Nathan Moody

Los Alamos National Laboratory, Pipelines and Partnership Office (PPO), Faculty Member

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Papers by Nathan Moody

MaRIE XFEL Physics Design Risks and Risk Mitigation Plans

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<title>Optimized THz emission from intrinsic Josephson junctions</title>

Terahertz Physics, Devices, and Systems V: Advance Applications in Industry and Defense, 2011

Approved for public release; distribution is unlimited.

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Scanning Photoemission Microscopy of Photo-cathode Surfaces

2006 IEEE International Vacuum Electronics Conference held Jointly with 2006 IEEE International Vacuum Electron Sources

We describe a scanning photoemission can provide real-time images with spatial resolution less mi... more We describe a scanning photoemission can provide real-time images with spatial resolution less microscope using afocusedlaser beam. We find the system than 100 nm and may include an energy filter. We are can provide photoemission images with -lOpm resolution, building a UHV chamber including a commercial version Images of Cs deposited in local areas on clean p-GaAs of this microscope, custom manipulator, load lock, showed that the Cs does not move significantly even when deposition, and surface analysis tools, the design is shown heated to 450C. in figure 1.

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Enhanced quantum efficiency of photoelectron emission, through surface textured metal electrodes

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2016

It is predicted that the quantum efficiency (QE) of photoelectron emission from metals may be enh... more It is predicted that the quantum efficiency (QE) of photoelectron emission from metals may be enhanced, possibly by an order of magnitude, through optimized surface texture. Through extensive computational simulations, it is shown that the absorption enhancement in select surface groove geometries may be a dominant contributor to enhanced QE and corresponds to localized Fabry–Perot resonances. The inadequacy of extant analytical models in predicting the QE increase, and suggestions for further improvement, are discussed.

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Fabrication and measurement of low work function cesiated dispenser photocathodes

A requirement for high power free electron lasers (FEL) is a high current, high quality electron ... more A requirement for high power free electron lasers (FEL) is a high current, high quality electron beam. This is achieved using a laser-switched photocathode. Even state-of-the-art high, efficiency photocathodes suffer from short lifetime, because contamination and evaporation processes damage the surface monolayer of photosensitive material. This research seeks to improve both efficiency and lifetime through a novel dispenser cathode, where the photosensitive layer is regenerated in situ. During regeneration, photosensitive material from a sub-surface reservoir diffuses to the surface through microscopic pores to repair the damaged layer. The goal of this research is to design and prototype a robust, lowworkfunction regenerable photocathode which exhibits long lifetime and high efficiency.

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Measurement of low workfunction cesiated metals for use in dispenser photocathodes

Photoemission measurements of cesiated tungsten and silver are reported that support the theory a... more Photoemission measurements of cesiated tungsten and silver are reported that support the theory and design of a custom dispenser photocathode. Most low-workfunction surfaces employ a delicate surface coating that enhances photoemission, but is vulnerable to contamination and is compromised with continued use. If this photosensitive layer could be periodically rejuvenated in situ, then the effective lifetime could be dramatically improved. A prototype dispenser cathode is presented, along with a simple method of determining its surface conditions. Lastly, the strong agreement between theory and experiment suggests that a model could eventually predict the efficiency and usefulness of more complex surfaces and coatings.

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Photoemission from coated surfaces: Comparison of theory to experiment

A comparison of a theoretical photoemission model with experimental measurements of the quantum e... more A comparison of a theoretical photoemission model with experimental measurements of the quantum efficiency (QE) of Tungsten (and Silver) coated with Cesium as a function of coverage and incident laser wavelength are made. The theory uses models of the work function reduction due to Cesium on bulk metals using Gyftopoulos-Levine theory, changes in the probability of emission due to scattering, a modified Fowler-Dubridge estimate of the probability of emission as a function of material parameters, and a quantum mechanical reflection factor. The agreement between theory and experiment for Cs on W is excellent. A recent study of Cs on Ag is shown and discussed.

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