Microtron Using a Superconducting Electron Linac

The superconducting linac of the 6 pass microtron (MUSL-1) described previously has been operated at 4.2 K for about 3 years with an energy gain of 2 MeV/meter. The duty factor has been limited to about 50% by thermal effects. A new helium liquefier supplies more than the 13 liters per hour required to operate the linac continuously at its maximum duty factor. The system can supply 5 μa of electrons with energies up to 19 MeV and has been operated on a 24 hour per day schedule for nuclear physics experiments. A larger system (MUSL-2) utilizing a surplus 3 MeV Van de Graaff as an injector and a 6 meter superconducting accelerator section made for us at Stanford University is being assembled in another area. Although the installation is not yet complete microwave tests indicate that the section can be operated continuously with an energy gain of 13 MeV with an input power of about 10 watts. For the initial operation of MUSL-2 the 6 pass hardware from MUSL-1 will be used to recirculate the electron beam through the new linac section to a final energy of 60 MeV.