Review of Recent Progress on Advanced Photocathodes for Superconducting RF Guns

Xiang, Rong; Schaber, Jana

doi:10.3390/mi13081241

Cited by 9 publications

(3 citation statements)

References 29 publications

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“…Cesium telluride and Multi-alkali antimonide cathodes have already demonstrated their capability of operating at high duty-cycle regimes with the required charge, QE, and QE lifetimes [42][43][44]. Detailed reviews of cathode materials and of their properties can be found elsewhere [45][46][47].…”

Section: Photocathodes and Lasersmentioning

confidence: 99%

“…Encouraging initial results from an R&D dedicated to the deposition of a layer of lead (a superconductor below 7.2 K) on niobium have demonstrated QE emissions of ~10 −3 that would allow operation at 100 kHz-class repetition rates [66]. The R&D effort now continues and focuses on improving the process reproducibility, the optimization of the surface roughness, and the characterization of the cathode intrinsic emittance and QE lifetime [47].…”

Section: Superconducting Rf Gunsmentioning

confidence: 99%

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High-brightness electron injectors for high-duty cycle X-ray free electron lasers

Sannibale

2023

Front. Phys.

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The successful development in the last two decades of X-ray free electron lasers (FELs) with their revolutionary brightness performance has been tightly dependent on the parallel development of electron guns and injectors capable of providing the high-brightness electron beams required by FELs lasing at these short wavelengths. The ultimate brightness delivered by a linear accelerator (linac) is already set at its injector and the remaining part of the accelerator can be only designed to preserve the injector performance. The technology to be used for the accelerator part of an X-Ray FEL strongly depends on the duty-cycle at which the FEL operates. Normal-conducting, room-temperature, copper-based radio frequency (RF) technology is typically used for low duty-cycles of up to approximately 10−3. For higher duty-cycles and up to continuous wave (CW) operation, the linac must rely on superconductive RF technology because, with the higher duty-cycle, the increasingly higher power dissipated in normal conducting RF structures becomes excessive for the warm technology. The situation changes in the lower energy part of the accelerator, where injector schemes, based on direct current, normal-conducting, and superconducting RF electron guns, are demonstrating the beam quality performance required by high-duty-cycle X-ray FELs. In this paper we start with a description of the requirements for such injectors, followed by an overview of the pursued technologies and schemes, and by a discussion on the main differences in terms of beam dynamics between low and high duty-cycle injectors.

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Section: Photocathodes and Lasersmentioning

confidence: 99%

Section: Superconducting Rf Gunsmentioning

confidence: 99%

High-brightness electron injectors for high-duty cycle X-ray free electron lasers

Sannibale

2023

Front. Phys.

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“…When used as a photocathode, the cesiated p-GaN can reach high quantum efficiency (QE) values of up to 70% [6][7][8] . The requirements for photocathodes for particle accelerator applications represent an extraordinary challenge with high expectations, for instance, a long lifetime, low thermal emittance, a fast response time, and high QE [9][10][11] . Recently, p-GaN has become increasingly popular as a potential electron source because it can be more robust than other semiconductor photocathodes.…”

mentioning

confidence: 99%

Influence of surface carbon on the performance of cesiated p-GaN photocathodes with high quantum efficiency

Schaber

Xiang

Teichert

et al. 2023

Sci Rep

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This study shows residual surface carbon’s influence on photocathodes’ quantum efficiency based on p-GaN grown on sapphire by metal organic chemical vapor deposition. An X-ray photoelectron spectrometer (XPS) built in an ultrahigh vacuum system allowed the in-situ monitoring of the photocathode surface beginning immediately after their cleaning and throughout the activation and degradation processes. An atomically clean surface is necessary to achieve a negative electron affinity, which is the main prerequisite for high quantum efficiency. The p-GaN samples were cleaned with ethanol and underwent a sub-sequential thermal vacuum cleaning. Although carbon and oxygen contaminations are expected to be undesired impurities from the metal organic chemical vapor deposition, which remained on the surface, p-GaN could still form a negative electron affinity surface when exclusively activated with cesium. After the activation with cesium, a shift to a higher binding energy of the photoemission peaks was observed, and a new species, a so-called cesium carbide, was formed, growing over time. The XPS data elucidated the critical role of these cesium carbide species in photocathode degradation. The X-ray damage to the p-GaN:Cs photocathodes, especially the influence on the cesium, was additionally discussed.

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Investigation of phosphorus-doped nanocrystalline diamond films for photocathode application

Горбачев

Vikharev

Afanasiev

et al. 2023

Vacuum

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Review of Recent Progress on Advanced Photocathodes for Superconducting RF Guns

Cited by 9 publications

References 29 publications

High-brightness electron injectors for high-duty cycle X-ray free electron lasers

High-brightness electron injectors for high-duty cycle X-ray free electron lasers

Influence of surface carbon on the performance of cesiated p-GaN photocathodes with high quantum efficiency

Investigation of phosphorus-doped nanocrystalline diamond films for photocathode application

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