Positive synergy of SF6 and HFO1234ze(E)

Abstract

We measured mixtures of SF 6 and HFO1234ze(E) (C 3 H 2 F 4 ) and determined the density-reduced critical electric field strength (E/N) crit in a pulsed Townsend experiment. HFO1234ze(E) is an environmentally friendly alternative to SF 6 since contrary to SF 6 , its global warming potential is negligible. While SF 6 is unsurpassed in its efficiency of attaching thermal electrons, HFO1234ze(E) appears to moderate electron energies very efficiently. Electron attachment to HFO1234ze(E), on the other hand, is much weaker. We find a positive synergism in SF 6 /HFO1234ze(E) mixtures in the sense that the mixture of both compounds has a higher electric field strength than each gas separately. A maximum (E/N) crit of 425 Td is reached for a mixture of 40% SF 6 and 60% HFO1234ze(E). A mixture of 90% HFO1234ze(E) and 10% SF 6 has a critical electric field strength of 360 Td, similar to pure SF 6 . We attribute this effect to the high efficiency of HFO1234ze(E) in moderating down the electron energies, which enhances electron attachment to SF 6 and reduces electron impact ionization.