Inductive Iris Impedance Matching Network for a Compact Waveguide DC Break

A custom waveguide dc break, developed for the versatile ECR for nuclear science (VENUS) ion source at Lawrence Berkeley National Laboratory, features an innovative impedance matching network. This network consists of two inductive irises located adjacent to a capacitive gap, which not only provides dc isolation but also facilitates the coupling of a new 2.4 kW Klystron, effectively doubling the power available for plasma production at the secondary frequency of 18 GHz. The design allows the ion source to operate at elevated potentials while keeping the RF system grounded, thereby ensuring efficient ion beam extraction and transportation to the cyclotron for acceleration, and maintaining easy access to the RF system. Simulations conducted with the ANSYS High-Frequency Structure Simulator, a finite element analysis tool, have demonstrated exceptional impedance matching at the Klystron frequency. These results have been corroborated by microwave measurements, showing excellent agreement.