A compact free-electron laser for generating coherent radiation in the extreme ultraviolet region

Shintake, T.; Tanaka, Hitoshi; Hara, Toru; Tanaka, Takashi; Togawa, Kazuaki; Yabashi, Makina; Otake, Yuji; Asano, Yoshihiro; Bizen, Teruhiko; Fukui, Toru; Goto, Shunji; Higashiya, A.; Hirono, T.; Hosoda, N.; Inagaki, Terumi; Inoue, S.; Ishii, Miho; Kim, Yujong; Kimura, Hiroaki; Kitamura, Masanobu; Kobayashi, Toshiaki; Maesaka, H.; Masuda, Taizo; Matsui, Shogo; Matsushita, Teruo; Maréchal, Xavier-Marie; Nagasono, Mitsuru; Ohashi, Haruhiko; Ohata, T.; Ohshima, Takashi; Onoe, K.; Shirasawa, Katsuhiko; Takagi, Tetsuya; Takahashi, Sunao; Takeuchi, Masao; Tamasaku, Kenji; Tanaka, R.; Tanaka, Yoshihito; Tanikawa, Takanori; Togashi, Tadashi; Wu, Shukui; Yamashita, Akihiro; Yanagida, K.; Zhang, Chao; Kitamura, Hideo; Ishikawa, Tetsuya

doi:10.1038/nphoton.2008.134

Cited by 422 publications

(222 citation statements)

References 15 publications

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“…However, these earlier works dealt with the laser pulses in the optical range whose pulse width is very long in comparison with the modern standard of femosecond laser technology. The advent of extreme ultraviolet (EUV) [7,8] and x-ray [9,10] freeelectron lasers (FELs), with femtosecond pulse widths, has led to renewed interest in two-photon processes in the EUV to x-ray regimes (see, e.g., [11][12][13][14][15][16][17][18][19]). In the present Letter we address a new opportunity opened by the ultrashort EUV FEL pulses to deviate the phase shift difference between ionization channels from the scattering phase shift difference, which is otherwise intrinsic to the target atom or molecule.…”

mentioning

confidence: 99%

Photoelectron angular distributions for the two-photon ionization of helium by ultrashort extreme ultraviolet free-electron laser pulses

Motomura

Ishikawa

et al. 2013

J. Phys. B: At. Mol. Opt. Phys.

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Phase-shift differences and amplitude ratios of the outgoing s and d continuum wave packets generated by two-photon ionization of helium atoms are determined from the photoelectron angular distributions obtained using velocity map imaging. Helium atoms are ionized with ultrashort extreme-ultraviolet free-electron laser pulses with a photon energy of 20.3, 21.3, 23.0, and 24.3 eV, produced by the SPring-8 Compact SASE Source test accelerator. The measured values of the phase-shift differences are distinct from scattering phase-shift differences when the photon energy is tuned to an excited level or Rydberg manifold. The difference stems from the competition between resonant and non-resonant paths in two-photon ionization by ultrashort pulses. Since the competition can be controlled in principle by the pulse shape, the present results illustrate a new way to tailor the continuum wave packet.

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mentioning

confidence: 99%

Photoelectron angular distributions for the two-photon ionization of helium by ultrashort extreme ultraviolet free-electron laser pulses

Motomura

Ishikawa

et al. 2013

J. Phys. B: At. Mol. Opt. Phys.

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“…For the prebunched beam ( Fig. 7) with a current of I ¼ 1000 A=m and duration of τ ¼ 0.485 ps, the total charge per bunch would be q ¼ Iτ ¼ 0.485 nC=m, which is close to the realistic value [53], however, there is no starting current requirement for coherent SPR from prebunched beam, as discussed in Sec. III C.…”

Section: Discussionmentioning

confidence: 55%

“…The optimized grating (h ¼ 100 μm and w ¼ 60 μm) would be able to produce coherent THz SPR at current ≈12-16 A=m (Fig. 6), corresponding to 0.12-0.16 kA=cm 2 (with a beam thickness of 10 μm), which is well below the available state-of-art beam current [53]. For the prebunched beam ( Fig.…”

Section: Discussionmentioning

confidence: 90%

Enhancement of coherent Smith-Purcell radiation at terahertz frequency by optimized grating, prebunched beams, and open cavity

Zhang

Ang

Gover

2015

Phys. Rev. ST Accel. Beams

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This paper studies various mechanisms to enhance the coherent Smith-Purcell radiation (SPR) at terahertz frequencies using particle-in-cell (PIC) simulations. A simple analytical dispersion relation is derived to predict the frequency of the evanescent surface wave of the open grating, which is excited by a backward-wave oscillation mechanism and emits radiation at harmonics of this frequency, and the cavity mode frequencies of the Orotron-like device, all in excellent agreement with the simulation data. The grating parameters are optimized to minimize the starting current of a continuous electron beam for exciting coherent SPR. It is demonstrated that a prebunched beam can be used to selectively excite coherent SPR at desired SPR angle and frequencies that are higher harmonics of the beam bunching frequency, where the starting current requirement is eliminated. Our PIC simulations show the dynamics of modes development and competition for the Orotron-like open cavity structure, which owns a lower starting current than the surface mode process. This oscillation mode dominates at steady state and enhances the radiated power by more than 2 orders of magnitude.

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“…where |Ψ (1) , t and |Ψ (2) , t are the first-and second-order perturbation corrections, respectively,…”

Section: Appendixmentioning

confidence: 99%

Determination of multiwavelength anomalous diffraction coefficients at high x-ray intensity

Son

Chapman

Santra

2013

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. The high-intensity version of multiwavelength anomalous diffraction (MAD) has a potential for solving the phase problem in femtosecond crystallography with x-ray free-electron lasers (XFELs). For MAD phasing, it is required to calculate or measure the MAD coefficients involved in the key equation, which depend on XFEL pulse parameters. In the present work, we revisit the generalized KarleHendrickson equation to clarify the importance of configurational fluctuations of heavy atoms induced by intense x-ray pulses, and investigate the high-intensity cases of transmission and fluorescence measurements of samples containing heavy atoms. Based on transmission/fluorescence and diffraction experiments with crystalline samples of known structures, we propose an experimental procedure to determine all MAD coefficients at high x-ray intensity, which can be used in ab initio phasing for unknown structures.

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A compact free-electron laser for generating coherent radiation in the extreme ultraviolet region

Cited by 422 publications

References 15 publications

Photoelectron angular distributions for the two-photon ionization of helium by ultrashort extreme ultraviolet free-electron laser pulses

Photoelectron angular distributions for the two-photon ionization of helium by ultrashort extreme ultraviolet free-electron laser pulses

Enhancement of coherent Smith-Purcell radiation at terahertz frequency by optimized grating, prebunched beams, and open cavity

Determination of multiwavelength anomalous diffraction coefficients at high x-ray intensity

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