Dielectric loss of supercritical helium

Abstract

The dielectric loss of supercritical helium has been investigated at several field strengths up to 20 MV m −1 rms at 50 Hz. Its loss tangent was observed to be extremely small when the helium was very pure. However, the loss of commercial-grade helium turned out to be a few μ rad at low field strength. The dielectric loss increased to 1 × 10 −5 rad at 5 MV m −1 but did not exceed 1 × 10 −5 rad even at 10 MV m −1.