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Limitations of emittance and source size measurement of laser-accelerated electron beams using the pepper-pot mask method

F. C. Salgado*, A. Kozan, D. Seipt, D. Hollatz, P. Hilz, M. C. Kaluza, A. Sävert, A. Seidel, D. Ullmann et al.

Y. Zhao and M. Zepf

  • *Contact author: felipe.salgado@uni-jena.de
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Phys. Rev. Accel. Beams 29, 022801 – Published 17 February, 2026

DOI: https://doi.org/10.1103/d4bl-67kt

Abstract

The pepper-pot method is a widely used technique, originally proposed for measuring the emittance of space-charge-dominated electron beams from radio-frequency photoinjectors. With recent advances in producing high-brightness electron beams via laser-wakefield acceleration (LWFA), the method has also been applied to evaluate emittance in this new regime. Here, the limitations of this method for measuring the emittance of LWFA electron beams are investigated, particularly in parameter regimes where the true beam emittance is overestimated. Conducting an experiment at the JETi200 laser system, we measured an upper bound for the geometric beam emittance of (26.2±7.3)  μm mrad using the pepper-pot method. This result is consistent with geant4 Monte Carlo simulations of the pepper-pot diagnostic, with an input beam–emittance parameter that matches both PIC simulations of the laser–plasma accelerator and an independent measurement using the transient optical grating method.

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Phys. Rev. Accel. Beams 29, 022801– Published 17 February, 2026
  • Received 1 November 2024
  • Revised 15 July 2025
  • Accepted 13 January 2026
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