Attachment of ferrite material used in an active matching network for LHCD on Alcator C-Mod

In order to increase power coupling efficiency of the Lower Hybrid Current Drive system (LHCD) on Alcator C-Mod an active double stub matching network is being developed. One aspect of this development requires application of ferrite material of certain geometry in a section of WR187 waveguide with expected operation in excess of 200kW of microwave power. This has proven to be a challenge due, in large part, to differences in the Coefficient of Thermal Expansion (CTE) between materials at the ferrite-waveguide and ferrite-coating interfaces, the inherent brittleness of ferrite material and the level of homogeneity in the samples. This paper will discuss a method to modify and attach ferrite material to the waveguide. As necessary, materials issues and processes will be discussed as will the effort to develop a set of guidelines to insure process integrity and repeatability across the multichannel LHCD matching network required for C-Mod and other machines.