Predictive models of field emission remain elusive, in part, due to the sensitivity of this process to emitter surface details at length scales ranging from macroscopic to atomic. Moving towards more fully predictive models requires that we develop techniques to disentangle contributions of features on the largest length scales, which can be easily measured and controlled, from contributions on smaller length scales, which are generally difficult to measure or control. Here, specific challenges are addressed, with an emphasis on comparisons between a Line Charge Model (LCM) and experimental measurements of ungated carbon fiber field emitter arrays. The LCM with appropriate corrections is used to understand the macroscale contributions to field enhancement and emission current for physical emitters, with contributions from the microscale structure isolated using suitable approximations. We will show that excellent agreement can be obtained between the LCM and experiments when the net contributions of the microscale structure are substantially similar across the emitters being used, and when appropriate corrections are introduced to account for the structure on the macroscale which is not already included in the LCM.

This report describes research done at Los Alamos in FY 1993 for the Hydrologic Resources Management Program. The US Department of Energy funds this research through two programs at the Nevada Test Site (NTS): defense and groundwater characterization. Los Alamos personnel have continued to study the high-pressure zone created in the aquifer under Yucca Flat. We analyzed data from a hole in this area (U-7cd) and drilled another hole and installed a water monitoring tube at U-4t. We analyzed water from a number of locations on the NTS where we know there are radionuclides in the groundwater and critiqued the effectiveness of this monitoring effort. Our program for analyzing postshot debris continued with material from the last nuclear test in September 1992. We supported both the defense program and the groundwater characterization program by analyzing water samples from their wells and by reviewing documents pertaining to future drilling. We helped develop the analytical methodology to be applied to water samples obtained in the environmental restoration and waste management efforts at the NTS. Los Alamos involvement in the Hydrologic Resources Management Program is reflected in the appended list of documents reviewed, presentations given, papers published, and meetings attended.

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Additively manufactured components were successfully fielded for the first time in a relativistic crossed-field device. Anode structures for a relativistic planar magnetron were 3-D printed from a photopolymer using a stereolithography printing process. One anode was electroplated with copper (RPM-12b), whereas the other was thermal sprayed with copper (RPM-12c). The coating thicknesses at the vane tips were approximately 0.18 and 0.23 mm, respectively. The performance and durability of these structures were evaluated in comparison with a solid aluminum anode (RPM-12a) fabricated via conventional machining. The experimental parameters were cathode voltages between −150 and −300 kV, voltage pulse lengths of 200 to 600 ns, axial magnetic fields of 0.13 to 0.31 T, peak anode currents from 1 to 7 kA, and a base operating pressure of 9 × 10 −6 torr. The 3-D printed anodes demonstrated microwave performance comparable to the aluminum anode, generating microwave powers in excess of 150 MW, with an average instantaneous peak total efficiency of 27% ± 10%. After 100 shots on each structure, neither anode showed any signs of operationally induced damage. The anodes did, however, have a higher rate of postshot outgassing, emitting 32% and 23% more CO 2 per shot, respectively.