SACLA hard-X-ray compact FEL

Huang, Zhirong; Lindau, I.

doi:10.1038/nphoton.2012.184

Cited by 42 publications

(26 citation statements)

References 4 publications

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“…It was shown theoretically by several groups that the band gap of MoS 2 can be strongly influenced by the application of strain, where biaxial compressive strain increases the band gap, while biaxial tensile strain decreases the band gap. The calculated values for band gap shift as a function of biaxial strain range from 105 to 190 meV/per cent [19][20][21][22]. A variation of the local biaxial strain can be generated during the growth process, which yields a temperature gradient across the substrate as the furnace is switched off.…”

Section: Photoluminescencementioning

confidence: 99%

A direct comparison of CVD-grown and exfoliated MoS₂using optical spectroscopy

Plechinger

Mann

Preciado

et al. 2014

Semicond. Sci. Technol.

106

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MoS 2 is a highly interesting material, which exhibits a crossover from an indirect band gap in the bulk crystal to a direct gap for single layers. Here, we perform a direct comparison between large-area MoS 2 films grown by chemical vapor deposition (CVD) and MoS 2 flakes prepared by mechanical exfoliation from mineral bulk crystal. Raman spectroscopy measurements show differences between the in-plane and out-of-plane phonon mode positions in CVD-grown and exfoliated MoS 2 . Photoluminescence (PL) mapping reveals large regions in the CVD-grown films that emit strong PL at room-temperature, and low-temperature PL scans demonstrate a large spectral shift of the A exciton emission as a function of position. Polarization-resolved PL measurements under near-resonant excitation conditions show a strong circular polarization of the PL, corresponding to a valley polarization.

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Section: Photoluminescencementioning

confidence: 99%

A direct comparison of CVD-grown and exfoliated MoS₂using optical spectroscopy

Plechinger

Mann

Preciado

et al. 2014

Semicond. Sci. Technol.

106

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“…In this list of high brightness electron beam applications, one stands out in terms of current and future impact-the central role played in creating the lasing medium for the XFEL, as typified by the LCLS [10]. The LCLS serves as a flagship and prototype of the fourth generation of x-ray light sources [11][12][13], introducing ultrafast high-flux, coherent hard x-ray pulses. The enabling of self-amplified spontaneous emission (SASE) FEL [14] operation using an exponential gain regime based on high brightness electron beams has produced x-ray light sources having over 10 orders of magnitude increase in peak photon spectral brilliance compared to preceding sources.…”

Section: Introductionmentioning

confidence: 99%

Next generation high brightness electron beams from ultrahigh field cryogenic rf photocathode sources

Rosenzweig

Cahill

Dolgashev

et al. 2019

Phys. Rev. Accel. Beams

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Recent studies of the performance of radio-frequency (rf) copper cavities operated at cryogenic temperatures have shown a dramatic increase in the maximum achievable surface electric field. We propose to exploit this development to enable a new generation of photoinjectors operated at cryogenic temperatures that may attain, through enhancement of the launch field at the photocathode, a significant increase in fivedimensional electron beam brightness. We present detailed studies of the beam dynamics associated with such a system, by examining an S-band photoinjector operated at 250 MV=m peak electric field that reaches normalized emittances in the 40 nm-rad range at charges (100-200 pC) suitable for use in a hard x-ray free-electron laser (XFEL) scenario based on the LCLS. In this case, we show by start-to-end simulations that the properties of this source may give rise to high efficiency operation of an XFEL, and permit extension of the photon energy reach by an order of magnitude, to over 80 keV. The brightness needed for such XFELs is achieved through low source emittances in tandem with high current after compression. In the XFEL examples analyzed, the emittances during final compression are preserved using microbunching techniques. Extreme low emittance scenarios obtained at pC charge, appropriate for significantly extending temporal resolution limits of ultrafast electron diffraction and microscopy experiments, are also reviewed. While the increase in brightness in a cryogenic photoinjector is mainly due to the augmentation of the emission current density via field enhancement, further possible increases in performance arising from lowering the intrinsic cathode emittance in cryogenic operation are also analyzed. Issues in experimental implementation, including cavity optimization for lowering cryogenic thermal dissipation, external coupling, and cryocooler system, are discussed. We identify future directions in ultrahigh field cryogenic photoinjectors, including scaling to higher frequency, use of novel rf structures, and enabling of an extremely compact hard x-ray FEL.

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“…Hard X-ray free-electron lasers (XFELs) (McNeil & Thompson, 2010), like the LCLS (Bostedt et al, 2016), SACLA (Huang & Lindau, 2012) and the European XFEL (Tschentscher et al, 2017), enabled by developments in electron accelerator technology, generate nearly full spatial and temporal coherent and 1 fs ultrafast X-ray pulses which is many orders of magnitude brighter than the brightest synchrotron source. The unique properties offered by the hard XFEL sources have led to a variety of groundbreaking, innovative experimental techniques, such as coherent diffraction imaging and serial femtosecond crystallography (Abbamonte et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

On-line monitoring of the spatial properties of hard X-ray free-electron lasers based on a grating splitter

Wei

Zhou

et al. 2019

J Synchrotron Radiat

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X‐ray free‐electron lasers (XFELs) play an increasingly important role in addressing the new scientific challenges relating to their high brightness, high coherence and femtosecond time structure. As a result of pulse‐by‐pulse fluctuations, the pulses of an XFEL beam may demonstrate subtle differences in intensity, energy spectrum, coherence, wavefront, etc., and thus on‐line monitoring and diagnosis of a single pulse are required for many XFEL experiments. Here a new method is presented, based on a grating splitter and bending‐crystal analyser, for single‐pulse on‐line monitoring of the spatial characteristics including the intensity profile, coherence and wavefront, which was suggested and applied experimentally to the temporal diagnosis of an XFEL single pulse. This simulation testifies that the intensity distribution, coherence and wavefront of the first‐order diffracted beam of a grating preserve the properties of the incident beam, by using the coherent mode decomposition of the Gaussian–Schell model and Fourier optics. Indicatively, the first‐order diffraction of appropriate gratings can be used as an alternative for on‐line monitoring of the spatial properties of a single pulse without any characteristic deformation of the principal diffracted beam. However, an interesting simulation result suggests that the surface roughness of gratings will degrade the spatial characteristics in the case of a partially coherent incident beam. So, there exists a suitable roughness value for non‐destructive monitoring of the spatial properties of the downstream beam, which depends on the specific optical path. Here, experiments based on synchrotron radiation X‐rays are carried out in order to verify this method in principle. The experimental results are consistent with the theoretical calculations.

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SACLA hard-X-ray compact FEL

Cited by 42 publications

References 4 publications

A direct comparison of CVD-grown and exfoliated MoS₂using optical spectroscopy

A direct comparison of CVD-grown and exfoliated MoS₂using optical spectroscopy

Next generation high brightness electron beams from ultrahigh field cryogenic rf photocathode sources

On-line monitoring of the spatial properties of hard X-ray free-electron lasers based on a grating splitter

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SACLA hard-X-ray compact FEL

Cited by 42 publications

References 4 publications

A direct comparison of CVD-grown and exfoliated MoS2using optical spectroscopy

A direct comparison of CVD-grown and exfoliated MoS2using optical spectroscopy

Next generation high brightness electron beams from ultrahigh field cryogenic rf photocathode sources

On-line monitoring of the spatial properties of hard X-ray free-electron lasers based on a grating splitter

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A direct comparison of CVD-grown and exfoliated MoS₂using optical spectroscopy

A direct comparison of CVD-grown and exfoliated MoS₂using optical spectroscopy