Theoretical study of laser-enhanced nuclear fusion reactions

(Press-News.org) Intense Laser and Nuclear Fusion
In a collaborative study, Assistant Professor Jintao Qi (Shenzhen Technology University), Professor Zhaoyan Zhou (National University of Defense Technology), and Professor Xu Wang (Graduate School of China Academy of Engineering Physics) investigated the theoretical processes of nuclear fusion in the presence of intense laser fields. The study addresses a central challenge in controlled fusion research: overcoming the strong Coulomb repulsion between positively charged nuclei, which conventionally necessitates heating fusion fuel to temperatures exceeding tens of millions of kelvin.

The analysis demonstrates that external laser fields can modify the relative collision energy of nuclei, thereby increasing the probability of quantum tunneling through the Coulomb barrier. Within this framework, laser fields serve as an assistive mechanism to enhance fusion reactions, complementing thermal effects rather than replacing them.

Unexpected Efficiency of Low-Frequency Lasers
The study systematically contrasts the effects of high-frequency lasers, such as X-ray free-electron lasers, with those of low-frequency lasers, including near-infrared solid-state systems. Contrary to conventional expectations, the results indicate that low-frequency lasers are more effective at enhancing fusion efficiency under comparable conditions.

While a single X-ray photon carries significantly higher energy than an optical photon, the theoretical analysis reveals that low-frequency laser fields facilitate the absorption and emission of a vast number of photons during a nuclear collision. This multi-photon interaction induces a broadening of the effective collision energy distribution, which can substantially increase tunneling probabilities.

Quantitative Enhancement of Fusion Probability
Using the Deuterium-Tritium fusion reaction as a benchmark, the study presents striking numerical results. For a collision energy of 1 keV—where fusion probability is typically very low—the application of a low-frequency laser (1.55 eV) with an intensity of 1020 W/cm² can enhance the fusion probability by three orders of magnitude. Increasing the intensity to 5×1021 W/cm² boosts the fusion efficiency by nine orders of magnitude.

This enhancement effectively bridges the gap between low-temperature and high-temperature fusion conditions. As the study highlights, the effective cross-section at a low energy of 1 keV with laser assistance becomes comparable to the cross-section at 10 keV without lasers.

Implications for Fusion Research
Although the current work is theoretical, it establishes a unified framework for analyzing laser-assisted fusion across different laser frequencies and intensities. The findings suggest that intense laser fields may help alleviate the stringent temperature requirements typically associated with controlled fusion experiments.

By modifying the collision energy distribution prior to tunneling, intense laser fields offer a viable mechanism to enhance fusion reaction rates under lower-energy conditions.

Future Directions in Laser–Nuclear Physics
The current study focuses on an idealized two-nucleus system. Future work will extend the theory to more realistic plasma environments, incorporating collective effects, laser-plasma interactions, and energy dissipation processes. These developments will be essential for assessing the feasibility of laser-assisted fusion in experimental settings.

This research contributes to the broader field of laser nuclear physics and provides theoretical guidance for future studies utilizing existing and next-generation high-intensity laser facilities.

The complete study is via by DOI: https://doi.org/10.1007/s41365-025-01879-x

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