Kerr Effect in Liquid Helium at Temperatures Below the Superfluid Transition

Abstract

The electro-optical Kerr effect induced by a slowly-varying applied electric field in liquid helium at temperatures below the λ-point is investigated. The Kerr constant of liquid helium is measured to be (1.43±0.02 (stat) ±0.04 (sys) )×10 −20 (cm/V) 2 at T = 1.5 K. Within the experimental uncertainty, the Kerr constant is independent of temperature in the range T = 1.5 K to 2.17 K, which implies that the Kerr constant of the superfluid component of liquid helium is the same as that of normal liquid helium. Our result also indicates that pair and higher correlations of He atoms in the liquid phase account for about 23% of the measured Kerr constant. Liquid nitrogen was used to test the experimental set-up, the result for the liquid nitrogen Kerr constant is (4.38±0.15)×10 −18 (cm/V) 2 . The knowledge of the Kerr constant in these media allows the Kerr effect to be used as a non-contact technique for measuring the magnitude and mapping out the distribution of electric fields inside these cryogenic insulants.

Kerr and Cotton–Mouton effects in atomic gases: a quantum-statistical study

“…In 2004 a measurement of the Kerr constant K exp was reported for the superfluid helium in the temperature range 1.5-2.17 K [40]. The measured value of K exp = (1.43 ± 0.06) × 10 −20 (cm/V) 2 can be compared with our calculations.…”

Fundamental Neutron Physics

“…The polarized 3 He slowly depolarizes in the storage chamber and must be periodically replenished: the low temperature dynamics of 3 He motion in superfluid 4 He makes this possible, and unpolarized test measurements have been performed [176,177]. One obtains d n by measuring the difference in the neutron and 3 He precession frequencies for the different orientation of the electric field, which can be measured optically in superfluid helium using the Kerr effect [178].…”

Precision polarimetry with real-time mitigation of optical-window birefringence

“…In a practical experimental setup, we expect Kerr effect signals of the order of 10 −5 -10 −6 rad. 1 In our laboratory, where low-temperature optical access is implemented with a set of 1-in.-diameter, 2-mm-thick, epoxy-mounted fused-silica windows, testing with 632 nm light showed that window birefringence introduces offsets in polarization rotation and ellipticity, the latter being defined as inverse tangent of ratio of the axes of the polarization ellipse, on the order of 0.1 rad, which also depend on the window temperature. This offset drifts within a range of about 10 −4 rad over periods of hundreds of seconds, and this noise overwhelms the typical signal from the Kerr effect of liquid helium.…”

“…11 In other experiments, notably Kerr effect experiments, modulation of the applied electric field is used to distinguish the signal from background noise. 1 Neither of these methods can be used in the application of Kerr effect for monitoring electric fields. Thus, we explore the feasibility of measuring and compensating for the optical-window birefringence drifts using the reflected light from the last optical surface before the sample.…”

“…Kerr effect, measured in liquid helium 1 and liquid nitrogen, 2 is a useful method for noncontact measurement and monitoring of the electric fields in low-temperature experiments. In particular, we have proposed to use this technique to monitor the electric field setup in the new search for the neutron electric dipole moment.…”