[Paper Review] On Seminal HEDP Research Opportunities Enabled by Colocating Multi-Petawatt Laser with High-Density Electron Beams

Sebastian Meuren, P. H. Bucksbaum+8 more|arXiv (Cornell University)|Feb 24, 2020

Laser-Plasma Interactions and Diagnostics6 references33 citations

TL;DR

The paper argues for colocating multi-Petawatt lasers with dense, high-energy electron beams to enable beam-driven QED cascades and dense electron-positron pair plasmas, outlining the scientific opportunities, necessary parameters, and a comparison of existing/planned facilities.

ABSTRACT

The scientific community is currently witnessing an expensive and worldwide race to achieve the highest possible light intensity. Within the next decade this effort is expected to reach nearly $10^{24}\,\mathrm{W}/\mathrm{cm^2}$ in the lab frame by focusing of 100 PW, near-infrared lasers. A major driving force behind this effort is the possibility to study strong-field vacuum breakdown and an accompanying electron-positron pair plasma via a quantum electrodynamic (QED) cascade [Edwin Cartlidge, "The light fantastic", Science 359, 382 (2018)]. Whereas Europe is focusing on all-optical 10 PW-class laser facilities (e.g., Apollon and ELI), China is already planning on co-locating a 100 PW laser system with a 25 keV superconducting XFEL and thus implicitly also a high-quality electron beam [Station of Extreme Light (SEL) at the Shanghai Superintense-Ultrafast Lasers Facility (SULF)]. This white paper elucidates the seminal scientific opportunities facilitated by colliding dense, multi-GeV electron beams with multi-PW optical laser pulses. Such a multi-beam facility would enable the experimental exploration of extreme HEDP environments by generating electron-positron pair plasmas with unprecedented densities and temperatures, where the interplay between strong-field quantum and collective plasma effects becomes decisive.

Motivation & Objective

• Motivate co-location of high-power lasers with dense, multi-GeV electron beams to access extreme HEDP regimes.
• Assess the experimental potential for beam-driven QED cascades and electron-positron pair plasmas under χ ≳ 10–100.
• Highlight relevance to strong-field QED, astrophysical plasmas, and future linear colliders.
• Provide a quantitative framework comparing facility capabilities and achievable quantum parameters.
• Identify key experimental and theoretical challenges requiring collaboration across theory, simulation, and experiment.

Proposed method

• Define the quantum parameter χ and the laser-plasma cascade parameter CL to quantify strong-field QED effects.
• Propose a benchmark scenario combining a multi-PW laser with a high-density, multi-GeV electron beam (e.g., 30 GeV, RF LINAC beams at SLAC).
• Use head-on collision geometry to estimate χ, a0, and CL for various facilities.
• Compare existing and planned facilities using Tab.1 to illustrate access to χ ≳ 1 and χ ≳ 10–100.
• Discuss formation of beam-driven QED cascades and resultant dense electron-positron plasmas and their interplay with collective plasma effects.
• Outline technological and scientific challenges in achieving the required focusing, density, and synchronization.

Experimental results

Research questions

• RQ1 What are the attainable χ values when colliding multi-PW laser pulses with high-density multi-GeV electron beams?
• RQ2 How dense and hot can beam-driven electron-positron pair plasmas become under realistic facility parameters?
• RQ3 What are the qualitative and quantitative differences between beam-driven QED cascades and laser-laser cascades in this regime?
• RQ4 What facility configurations (beam energy, density, laser power, focal spot) maximize access to the deep quantum regime (χ ≳ 1, χ ≳ 10–100)?
• RQ5 What experimental and theoretical challenges must be overcome to realize and interpret these extreme interactions?

Key findings

• A co-located multi-PW laser with a high-density, multi-GeV electron beam enables access to beam-driven QED cascades and dense pair plasmas that are not reachable with all-optical facilities alone.
• For head-on collisions, χ can reach values of order tens to a few hundred with 30–60 GeV electrons and 3–10 PW lasers, enabling cascades and plasmas with densities exceeding the initial beam by at least an order of magnitude.
• Beam-driven cascades offer controllability by tuning electron beam parameters, providing a clearer path to validating simulations and scaling laws than laser-laser cascades.
• Achieving the necessary extreme focusing (≈14 μm^2) and maintaining high beam densities represent key technical challenges, requiring dedicated facilities and design (β-function, emittance, jitter considerations).
• The work emphasizes that such a facility would uniquely position the U.S. at the forefront of high-intensity laser frontier research and enable exploration of strong-field QED and HEDP in regimes relevant to astrophysics and future colliders.