The Association for Women in Mathematics (AWM) in cooperation with the Society for Industrial and Applied Mathematics (SIAM) and with funding from the Department of Energy initiated a new lecture series. The purpose of the lecture series is to increase the visibility of women who have made significant contributions in applied or computational mathematics. The AWM-SIAM Sonia Kovalevsky Lecture is presented at the SIAM Annual Meeting which is a national conference. The lecturer is a woman who has made distinguished contributions in applied or computational mathematics. The lecturer is determined by the Selection Committee which consists of two members of AWM and two members of SIAM, appointed by the presidents of these organizations. The committee may solicit nominations from other members of the scientific and engineering community. The lectureship may be awarded to any woman in the scientific or engineering community.

Evidence is presented concerning the effect of surfaces on the segmental motion of PEO-based polymer electrolytes in lithium batteries. For dry systems with no moisture the effect of surfaces of nano-particle fillers is to inhibit the segmental motion and to reduce the lithium ion transport. These effects also occur at the surfaces in composite electrodes that contain considerable quantities of carbon black nano-particles for electronic connection. The problem of reduced polymer mobility is compounded by the generation of salt concentration gradients within the composite electrode. Highly concentrated polymer electrolytes have reduced transport properties due to the increased ionic cross-linking. Combined with the interfacial interactions this leads to the generation of low mobility electrolyte layers within the electrode and to loss of capacity and power capability. It is shown that even with planar lithium metal electrodes the concentration gradients can significantly impact the interfacial impedance. The interfacial impedance of lithium/PEO-LiTFSI cells varies depending upon the time elapsed since current was turned off after polarization. The behavior is consistent with relaxation of the salt concentration gradients and indicates that a portion of the interfacial impedance usually attributed to the SEI layer is due to concentrated salt solutions next to the electrode surfaces …

Lawrence Livermore National Laboratory has designed and constructed a test stand to improve the voltage regulation in our Flash X-Ray (FXR) accelerator cell. The goal is to create a more mono-energetic electron beam that will create an x-ray source with a smaller spot size. Studying the interaction of the beam and pulse-power system with the accelerator cell will improve the design of high-current accelerators at Livermore and elsewhere. On the test stand, a standard FXR cell is driven by a flexible pulse-power system and the beam current is simulated with a switched center conductor. The test stand is fully instrumented with high-speed digitizers to document the effect of impedance mismatches when the cell is operated under various full-voltage conditions. A time-domain reflectometry technique was also developed to characterize the beam and cell interactions by measuring the impedance of the accelerator and pulse-power component. Computer models are being developed in parallel with the testing program to validate the measurements and evaluate different design changes. Both 3D transient electromagnetic and circuit models are being used.

Triggered, multi-channel, surface discharges or surface flashover switching have been investigated as a low inductance, low pulse rate switch for conducting large currents. This paper discusses the investigation of UV (355 nm) laser triggered, single channel, low inductance, ns closure and sub-ns jitter switches for applications in switching high dielectric constant, compact pulse forming lines into accelerator loads. The experimental arrangement for evaluating the switch performance and for measuring the high field dielectric constant of the pulse forming lines is presented. Experimental results of delay and jitter measurements versus optical energy on the flashover surface and dc electric field charge.

The maximum vacuum insulator surface dielectric strength determines the acceleration electric field gradient possible in a short pulse accelerator. Previous work has indicated that higher electric field strengths along the insulator-vacuum interface might be obtained as the pulse duration is decreased. In this work, a 250 kV, single ns wide impulse source was applied to small diameter, segmented insulators samples in a vacuum to evaluate the multi-layer surface dielectric strength of the sample construction. Resonances in the low inductance test geometry were used to obtain unipolar, pulsed electric fields in excess of 100 MV/m on the insulator surface. The sample construction, experimental arrangement and experimental results are presented for the initial data in this work. Modeling of the multi-layer structure is discussed and methods of improving insulator surface dielectric strength in a vacuum are proposed.