Abstract
Keywords
1 Introduction
Scientists and engineers use Einstein’s famous energy–mass equivalence, , to calculate the transformation of part of the mass of nuclei into energy by nuclear fission or fusion reactions (via differences in the rest mass energy when large nuclei are split or small nuclei combined). Quantum electrodynamics (QED) predicts that the reverse can also be achieved: transforming the energy of the laser photons into mass, via the generation of electron–positron pairs. Nevertheless, the QED effect like electron–positron avalanche pair production to appear spontaneously from vacuum requires a very high, Schwinger electric field[
Examples of new laser facilities under construction with interaction chambers dedicated to QED experiments are: extreme light infrastructure – nuclear physics (ELI-NP)[
Recently, experimental evidence was reported[
Sign up for High Power Laser Science and Engineering TOC. Get the latest issue of High Power Laser Science and Engineering delivered right to you!Sign up now
Theoretical studies of colliding laser beams in solid and near-critical plasmas at intensities of , and even predict efficient conversion of laser energy into dense electron–positron pairs and bursts of energetic Gamma rays[
2 High field physics, QED processes with colliding PW laser pulses
Important processes in ultra-high laser fields are in Refs.[ Nonlinear, multiphoton, inverse Compton scattering in which up to 40% of the energy of the laser accelerated electrons is re-radiated as Gamma-ray photons in the presence of the laser field: RR in which the accelerated electron recoils from the emission of the high energy Gamma-ray photon. Electron–positron pair production by the multiphoton Breit–Wheeler (BW) process:
The parameter determines the importance of strong-field QED effects[
While laser technology is continuously increasing , in the medium term . Nevertheless, in order to achieve , we can experimentally maximize: the Lorentz factor, the ‘geometric factor’,
Maximizing , by maximizing and can be achieved by colliding two PW laser pulses as shown in Figure The first focused PW laser pulse accelerates electrons to relativistic energies from a gas target or a solid target. The second tightly focused PW laser pulse provides the ultra-intense electromagnetic field in its focus. The relativistic electrons accelerated by the ‘first PW pulse’ travel through the focus of the ‘second PW pulse’, are immersed in this ultra-intense electromagnetic field and generate the QED effects resulting in copious Gamma-photon and electron–positron pair production. The relativistic Lorentz factor,
3 ELI-NP 2
The ELI-NP facility in Romania has a unique laser system for colliding 10 PW laser pulses[
Each 10 PW laser pulse will have energy of J/pulse and pulse duration of fs. The beams will be nearly diffraction limited with a Strehl ratio of 0.9. The laser intensity contrast above pre-pulses will be very high: , and . These properties are highly desirable for focusing to ultra-high intensity on solid targets. The laser system will have a high pulse repetition rate of 1 pulse/min for the pulses. The laser beam cross section will be large: cm diameter. The pulses will be directed into the interaction areas. A laser beam delivery system[
The E6 interaction chamber at ELI-NP is dedicated to QED experiments with two counter-propagating, focused, colliding 10 PW laser pulses in gas targets[
The E1 interaction chamber at ELI-NP is dedicated to nuclear physics experiments with one or two 10 PW pulses focused with short focal length mirrors on solid targets[
4 Radiation-reaction measurements with two colliding pulses at Astra Gemini PW facility
Experimental evidence of RR QED effect with colliding laser pulses has been obtained in two experiments carried out by the collaboration led by the Queen’s University Belfast–Imperial College London[
In the first experiment[
Radiation-reaction effects were observed experimentally. Low-energy electron beams were observed on all successful collision shots as well as the correlation between the post-collision electron beam energy and the Gamma ray yield. The spectrum hard Gamma photons were measured, with energy , which carried a significant fraction of the initial electron energy[
In the second experiment[
5 Synchronization of focused femtosecond colliding PW laser pulses
In order to successfully collide PW femtosecond laser pulses, one needs to ensure the synchronization of the two focused pulses to better than the pulse duration. This is, for example, 45 fs for experiments with the colliding pulses in Astra Gemini PW Laser Facility (Section
Experimentally, the femtosecond-level synchronization of the focused femtosecond pulses is measured and optimized in situ, in the focal spot of the two colliding pulses[
6 SHINE Facility: 100 PW pulse and 10 keV XFEL pulse for QED experiments
A further scaling in laser-pulse power from 10 PW to 100 PW and in laser intensity from to is planned for the new SEL[
A second, synchronized, 1 PW laser pulse will be available at the SEL facility. One can envisage QED experiments with two colliding 100 PW and 1 PW laser pulses. The 1 PW laser pulse will accelerate the electron bunch to ultra-relativistic energies. The ultra-relativistic electrons accelerated by the ‘first 1 PW pulse’ will travel through the focus of the ‘second 100 PW pulse’ where they are immersed in this ultra-intense, , electromagnetic field and will generate the QED effects which will result in Gamma photons and electron–positron pair production. In this configuration, the X-ray pulse from the XFEL could be used as a probe pulse to look at Thomson scattering for example.
Another intriguing experiment would be to accelerate the electron bunch (LWFA) with the 100 PW pulse focused with an F/1000, extremely long effective focal length system: . This could be achieved either by installing a 1000 m focal length mirror in the tunnel connecting SEL to the XFEL, or by focusing the laser beam with a telescope constructed of plasma mirrors (DN private communication). The plasma mirrors within the telescope would need replacing after each laser pulse. Such a geometry could investigate the acceleration of the electron bunch to multi-100 GeV energies in a single acceleration stage. The presently accepted scheme[
7 Simulation of copious electron–positron pair production with 2
Simulations of colliding 10 PW laser pulses focused to ultra-high intensities predict large production of electron–positron pairs and very high laser energy conversion efficiency to hard Gamma photons [
In an interaction scheme simulation using laser parameters similar to the ELI-NP design capability, two counter-propagating ultra-intense laser pulses (, 40 fs pulse duration) are focused from two opposite directions on the near-critical-density plasmas filled inside two cone targets[
A second scheme[
A third scheme[
A fourth scheme[
A fifth simulation scheme[
8 Conclusions
At the Schwinger laser intensity of the QED theory predicts that a large part of the energy of the laser photons will be transformed to hard Gamma photons and even to matter: electron–positron pairs. The new laser facilities under construction, will use the interaction of two colliding PW laser pulses to reach the QED regime in experiments with the focused laser intensities which will become available in the near term: and above. The first PW laser pulse will accelerate an electron bunch to relativistic energies of several GeV/electron, using either gas or solid targets; and the second PW laser pulse will be focused to the maximum intensity on the relativistic electron bunch in order to generate the QED effects. In this interaction geometry the relativistic electron experiences a much larger electric field, approaching the Schwinger field, in his own frame of reference than the actual laser electric field in the laboratory frame of reference.
The new ELI-NP Laser Facility[
Theoretical simulations[
References
[1] J. Schwinger. Phys. Rev., 82, 664(1951).
[2] C. Danson, D. Hillier, N. Hopps, D. Neely. High Power Laser Sci. Eng., 3, e3(2015).
[3] I. C. E. Turcu, F. Negoita, D. A. Jaroszynski, P. Mckenna, S. Balascuta, D. Ursescu, I. Dancus, M. O. Cernaianu, M. V. Tataru, P. Ghenuche, D. Stutman, A. Boianu, M. Risca, M. Toma, C. Petcu, G. Acbas, S. R. Yoffe, A. Noble, B. Ersfeld, E. Brunetti, R. Capdessus, C. Murphy, C. P. Ridgers, D. Neely, S. P. D. Mangles, R. J. Gray, A. G. R. Thomas, J. G. Kirk, A. Ilderton, M. Marklund, D. F. Gordon, B. Hafizi, D. Kaganovich, J. P. Palastro, E. D’humieres, M. Zepf, G. Sarri, H. Gies, F. Karbstein, J. Schreiber, G. G. Paulus, B. Dromey, C. Harvey, A. Di Piazza, C. H. Keitel, M. C. Kaluza, S. Gales, N. V. Zamfir. Rom. Rep. Phys., 68, S145(2016).
[4] F. Negoita, M. Roth, P. G. Thirolf, S. Tudisco, F. Hannachi, S. Moustaizis, I. Pomerantz, P. McKenna, J. Fuchs, K. Sphor, G. Acbas, A. Anzalone, P. Audebert, S. Balascuta, F. Cappuzzello, M. O. Cernaianu, S. Chen, I. Dancus, R. Freeman, H. Geissel, P. Genuche, L. A. Gizzi, F. Gobet, G. Gosselin, M. Gugiu, D. P. Higginson, E. D’humières, C. Ivan, D. Jaroszynski, S. Kar, L. Lamia, V. Leca, L. Neagu, G. Lanzalone, V. Méot, S. R. Mirfayzi, I. O. Mitu, P. Morel, C. Murphy, C. Petcu, H. Petrascu, C. Petrone, P. Raczka, M. Risca, F. Rotaru, J. J. Santos, D. Schumacher, D. Stutman, M. Tarisien, M. Tataru, B. Tatulea, I. C. E. Turcu, M. Versteegen, D. Ursescu, S. Gales, N. V. Zamfir. Rom. Rep. Phys., 68, S37(2016).
[6] B. Shen, Z. Bu, J. Xu, T. Xu, L.-L. Ji, R. Li, Z. Xu. Plasma Phys. Control. Fusion, 60(2018).
[7] D. Strickland, G. Mourou. Opt. Commun., 56, 219(1985).
[8] J. M. Cole, K. T. Behm, E. Gerstmayr, T. G. Blackburn, J. C. Wood, C. D. Baird, M. J. Duff, C. Harvey, A. Ilderton, A. S. Joglekar, K. Krushelnick, S. Kuschel, M. Marklund, P. McKenna, C. D. Murphy, K. Poder, C. P. Ridgers, G. M. Samarin, G. Sarri, D. R. Symes, A. G. R. Thomas, J. Warwick, M. Zepf, Z. Najmudin, S. P. D. Mangles. Phys. Rev. X, 8(2018).
[9] K. Poder, M. Tamburini, G. Sarri, A. Di Piazza, S. Kuschel, C. D. Baird, K. Behm, S. Bohlen, J. M. Cole, D. J. Corvan, M. Duff, E. Gerstmayr, C. H. Keitel, K. Krushelnick, S. P. D. Mangles, P. McKenna, C. D. Murphy, Z. Najmudin, C. P. Ridgers, G. M. Samarin, D. R. Symes, A. G. R. Thomas, J. Warwick, M. Zepf. Phys. Rev. X, 8(2018).
[10] C. J. Hooker, J. L. Collier, O. Chekhlov, R. Clarke, E. Divall, K. Ertel, B. Fell, P. Foster, S. Hancock, A. Langley, D. Neely, J. Smith. J. Phys. IV, 133, 673(2006).
[11] X.-L. Zhu, T.-P. Yu, Z.-M. Sheng, Y. Yin, I. C. E. Turcu, A. Pukhov. Nature Commun., 7(2016).
[12] H.-Z. Li, T.-P. Yu, J.-J. Liu, Y. Yin, X.-L. Zhu, R. Capdessus, F. Pegoraro, Z.-M. Sheng, P. McKenna, F.-Q. Shao. Sci. Rep., 7(2017).
[13] J.-J. Liu, T.-P. Yu, Y. Yin, X.-L. Zhu, F.-Q. Shao. Opt. Express, 24(2016).
[14] J.-X. Liu, Y.-Y. Ma, T.-P. Yu, J. Zhao, X.-H. Yang, L.-F. Gan, G-B. Zhang, Y. Zhao, S.-J. Zhang, J.-J. Liu, H.-B. Zhuo, F.-Q. Shao, S. Kawata. Plasma Phys. Control. Fusion, 58(2016).
[15] X.-L. Zhu, X.-L. Zhu, M. Chen, T.-P. Yu, S.-M. Weng, L.-X. Hu, P. McKenna, Z.-M. Sheng. Appl. Phys. Lett., 112(2018).
[17] W. Y. Liu, W. Luo, T. Yuan, J. Y. Yu, M. Chen, Z. M. Sheng. Phys. Plasmas, 24(2017).
[19] J. Y. Yu, T. Yuan, W. Y. Liu, M. Chen, W. Luo, S. M. Weng, Z. M. Sheng. Plasma Phys. Control. Fusion, 60(2018).
[21] V. I. Ritus. J. Russ. Laser Res., 6, 497(1985).
[22] J. G. Kirk, A. R. Bell, I. Arka. Plasma Phys. Control. Fusion, 51(2009).
[23] A. Di Piazza, C. Müller, K. Z. Hatsagortsyan, C. H. Keitel. Rev. Mod. Phys., 84, 1177(2012).
Set citation alerts for the article
Please enter your email address