Susanne Schubert
Brookhaven National Laboratory
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Featured researches published by Susanne Schubert.
APL Materials | 2013
Susanne Schubert; Miguel Ruiz-Osés; I. Ben-Zvi; T. Kamps; Xue Liang; Erik M. Muller; K. Müller; Howard A. Padmore; T. Rao; X. Tong; T. Vecchione; John Smedley
Alkali-antimonide photocathodes were grown on Si(100) and studied by means of XPS and UHV-AFM to validate the growth procedure and morphology of this material. The elements were evaporated sequentially at elevated substrate temperatures (first Sb, second K, third Cs). The generated intermediate K-Sb compound itself is a photocathode and the composition of K2.4Sb is close to the favored K3Sb stoichiometry. After cesium deposition, the surface layer is cesium enriched. The determined rms roughness of 25 nm results in a roughness domination of the emittance in the photoinjector already above 3 MV/m.
APL Materials | 2014
Miguel Ruiz-Osés; Susanne Schubert; Klaus Attenkofer; I. Ben-Zvi; Xue Liang; Erik M. Muller; Howard A. Padmore; T. Rao; T. Vecchione; Jared Wong; Junqi Xie; John Smedley
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 A . 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.
Journal of Applied Physics | 2016
Susanne Schubert; Jared Wong; J. Feng; Siddharth Karkare; Howard A. Padmore; Miguel Ruiz-Osés; John Smedley; Erik Muller; Zihao Ding; Mengjia Gaowei; Klaus Attenkofer; Xue Liang; Junqi Xie; Julius Kühn
Bi-alkali antimonide photocathodes are one of the best known sources of electrons for high current and/or high bunch charge applications like Energy Recovery Linacs or Free Electron Lasers. Despite their high quantum efficiency in visible light and low intrinsic emittance, the surface roughness of these photocathodes prohibits their use as low emittance cathodes in high accelerating gradient superconducting and normal conducting radio frequency photoguns and limits the minimum possible intrinsic emittance near the threshold. Also, the growth process for these materials is largely based on recipes obtained by trial and error and is very unreliable. In this paper, using X-ray diffraction, we investigate the different structural and chemical changes that take place during the growth process of the bi-alkali antimonide material K2CsSb. Our measurements give us a deeper understanding of the growth process of alkali-antimonide photocathodes allowing us to optimize it with the goal of minimizing the surface roughness to preserve the intrinsic emittance at high electric fields and increasing its reproducibility.
Proceedings of SPIE | 2014
Junqi Xie; M. Demarteau; R. G. Wagner; Miguel Ruiz-Osés; Xue Liang; I. Ben-Zvi; Klaus Attenkofer; Susanne Schubert; John Smedley; Jared Wong; Howard A. Padmore; Arthur R. Woll
Bi-alkali antimonide photocathode is an essential component in fast timing response photomultipliers. Real-time in-situ grazing incidence x-ray diffraction and post-growth x-ray reflectivity measurement were performed to study the photocathode deposition process on glass substrate. Grazing incidence x-ray diffraction patterns show the formation of Sb crystalline, dissolution of crystalline phase Sb by the application of K vapor and reformation of refined crystal textures. XRR result exhibits that the film thickness increases ~ 4.5 times after K diffusion and almost have no change after Cs diffusion. Further investigation is expected to understand the photocathode growth process and provide guidelines for photocathode development.
Journal of Applied Physics | 2017
Zihao Ding; Mengjia Gaowei; John Sinsheimer; Junqi Xie; Susanne Schubert; Howard A. Padmore; Erik M. Muller; John Smedley
K2CsSb is a promising photocathode candidate to serve as an electron source in next-generation light sources such as Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). As the traditional recipe for creation of K2CsSb photocathodes typically results in a rough surface that deteriorates electron beam quality, significant effort has been made to explore novel growth methods for K2CsSb photocathodes. In this paper, a method of ternary co-evaporation of K, Cs, and Sb is described. By using in-situ synchrotron X-ray techniques, the quality of the photocathode is characterized during and after the growth. K2CsSb photocathodes grown by this method on Si (100) and MgO (001) substrates show strong (222) texture, and the two photocathodes exhibit 1.7% and 3.4% quantum efficiencies at a wavelength of 530 nm, with a rms surface roughness of about 2–4 nm. This represents an order of magnitude reduction in roughness compared to typical sequential deposition and should result in a significant improvement in the...
5th Int. Particle Accelerator Conf. (IPAC'14), Dresden, Germany, June 15-20, 2014 | 2014
John Smedley; Klaus Attenkofer; Ilan Ben-Zvi; Jeff DeFazio; Xue Liang; Erik Muller; Howard A. Padmore; T. Rao; Miguel Ruiz-Osés; Susanne Schubert; Jared Wong; Junqi Xie
The next generation of x-ray light sources will need reliable, high quantum efficiency photocathodes. These cathodes will likely be from the alkali antimonide family, which currently holds the record for highest average current achieved from a photoinjector. In this work, we explore a new option for delivering these cathodes to a machine which requires them: use of sealed commercial vacuum tubes. Several sealed tubes have been introduced into a vacuum system and separated from their housing, exposing the active photocathode on a transport arm suitable for insertion into an injector. The separation was achieved without large loss of QE. These cathodes have been compared to those grown via traditional methods, both in terms of QE and in terms of crystalline structure, and found to be similar.
Journal of Physics D | 2017
Junqi Xie; M. Demarteau; R. G. Wagner; Susanne Schubert; Mengjia Gaowei; Klaus Attenkofer; John J. Walsh; John Smedley; Jared Wong; J. Feng; Howard A. Padmore; Miguel Ruiz-Osés; Zihao Ding; Xue Liang; Erik M. Muller; I. Ben-Zvi
Archive | 2014
J. Völker; R.Barday; Andreas Jankowiak; T. Kamps; J. Rudolph; Susanne Schubert; S. Wesch; T. Weis
Archive | 2013
Axel Neumann; Wolfgang Anders; A. Burrill; Andreas Jankowiak; T. Kamps; Jens Knobloch; Oliver Kugeler; P Lauinger; Alexander Matveenko; M Schmeisser; Jens Völker; Gianluigi Ciovati; Peter Kneisel; Robert Nietubyć; Susanne Schubert; John Smedley; Jacek Sekutowicz; Volkov; I Will; Evgeny Zaplatin
Archive | 2014
Martin Schmeißer; Andreas Jankowiak; T. Kamps; Susanne Schubert