Conveners
Session 6: Theory & Materials
- John Lewellen (Los Alamos National Laboratory)
In my presentation, I will give the overview of the model, which we develop at the University of Helsinki. I will describe the motivation for the hypothesis, which gave a new angle in studies of material response to high electric field effects. We analyze the behavior of surface atoms under applied electric field to understand the macroscopic changes of properties of material surfaces. To...
High Gradient breakdown is commonly assumed to trigger due to the formation of localized plasma enabling breakdown initiation. In this talk I will describe a model in which the initiating process is caused by stochastic fluctuations of the mobile dislocation population in the cathode. In this model, the mobile dislocation density normally fluctuates, with a finite probability to undergo a...
A notable bottleneck in achieving high-gradient RF technology is dictated by the onset of RF breakdown. While the bulk mechanical properties are known to significantly affect the breakdown propensity, the underlying mechanisms coupling EM fields to bulk plastic deformation in experimentally relevant thermal and electrical loading conditions remain to be identified at the atomic scale. Here,...
The development of novel copper alloys with increased breakdown limits is crucial for the design of higher energy and more compact accelerators that operate at lower cost. Adding solute atoms in copper is a promising strategy to improve the breakdown limits, as solute strengthening can improve mechanical properties by limiting the plastic deformation under thermal loading. However, thermal...
A popular approach for modeling field emission in particle-in-cell (PIC) simulations is to employ a calibrated Fowler-Nordheim emission model. In this approach, the calibrated geometric enhancement factor, β, is often tuned to extremely large values (10-1000) to reproduce experimentally observed
currents. It is an open question if such high-β features actually exist, and thus whether this...
Diamond possesses extraordinary mechanical, thermal, and electronic properties – the name “diamond” is derived from “adamas,” meaning “invincible” – and has been deemed the ultimate frontier and engineering material of the 21st century. Indeed, diamond has the potential to reshape or revolutionize a wealth of applications across quantum computing, power grid infrastructure, implantable...
A novel quantity for predicting the ultimate performance of high-gradient radiofrequency accelerating structures will be presented and compared with earlier quantities that it builds on such as the modified Poynting vector, Sc. This new method models a nascent RF breakdown as a current-carrying antenna and calculates the coupling of the antenna to the RF power source. With the help of a simple...
Although vacuum arcs have been studied intensively for more than a century, the physical mechanisms involved in their ignition have not been fully understood yet. This is mainly due to the extreme nature and high complexity of the physical processes involved. Extreme phase changes occur in a sub-nanosecond timespan, involving various physical processes that occur at an atomic level and scale...