"The problem of radiation derange to the walls of two types of vacuum chamber for the 6 Bev Cambridge Electron Accelerator was studied. Radiation damage may arise from the synchrotron radiation and from electrons which are not accepted at injection. The synchrotron radiation produces a large amount of secondary x radiation which is isotropic, and therefore complicates the arrangement of internal shielding. The 20 Mev electrons from the lines cannot be attenuated by shielding. It is concluded that dosages of the order of 10/sup 7/ rad/day near the inflector are unavoidable. This would exceed the allowable dosage for a tube made by cementing a stainless steel liner to supporting ribs, and also exceed the test dosages (so far as we know) for alumina ceramics."