Dark current studies on a normal-conducting high-brightness very-high-frequency electron gun operating in continuous wave mode

Huang, Ruixuan; Filippetto, D.; Papadopoulos, C.; Qian, Houjun; Sannibale, F.; Zolotorev, M.

doi:10.1103/physrevstab.18.013401

Cited by 30 publications

(17 citation statements)

References 18 publications

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“…A superconducting rf photoinjector at Rossendorf shows nanoampere levels of dark current [23,24]. Although the dark current from the Advanced Photo-injector EXperiment (APEX) warm rf gun at the Lawrence Berkeley National Laboratory was measured to be greater than nanoampere level [25], a recent study showed the dark current was 0.1 nA at 750 keV [26].…”

Section: Dark Current Measurementmentioning

confidence: 99%

Operational experience of a 500 kV photoemission gun

Nishimori

Nagai

Hajima

et al. 2019

Phys. Rev. Accel. Beams

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Operational experience of a 500 kV photoemission gun at the compact energy recovery linac (cERL) of the High Energy Accelerator Research Organization is presented. The gun, developed at the Japan Atomic Energy Agency, was found to have failures in two out of the ten-segment ceramic insulator just after installation at cERL. The gun had been operated at 390 kV with eight segments until April 2015 and provided a 0.9 mA beam. An additional two-segment insulator was installed on the top of the existing insulators to recover the high-voltage performance. The gun was then conditioned up to 539 kV and has been operated stably at 500 kV. No discharge caused by the gun itself was observed at 500 kVonce the high threshold voltage for stable operation exceeded 500 kV. A dark current of a few picoamperes was generated at 500 kV from a photocathode puck with a semiconducting wafer, while no dark current was observed without a semiconducting wafer. Stable generation of a 500 keV beam with current greater than 0.8 mA was demonstrated for more than two hours.

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Section: Dark Current Measurementmentioning

confidence: 99%

Operational experience of a 500 kV photoemission gun

Nishimori

Nagai

Hajima

et al. 2019

Phys. Rev. Accel. Beams

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“…The field emission of electrons from a surface exposed to an electric field is a well-known phenomenon, described by the Fowler-Nordheim equation [15]. We express the current I FN (in A) extracted for a given macroscopic electric field EðtÞ on the cathode surface (in V/m) as [16,17]:…”

Section: A Low Energy Sectionmentioning

confidence: 99%

Low energy dark current collimation system in single-pass linacs

Bettoni

Craievich

Pedrozzi

et al. 2018

Phys. Rev. Accel. Beams

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The dark current emitted from a surface of a radio frequency cavity may be a severe issue for the activation and the protection of the components of linear accelerators, if this current is lost in an uncontrolled manner. For a single-pass linac based on a photo-injector, we studied the possibility of using a collimator installed at low energy (below 10 MeV) to dump the maximum fraction of the dark current before it is transported along the linac. We developed and experimentally verified an emission and tracking model that we used to study and optimize the dark current mitigation at SwissFEL test facility. We optimized a collimator, which is expected to reduce by two orders of magnitude the transport of the dark current to the first compressor. We have also verified the effects of wakefield excited by the beam itself passing through the collimator at such a low energy, comparing the results of beam-based measurements with an analytical model.

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“…A detailed description of the gun performance can be found elsewhere 10 . Additionally, dark current has been fully characterized 22 and dramatically reduced by dry-ice cleaning combined with careful mechanical polishing of the central cathode and anode areas. Extensive tests demonstrated the capability of Cesium Telluride (Cs 2 Te) cathodes, produced by INFN/LASA, to operate at the challenging regime imposed by X-ray FEL applications 23 .…”

Section: Conclusion and Final Considerationsmentioning

confidence: 99%

Mechanical design and fabrication of the VHF-gun, the Berkeley normal-conducting continuous-wave high-brightness electron source

Wells

Ghiorso

Staples

et al. 2016

Review of Scientific Instruments

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A high repetition rate, MHz-class, high-brightness electron source is a key element in future high-repetition-rate x-ray free electron laser-based light sources. The VHF-gun, a novel low frequency radio-frequency gun, is the Lawrence Berkeley National Laboratory (LBNL) response to that need. The gun design is based on a normal conducting, single cell cavity resonating at 186 MHz in the VHF band and capable of continuous wave operation while still delivering the high accelerating fields at the cathode required for the high brightness performance. The VHF-gun was fabricated and successfully commissioned in the framework of the Advanced Photo-injector EXperiment, an injector built at LBNL to demonstrate the capability of the gun to deliver the required beam quality. The basis for the selection of the VHF-gun technology, novel design features, and fabrication techniques are described.

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Dark current studies on a normal-conducting high-brightness very-high-frequency electron gun operating in continuous wave mode

Cited by 30 publications

References 18 publications

Operational experience of a 500 kV photoemission gun

Operational experience of a 500 kV photoemission gun

Low energy dark current collimation system in single-pass linacs

Mechanical design and fabrication of the VHF-gun, the Berkeley normal-conducting continuous-wave high-brightness electron source

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