Constructing and Characterizing a Scanning SQUID Microscope for a Cryogen Free Dilution Refrigerator

Superconducting quantum interference devices, or SQUIDs, are highly sensitiveto magnetic flux and can be used to perform magnetic imaging at cryogenic tem- peratures. In this dissertation, I describe the first scanning SQUID microscope in a cryogen-free dilution refrigerator. First, I briefly describe basic SQUID theory, how to perform scanning SQUID microscopy, and how to design SQUIDs suited for microscopy. Next, I discuss both the apparatus and method to systematically characterize SQUIDs. I demonstrate that while heuristics provide guidance for finding low noise operating points, one often misses the best noise performance of the SQUID found by a systematic search. I also briefly discuss how to use ma- chine learning to predict SQUID noise. I then describe in depth the design of the SQUID microscope, focusing on explaining the reasons behind various features of the coldfinger and microscope. Finally, I describe how to characterize vibrations in our microscope using images of a vortex in a superconductor.

Name thesis:degree_name

Ph. D., Applied Physics

Level thesis:degree_level

Doctor of Philosophy

Discipline thesis:degree_discipline

Applied Physics

Grantor

Cornell University

Year dc:date.issued

2021

Author dc:creator

• Low, David

Committee members dc:contributor.committeemember

• Selman, Bart
• Nowack, Katja C.

Statement dc:rights

• Attribution 4.0 International

Licence dc:rights.uri

• https://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

DOI

https://doi.org/10.7298/xxa1-4w48

Dc Identifier Other

ProQuest Submission ID: 12837
ProQuest Publication ID: 28777139

OAI identifier oai:identifier

oai:ecommons.cornell.edu:1813/110839