Low intrinsic emittance in modern photoinjector brightness

Pierce, Christopher M.; Andorf, Matthew; Lu, Edmond; Gulliford, Colwyn; Bazarov, Ivan; Maxson, Jared; Gordon, Mollie; Kim, Young-Kee; Norvell, Nora; Dunham, Bruce; Raubenheimer, T.O.

doi:10.1103/physrevaccelbeams.23.070101

Cited by 19 publications

(10 citation statements)

References 51 publications

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“…Recent simulations of photo injector brightness demonstrate that identifying novel photocathode materials could increase their brightness, and consequently that of XFELs, by up to two orders of magnitude. [9] Despite the large potential increase in beam brightness that can be realized from discovering new ultrabright photocathode materials, a relatively small number of photocathode materials have been experimentally explored. The time-intensive and challenging nature of measuring the electron beam brightness from photocathode materials has limited experimental studies to only focus on less than 20 materials.…”

Section: Introductionmentioning

confidence: 99%

Novel Ultrabright and Air‐Stable Photocathodes Discovered from Machine Learning and Density Functional Theory Driven Screening

et al. 2021

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The high brightness, low emittance electron beams achieved in modern X‐ray free‐electron lasers (XFELs) have enabled powerful X‐ray imaging tools, allowing molecular systems to be imaged at picosecond time scales and sub‐nanometer length scales. One of the most promising directions for increasing the brightness of XFELs is through the development of novel photocathode materials. Whereas past efforts aimed at discovering photocathode materials have typically employed trial‐and‐error‐based iterative approaches, this work represents the first data‐driven screening for high brightness photocathode materials. Through screening over 74 000 semiconducting materials, a vast photocathode dataset is generated, resulting in statistically meaningful insights into the nature of high brightness photocathode materials. This screening results in a diverse list of photocathode materials that exhibit intrinsic emittances that are up to 4x lower than currently used photocathodes. In a second effort, multiobjective screening is employed to identify the family of M2O (M = Na, K, Rb) that exhibits photoemission properties that are comparable to the current state‐of‐the‐art photocathode materials, but with superior air stability. This family represents perhaps the first intrinsically bright, visible light photocathode materials that are resistant to reactions with oxygen, allowing for their transport and storage in dry air environments.

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Section: Introductionmentioning

confidence: 99%

Novel Ultrabright and Air‐Stable Photocathodes Discovered from Machine Learning and Density Functional Theory Driven Screening

et al. 2021

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“…In Fig. 1 (e), weak half-order streaks are present in the RHEED pattern along the [11] azimuth, evidenced by the line profiles in (f). These correspond to forbidden odd-index reflections in either the F m 3m or the F d 3m Cs 3 Sb structure; their presence may signal the presence of lattice distortions (either intrinsic or induced by defects or vacancies) or a surface reconstruction.…”

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confidence: 90%

“…According to Liouville's theorem, the brightness of any electron beam in a linear accelerator can be no greater than at its source [9,10]. Thus, the photoemission performance of photocathodes can determine the ultimate performance of accelerators ranging from meters to kilometers in length [11]. Photocathodes are also the critical enabling technology for many photon detectors, ranging from photomultipliers [12], image intensifiers and ultrafast time-resolved streak cameras [13], to detectors for high energy physics applications [14].…”

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confidence: 99%

A single-crystal alkali antimonide photocathode: high efficiency in the ultra-thin limit

Parzyck,

Galdi,

Nangoi

et al. 2021

Preprint

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“…These optimizations are described in Refs. [9,35,36]. Each case shown here is an individual from a MOGA Pareto optimal frontier.…”

Section: Description Of DC and Ncrf Gun Ued Beamlinesmentioning

confidence: 99%

“…While some of this brightness can be restored via emittance compensation, some is lost to nonlinear distortions which are challenging to reverse [7,8]. However, it has been shown in many modern applications that reducing the MTE of the photocathode can still lead to large gains in brightness [9].…”

Section: Introductionmentioning

confidence: 99%

Point-to-Point Coulomb Effects in High Brightness Photoelectron Beamlines for Ultrafast Electron Diffraction

Gordon,

van der Geer,

Maxson

et al. 2021

Preprint

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In an effort to increase spatial and temporal resolution of ultrafast electron diffraction and microscopy, ultra-high brightness photocathodes are actively sought to improve electron beam quality. Beam dynamics codes often approximate the Coulomb interaction with mean-field space charge, which is a good approximation in traditional beams. However, point-to-point Coulomb effects, such as disorder induced heating and the Boersch effect, can not be neglected in cold, dense beams produced by such photocathodes. In this paper, we introduce two new numerical methods to calculate the important effects of the photocathode image charge when using a point-to-point interaction model. Equipped with an accurate model of the image charge, we calculate the effects of point-topoint interactions on two high brightness photoemission beamlines for ultrafast diffraction. The first beamline uses a 200 keV gun, whereas the second uses a 5 MeV gun, each operating in the singleshot diffraction regime with 10 5 electrons/pulse. Assuming a zero photoemission temperature, it is shown that including stochastic Coulomb effects increases the final emittance of these beamlines by over a factor of 2 and decreases the peak transverse phase space density by over a factor of 3 as compared to mean-field simulations. We then introduce a method to compute the energy released by disorder induced heating using the pair correlation function. This disorder induced heating energy was found to scale very near the theoretical result for stationary ultracold plasmas, and it accounts for over half of the emittance growth above mean-field simulations.

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Low intrinsic emittance in modern photoinjector brightness

Cited by 19 publications

References 51 publications

Novel Ultrabright and Air‐Stable Photocathodes Discovered from Machine Learning and Density Functional Theory Driven Screening

Novel Ultrabright and Air‐Stable Photocathodes Discovered from Machine Learning and Density Functional Theory Driven Screening

A single-crystal alkali antimonide photocathode: high efficiency in the ultra-thin limit

Point-to-Point Coulomb Effects in High Brightness Photoelectron Beamlines for Ultrafast Electron Diffraction

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