arXiv subjects

Henrik Nordborg

Publications and source records attributed to Henrik Nordborg.

4 recordsLinked to original sources

arXiv2016

Modeling and Simulation of the Current Quenching Behavior of a Line Lightning Protection Device

We develop a consistent model for a Line Lightning Protection Device and demonstrate that this model can explain the two modes of current quenching -- impulse quenching and current zero quenching -- observed in such devices. A dimensional analysis shows that impulse quenching can always be obtained if the power loss from the electric arcs is large enough as compared to $U_0 I_f$, where $U_0$ is the grid voltage and $I_f$ is the maximum follow current after a lightning strike. We further show that the two modes of quenching can be reproduced in a full 3D arc simulations coupled to the appropriate circuit model. This means the arc simulations can be used for optimization and development of future LLPDs.

physics.plasm-ph↗

arXiv1997

Thermodynamics of the first-order vortex lattice melting transition in YBa$_2$Cu$_3$O$_{7-δ}$

Using the London approximation within the high field scaling regime, we calculate the jump in the specific heat $Δc$ at the first-order melting transition of the vortex lattice in YBa$_2$Cu$_3$O$_{7-δ}$. This has recently been measured [A. Schilling et al., Phys. Rev. Lett. (78), 4833 (1997)] and reported to be at least 100 times higher than expected from the fluctuations of field induced vortices alone. We demonstrate how the correct treatment of the temperature dependence of the model parameters, which are singular at the mean-field $B_{c2}$ line, leads to good agreement between the predictions of the London model and the size of the experimental jump. In addition, we consider the changes in the slopes of the magnetization $Δ(\partial M/\partial T)$ and $Δ(\partial M/\partial H)$ at the transition. Using continuum anisotropic scaling theory we demonstrate the consistency of measurements at different angles of the magnetic field with respect to the crystal c-axis.

cond-mat.supr-con↗

arXiv1997

Vortices and 2D bosons: A Path-Integral Monte Carlo Study

The vortex system in a high-T_c superconductor has been studied numerically using the mapping to 2D bosons and the path-integral Monte Carlo method. We find a single first-order transition from an Abrikosov lattice to an entangled vortex liquid. The transition is characterized by an entropy jump dS = 0.4 k_B per vortex and layer (parameters for YBCO) and a Lindemann number c_L = 0.25. The increase in density at melting is given by dρ= 6.0*10^{-4} / λ(T)^2. The vortex liquid corresponds to a bosonic superfluid, with ρ_s = ρeven in the limit λ-> \infty.

cond-mat.supr-con↗

arXiv1995

Low-Field Phase Diagram of Layered Superconductors: The Role of Electromagnetic Coupling

We determine the position and shape of the melting line in a layered superconductor taking the electromagnetic coupling between layers into account. In the limit of vanishing Josephson coupling we obtain a new generic reentrant low-field melting line. Finite Josephson coupling pushes the melting line to higher temperatures and fields and a new line shape $B_{\rm m} \propto (1-T/T_c)^{3/2}$ is found. We construct the low-field phase diagram including melting and decoupling lines and discuss various experiments in the light of our new results.

supr-con↗