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Planar Arrays of Superheated Superconductors: fabrication, testing, and exploring the superconducting transition

University of British Columbia

The Planar Array of Superheated Superconductors (PASS) has been suggested as a possible detector for dark matter and other weakly interacting particles. This work concentrates on overcoming the problems in device fabrication which prevent the PASS detector from being a viable detector for these low flux, low energy particles. We also examined whether γ-ray and α-particle irradiation could nucleate the superconducting state. Improvements were made throughout the device fabrication process with the goal of producing a working PASS sample that demonstrates complete avalanche multiplication. Despite better sample surface morphology, greater cleanliness, and improvements in lithography resolution it was not possible to fabricate a sample that would exhibit a full line avalanche. A 127 x 115 tin PASS sample was fabricated by scientists at the 3M company using an embossing technique rather than lithography. We examined this sample to determine whether a PASS device fabricated in this manner would function as a sensitive particle detector. We found that the superheated transition width ΔTsh was about 60 mT. This is not as good as those produced photo lithographically at UBC (ΔTsh~30mT) but this result is encouraging as the embossing technique is applicable to large scale fabrication. Lastly, a supercooled normal indium PASS sample was irradiated with γ-rays and α-particles to see if energy deposition could nucleate the formation of the superconducting state by a process much like the Baked Alaska of A. J. Leggett. We found that γ-rays enhanced the formation of the superconducting state while α-particles did not. These results are consistent within the framework of a Baked Alaska theory for superconductors. (Certain scientific formulae used in this abstract could not be reproduced exactly.)

Thesis/Dissertation

application/pdf

2009-05-22

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http://hdl.handle.net/2429/8071

Physics

University of British Columbia

UBCV

DSpace