Thermo-Mechanical Emission and Detection of Ballistic Quasi-Particles in ³ He- B at Low Temperatures: A Quasi-Particle Spectrometer

Abstract

A filamentary wire resonator will generate quasi-particles in 3He-B when driven beyond a critical velocity. By using such a resonator as a source of quasi-particles and a second wire resonator as a quasi-particle detector, we have been able to emit and detect a ballistic quasi-particle beam over a distance of 3 mm in 3He-B at temperatures below 0.3 Tc. From the preliminary experiment the momentum of the quasi-particle beam can be measured and a direct (but as yet very approximate) measurement made of the quasi-particle mean free path.

Microkelvin physics

“…At the lowest temperatures the quasiparticles are emitted as a ballistic pulse which can travel many metres before being dissipated by collisions. We can thus construct a quasiparticle spectrometer in which a wire driven supercritically is used as a source to create a pulsed quasiparticle wind which can excite another wire resonator at some distance (Coates et al 1986). Once these devices are perfected we can envisage using them to study directly the influences on the trajectories of the quasiparticles of various quantities such as magnetic fields, supercurrents and so forth.…”