Photocathode behavior during high current running in the Cornell energy recovery linac photoinjector

Cultrera, L.; Maxson, Jared; Bazarov, Ivan; Belomestnykh, S.; Dobbins, John; Dunham, Bruce; Karkare, Siddharth; Kaplan, R.; Kostroun, V. O.; Li, Yulin; Liu, Xianghong; Löhl, Florian; Smolenski, K.; Zhao, Zhi; Rice, D.; Quigley, Peter; Tigner, M.; Veshcherevich, V.; Finkelstein, K. D.; Dale, Darren; Pichler, Benjamin

doi:10.1103/physrevstab.14.120101

Cited by 34 publications

(21 citation statements)

References 10 publications

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“…However, for the generation of a high current and high brightness electron beam, Cs-K-Sb photocathodes are employed. Thus far Cs-K-Sb photocathodes have been used in DC photoinjectors [4][5][6][7]. Recently their performance has also been tested in an SRF photoinjector [8].…”

Section: Introductionmentioning

confidence: 99%

Towards the operation of Cs-K-Sb photocathodes in superconducting rf photoinjectors

Schmeißer

Mistry

Kirschner

et al. 2018

Phys. Rev. Accel. Beams

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High quantum efficiency photocathodes are mandatory for the operation of photoinjector driven electron accelerators with high average current and high brightness beams. Photocathodes based on bi-alkali antimonides, e.g., CsK 2 Sb, exhibit high quantum efficiencies for visible light and can be operated close to the photoemission threshold, thus they are suitable candidates to provide high current and low emittance electron beams. In this paper, a codeposition procedure of K and Cs on Sb resulting in high quantum efficiency photocathodes is presented and compared to the sequential growth procedure that was established for photomultiplier and accelerator applications. In-situ x-ray photoelectron spectroscopy is applied to gain insights into the reaction pathway of antimony with alkali metals, and to optimize the growth process of CsK 2 Sb on Mo. It has been found that the average stoichiometry of the samples is similar after both procedures. The study also presents the behavior of the photocurrent at cryogenic temperatures, the influence of cooling and warmup cycles on the photocathode lifetime and our experience with storage and transport. This work demonstrates that our codeposition growth procedure reproducibly delivers high quantum efficiency photocathodes, and that their quantum efficiency, when excited with green photons, is not influenced by cryogenic temperatures.

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Section: Introductionmentioning

confidence: 99%

Towards the operation of Cs-K-Sb photocathodes in superconducting rf photoinjectors

Schmeißer

Mistry

Kirschner

et al. 2018

Phys. Rev. Accel. Beams

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“…Si(100) was chosen as substrate because it provides an atomically flat surface, enabling a precise measurement of the roughness introduction due to the material growth. Also, it has been reported that the combination of K 2 CsSb grown on Si(100) was used as photocathode in a photoinjector 7 and the conductivity of the p-type Si-wafer simplifies the quantum efficiency measurement. Cathodes were grown following the recipe described by Sommer for the preparation of photomultiplier tubes (PMT), 8 where the sequence of evaporation starts with the antimony deposition onto the substrate, and subsequent alkali evaporations are performed sequentially, first potassium and then cesium.…”

mentioning

confidence: 99%

Direct observation of bi-alkali antimonide photocathodes growth via in operando x-ray diffraction studies

et al. 2014

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Alkali antimonides have a long history as visible-light-sensitive photocathodes. This work focuses on the process of fabrication of the bi-alkali photocathodes, K2CsSb. In-situ synchrotron x-ray diffraction and photoresponse measurements were used to monitor phase evolution during sequential photocathode growth mode on Si(100) substrates. The amorphous-to-crystalline transition for the initial antimony layer was observed at a film thickness of 40 Å . The antimony crystalline structure dissolved upon potassium deposition, eventually recrystallizing upon further deposition into K-Sb crystalline modifications. This transition, as well as the conversion of potassium antimonide to K2CsSb upon cesium deposition, is correlated with changes in the quantum efficiency.

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“…Typically, the substrate is heated to remove the adsorbed gases and oxide layers. A QE of up to 12% at 532 nm was obtained in the Average Power Laser Experiment (APLE) project at Boeing, and have similar values at Cornell University and BNL [4,5,6]. The achievement of the third requirement for the cathode, a long operational lifetime, is dictated by the vacuum contamination and/or ion-back bombardment of the cathode in the gun environment.…”

Section: Introductionmentioning

confidence: 70%

Enhancement of photoemission from and postprocessing ofK2CsSbphotocathode using excimer laser

Wang

Rao

Ben‐Zvi

2014

Phys. Rev. ST Accel. Beams

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The high quantum efficiency at visible wavelengths of alkali-antimonide photoemissive materials, such as K 2 CsSb, makes them excellent potential photocathodes for high-current applications. We have developed a technique of using an ultraviolet laser to clean the cathode's substrate and thus enhance the photoyield of a K 2 CsSb photocathode subsequently deposited on the substrate. We have shown that the quantum efficiency of the cathode from the laser-exposed substrate can be at least 50% higher than that of an unexposed surface. We have also formulated a nonthermal technique for completely removing the cathode from the substrate while preserving an ultrahigh vacuum to assure the regrowth of the cathode. The bialkali cathode is dissociated and then removed completely upon 10 s exposure to a 248 nm laser beam with 3.5 mJ=mm 2 of energy density at a 30 Hz repetition frequency. Here, we discuss these experimental results and their potential applications. We also describe applications of this technique to reduce the beam's halo and its emittance.

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Photocathode behavior during high current running in the Cornell energy recovery linac photoinjector

Cited by 34 publications

References 10 publications

Towards the operation of Cs-K-Sb photocathodes in superconducting rf photoinjectors

Towards the operation of Cs-K-Sb photocathodes in superconducting rf photoinjectors

Direct observation of bi-alkali antimonide photocathodes growth via in operando x-ray diffraction studies

Enhancement of photoemission from and postprocessing ofK2CsSbphotocathode using excimer laser

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