Referierte Publikationen

2021

M. Zimmer, S. Scheuren, T. Ebert, G. Schaumann, B. Schmitz, J. Hornung, V. Bagnoud, C. Rödel, and M. Roth
Analysis of laser-proton acceleration experiments for development of empirical scaling laws
Phys. Rev. E, 104 :045210 (October 2021)
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G. Gaigalas, and S. Fritzsche
Angular coefficients for symmetry-adapted configuration states in jj-coupling
Comput. Phys. Commun., 267 :108086 (October 2021)
Abstract:
In atomic structure and collision theory, the efficient spin-angular integration is known to be crucial and often decides, how accurate the properties and behavior of atoms can be predicted numerically. Various methods have been developed in the past to keep the computation (and implementation) of the spin-angular integration feasible for complex shell structures, including open d- and f-shell elements. To support such computations, we here provide a new implementation of the angular coefficients for jjcoupled and symmetry-adapted configuration states that is entirely built upon the quasi-spin formalism. The moduleSpinAngularis based on Julia, a new programming language for scientific computing, and supports a simple access to all (completely) reduced tensors, coefficients of fractional parentage for subshells with j <= 9/2 as well as the re-coupling coefficients from this formalism. Moreover, this module has been worked out for multiple purposes, including 1) the accurate calculation of atomic properties, 2) further studies on spin-angular integration theory, 3) the development of new or existing computer programs as well as 4) the manipulation of reduced matrix elements from this theory. The present implementation will therefore help advance the algebraic evaluation of many-electron (transition) amplitudes and to apply the theory to newly emerging research areas.
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C. Jauregui, C. Stihler, S. Kholaif, Y. Tu, and J. Limpert
Control and stabilization of the modal content of fiber amplifiers using traveling waves
Opt. Express, 29 :34452 (October 2021)
Abstract:
In this work we present a novel way to manipulate the effect of transverse mode instability by inducing traveling waves in a high-power fiber system. What sets this technique apart is the fact that it allows controlling the direction of the modal energy flow, for the first time to the best of our knowledge. Thus, using the method proposed in this work it will be possible to transfer energy from the higher-order mode into the fundamental mode of the fiber, which mitigates the effect of transverse mode instability, but also to transfer energy from the fundamental mode into the higher-order mode. Our simulations indicate that this approach will work both below and above the threshold of transverse mode instability. In fact, our model reveals that it can be used to force a nearly pure fundamental mode output in the fiber laser system almost independently of the input coupling conditions. In this context, this technique represents the first attempt to exploit the physics behind the effect of transverse mode instability to increase the performance of fiber laser systems.
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D. Wanisch, and S. Fritzsche
Delocalization of quantum information in long-range interacting systems
Phys. Rev. A, 104 :042409 (October 2021)
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We investigate the delocalization of quantum information in the nonequilibrium dynamics of the XY spin chain with asymptotically decaying interactions similar to 1/r(alpha). As a figure of merit, we employ the tripartite mutual information (TMI), the sign of which indicates if quantum information is predominantly shared globally. Interestingly, the sign of the TMI distinguishes regimes of the exponent a that are known for different behaviors of information propagation. While an effective causal region bounds the propagation of information, if interactions decay sufficiently fast, this information is mainly delocalized, which leads to the necessity of global measurements. Furthermore, the results indicate that mutual information is monogamous for all possible partitionings in this case, implying that quantum entanglement is the dominant correlation. If interactions decay sufficiently slow, though information can propagate (quasi-)instantaneously, it is mainly accessible by local measurements at early times. Furthermore, it takes some finite time until correlations start to become monogamous, which suggests that entanglement is not the dominant correlation at early times. Our findings give new insights into the dynamics and structure of quantum information in many-body systems with long-range interactions, and might get verified on state-of-the-art experimental platforms.
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J. Buldt, H. Stark, M. Mueller, C. Grebing, C. Jauregui, and J. Limpert
Gas-plasma-based generation of broadband terahertz radiation with 640 mW average power
Opt. Lett., 46 :5256 (October 2021)
Abstract:
We present a high-power source of broadband terahertz (THz) radiation covering the whole THz spectral region (0.1-30 THz). The two-color gas plasma generation process is driven by a state-of-the-art ytterbium fiber chirped pulse amplification system based on coherent combination of 16 rod-type amplifiers. Prior to the THz generation, the pulses are spectrally broadened in a multipass cell and compressed to 37 fs with a pulse energy of 1.3 mJ at a repetition rate of 500 kHz. A gas-jet scheme has been employed for the THz generation, increasing the efficiency of the process to 0.1%. The air-biased coherent detection scheme is implemented to characterize the full bandwidth of the generated radiation. A THz average power of 640 mW is generated, which is the highest THz average power achieved to date. This makes this source suitable for a variety of applications, e.g., spectroscopy of strongly absorbing samples or driving nonlinear effects for the studies of material properties.
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A. Thomas, and D. Seipt
Modeling chromatic emittance growth in staged plasma wakefield acceleration to 1 TeV using nonlinear transfer matrices
Phys. Rev. ST Accel. Beams, 24 :104602 (October 2021)
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L. Du, F. Roeder, Y. Li, M. Shalaby, B. Beleites, F. Ronneberger, and A. Gopal
Organic crystal-based THz source for complex refractive index measurements of window materials using single-shot THz spectroscopy
Appl. Phys. A, 127 :846 (October 2021)
Abstract:
We employed N-benzyl-2-methyl-4-nitroaniline (BNA) crystals bonded on substrates of different thermal conductivity to generate THz radiation by pumping with 800 nm laser pulses. Crystals bonded on sapphire substrate provided four times more THz yield than glass substrate. A pyrodetector and a single-shot electro-optic (EO) diagnostic were employed for measuring the energy and temporal characterisation of the THz pulse. Systematic studies were carried out for the selection of a suitable EO crystal, which allowed accurate determination of the emitted THz spectrum from both substrates. Subsequently, the THz source and single-shot electro-optic detection scheme were employed to measure the complex refractive index of window materials in the THz range.
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M. Almassarani, S. Meng, B. Beleites, F. Ronneberger, G. Paulus, and A. Gopal
Parametric Study of Proton Acceleration from Laser-Thin Foil Interaction
Plasma, 4 :670 (October 2021)
Abstract:
We experimentally investigated the accelerated proton beam characteristics such as maximum energy and number by varying the incident laser parameters. For this purpose, we varied the laser energy, focal spot size, polarization, and pulse duration. The proton spectra were recorded using a single-shot Thomson parabola spectrometer equipped with a microchannel plate and a high-resolution charge-coupled device with a wide detection range from a few tens of keV to several MeV. The outcome of the experimental findings is discussed in detail and compared to other theoretical works.
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F. C. Salgado, K. Grafenstein, A. Golub, A. Dopp, A. Eckey, D. Hollatz, C. Müller, A. Seidel, D. Seipt, S. Karsch, and M. Zepf
Towards pair production in the non-perturbative regime
New J. Phys., 23 :105002 (October 2021)
Abstract:
The interaction of light with the quantum-vacuum is predicted to give rise to some of the most fundamental and exotic processes in modern physics, which remain untested in the laboratory to date. Electron-positron pair production from a pure vacuum target, which has yet to be observed experimentally, is possibly the most iconic. The advent of ultra-intense lasers and laser accelerated GeV electron beams provide an ideal platform for the experimental realisation. Collisions of high energy gamma-ray photons derived from the GeV electrons and intense laser fields result in detectable pair production rates at field strengths that approach and exceed the Schwinger limit in the centre-of-momentum frame. A detailed experiment has been designed to be implemented at the ATLAS laser at the centre of advanced laser applications. We show full calculations of the expected backgrounds and beam parameters which suggest that single pair events can be reliably generated and detected.
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M. Chambonneau, M. Blothe, Q. Li, V. Fedorov, T. Heuermann, M. Gebhardt, C. Gaida, S. Tertelmann, F. Sotier, J. Limpert, S. Tzortzakis, and S. Nolte
Transverse ultrafast laser inscription in bulk silicon
Phys. Rev. Research, 3 :043037 (October 2021)
Abstract:
In-volume ultrafast laser direct writing of silicon is generally limited by strong nonlinear propagation effects preventing the production of modifications. By using advantageous spectral, temporal, and spatial conditions, we demonstrate that modifications can be repeatably produced inside silicon. Our approach relies on irradiation at approximate to 2 mu m wavelength with temporally distorted femtosecond pulses. These pulses are focused in a way that spherical aberrations of different origins mutually balance, as predicted by point spread function analyses and in good agreement with nonlinear propagation simulations. We also establish the laws governing modification growth on a pulse-to-pulse basis, which allows us to demonstrate transverse inscription inside silicon with various line morphologies depending on the irradiation conditions. We finally show that the production of single-pulse repeatable modifications is a necessary condition for reliable transverse inscription inside silicon.
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F. Karbstein, and R. Oude Weernink
X-ray vacuum diffraction at finite spatiotemporal offset
Phys. Rev. D, 104 :076015 (October 2021)
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We study the nonlinear QED signature of x-ray vacuum diffraction in the head-on collision of optical high-intensity and x-ray free-electron laser pulses at finite spatiotemporal offsets between the laser foci. The high-intensity laser driven scattering of signal photons outside the forward cone of the x-ray probe constitutes a prospective experimental signature of quantum vacuum nonlinearity. Resorting to a simplified phenomenological ad hoc model, it was recently argued that the angular distribution of the signal in the far-field is sensitive to the wavefront curvature of the probe beam in the interaction region with the high-intensity pump. In this work, we model both the pump and probe fields as pulsed paraxial Gaussian beams and reanalyze this effect from first principles. We focus on vacuum diffraction both as an individual signature of quantum vacuum nonlinearity and as a potential means to improve the signal-to-background separation in vacuum birefringence experiments.
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F. Kröger, G. Weber, S. Hirlaender, R. Alemany-Fernandez, M. Krasny, T. Stöhlker, I. Tolstikhina, and V. Shevelko
Charge‐State Distributions of Highly Charged Lead Ions at Relativistic Collision Energies
Ann. Phys. (Berlin), 534 :2100245 (September 2021)
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H. Abramowicz, U. Acosta, M. Altarelli, R. Assmann, Z. Bai, T. Behnke, Y. Benhammou, T. Blackburn, S. Boogert, O. Borysov, M. Borysova, R. Brinkmann, M. Bruschi, F. Burkart, K. Büßer, N. Cavanagh, O. Davidi, W. Decking, U. Dosselli, N. Elkina, A. Fedotov, M. Firlej, T. Fiutowski, K. Fleck, M. Gostkin, C. Grojean, J. Hallford, H. Harsh, A. Hartin, B. Heinemann, T. Heinzl, L. Helary, M. Hoffmann, S. Huang, X. Huang, M. Idzik, A. Ilderton, R. Jacobs, B. Kämpfer, B. King, H. Lahno, A. Levanon, A. Lévy, I. Levy, J. List, W. Lohmann, T. Ma, A. J. Macleod, V. Malka, F. Meloni, A. Mironov, M. Morandin, J. Moron, E. Negodin, G. Perez, I. Pomerantz, R. Pöschl, R. Prasad, F. Quéré, A. Ringwald, C. Rödel, S. Rykovanov, F. Salgado, A. Santra, G. Sarri, A. Sävert, A. Sbrizzi, S. Schmitt, U. Schramm, S. Schuwalow, D. Seipt, L. Shaimerdenova, M. Shchedrolosiev, M. Skakunov, Y. Soreq, M. Streeter, K. Swientek, N. Hod, S. Tang, T. Teter, D. Thoden, A. I. Titov, O. Tolbanov, G. Torgrimsson, A. Tyazhev, M. Wing, M. Zanetti, A. Zarubin, K. Zeil, M. Zepf, and A. Zhemchukov
Conceptual design report for the LUXE experiment
Eur. Phys. J. Special Topics, 230 :2445 (September 2021)
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F. Karbstein
Derivative corrections to the Heisenberg-Euler effective action
J. High Energ. Phys., 09 :070 (September 2021)
Abstract:
We show that the leading derivative corrections to the Heisenberg-Euler effective action can be determined efficiently from the vacuum polarization tensor evaluated in a homogeneous constant background field. After deriving the explicit parameter-integral representation for the leading derivative corrections in generic electromagnetic fields at one loop, we specialize to the cases of magnetic- and electric-like field configurations characterized by the vanishing of one of the secular invariants of the electromagnetic field. In these cases, closed-form results and the associated all-orders weak-and strong-field expansions can be worked out. One immediate application is the leading derivative correction to the renowned Schwinger-formula describing the decay of the quantum vacuum via electron-positron pair production in slowly-varying electric fields.
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B. Ying, F. Machalett, V. Huth, M. Kuebel, A. Sayler, T. Stoehlker, G. Paulus, and P. Wustelt
Experimental study of the laser-induced ionization of heavy metal and metalloid ions: Au+ and Si2+ in intense and sculpted femtosecond laser fields
J. Phys. B, 54 :174002 (September 2021)
Abstract:
We implement a liquid metal ion source in a 3D coincidence momentum spectroscopy setup for studying the interaction of ionic targets with intense laser pulses. Laser intensities of up to 4 . 10(16) W cm(-2) allow for the observation of up to ten-fold ionization of Au+-ions and double ionization of Si2+-ions. Further, by utilizing two-color sculpted laser fields to control the ionization process on the attosecond time scale, we demonstrate the capability to resolve the recoil ion momenta of heavy metal atoms. Simulations based on a semiclassical model assuming purely sequential ionization reproduce the experimental data well. This work opens up the use of a range of metallic and metalloid ions, which have hardly been investigated in strong-field laser physics so far.
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A. Mueller, M. Martins, J. Borovik, T. Buhr, A. Perry-Sassmannshausen, S. Reinwardt, F. Trinter, S. Schippers, S. Fritzsche, and A. S. Kheifets
Role of L-shell single and double core-hole production and decay in m-fold (1 <= m <= 6) photoionization of the Ar+ ion
Phys. Rev. A, 104 :033105 (September 2021)
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Multiple ionization of the Ar+(3s(2)3p(5)) ion by a single photon has been investigated in the photon-energy range 250-1800 eV employing the photon-ion merged-beams technique. Absolute partial cross sections were measured for all Ar(1+m)+ product-ion channels with 1 <= m <= 6 covering a size range from several tens of Mb down to a few b. Narrow 2p-subshell excitation resonances were observed in all channels up to quadruple ionization at a photon-energy bandwidth of 52 meV. Double excitations involving a 2p and a 3s or 3p electron were also studied at high resolution and the measurements of the broad 2s excitation resonances directly showed their natural widths. Contributions of direct photo double ionization (PDI) to the production of the highest final Ar ion charge states are revealed, with PDI of the 2s subshell being mainly responsible for the production of Ar7+. The experiment made use of the PIPE setup installed at beamline P04 of the PETRA III synchrotron light source of DESY in Hamburg. The measurements were supported by theoretical calculations to identify the main contributions to the observed cross sections. Comparisons of theory and experiment show remarkable agreement but also hint to additional ionizationmechanisms that are not considered in the theoretical models such as core ionization accompanied by excitations with subsequent Auger decays leading to net m-fold ionization with m >= 4.
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A. V. Volotka, J. Hofbrucker, and S. Fritzsche
Steering of circular dichroism in biharmonic ionization of atoms
Phys. Rev. A, 104 :L031103 (September 2021)
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S. Fritzsche
Symbolic Evaluation of Expressions from Racah s Algebra
Symmetry, 13 :1558 (September 2021)
Abstract:
Based on the rotational symmetry of isolated quantum systems, Racah s algebra plays a significant role in nuclear, atomic and molecular physics, and at several places elsewhere. For N-particle (quantum) systems, for example, this algebra helps carry out the integration over the angular coordinates analytically and, thus, to reduce them to systems with only N (radial) coordinates. However, the use of Racah s algebra quickly leads to complex expressions, which are written in terms of generalized Clebsch-Gordan coefficients, Wigner n-j symbols, (tensor) spherical harmonics and/or rotation matrices. While the evaluation of these expressions is straightforward in principle, it often becomes laborious and prone to making errors in practice. We here expand Jac, the Jena Atomic Calculator, to facilitate the sum-rule evaluation of typical expressions from Racah s algebra. A set of new and revised functions supports the simplification and subsequent use of such expressions in daily research work or as part of lengthy derivations. A few examples below show the recoupling of angular momenta and demonstrate how Jac can be readily applied to find compact expressions for further numerical studies. The present extension makes Jac a more flexible and powerful toolbox in order to deal with atomic and quantum many-particle systems.
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A.-L. Viotti, S. Ališauskas, H. Tuennermann, E. Escoto, M. Seidel, K. Dudde, B. Manschwetus, I. Hartl, and C. Heyl
Temporal pulse quality of a Yb:YAG burst-mode laser post-compressed in a multi-pass cell
Opt. Lett., 46 :4686 (September 2021)
Abstract:
Nonlinear pulse post-compression represents an efficient method for ultrashort, high-quality laser pulse production. The temporal pulse quality is, however, limited by amplitude and phase modulations intrinsic to post-compression. We here characterize in frequency and time domain with high dynamic range individual post-compressed pulses within laser bursts comprising 100-kHz-rate pulse trains. We spectrally broaden 730 fs, 3.2 mJ pulses from a Yb:YAG laser in a gas-filled multi-pass cell and post-compress them to 56 fs. The pulses exhibit a nearly constant energy content of 78% in the main peak over the burst plateau, which is close to the theoretical limit. Our results demonstrate attractive pulse characteristics, making multi-pass post-compressed lasers very applicable for pump-probe spectroscopy at, e.g., free-electron lasers or as efficient drivers for secondary frequency conversion stages.
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Y. Zhang, C. L. Zhong, S. P. Zhu, X. T. He, M. Zepf, and B. Qiao
Obtaining Intense Attosecond Pulses in the Far Field from Relativistic Laser-Plasma Interactions
Physical Review Applied, 16 :024042 (August 2021)
Abstract:
In this paper, we show that the Gouy phase shift plays a key role in the far-field waveform evolution of the reflected harmonic radiations from plasma surfaces driven by a relativistic Gaussian laser. With a proper adjustment of laser focal position away from the plasma surface, the inherent separations between the peaks of different harmonic carrier waves as well as the fundamental wave due to different wavelengths can be cleared away when they propagate from near to far field, since they experience the same Gouy phase shift of pi/2. Using this method, intense attosecond pulses can be obtained in the far field with no need of any spectral filters. Three-dimensional particle-in-cell simulations show that far-field attosecond pulses with intensity of 4 x 1015 W/cm2 (2.56 x 1017 W/sr; 65 times increase) and duration of 76 as (50% decrease) can be obtained by lasers at intensities of 1021 W/cm2. Such brilliant pulses with fully reserved spectra significantly benefit applications in attosecond science.
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A. Koszorus, L. J. Vormawah, R. Beerwerth, M. L. Bissell, P. Campbell, B. Cheal, C. S. Devlin, T. Eronen, S. Fritzsche, S. Geldhof, H. Heylen, J. D. Holt, A. Jokinen, S. Kelly, I. D. Moore, T. Miyagi, S. Rinta-Antila, A. Voss, and C. Wraith
Proton-neutron pairing correlations in the self-conjugate nucleus Sc-42
Phys. Rev. B, 819 :136439 (August 2021)
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Collinear laser spectroscopy of the N = Z = 21 self-conjugate nucleus Sc-42 has been performed at the JYFL IGISOL IV facility in order to determine the change in nuclear mean-square charge radius between the I-pi = 0(+) ground state and the I-pi = 7(+) isomer via the measurement of the Sc-42g,Sc-42m isomer shift. New multi-configurational Dirac-Fock calculations for the atomic mass shift and field shift factors have enabled a recalibration of the charge radii of the Sc42-46 isotopes which were measured previously. While consistent with the treatment of proton-neutron, proton-proton and neutron-neutron pairing on an equal footing, the reduction in size for the isomer is observed to be of a significantly larger magnitude than that expected from both shell-model and ab-initio calculations. The measured nuclear magnetic dipole moment and electric quadruple moment, on the other hand, are in good agreement with simple empirical estimates and shell-model calculations.
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B. Lei, D. Seipt, M. Shi, B. Liu, J. Wang, M. Zepf, and S. Rykovanov
Relativistic modified Bessel-Gaussian beam generated from plasma-based beam braiding
Phys. Rev. A, 104 :021501 (August 2021)
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We theoretically and numerically demonstrate the generation of a relativistic modified Bessel-Gaussian beam (MBGB) via plasma-based beam braiding. It is realized by injecting several intense Gaussian pulses with well-designed offsets and angles into an underdense plasma channel which acts as a laser-pulse combiner via refractive coupling. The MBGB propagates stably in the plasma channel with a well-controlled orbital angular momentum of large value, exciting a twisted plasma wave. After leaving the plasma, it becomes unguided and survives in vacuum for at least hundreds of femtoseconds. This method is insensitive to the initial laser injection conditions and thus should be robust for experimental implementation. It provides an alternative approach in generating high-quality tunable intense optical vortex beams which are desired for various applications.
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M. Mueller, C. Aleshire, J. Buldt, H. Stark, C. Grebing, A. Klenke, and J. Limpert
Scaling potential of beam-splitter-based coherent beam combination
Opt. Express, 29 :27900 (August 2021)
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The impact of nonlinear refraction and residual absorption on the achievable peakand average power in beam-splitter-based coherent beam combination is analyzed theoretically. While the peak power remains limited only by the aperture size, a fundamental average power limit is given by the thermo-optical and thermo-mechanical properties of the beam splitter material and its coatings. Based on our analysis, 100 kW average power can be obtained with state-of-the-art optics at maintained high beam quality (M-2 <= 1.1) and at only 2% loss of combining efficiency. This result indicates that the power-scaling potential of today\textquotesingle s beam-splitter-based coherent beam combination is far from being depleted. A potential scaling route to megawatt-level average power is discussed for optimized beam splitter geometry.
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F. Karbstein, C. Sundqvist, K. S. Schulze, I. Uschmann, H. Gies, and G.G. Paulus
Vacuum birefringence at x-ray free-electron lasers
New J. Phys., 23 :095001 (August 2021)
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We study the perspectives of measuring the phenomenon of vacuum birefringence predicted by quantum electrodynamics using an x-ray free-electron laser (XFEL) alone. We devise an experimental scheme allowing two consecutive XFEL pulses to collide under a finite angle, and thus act as both pump and probe field for the effect. The signature of vacuum birefringence is encoded in polarization-flipped signal photons to be detected with high-purity x-ray polarimetry. Our findings for idealized scenarios underline that the discovery potential of solely XFEL-based setups can be comparable to those involving optical high-intensity lasers. For currently achievable scenarios, we identify several key details of the x-ray optical ingredients that exert a strong influence on the magnitude of the desired signatures.
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D. Wu, Z. M. Sheng, W. Yu, S. Fritzsche, and X. T. He
A pairwise nuclear fusion algorithm for particle-in-cell simulations: Weighted particles at relativistic energies
AIP Adv., 11 :075003 (July 2021)
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