All-optical nonlinear Compton scattering achieved with multi-petawatt laser producing ultra-bright gamma rays
by Riko Seibo
Tokyo, Japan (SPX) Nov 26, 2024

In a major advancement for strong field physics, researchers from the Institute for Basic Science's Center for Relativistic Laser Science (CoReLS) in Korea have successfully demonstrated nonlinear Compton scattering (NCS) using a groundbreaking all-optical setup. This achievement, recently published in 'Nature Photonics', uses the 4-petawatt laser at Gwangju Institute of Science and Technology (GIST) to explore high-energy electron-photon interactions, bypassing the need for traditional large-scale particle accelerators.

The experiment involved a laser-only approach to electron-photon collisions, employing a single multi-petawatt laser for both particle acceleration and collision. This method allowed researchers to approach phenomena near the "Schwinger limit," the theoretical laser intensity threshold where space-time itself generates matter-antimatter pairs.

Innovative Approach to Nonlinear Quantum Electrodynamics
To achieve NCS, electrons absorb multiple laser photons and emit a single high-energy gamma-ray photon. While current lasers remain far below the Schwinger limit of 2x10? W/cm, the team used an ultra-relativistic electron beam to boost the perceived laser intensity via Einstein's relativity. In the electron's reference frame, the laser intensity appeared close to 50% of the Schwinger limit, enabling nonlinear quantum electrodynamics (QED) effects.

Using the CoReLS laser, the researchers split the beam into two parts. One beam was focused into a gas-filled cell to create a plasma wave through laser wakefield acceleration (LWFA), accelerating electrons to nearly the speed of light. The second beam was directed at these electrons as a tightly focused pulse lasting just 20 femtoseconds, achieving the precise timing and spatial alignment required for effective collisions.

Producing Ultra-Bright Gamma Rays
In these collisions, electrons absorbed energy equivalent to 400 laser photons and emitted gamma-ray photons with energies ranging from tens to hundreds of megaelectronvolts. Careful measurements, verified by Monte Carlo simulations and particle-in-cell modeling, confirmed the occurrence of nonlinear Compton scattering. The resulting gamma-ray beam was 1,000 times brighter than previous laboratory achievements at this energy scale.

Applications and Implications
This success opens new pathways for investigating nuclear processes and understanding antimatter production mechanisms, such as the Breit-Wheeler process for electron-positron pair generation. These findings also enhance the potential for exploring photon-photon collisions in unprecedented detail.

This experiment marks a significant leap in our understanding of strong field QED phenomena and demonstrates the remarkable capabilities of multi-petawatt lasers in mimicking astrophysical conditions.

Research Report:All-optical nonlinear Compton scattering performed with a multi-petawatt laser

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