A crossbow having an increased powerstroke and reduced noise. The device transmits an electromagnetic pulse having a circular polarization and receives a return signal over a period of time. The seal pack carrier and seal pack define a high-pressure plenum which abuts the downstream side of the seal pack, and which can be pressurized to apply a force to the seal pack in the upstream direction. Further, the polyimide passivation and planerization methodology provides unexpected processing advantages with respect to application in the fabrication of resonant tunneling diodes.