Conceptual Design for the LCLS 120 Hz Gun Load Lock

A load lock for the LCLS 120 Hz RF gun is required for the rapid interchange of cathodes onto the gun as well as to avoid exposing the cathode to contamination during installation. Implementing a load lock allows the gun to be operational in less then 1 hour after a cathode change since no bake out is required and minimal rf conditioning will be needed. A conceptual drawing of the load lock proposed by SLAC is shown in the figure. The load lock approach adopted by SLAC requires two load-lock transporters: one mounted on the gun and another in the cathode processing lab where cathodes are prepared and stored for use on the gun. A single cathode is mounted in each transporter, eliminating the need for transferring cathodes under vacuum from a storage carousel, or ''6-pack''. This design has the advantage of greatly reducing the mechanical complications of transferring cathodes and connecting them to cooling lines while under high vacuum. Cooling of the cathode is necessary, given the gun cooling requirements as detailed in the LCLS Technical Note ''Design Considerations for the LCLS RF Gun''. The cathode size is approximately the same as that of the standard BNL/SLAC/UCLA gun whichmore » has an RF seal at the outer diameter of the cathode cavity to avoid RF breakdown.« less