Status of the High Power Couplers for ESS Elliptical Cavities

In the framework of the European Spallation Source (ESS), CEA Paris-Saclay is responsible for the delivery of 30 cryomodules (9 medium beta (β = 0.67) and 21 high beta (β = 0.86) ones). Each cryomodule contains 4 elliptical cavities equipped with a radio frequency power coupler. The ESS nominal pulse is 1.1 MW maximum peak power over a width of 3.6 ms at a repetition rate of 14 Hz. The design of the couplers for medium beta and for high beta cavities is the same, except a small difference of the antenna penetration to adjust the Q_{ext}. The mass production of the 120 couplers started and all the medium beta couplers have been conditioned at room temperature. The first cryomodules equipped with the power couplers were successfully tested at high RF power and with cavities at 2K reaching the ESS nominal pulse. The main issue at the start of the series production could be fixed and it was due to bad TiN coatings that caused abnormal dielectric losses in the window. Thus, this paper deals with the TiN coating defect, presents the conditioning procedure and gives a conditioning report of these 36 couplers.