FPC and HOM Coupler Test Boxes for HL-LHC Crab Cavities

The LHC luminosity upgrade will involve the installation of thirty-two 400 MHz SRF crab cavities. The cavities have two variants known as the RF dipole and double quarter-wave crab cavities. Each cavity has a fundamental power coupler (FPC) at 400 MHz and two or three HOM couplers. Before integration onto the cavities it is necessary to condition the FPC, and to measure the transmission on the HOM couplers at low power to ensure the operate as designed, each requiring a special test box. The FPC test box should provide a high transmission between two couplers without creating high surface fields. The low power HOM test boxes should be terminated to a load such that the natural stop and pass-bands of the couplers are preserved allowing the reflection to me measured and compared to simulations. In addition, due to the possibility of high HOM power in the LHC crab cavities, the concept of creating a broadband high power HOM coupler test box in order to condition and test the couplers at high power has been investigated. The Rf design of all test boxes is presented and discussed.