Numerical Calculation of Losses of Trapped Vortices Under Strong RF Meissner Current and DC Superheating Field in Type II Superconductors

<p>Research on the vortex dynamics and enhancing of superheating field in superconductors has attracted much attention in accelerator physics community to develop next-generation high-performance accelerator cavities. However, the extreme dynamics of curvilinear elastic vortices driven by very strong currents close to the depairing limit or superheating field of a superconductor with a nanostructured surface has not been well understood. We calculated the superheating field H<em>_sh</em> and critical momentum kc characterizing the wavelength of the instability λ<em>_m</em> of the Meissner state to flux penetration by solving numerically the Ginzburg-Landau equations. A bulk superconductor, superconductor with the inhomogeneous surface disorder (S-S), and multilayered surface (S-I-S) have been thoroughly investigated in this work. Our result showed that S-S and S-I-S structures can enhance the superheating field well above their clean limit. In this work extensive numerical simulation of the power dissipated by an oscillating vortex segment driven by the surface <em>ac</em> Meissner currents was performed. Our simulations take into account the nonlinear vortex line tension, vortex mass, Bardeen-Stephen viscous vortex drag applicable at low fields, and nonlinear Larkin-Ovchinnikov (LO) viscous drag coefficient <em>η(v)</em> at high fields and pinning force. We showed that the LO decrease of <em>η(v)</em> with the vortex velocity v could radically change the field dependence of the surface resistance Ri(H) caused by trapped vortices. At low frequencies<em> Ri(H)</em> exhibits a conventional increase with H. However, as frequency increases, the surface resistance becomes a nonmonotonic function of <em>H</em> which decreases with <em>H</em> at higher fields irrespective of the pinning distribution. Overheating can mask the descending field dependence of <em>Ri(H</em>) as frequency increases. Our numerical simulations also show that the LO effect can cause a vortex bending instability at high field amplitudes and frequencies, giving rise to the formation of dynamic kinks along with the vortex when a vortex is pinned strongly to one end. Nonlinear losses of trapped vortices in thick films under high-amplitude RF fields as functions of frequency, mean free path and pinning characteristics have been calculated.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date.available

2021

Author dc:creator

• Pathirana, Walive Pathiranage Manula Randhika

Contributors dc:contributor

• Alexander Gurevich
• Jean R. Delayen
• G. Ciovati
• A.L. Godunov
• Ruhai Zhou

• Flux pinning
• Nonlinear dynamics
• Particle accelerators
• Superconductivity
• Superheating field
• Vortices in superconductors
• Physics
• Semiconductor and Optical Materials

Statement dc:rights

• <p>In Copyright. URI: <a href="http://rightsstatements.org/vocab/InC/1.0/">http://rightsstatements.org/vocab/InC/1.0/</a> This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).</p>

Identifier

9798460433438

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:physics_etds-1132