Development of the L-band RF gun

We report progress in development of the L-band RF gun in collaboration with KEK, Hiroshima University. The RF gun is equipped with many water cooling channels because the average input RF power will reach 25 kW to the RF gun without any frequency tuning device. We reported at the PASJ meeting last year that we had cooling water leakage from brazing parts between the main body and stainless steel water pipes and we were fixing it. We fix the leaking using liquid gasket and Vacseal, which are sucked in the leaking parts from outside by evacuating a water channel with appropriate treatment. After Vacseal thinned quadruple with trichloroethylene is sucked in the leaking, the part is heated to approximately 200 C using a heat gun for an hour. The temperature is not enough high to harden but it works for small leak. The viscosity of liquid gasket is too high to be sucked in a recess but it is found that its viscosity becomes sufficiently low when it is heated. Thus the water leakage problem has been solved. The resonance frequency and the electric field balance between the half and the full cells are corrected, using a device named the torture machine together with special jigs, from 1301.525 MHz and 0.6 to 1 to 1300.211 MHz and 0.934 to 1, which are expected to be 1300.160 MeV and 1 to 1 at room temperature. The high power test of the L-band RF gun is being conducted at the Superconducting RF Test Facility (STF) of KEK. (author)