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Giant collimated gamma-ray flashes


Bright sources of high-energy electromagnetic radiation are widely employed in fundamental research, industry and medicine1,2. This motivated the construction of Compton-based facilities planned to yield bright gamma-ray pulses with energies up to3 20 MeV. Here, we demonstrate a novel mechanism based on the strongly amplified synchrotron emission that occurs when a sufficiently dense ultra-relativistic electron beam interacts with a millimetre-thickness conductor. For electron beam densities exceeding approximately 3 × 1019 cm−3, electromagnetic instabilities occur, and the ultra-relativistic electrons travel through self-generated electromagnetic fields as large as 107–108 gauss. This results in the production of a collimated gamma-ray pulse with peak brilliance above 1025 photons s−1 mrad−2 mm−2 per 0.1% bandwidth, photon energies ranging from 200 keV to gigaelectronvolts and up to 60% electron-to-photon energy conversion efficiency. These findings pave the way to compact, high-repetition-rate (kilohertz) sources of short (30 fs), collimated (milliradian) and high-flux (>1012 photons s−1) gamma-ray pulses.

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Fig. 1: The transverse electron beam density.
Fig. 2: The longitudinal electron beam density.
Fig. 3: Electromagnetic fields.
Fig. 4: Number of emitted photons and conversion efficiency per electron.
Fig. 5: The photon beam brilliance.


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The authors would like to thank N. Kumar for valuable discussions and suggestions.

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Authors and Affiliations



A.B. initially conceived the research project with input from M.T., configured and carried out the simulations, generated the figures and wrote the bulk of the manuscript. M.T. implemented the routines accounting for multiple scattering, bremsstrahlung and synchrotron radiation into the particle-in-cell code EPOCH. A.B. and M.T. discussed the physics, and analysed and interpreted the results of the simulations. C.H.K. supervised the project. All authors contributed to the preparation of the manuscript.

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Correspondence to Matteo Tamburini.

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Benedetti, A., Tamburini, M. & Keitel, C.H. Giant collimated gamma-ray flashes. Nature Photon 12, 319–323 (2018).

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