Feasibility Study for High Performance Vacuum Chamber

For longer beam lifetime, many accelerators have employed ante-chamber type of beam ducts to reduce photon-induced desorption gas around the beam orbit. Still more reduction, however, can be expected if an Xray transparent membrane, such as beryllium thin film, is installed between the beam chamber and the antechamber because X-rays from the stored beam pass through the membrane while gas molecules desorbed in the ante-chamber are shut out by the membrane. Similarly, photoelectrons and secondary electrons traveling from the ante-chamber to the beam chamber are also shut out by the membrane; this function is expected to mitigate beamphotoelectron instability in positron storage rings. Feasibility study for this type of vacuum chamber has been started at Photon Factory (PF), and the result of the first-stage experiment will be presented.