Controlled Porosity Cathodes From Sintered Tungsten Wires

Ives, R. Lawrence; Falce, Lou; Schwartzkopf, S.; Witherspoon, R.

doi:10.1109/ted.2005.859650

Cited by 37 publications

(13 citation statements)

References 6 publications

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“…The cathode used for proof-of-principle QE maps is cesiated tungsten of the controlled porosity reservoir design being investigated by the University of Maryland [12]. The goal of this design is to increase both electron emission uniformity and cathode lifetime.…”

Section: Methodsmentioning

confidence: 99%

Photocathode quantum efficiency mapping at high resolution using a digital micromirror device

Riddick

Montgomery

Fiorito

et al. 2013

Phys. Rev. ST Accel. Beams

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An electron beam's quality is fundamentally limited by its attributes at the cathode. The emission from photocathodes can be bright, but not necessarily uniform. Quantum efficiency (QE) maps generated by selectively illuminating the cathode surface reveal this nonuniformity. In this paper a proof-of-principle experiment is described in which a high resolution map of the QE is generated using a digital micromirror device. We show a substantial improvement over the best results reported for laser raster scanning.

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Section: Methodsmentioning

confidence: 99%

Photocathode quantum efficiency mapping at high resolution using a digital micromirror device

Riddick

Montgomery

Fiorito

et al. 2013

Phys. Rev. ST Accel. Beams

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“…Practical advantages of the reservoir over the impregnant design included longer life and a more tractable diffusion model. Fabrication of the CPR cathodes 18 involved sintering tungsten Electron Discharge Machining (EDM) wire (typically 20 micron diameter) for several weeks into a bundle hexagonally symmetric cross-section, and slicing emitter discs from the bundle using EDM. Semitriangular pores were typically 4 microns across, as schematically illustrated in Fig.…”

Section: Experimental Qualificationmentioning

confidence: 99%

Modeling the resupply, diffusion, and evaporation of cesium on the surface of controlled porosity dispenser photocathodes

Pan

Jensen

Montgomery

2013

Journal of Applied Physics

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A controlled porosity dispenser (CPD) photocathode is currently being explored and developed to replace the Cs during operation and increase photocathode lifetime. Experimental results from cesium (Cs) emission of a sintered-wire tungsten CPD are presented and are used to inform a theoretical model of Cs resupply, diffusion, and evaporation on the surface of the photocathode. The evaporation of Cs from a tungsten surface is modeled using an effective one-dimensional potential well representation of the binding energy. The model accounts for both local and global interactions of Cs with the surface metal as well as with other Cs atoms. It is found that for typical activation temperatures within the range of 500 K–750 K, differences of less than 5% between the quantum efficiency (QE) maximum and minimum over ideal homogenous surfaces occur, even when variations to mimic surface non-uniformity due to pore blockage are included. The theoretical evaporation rates of sub-monolayer surface coverage of Cs compare well to the data of Taylor and Langmuir [I. Langmuir and J. B. Taylor, Phys. Rev. 40, 463–464 (1932)] and reproduce the nonlinear behavior of evaporation with varying coverage and temperature.

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“…CCR's advanced tungsten material for dispenser cathodes provides uniform porosity and control of diffusion from a reservoir of materials designed to reduce the surface work function [11,12,13]. The material is fabricated by winding tungsten wire onto a molybdenum form and sintering.…”

Section: Introductionmentioning

confidence: 99%