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  • Open Access

Dual-pulse micronozzle acceleration of sub-GeV-class protons

D. Pan and M. Murakami*

  • *Contact author: murakami.masakatsu.ile@osaka-u.ac.jp
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Phys. Rev. Accel. Beams 29, 073601 – Published 13 July, 2026

DOI: https://doi.org/10.1103/kjnr-rfy9

Abstract

We propose a dual-pulse micronozzle acceleration scheme that enables phase-locked acceleration of laser-driven protons, mitigating the conventional trade-off between maximum energy and laser-to-proton conversion efficiency. By introducing a delay-tuned synchronization window, a compact proton front generated by a shaping prepulse is injected into, and remains copropagating with, a quasistatic axial electric field driven by a delayed main pulse in a micronozzle cavity. This phase locking maintains the relative phase between the proton bunch and the accelerating field over an extended interaction length and duration, thereby suppressing thermal debunching and prolonging the effective acceleration stage. At main-pulse intensities of the order of 1021  W/cm2, sub-GeV-class proton cutoffs are achieved with a total laser-to-proton conversion efficiency of ∼20%. Notably, the efficiency of the application-relevant high-energy component exceeds ∼13% for protons with energies Ep>100  MeV, indicating preferential energy loading into a compact, directed proton population rather than quasithermal sheath expansion. Comparative simulations with an unconfined dual-pulse hydrogen-rod target demonstrate that this performance gain arises from the combined effects of temporal synchronization and geometric confinement, which sustain a long-lived axial accelerating channel advected downstream with the proton front. An analytical model for the synchronization condition is developed and validated against the simulation data. Three-dimensional particle-in-cell simulations support that the phase-locking mechanism and the associated spectral hardening are preserved in 3D slit-nozzle geometries, with the confined target yielding cutoff energies ∼60% higher than an unconfined hydrogen rod under identical laser conditions. These results identify phase-locked acceleration in a confined laser-driven structure as a practical design principle for compact, high-yield sub-GeV-class proton drivers, with direct relevance to secondary-particle sources such as pion and muon production, accelerator-driven systems, and laser-based neutron sources.

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Phys. Rev. Accel. Beams 29, 073601– Published 13 July, 2026
  • Received 14 January 2026
  • Accepted 12 June 2026
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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.

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