Quasiparticle beam profile measurements in superfluid helium 3 - B

Ahlstrom, Sean (2016) Quasiparticle beam profile measurements in superfluid helium 3 - B. PhD thesis, UNSPECIFIED.

[img]
Preview
PDF (2016AhlstromPhD)
2016SeanLeeAhlstromPhD.pdf - Published Version
Available under License Creative Commons Attribution-NoDerivs.

Download (7MB)

Abstract

This thesis details experiments in the ballistic regime of superfluid 3He-B at temperatures around 100 ➭K. In this thesis, the quasiparticle beam profile from a Black-Body radiator and a vibrating wire resonator is measured using a quasiparticle camera which consists of 25 tuning forks. The vibrating wire resonator is found to have a very thinly spread beam at velocities slightly higher than the pair-breaking critical velocity which spreads out at higher velocities. At 21 mm/s the vibrating resonator is found to have a more focused beam than the Black-Body radiator where both beam profiles are found to be focused around the centre of the quasiparticle camera. A theoretical model is created in order to model the spread and intensity of the experimental beam profile from the Black-Body radiator. In this thesis, the response of some of the probes to thermal damping is measured in the form of the geometrical constants γ and λ. The geometrical constant λ is related to the velocity dependence of the probe to thermal damping and is found for two wires of varying diameter, a tuning fork and its overtone mode in which all the values of λ were close to unity. The geometrical constant γ is related to the sensitivity of a probe to thermal damping. This is found for a Black-Body radiator and then used to derive the sensitivity for other wires in the cell in thermal equilibrium with it. Two resonant modes of a small tuning fork are used to do a Black-Body radiator calibration on the area around the tuning fork which is used to find the sensitivity of 25 tuning forks (pixels) in the quasiparticle camera.

Item Type:
Thesis (PhD)
Subjects:
ID Code:
83024
Deposited By:
Deposited On:
21 Nov 2016 09:48
Refereed?:
No
Published?:
Published
Last Modified:
29 Nov 2020 07:15