum chamber is particularly suitable for use in an ion implantation system in the presence of a time varying magnetic field.