Special Collection on Laser-Plasma Particle Acceleration
By Victor Malka, Member of the PRX Editorial Board, and the Editors
We are very pleased to offer the readers of Physical Review X a new, carefully curated collection of articles from the vibrant field of laser-plasma particle acceleration. Some of the articles have already been published, and others will be forthcoming. This Collection is the latest in the journal’s series of Special Collections on current or emerging fields and topics.
The fundamental concept underlying laser-plasma particle accelerators (LPAs) has two essential elements: The generation of intense electric fields from laser-plasma interactions, and the use of such fields to accelerate charged particles such as electrons, protons, or ions to produce high-energy particle beams or electromagnetic radiation. When a high-intensity laser beam hits a target of solid material, it turns the target into a plasma, a gas of electrons and ions in which an ultraintense electric field can be generated and sustained under the right conditions. For this electric field to be suitable for light-mass particle acceleration, the electrons in the plasma must be made to collectively move along the same direction with the same phase. This so-called electron plasma oscillation can lead to intense electric fields with amplitudes exceeding—by 3 orders of magnitude—those of the radio-frequency fields commonly used in conventional particle accelerators.
The efficient acceleration of particles based on this fundamental concept was just a dream a few decades ago. Today that dream is coming true, and we are witnessing a scientific revolution as many groups around the world contribute to this pursuit and produce outstanding research. In certain performance measures, the particle and radiation beams delivered by LPAs are now on the way to overtaking those produced by conventional accelerators. For example, the compact delivery of hundreds of MeV monoenergetic electron beams of extreme brightness has already been achieved.
In addition to the unfolding scientific revolution, a technological revolution may also be on the horizon. We may expect—in the not-too-distant future—many potential applications of the particle and radiation beams. High-energy electron or proton beams may be used for nondestructive inspection of materials for security or quality-control purposes. X rays emitted from the LPA-particle beams may be used for early cancer detection. The increasing number of groups in the field has also motivated laser manufacturers to improve their products and provide more reliable, more compact, and even more economical, powerful lasers—fueling an industrial boom of its own.
The scientific vitality and diversity of this field is, we believe, vividly captured by the articles in this Collection, although it is by no means a complete coverage of all the developments and directions in the field. The articles by Poder et al. [PRX 8, 031004 (2018)] and Cole et al. [PRX 8, 011020 (2018)] use LPAs to open up a new frontier of fundamental research on quantum electrodynamics in a regime not accessible before. The article by Kozlova et al. [PRX 10, 011061 (2020)] reports producing, by means of plasma-density shaping, betatron radiation with enhanced energy and flux without having to increase the laser energy. It is a major step toward developing this radiation source into one that will be viable for applications.
The physics of particle-beam-driven plasma wakefields was previously studied only with large-scale particle accelerators. The articles by Götzfried et al. [PRX 10, 041015 (2020)] and Gilljohann et al. [PRX 9, 011046 (2019)] demonstrate that the physics can now be explored in the settings of LPAs. On another crucial, more technical front, two contributions make significant strides in different ways. Maier et al. [PRX 10, 031039 (2020)] leverage the recent progress of laser technology and metrology to reliably deliver more than 100,000 electron bunches in around 24 hours, bringing the field a big step closer to the desired steady operation of LPAs of electrons. Debus et al. [PRX 9, 031044 (2019)] offer the novel and experimentally feasible idea of using ultrashort laser pulses with tilted pulse fronts to overcome the dephasing and depletion limits of laser wakefield acceleration. In yet another important direction, a forthcoming article by Zaïm et al. demonstrates that novel approaches with direct laser acceleration of electrons generated from a solid-surface interaction can reveal interesting physics and show alternative technological possibilities.
We hope that you, our readers, will enjoy this sampling of exciting developments in LPA research and that you will gain from it knowledge and inspiration for your own work.
Last but not least, putting together this Collection has made us realize more than before how fortunate PRX is to have received the good will and the manifest support from the LPA community and to have built a solid connection with it. To our mind, the Collection showcases some of the best fruits grown out of that connection. Its special publication expresses our deep gratitude to this community. With it we also reaffirm to the community the same commitment we make to the wide physics community: We will select responsibly the very best research results that have the potential to make a profound, wide, and lasting impact both scientifically and technologically; and we will disseminate those results to a broad readership and with a high visibility.
Victor Malka Member of the Editorial Board and The Editors Physical Review X