Abstract
Electromagnetic cascades have the potential to act as a high-energy photon source of unprecedented brightness. Such a source would offer new experimental possibilities in fundamental science, but in the cascade process radiation reaction and rapid electron-positron plasma production seemingly restrict the efficient production of photons to sub-GeV energies. Here, we show how to overcome these energetic restrictions and how to create a directed GeV photon source, with unique capabilities as compared to existing sources. Our new source concept is based on a controlled interplay between the cascade and anomalous radiative trapping. Using specially designed advanced numerical models supported with analytical estimates, we demonstrate that the concept becomes feasible at laser powers of around 7 PW, which is accessible at soon-to-be-available facilities. A higher peak power of 40 PW can provide photons with GeV energies in a well-collimated 3-fs beam, achieving peak brilliance .
- Received 30 November 2016
DOI:https://doi.org/10.1103/PhysRevX.7.041003
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Almost any physical investigation involves the use of light, or photons, as a probe. High-energy photons are required to probe fundamental quantum processes, and interactions between lasers and matter can generate such photons; a charged particle can absorb laser photons and, in giving up some of its own energy, re-emit the photons at a much higher energy. This has led to great interest in using intense laser facilities to create high-energy photon sources, but there are seemingly unavoidable physical restrictions on their energy. In particular, the generation of high-energy photons leads to the start of an avalanche, or cascade, of electron-positron pairs that, while creating more photons, rapidly draws too much energy from the system, making the source unsustainable. We show that there is in fact a way to overcome such restrictions and create a source of giga-electron-volt (GeV) photons with unprecedented brightness.
The key to our concept is the use of particle-trapping phenomena to initiate a new scenario in which particle cascades and highly nonlinear particle dynamics induce and support each other but, crucially, in a controllable manner. By matching the intensity and duration of the laser pulse, it is possible to induce a cascade that is held at a subcritical level, avoiding significant depletion effects while sustaining photon production. In this scenario, laser radiation is converted into a well-collimated flash of GeV photons. The resulting source has parameters exceeding those provided by existing laser-based sources by several orders of magnitude.
Our concept is feasible for upcoming laser facilities and could enable a new era of experiments in photonuclear and quark-nuclear physics.