An emitter assembly can include a proximal shaft, a distal shaft, a shunt that connects the proximal shaft to the distal shaft, and a tip that is connected to a distal end of the distal shaft. An inner conductor can extend through the proximal shaft, the shunt, and the distal shaft and into the tip to provide microwave energy to the tip. An outer conductor can extend into the shunt. The shunt can therefore form an electrical connection between the outer conductor and a proximal ring of electrically conductive material formed on an exterior surface of the distal shaft. Distal shaft can be made of a thermally conductive but electrically insulated material to facilitate transfer of heat from the distal shaft to the proximal shaft.