Study of the Shielded Double Helical Antenna for Methane Ionisation

A double helical antenna excited by microwave power provides super high-density ionisation in gas inside dielectric tube at certain conditions. Designed antenna and matching circuit have resonant frequency of 434 MHz reserved for industrial, scientific and medical (ISM) applications. Frequency bandwidth at coupling optimization reach ±3% at -3 dB level that improve absorption of microwave power for variable antenna load determined by helicon discharge. To prevent power loss due to radiation outside dielectric tube electromagnetic shield around antenna is applied. The shield also concentrate electromagnetic field inside the tube increasing ionisation efficiency. The results of experimental study and computer simulation are presented.