A low emittance and high efficiency visible light photocathode for high brightness accelerator-based X-ray light sources

Vecchione, T.; Ben‐Zvi, I.; Dowell, D.H.; Feng, Jun; Rao, T.; Smedley, J.; Wan, Weishi; Padmore, H. A.

doi:10.1063/1.3612916

Cited by 61 publications

(44 citation statements)

References 12 publications

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“…This photon energy flexibility allows driving photoemission from various different cathode materials. The two main cathodes to be tested in the near future are CsK 2 Sb produced at Lawrence Berkeley National Laboratory (LBNL) [33,34], and Cs 2 Te developed in collaboration with INFN Milano LASA [22]. Both materials offer QEs > 1%, with photoemission in the visible for the antimonide, and in the UV for the telluride.…”

Section: Apex Phase 0 Commissioning Resultsmentioning

confidence: 99%

Advanced photoinjector experiment photogun commissioning results

Sannibale¹,

Filippetto²,

Papadopoulos³

et al. 2012

Phys. Rev. ST Accel. Beams

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The Advanced Photoinjector Experiment (APEX) at the Lawrence Berkeley National Laboratory is dedicated to the development of a high-brightness high-repetition rate (MHz-class) electron injector for x-ray free-electron laser (FEL) and other applications where high repetition rates and high brightness are simultaneously required. The injector is based on a new concept rf gun utilizing a normal-conducting (NC) cavity resonating in the VHF band at 186 MHz, and operating in continuous wave (cw) mode in conjunction with high quantum efficiency photocathodes capable of delivering the required charge at MHz repetition rates with available laser technology. The APEX activities are staged in three phases. In phase 0, the NC cw gun is built and tested to demonstrate the major milestones to validate the gun design and performance. Also, starting in phase 0 and continuing in phase I, different photocathodes are tested at the gun energy and at full repetition rate for validating candidate materials to operate in a high-repetition rate FEL. In phase II, a room-temperature pulsed linac is added for accelerating the beam at several tens of MeV to reduce space charge effects and allow the measurement of the brightness of the beam from the gun when integrated in an injector scheme. The installation of the phase 0 beam line and the commissioning of the VHF gun are completed, phase I components are under fabrication, and initial design and specification of components and layout for phase II are under way. This paper presents the phase 0 commissioning results with emphasis on the experimental milestones that have successfully demonstrated the APEX gun capability of operating at the required performance.

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Section: Apex Phase 0 Commissioning Resultsmentioning

confidence: 99%

Advanced photoinjector experiment photogun commissioning results

Sannibale¹,

Filippetto²,

Papadopoulos³

et al. 2012

Phys. Rev. ST Accel. Beams

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“…In the last years, the electron beam physics community has identified photocathodes as a key area of research needed to meet the challenges of next generation light sources, where in particular, electron beams with very high repetition rate and low emittance will be required. 1,2 Bi-Alkali antimonide cathodes are prime candidates for next generation photoinjectors and have been the subject of intense research activity, [3][4][5][6] but much about the materials science of these systems needs to be explored before they can be adopted as robust technologies. Here, we present results from a new tool for production and analysis of accelerator photocathodes.…”

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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“…The mA-class current requirement for the gun imposes the use of high quantum efficiency (QE) semiconductor photocathodes if a realistic laser power is considered. Owing to its high QE, low emittance and a fast response time in the visible range, K-Cs-Sb has emerged as an excellent photocathode material for such high repetitionrate FEL applications which require mA range current requirements [2]. The use of these cathode materials has been successfully demonstrated in low field dc gun based photoinjectors designed to deliver several tens of mA currents [3].…”

Section: Introductionmentioning

confidence: 99%

Temperature-dependent quantum efficiency degradation of K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method

Ding

Karkare

Feng

et al. 2017

Phys. Rev. Accel. Beams

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K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method have been found to have excellent quantum efficiency (QE) and outstanding near-atomic surface smoothness and have been employed in the VHF gun in the Advanced Photoinjector Experiment (APEX), however, their robustness in terms of their lifetime at elevated photocathode temperature has not yet been investigated. In this paper, the relationship between the lifetime of the K-Cs-Sb photocathode and the photocathode temperature has been investigated. The origin of the significant QE degradation at photocathode temperatures over 70°C has been identified as the loss of cesium atoms from the K-Cs-Sb photocathode, based on the in situ x-ray analysis on the photocathode film during the decay process. The findings from this work will not only further the understanding of the behavior of K-Cs-Sb photocathodes at elevated temperature and help develop more temperature-robust cathodes, but also will become an important guide to the design and operation of the future high-field rf guns employing the use of such photocathodes.

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A low emittance and high efficiency visible light photocathode for high brightness accelerator-based X-ray light sources

Cited by 61 publications

References 12 publications

Advanced photoinjector experiment photogun commissioning results

Advanced photoinjector experiment photogun commissioning results

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

Temperature-dependent quantum efficiency degradation of K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method

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