Modeling surfaces in the context of pulsed-power : work functions, electron emission and dynamic response.

Cochrane, Kyle Robert (Ktech Corporation, Albuquerque, NM) ; Chantrenne, Sophie (SAIC, Albuquerque, NM) ; Mattsson, Thomas Kjell Rene ; Faleev, Sergey V. (SNAMI Inc., AL)

Sandia National Laboratories

关键词: Work Functions;    Functionals;    Oxidation;    24 Power Transmission And Distribution;    Power Transmission Lines;   

DOI  :  10.2172/993887
RP-ID  :  SAND2009-6241
RP-ID  :  AC04-94AL85000
RP-ID  :  993887

美国|英语

来源: UNT Digital Library

【 摘 要 】

The ability to quickly understand and deal with issues on ZR, or to virtually design a future ZX accelerator, requires a physics-based capability to simulate all key pulsed power components. Highly important for gas switches and transmission lines are surface phenomena: thermionic emission, photoemission, field emission, and ion-surface dynamics. These are complex processes even at normal conditions, when coupled to the dynamic environment in pulsed power components, the current state of the art of understanding is not at the level of science based predictive modeling. Modeling efforts at the macroscopic level (finite element based hydrodynamic simulations) require detailed information of these processes to yield more reliable results. This is the final report of an LDRD project in the science of extreme environments investment area; the project was focused on describing the physics of surfaces of materials of interest in pulsed-power components. We have calculated the temperature dependence of work functions for metals from first principles using density functional theory (DFT) as well as investigated the effect of initial oxidation and alloying. By using the GW method, we have gone beyond DFT to calculate work functions for Al. The GW work required base-lining the GW results for different systems, since GW lacks a description of total energy. Lastly, we investigated the more macroscopic physics of how a surface and bulk material responds to a very high current under a short time, representative for current loads in pulsed-power components, with emphasis on materials modeling. These simulations were made using two hydrodynamic codes, ALEGRA and MACH2, in order to focus on the materials models themselves.