An Efficient Procedure to Identify and Quantify New Molecules for Insulating Gas Mixtures

C. M. Franck, D. A. Dahl, M. Rabie, P. Haefliger, M. Koch

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


In this contribution, a new procedure to systematically identify and quantify novel molecular gases with low global warming potential for application in high voltage insulation as gas mixtures is presented. The attention is focused on highly efficient procedures to be able to scan a large number of candidate gases. To identify new molecules, we derived an empirical correlation between the electric strength of a gas and certain molecular properties, like polarizability or dipole moment, which can be calculated by means of density functional theory. The swarm parameters of these pre-selected molecules in mixtures with buffer gases is then quantified, using a newly set-up Pulsed Townsend experiment. The setup operates with a high degree of automation to enable systematic evaluation of gas mixtures not to miss possible synergistic effects. Key element of this PT setup is a new photocathode that works with a high quantum efficiency and long lifetime even when exposed to reactive species during the measurements. Moreover, for an automated operation it is important to know precisely in which range the experiment can be operated, i.e. for example to know up to which electron density space charge effects can be neglected. Finally, the measured swarm parameters need to be translated into breakdown voltage strengths of different electrode arrangements and different applied voltage wave shapes. For this, a model of the the streamer to leader transition in SF6 will be applied to other strong electronegative gases in future studies to test if the model is universally valid.

Original languageEnglish
Pages (from-to)3-13
Number of pages11
JournalContributions to Plasma Physics
Issue number1
StatePublished - Jan 2014
Externally publishedYes


  • High Voltage Insulation
  • Pulsed Townsend discharge
  • SF6 replacements
  • Swarm parameters


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