Effects of physical and chemical surface roughness on the brightness of electron beams from photocathodes

Gevorkyan, Gevork S.; Karkare, Siddharth; Emamian, Sahand; Bazarov, Ivan; Padmore, H. A.

doi:10.1103/physrevaccelbeams.21.093401

Cited by 30 publications

(9 citation statements)

References 21 publications

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“…A detailed study of the effect of these structures on the electron MTEs will require more accurate measurements possibly performed with a smaller laser spot size to correlate the position on the cathode surface with the MTEs and QE. It is expected that such structures will increase the divergence of the beam and hence affect the MTE of electrons [25]. The decrease in QE deduced by the reduced integrated intensity on the beam images indicates that the QE performances measured in these samples still have large margins for improvement.…”

Section: Discussionmentioning

confidence: 99%

Photoemission characterization of N-polar III-Nitride photocathodes as bright electron beam source for accelerator applications

Cultrera,

Rocco,

Shahedipour-Sandvik

et al. 2021

Preprint

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We report on the growth and characterization of a new class of photocathode structures for application as electron sources to produce high brightness electron beams for accelerator applications. The sources are realized using III-Nitride materials and are designed to leverage the strong polarization field characteristic of this class material while grown in their wurtzite crystal structure to produce a negative electron affinity condition without the use of Cs, possibly allowing these materials to be operated in RF gun. A Quantum Efficiency (QE) of about 1x10 −3 and a Mean Transverse Energy (MTE) of electron of about 100 meV are measured at the operating wavelength of 265 nm. In a vacuum level of 3x10 −10 Torr the QE does not decrease after more than 24 hours of continuous operation. The lowest MTE, about 50 meV, is measured at 300 nm where the measured QE is 1.5x10 −5 . Surface characterizations reveal possible contribution to the MTE due to the surface morphology calling for more detailed studies.

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Section: Discussionmentioning

confidence: 99%

Photoemission characterization of N-polar III-Nitride photocathodes as bright electron beam source for accelerator applications

Cultrera,

Rocco,

Shahedipour-Sandvik

et al. 2021

Preprint

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“…Their high surface reactivity makes them subject to atmospheric contamination, which should be reduced to a minimum to prevent deterioration as well as to enhance sample durability and photoemission yield [6,26,27]. Likewise, surface roughness can be detrimental for the lifetime and the performance of the materials [9,[28][29][30][31]. Established growth methods for alkali-based photocathodes are based on sequential deposition or co-deposition techniques [12,32,33].…”

Section: Introductionmentioning

confidence: 99%

Ab Initio Quantum-Mechanical Predictions of Semiconducting Photocathode Materials

Cocchi

Saßnick

2021

Micromachines

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Ab initio quantum–mechanical methods are well-established tools for material characterization and discovery in many technological areas. Recently, state-of-the-art approaches based on density-functional theory and many-body perturbation theory were successfully applied to semiconducting alkali antimonides and tellurides, which are currently employed as photocathodes in particle accelerator facilities. The results of these studies have unveiled the potential of ab initio methods to complement experimental and technical efforts for the development of new, more efficient materials for vacuum electron sources. Concomitantly, these findings have revealed the need for theory to go beyond the status quo in order to face the challenges of modeling such complex systems and their properties in operando conditions. In this review, we summarize recent progress in the application of ab initio many-body methods to investigate photocathode materials, analyzing the merits and the limitations of the standard approaches with respect to the confronted scientific questions. In particular, we emphasize the necessary trade-off between computational accuracy and feasibility that is intrinsic to these studies, and propose possible routes to optimize it. We finally discuss novel schemes for computationally-aided material discovery that are suitable for the development of ultra-bright electron sources toward the incoming era of artificial intelligence.

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“…Nonetheless, the minimum mean transverse energy measured in polycrystalline Cs 3 Sb, ∼ 20 meV at 90 K [53], is a factor of 2.6 larger than the free-electron thermal limit estimate [54], and an order of magnitude larger than the minimum predicted by our DFT-based ab initio photoemission theory [55]. Fully utilizing the electron band structure and maximizing photoemission brightness requires an atomically ordered surface [21,52,56], which has not been possible in alkali antimonides until now.…”

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confidence: 97%

A single-crystal alkali antimonide photocathode: high efficiency in the ultra-thin limit

Parzyck,

Galdi,

Nangoi

et al. 2021

Preprint

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Effects of physical and chemical surface roughness on the brightness of electron beams from photocathodes

Cited by 30 publications

References 21 publications

Photoemission characterization of N-polar III-Nitride photocathodes as bright electron beam source for accelerator applications

Photoemission characterization of N-polar III-Nitride photocathodes as bright electron beam source for accelerator applications

Ab Initio Quantum-Mechanical Predictions of Semiconducting Photocathode Materials

A single-crystal alkali antimonide photocathode: high efficiency in the ultra-thin limit

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