High gradient rf gun studies of CsBr photocathodes

Vecchione, T.; Maldonado, Juan R.; Gierman, S.M.; Corbett, Jeff; Hartmann, Nick; Pianetta, P.; Hesselink, Lambertus; Schmerge, John

doi:10.1103/physrevstab.18.040701

Cited by 3 publications

(3 citation statements)

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“…remained at around 0.02% for 24 h of continuous operation. 24) As these reports suggest, we surmised that a protective thin layer of sufficient thickness may improve the lifetime of a photocathode even in an rf gun.…”

Section: Introductionmentioning

confidence: 88%

“…22) A group at Stanford University, meanwhile, has described research on a CsBr-coated Cu photocathode (CsBr/Cu). 23,24) According to their reports, the Q.E. of the CsBr/Cu photocathode remained above 0.1% at 257 nm and showed no substantial deleterious effects in the source development test stand in measurements continued for over 250 h. One of the advantages of CsBr compared to Cs-Te, they asserted, was a very small spot growth effect.…”

Section: Introductionmentioning

confidence: 99%

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Study on a long-life photocathode with an CsBr protective layer for an rf electron gun

Ono

Miyamatsu

Tamba

et al. 2019

Jpn. J. Appl. Phys.

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A photocathode with a high quantum efficiency (Q.E.) and long lifetime can be fabricated by evaporating a protective layer onto a high Q.E. semiconductor photocathode. In this study we tried to improve the stability and lifetime of a Cs-Te photocathode by coating a CsBr protective layer of 20 nm in thickness over the surface. After the protective layer was applied, we measured the Q.E. of the photocathode and the lifetime in the evaporation chamber. The Q.E. of the coated Cs-Te was confirmed to be about 0.80% and to remain unchanged for a period of longer than 25 d. The effectiveness of the protective layer against exposure of the Cs-Te photocathode to oxygen gas was also confirmed for the first time. Our experiments were the first to show a lifetime improvement of a photocathode installed inside an rf gun compared to the same type of photocathode with no protective coating.

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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Study on a long-life photocathode with an CsBr protective layer for an rf electron gun

Ono

Miyamatsu

Tamba

et al. 2019

Jpn. J. Appl. Phys.

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“…An initial step change in QE after film deposition is followed by a further increase in QE after a period of irradiation by an unfocused ultraviolet (UV) laser for several hours, the so-called laser activation (LA) process. [6][7][8][9] In order to assess the viability of CsBr/Cu photocathodes, studies have investigated also their lifetime, the transverse momenta of emitted electrons, 10 measured emittance and robustness with regards to the atmosphere with largely positive results. 11 Initial evidence suggests that CsBr/Cu fulfils the requirements and desiderata of a functioning photocathode.…”

Section: Introductionmentioning

confidence: 99%

A mechanism of Cu work function reduction in CsBr/Cu photocathodes

Halliday

Hess

Shluger

2016

Phys. Chem. Chem. Phys.

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Thin films of CsBr deposited on Cu(100) have been proposed as next-generation photocathode materials for applications in particle accelerators and free-electron lasers. However, the mechanisms underlying an improved photocathode performance as well as their long-term stability remain poorly understood. We present Density Functional Theory (DFT) calculations of the work function reduction following the application of CsBr thin film coatings to Cu photocathodes. The effects of both flat and rough interface and van der Waals forces are examined. Calculations suggest that CsBr films can reduce the Cu(100) work function by about 1.5 eV, which would explain the observed increase in quantum efficiency (QE) of coated vs. uncoated photocathodes. A model explaining the experimentally observed laser activation of photocathodes is provided whereby the photo-induced creation of Br vacancies and Cs-Br di-vacancies and their subsequent diffusion to the Cu/CsBr interface lead to a further increase in QE after a period of laser irradiation.

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