Open Access
Add to BibSonomy
Abstract
Using a Dazzler system and tilting a compressor grating, we provide an effective way of using the laser group delay dispersion to continuously steer the electron beam accelerated by an asymmetric laser wakefield. The deviation angle of the electron beam was the same as that of the angularly chirped laser pulse from its initial optical axis, which is determined by the laser pulse-front-tilt (PFT). This method can be utilized to continuously control over the pointing direction of electron bunches to the requisite trajectories, especially for practical applications in highly sensitive alignment devices such as electron-positron colliders or undulators. Additionally, we investigate the effect of PFT on the properties of the electron beam.
© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
1. Introduction
Laser wakefield acceleration (LWFA) was initially developed many years ago [1] and great progress has been made based on chirped-pulse-amplification technology [2]. An ultrashort laser pulse with ultrahigh peak power can drive nonlinear plasma waves [3] of which the longitudinal electric fields can be very strong to accelerate electrons to several GeV [4,5]. The peak current of electron beams has been generated to tens of kA [6,7]. The properties of the produced electrons, including pointing stability, reproducibility and tunability, are significant for practical applications. For instance, the pointing direction of electron beams is vital for electron-positron colliders or undulators [8–10]. The all-optical method of rotating the compressor grating to control over the pointing direction of LWFA electron-beams was first experimentally developed by Popp et al. [11]. However, it is impractical for users to realign the laser beam path once the compressor grating is tilted. So, the electrons cannot be steered continuously using this method. Another experimental scheme to control the electrons with a static tilted magnetic field is designed ingeniously by Nakanii et al. [12]. However, the electron energy is limited to approximately 10 MeV because of the density threshold. At low plasma density, the refraction effect stops working using this method. It is noteworthy that the low plasma density is necessary for generating high-energy electrons in a laser wakefield accelerator [13]. So, continuously guiding energetic electron beams with a low energy spread without changing the optical alignment is still a significant challenge.
The angular misalignment often emerges in the double pass compressor gratings and will cause an unwanted angular chirp (AC) in the pulse near field. If we consider a small deviation δ between the two gratings parallel to its grooves, the AC can be calculated as β=dθ/dλ=2δ(tanε)/(dcosα) [14]. Here α, ε and d are the angle of incidence, diffraction angle of a single grating and the groove spacing, respectively. In general, the PFT p consists of two terms: p = pAC+pSC+GDD, where the first term pAC is introduced by the AC, while the second term pSC+GDD is induced by the spatial chirp and laser group delay dispersion (GDD) [15]. In LWFA, the laser pulse with PFT will excite an asymmetric wakefield, which will force the pulse to deviate from its initial axis and alter the way the electrons are injected and accelerated [11,16,17].
In this letter, we study the effect of GDD on the pointing directions and properties of electron beams accelerated by an angularly chirped laser excited wakefield. The deviations are completely determined by the evolution of laser PFT. In the ionization injection regime, the asymmetric wake deflects the electrons from the initial optical axis, by the same angle as the angle of the laser pulse directions. Thus, the pointing directions of accelerated electron beams can be steered by controlling AC and GDD.
2. Experimental setup
The Pulsar chirped-pulse-amplification laser system delivers 25-fs, 800-nm laser pulses with energies of ∼400 mJ on a pure-nitrogen gas target. The p-polarized pulse focused by an f=50.8 cm gold coated off-axis parabola (OAP) mirror had a spot size of w0=9.5 µm and normalized vector potential of a0=1.8. The experimental setup is shown in Fig. 1, as characterized in [18]. The laser-driven electron accelerator is operating in the self-guided nonlinear regime. The Gaussian spatial profile of the laser beam was captured by the BeamGage (Spiricon OPHIR Photonics). The supersonic gas jet was produced by a 1.2 mm nozzle, which was able to generate supersonic gas flow with a Mach number ∼5. The plasma density profile measured by a Nomarski interferometer was comprised of a plateau of 800 µm and 300 µm gradients on both sides. The background electron density in the plateau of every shot was ne∼8.0×1018cm-3 while electron injection occurred. The position of the laser focus was set 2 mm above the nozzle and near the tail of the gas jet to optimize the properties of electron bunches. Then, the stable electron beams can be obtained. Without AC, the pointing stability (RMS) of 30 continuous shots of electron beams was 0.54 mrad. If the AC exists, the overall beam width will increase from w0 due to spatial chirp, which is seen in Fig. 1(b). The spot size at the focus will be enlarged and become elliptical [19]. In general, the factor between the major and minor axes is very small. The AC from the grating misalignment cannot be determined solely from the shape of the focal spot. Here, we artificially introduce a large AC of β=37.0 µrad/nm to intuitively show this physical phenomenon. Additionally, the pulse duration will be lengthened due to the introduction of GDD φ(2)(z)= φ(2)-2πλβ2z/ω2. Here, φ(2) is specified in the near field, z is the position of the ultrashort-pulse in the propagation direction, and ω is the angular frequency of the pulse. These spatio-temporal coupling distortions cause a two-fold reduction of the laser intensity.
Fig. 1. Experimental setup. The inserts (a) and (b) show the laser focal spot without AC and with AC of β=37.0 µrad/nm, respectively.
Thomson scattered images from a top-view were recorded by a commercial digital single lens reflex camera, which can be used to monitor the laser deflection from its initial propagation direction. This visible camera has an image resolution of 1.36 µm/pixel, which can also detect the nonlinear self-evolution of laser pulses in plasma and a rapidly blue-shifted Thomson scattering signal [20]. The electron beams emitted from the gas jet were monitored by a phosphor screen (DRZ) coupled with a 16-bit charged-coupled device (CCD) camera. The electron information including pointing direction, charge and divergence could be captured with the CCD. Moreover, the electrons were dispersed by an 8 cm-long magnetic spectrometer with magnetic field of 0.9 T. The magnetic electron spectrometer was placed at a distance of 60 cm away from the gas jet. A Fuji BAS-SR imaging plate (IP) covered with 15 µm aluminum foil was placed behind the magnet in air to record the electron charge and spectrum. The photo-stimulated luminescence value deposited on each IP corresponds to an electron energy, which has been calibrated [21]. The accelerated electron bunch has a broadband energy spectrum with energy detection limit above 40 MeV. The point to point fluctuations of electron bunches are slightly increased; they are below 1.73 mrad (in x direction) even for the largest β. The increased instability can be explained by the reduction of the laser intensity leading to the damped and less reliable nonlinear laser-plasma interaction.
In the compressor, α and ε satisfy the diffraction equation of grating. In the case of our laser system, α, ε and d are 50.50°, 24.35° and 675.68 nm, respectively. When one of the two compressor gratings is rotated around the axis parallel to the groove, the angularly chirped or pulse-front tilted laser beam will be introduced. As a result, the light path might be altered. Thus, it needs to be realigned by turning the last mirror in the compressor. In the Pulsar, the Dazzler (or acousto-optic programmable dispersive filter) [22] is used to manipulate the spectral phase, φ(ω), of a laser pulse. One of the spectral phase term, ${\partial ^2}\phi ({{\omega_0}} )/\partial {\omega ^2}$, the GDD, is utilized to describe the linear chirp [23]. The GDD can be controlled via the Dazzler system or varying the compressor grating distance. Here, we adopt the Dazzler (from Fastlite) to investigate the effect of GDD with angularly chirped laser pulses on LWFA-electrons.
3. Results and discussions
The top-view images of Thomson scattering clearly demonstrate that the angularly chirped laser pulse is deflected from its initial optical axis in plasma, shown in Figs. 2(a)–2(c). Evidently, the laser is deflected upwards (downwards) while β is negative (positive). And the deviation angles γ1 and γ2 are -16.10 mrad and 14.45 mrad, respectively, as shown in Figs. 2(a) and 2(c). Here, the minus sign represents an upwards direction.
Fig. 2. Thomson scattered images from top-view for different β: (a) -2.94, (b) 0.37 and (c) 1.47 µrad/nm. The white dashed line represents the initial laser axis. γ1 and γ2 stand for the deviation angles of the laser from its initial direction. The aspect ratio is 1.18.
When the ultrashort laser pulse propagates with AC, different spectral phase shift in transverse direction is created and causes the position-dependent laser components of linear phase chirp. The laser intensity front is tilted with respect to the laser phase front by the angle tanψ=λβ [14,24]. Different colors separate from each other and the spatial chirp can be induced. The product of spatio-temporal coupling distortions contributes to the total PFT, which causes the rapid evolution of PFT at propagation distance z. If the laser beam is collimated, the PFT can be characterized by [15]
Fig. 3. Rapid evolutionary behavior of PFT in the vicinity of the focus. (a) φ(2)=0 fs2. PFT angle ψ as a function of propagation distance z for β=1.47, 0.37, 0, -0.48 and -2.94 µrad/nm. (b) β=-2.94 µrad/nm. PFT angle ψ as a function of GDD for φ(2)=500, 200, 0, -200 and -500 fs2.
When the laser pulse with tilted intensity propagates through the plasma, the laser properties will evolve. The PFT ψ dynamically changes in plasma and will lead to the distortion and asymmetry of the laser wakefield. The asymmetric laser wakefield will contribute to the transverse plasma density gradient which leads to a transverse phase velocity gradient of the laser and the plasma refractive index perpendicular to the initial optical axis varying rapidly [11,26]. The drive laser pulse would be guided towards the lower density regions and be pushed transversely. Eventually, the laser with PFT will change its propagation direction and be steered due to the evolution of PFT through the entire plasma length.
If the laser pulse is deflected from its initial direction, the asymmetric transverse wakefield is subsequently shifted from its original equilibrium position and the transverse focusing electric field in plasma will drive the electrons towards the bubble center axis. The electrons will perform transverse betatron oscillations around its new equilibrium position. During the entire process, the electron bunch always follows the actual laser propagation direction and finally is emitted in the same direction of the laser deflection. The electron beam relative to Figs. 2(a) and 2(c) diverges from the initial laser propagation direction by angles of -15.58 and 13.78 mrad respectively, almost the same as the deflection of final laser pulse. While, for small β, the deflections of both the laser beam (seen in Fig. 2(b)) and the electron beams are very small. Above all, the pointing directions of accelerated electrons can be steered and are completely determined by the evolution of laser PFT.
The pointing deviations of the electron beams were very sensitive to GDD φ(2) for a different AC β, as shown in Figs. 4(a)–4(c). The deviation direction is in the x-z plane where the laser pulse is angularly chirped, and no obvious deflection was observed in the perpendicular y-z plane, as seen in Fig. 4(b). The highest angular deviation of electrons is more than 20 mrad when β=-2.94 µrad/nm. Figure 4(c) further illustrates the linear relationship between the net deviation of electrons from their center position and φ(2) for certain values of β. We use the linear fitting relationship X = aφ(2)+b to show the dependence of electron beam deviations on φ(2), where b is a constant. The insert in Fig. 4(c) depicts the linear relationship between β and the slope a, a = kβ, where k is a constant. Therefore, it is indicated that the pointing directions of electron-beams are able to be predictable and guided using a simple formula by controlling AC and GDD, X = kβφ(2)+b.
Fig. 4. (a-c) Angular deviation of electrons changed with φ(2) for different β: (a) Deviations of electron bunches captured on CCD. The white dashed line is the initial optical axis and the green dashed line is the center-to-center connector of the electron beams. The aspect ratio is 1. (b) Horizontal vs. vertical deviation. (c) Horizontal deviation vs. φ(2). The insert shows the linear fitting of β and slope a. Every dot is averaged for several shots of electron beam pointing distributions. (d) Laser deflection angle calculated from the theory for the same parameters in the experiment.
When β=-0.48 µrad/nm and the laser pulse was recompressed to the shortest duration, the typical energy distribution recorded on the IP is shown in Fig. 5(a). The average electron charge is ∼25 pC with energy above 40 MeV and the electron spectrum after spectrometer also stays relatively stable which can be accelerated to ∼180 MeV. When the compressor gratings are misaligned, the GDD will be induced in the compressor and a slight temporal stretching is produced after the propagation distance z. The pulse duration will increase from τ0 and should be compensated by the Dazzler system, where τ0 is the Fourier-limited pulse duration. For β=-2.94, 0.37 and 1.47 µrad/nm, the laser pulses were recompressed to their shortest duration τ0∼25 fs at φ(2)=-1100, 50 and 500 fs2 (the black dashed line in Figs. 5(b)–5(e)), respectively. The pulse duration was measured by a Wizzler (from Fastlite). We further investigate the effect of PFT on the properties of accelerated electron, including the charge, peak intensity, horizontal and vertical divergence of electron bunches for different β, as depicted in Figs. 5(b)–5(e). The electron signal on the DRZ was calibrated to the absolute charge with IP. In the small range of 360 fs2, the properties of electrons were affected very little (the green dashed line in Figs. 5(b)–5(e)) and independent of PFT. We also observed that the final energy spectrum of the electron bunch was not significantly affected by the presence of PFT. However, if larger GDD is added for each β, the lengthened pulse duration and the increased laser spot size in the transverse direction will result in the laser intensity decreasing. The electrons cannot be generated if φ(2) goes beyond the particular range due to the termination of ionization injection. Furthermore, the reduction of the laser intensity due to the introduction of GDD will dramatically deteriorate the properties of LWFA-electrons. A trade-off should been made between optimized electron properties and electron beam steering. If we want to steer the pointing directions of electrons without sacrificing the properties of electrons, we must modify the GDD in a small range for each value of β.
Fig. 5. (a) Average electron spectrum of five continuous shots recorded on the IP when β=-0.48 µrad/nm. The IP is scanned after every single shot. The error bar is calculated from the standard deviation. The insert is the typical electron signal on the IP after the magnet of 0.9 T. Effect on the properties of the electron beams changed with φ(2) for different β: (b) charge, (c) peak intensity, (d) horizontal and (e) vertical divergence. Here, the peak intensity represents charge density in the center of the beam and is normalized to 1. Three black dashed lines represent the optimum electron bunch when the pulse duration is corrected with the Dazzler system.
This method can be utilized to continuously guide the electron beam pointing direction to the requisite trajectories, which is very useful in practical use. For example, either the all-optical inverse Compton scattering [27,28] or the laser-driven linear collider [29] has very high requirements for the overlap between the electron beam and the colliding beam in space and time. The micrometer-scale deviation will drastically reduce the effectiveness of the physical interaction. This technique offers attractive prospects for driving a bunch of electrons to the colliding point precisely.
More importantly, the magnitude of the electron beam’s deviation is one order larger than the angular misalignment of gratings. The electron beams will not be deflected from their centers once the PFT is changed only if the compressor gratings are strictly parallel to each other. The high degree of sensitivity between the electron beam’s pointing direction and the PFT provides a precise tool to adjust the parallelism between the compressor gratings of a chirped-pulse-amplification system.
During the submission of this manuscript, an independent work has been published on a similar technique for steering electron beams produced by an asymmetric laser wakefield [30]. After comparing, we find that the physical mechanism is the same and the experimental results are complementary. According to Eq. (9) in [30], we make two assumptions: the evolution of laser pulse is unaffected by the plasma and keeps wave number of plasma a constant. With these simplifying assumptions, the laser defection angle is obtained by integrating the laser deflection rate along the laser-plasma interaction distance $\xi $∼1 mm, as seen in Fig. 4(d). Obviously, the predictions of laser steering are consistent with the measured trends of electron beam steering in Fig. 4(c). Both the net deviation angles of laser pulses and electron beams show the similar linear relationship with φ(2) for each value of β. However, their slopes have small differences. It is difficult to predict the laser steering accurately owing to the lack of laser evolution in the nonlinear laser-plasma interaction process.
4. Conclusion
In summary, we present an effective method to precisely steer the LWFA electron beams with laser GDD. The effect of PFT caused by angular dispersion and temporal change of femtosecond pulses on the LWFA-electron pointing directions and properties has been systematically investigated. Using a Dazzler system and tilting a compressor grating, the electron-pointing directions can be manipulated. This method is vital to guide the electrons to the requisite trajectories for practical applications. It also provides the basic principle for determining and adjusting the parallelism of the grating compressor in vacuum, leading to a new way to precisely diagnose the spatio-temporal distorted pulses with PFT.
Funding
Science Challenge Project (TZ2018005); National Key Research and Development Program of China (2017YFA0403301); National Natural Science Foundation of China (11991073, 11721404, 11805266, 11905289, 61975229); Key Program of CAS (XDB17030500).
Disclosures
The authors declare no conflicts of interest.
References
1. T. Tajima and J. M. Dawson, “Laser Electron Accelerator,” Phys. Rev. Lett. 43(4), 267–270 (1979). [CrossRef]
2. D. Strickland and G. Mourou, “Compression of amplified chirped optical pulses,” Opt. Commun. 55(6), 447–449 (1985). [CrossRef]
3. E. Esarey, C. B. Schroeder, and W. P. Leemans, “Physics of laser-driven plasma-based electron accelerators,” Rev. Mod. Phys. 81(3), 1229–1285 (2009). [CrossRef]
4. X. Wang, R. Zgadzaj, N. Fazel, Z. Li, S. A. Yi, X. Zhang, W. Henderson, Y. Y. Chang, R. Korzekwa, H. E. Tsai, C. H. Pai, H. Quevedo, G. Dyer, E. Gaul, M. Martinez, A. C. Bernstein, T. Borger, M. Spinks, M. Donovan, V. Khudik, G. Shvets, T. Ditmire, and M. C. Downer, “Quasi-monoenergetic laser-plasma acceleration of electrons to 2 GeV,” Nat. Commun. 4(1), 1988 (2013). [CrossRef]
5. W. P. Leemans, A. J. Gonsalves, H. S. Mao, K. Nakamura, C. Benedetti, C. B. Schroeder, C. Tóth, J. Daniels, D. E. Mittelberger, S. S. Bulanov, J. L. Vay, C. G. R. Geddes, and E. Esarey, “Multi-GeV electron beams from capillary-discharge-guided subpetawatt laser pulses in the self-trapping regime,” Phys. Rev. Lett. 113(24), 245002 (2014). [CrossRef]
6. Y. F. Li, D. Z. Li, K. Huang, M. Z. Tao, M. H. Li, J. R. Zhao, Y. Ma, X. Guo, J. G. Wang, M. Chen, N. Hafz, J. Zhang, and L. M. Chen, “Generation of 20 kA electron beam from a laser wakefield accelerator,” Phys. Plasmas 24(2), 023108 (2017). [CrossRef]
7. J. P. Couperus, R. Pausch, A. Köhler, O. Zarini, J. M. Krämer, M. Garten, A. Huebl, R. Gebhardt, U. Helbig, S. Bock, K. Zeil, A. Debus, M. Bussmann, U. Schramm, and A. Irman, “Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator,” Nat. Commun. 8(1), 487 (2017). [CrossRef]
8. W. P. Leemans and E. Esarey, “Laser-driven plasma-wave electron accelerators,” Phys. Today 62(3), 44–49 (2009). [CrossRef]
9. M. Fuchs, R. Weingartner, A. Popp, Z. Major, S. Becker, J. Osterhoff, I. Cortrie, B. Zeitler, R. Hörlein, G. D. Tsakiris, U. Schramm, T. P. Rowlands-Rees, S. M. Hooker, D. Habs, F. Krausz, S. Karsch, and F. Grüner, “Laser-driven soft-X-ray undulator source,” Nat. Phys. 5(11), 826–829 (2009). [CrossRef]
10. A. R. Maier, A. Meseck, S. Reiche, C. B. Schroeder, T. Seggebrock, and F. Grüner, “Demonstration Scheme for a Laser-Plasma-Driven Free-Electron Laser,” Phys. Rev. X 2(3), 031019 (2012). [CrossRef]
11. A. Popp, J. Vieira, J. Osterhoff, Z. Major, R. Hörlein, M. Fuchs, R. Weingartner, T. P. Rowlands-Rees, M. Marti, R. A. Fonseca, S. F. Martins, L. O. Silva, S. M. Hooker, F. Krausz, F. Gruner, and S. Karsch, “All-Optical Steering of Laser-Wakefield-Accelerated Electron Beams,” Phys. Rev. Lett. 105(21), 215001 (2010). [CrossRef]
12. N. Nakanii, T. Hosokai, K. Iwasa, S. Masuda, A. Zhidkov, N. Pathak, H. Nakahara, Y. Mizuta, N. Takeguchi, and R. Kodama, “Transient magnetized plasma as an optical element for high power laser pulses,” Phys. Rev. Spec. Top.--Accel. Beams 18(2), 021303 (2015). [CrossRef]
13. W. Lu, M. Tzoufras, C. Joshi, F. S. Tsung, W. B. Mori, J. Vieira, R. A. Fonseca, and L. O. Silva, “Generating multi-GeV electron bunches using single stage laser wakefield acceleration in a 3D nonlinear regime,” Phys. Rev. Spec. Top.--Accel. Beams 10(6), 061301 (2007). [CrossRef]
14. G. Pretzler, A. Kasper, and K. J. Witte, “Angular chirp and tilted light pulses in CPA lasers,” Appl. Phys. B 70(1), 1–9 (2000). [CrossRef]
15. S. Akturk, X. Gu, E. Zeek, and R. Trebino, “Pulse-front tilt caused by spatial and temporal chirp,” Opt. Express 12(19), 4399–4410 (2004). [CrossRef]
16. R. J. Garland, K. Poder, J. Cole, W. Schumaker, D. Doria, L. A. Gizzi, G. Grittani, K. Krushelnick, S. Kuschel, S. P. D. Mangles, Z. Najmudin, D. Symes, A. G. R. Thomas, M. Vargas, M. Zepf, and G. Sarri, “Optimisation of the pointing stability of laser-wakefield accelerated electron beams,” arXiv:1407.6979v1 (2014).
17. M. Thévenet, D. E. Mittelberger, K. Nakamura, R. Lehe, C. B. Schroeder, J. L. Vay, E. Esarey, and W. P. Leemans, “Pulse front tilt steering in laser plasma accelerators,” Phys. Rev. Accel. Beams 22(7), 071301 (2019). [CrossRef]
18. C. Zhu, J. Wang, J. Feng, Y. Li, D. Li, M. Li, Y. He, J. Ma, J. Tan, B. Zhang, W. Yan, and L. Chen, “Inverse Compton scattering x-ray source from laser electron accelerator in pure nitrogen with 15 TW laser pulses,” Plasma Phys. Controlled Fusion 61(2), 024001 (2019). [CrossRef]
19. H. P. Vincenti, “Génération d’impulsions attosecondes sur miroir plasma relativiste,” Ph.D. dissertation, Phys. Dept., École Polytech., Palaiseau, France (2013).
20. J. Wang, J. Feng, C. Zhu, Y. Li, Y. He, D. Li, J. Tan, J. Ma, and L. Chen, “Small energy spread electron beams from laser wakefield acceleration by self-evolved ionization injection,” Plasma Phys. Controlled Fusion 60(3), 034004 (2018). [CrossRef]
21. N. Nakanii, K. Kondo, T. Yabuuchi, K. Tsuji, K. A. Tanaka, S. Suzuki, T. Asaka, K. Yanagida, H. Hanaki, T. Kobayashi, K. Makino, T. Yamane, S. Miyamoto, and K. Horikawa, “Absolute calibration of imaging plate for GeV electrons,” Rev. Sci. Instrum. 79(6), 066102 (2008). [CrossRef]
22. P. Tournois, “Acousto-optic programmable dispersive filter for adaptive compensation of group delay time dispersion in laser systems,” Opt. Commun. 140(4-6), 245–249 (1997). [CrossRef]
23. A. Weiner, “Ultrafast Optics (Wiley Series in Pure and Applied Optics),” John Wiley & Sons, Inc., Publication (2009).
24. J. Osterhoff, “Stable, ultra-relativistic electron beams by laser-wakefield acceleration,” Ph.D. dissertation, FAKULTÄT FÜR PHYSIK DER LUDWIG-MAXIMILIANS-UNIVERSITÄT IN MÜNCHEN (2009).
25. K. Nakamura, H. S. Mao, A. J. Gonsalves, H. Vincenti, D. E. Mittelberger, J. Daniels, A. Magana, C. Toth, and W. P. Leemans, “Diagnostics, Control and Performance Parameters for the BELLA High Repetition Rate Petawatt Class Laser,” IEEE J. Quantum Electron. 53(4), 1–21 (2017). [CrossRef]
26. Y. Ma, D. Seipt, S. J. D. Dann, M. J. V. Streeter, C. A. J. Palmer, L. Willingale, and A. G. R. Thomas, “Angular streaking of betatron X-rays in a transverse density gradient laser-wakefield accelerator,” Phys. Plasmas 25(11), 113105 (2018). [CrossRef]
27. N. D. Powers, I. Ghebregziabher, G. Golovin, C. Liu, S. Chen, S. Banerjee, J. Zhang, and D. P. Umstadter, “Quasi-monoenergetic and tunable X-rays from a laser-driven Compton light source,” Nat. Photonics 8(1), 28–31 (2014). [CrossRef]
28. W. Yan, C. Fruhling, G. Golovin, D. Haden, J. Luo, P. Zhang, B. Zhao, J. Zhang, C. Liu, M. Chen, S. Chen, S. Banerjee, and D. Umstadter, “High-order multiphoton Thomson scattering,” Nat. Photonics 11(8), 514–520 (2017). [CrossRef]
29. C. B. Schroeder, E. Esarey, C. G. R. Geddes, C. Benedetti, and W. P. Leemans, “Physics considerations for laser-plasma linear colliders,” Phys. Rev. Spec. Top.--Accel. Beams 13(10), 101301 (2010). [CrossRef]
30. D. E. Mittelberger, M. Thévenet, K. Nakamura, A. J. Gonsalves, C. Benedetti, J. Daniels, S. Steinke, R. Lehe, J.-L. Vay, C. B. Schroeder, E. Esarey, and W. P. Leemans, “Laser and electron deflection from transverse asymmetries in laser-plasma accelerators,” Phys. Rev. E 100(6), 063208 (2019). [CrossRef]
