Abstract
We describe the development of a two-dimensional quasiparticle detector for use in visualising quantum turbulence in superfluid $$^3$$ He-B at ultra-low temperatures. The detector consists of a $$5 \times 5$$ matrix of pixels, each a 1 mm diameter hole in a copper block containing a miniature quartz tuning fork. The damping on each fork provides a measure of the local quasiparticle flux. The detector is illuminated by a beam of ballistic quasiparticles generated from a nearby black-body radiator. A comparison of the damping on the different forks provides a measure of the cross-sectional profile of the beam. Further, we generate a tangle of vortices (quantum turbulence) in the path of the beam using a vibrating wire resonator. The vortices cast a shadow onto the face of the detector due to the Andreev reflection of quasiparticles in the beam. This allows us to image the vortices and to investigate their dynamics. Here we give details of the design and construction of the detector and show some preliminary results for one row of pixels which demonstrates its successful application to measuring quasiparticle beams and quantum turbulence.
Highlights
Quartz tuning forks are commercially available and commonly used as a frequency standard for timing devices such as watches
We have developed a 2-dimensional detector to form a rudimentary quasiparticle camera to image quantum turbulence in superfluid 3He-B in the low temperature limit
The detector has 25 pixels formed by miniature quartz tuning forks in cylindrical cavities in a copper matrix
Summary
Quartz tuning forks are commercially available and commonly used as a frequency standard for timing devices such as watches. Quartz tuning forks have very high quality factors, of order 105, making them sufficiently sensitive to study the mechanical properties of helium fluids at low temperatures They have found many applications in superfluids research including measurements of viscosity [5,6,7], quantum turbulence in 4He [8,9,10], cavitation [11], Andreev scattering in 3He-B [12,13] and acoustic modes [14,15,16]. If some excitations in the beam undergo Andreev scattering, they accurately retrace their path back into the radiator causing a rise in the temperature (excitation density) within the radiator This technique has been used to directly measure Andreev reflection from the flow generated by a vortex lattice [32] and by quantum turbulence [33,34]. Based on calculations of Andreev reflection [37], we believe that the detector should be capable of detecting a single vortex line
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