  Organometallic liquids provide good properties for ionization detectors.
TriMethyl Bismuth (TMBi) has been proposed as a detector medium with charge and
Cherenkov photon readout for Positron Emission Tomography. In this work, we
present studies for the handling of TMBi at different electric fields and under
different environmental conditions to find applicable configurations for the
suppression of electrical breakdowns in TMBi at room temperature. A simple
glass cell with two electrodes filled with TMBi was constructed and tested
under different operation conditions. Working at the vapour pressure of TMBi at
room temperature of about 40 mbar and electric fields of up to 20 kV/cm in
presence of a small oxygen contamination we found the formation of a discharge
channel in the liquid and a steady increase in the current. Further reduction
of pressure by pumping caused the TMBi to boil and a spontaneous combustion.
Eliminating the oxygen contamination led the TMBi under the same condition to
only decompose. When operating the setup under an argon atmosphere of 1 bar we
did not observe breakdowns of the electrical potential up to field strengths of
20 kV/cm. Still, in presence of a small oxygen contamination fluctuating
currents in the nA range were observed, but no decomposition or combustion. We
conclude from our experiments that TMBi at room temperature in a pure argon
atmosphere of 1 bar remains stable against electrical breakdown at least up to
electric field strengths of 20 kV/cm, presumably because the formation of
gaseous TMBi was prevented.
