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Laboratory observation of collective beam-plasma instabilities in a relativistic pair jet

J W D Halliday, C D Arrowsmith, A M Goillot, P J Bilbao, P Simon, V Stergiou, S Zhang, P Alexaki, M Bochmann, A F A Bott, S Burger, H Chen, F D Cruz, T Davenne, A Dyson, A Ebn Rahmoun, I Efthymiopoulos, D H Froula, J T Gudmundsson, D Haberberger, T Hodge, S Iaquinta, E E Los, G Marshall, F Miniati, S Parker, B Reville, P Rousiadou, S Sarkar, A A Schekochihin, K G Schlesinger, L O Silva, T Silva, R Simpson, E Soria, R M G M Trines, T Vieu, N Charitonidis, R Bingham, G Gregori

Abstract

We report on a measurement of collective behavior in a relativistic electron-positron pair plasma produced in the laboratory. Using the Fireball platform at CERN's HiRadMat facility, 440 GeV protons were used to generate an ultra-relativistic, charge-neutral electron-positron pair beam that propagated through an ambient RF discharge plasma. Magnetic-field amplification due to a beam-plasma instability was diagnosed using a high-sensitivity Faraday-rotation probe, supported by detailed characterization of the diagnostic impulse response. The measured path-integrated magnetic field agrees quantitatively with predictions from particle-in-cell simulations. The results provide a critical benchmark for models of relativistic beam-plasma interactions in astrophysical contexts such as blazar jets and pulsar-wind nebulae.

Laboratory observation of collective beam-plasma instabilities in a relativistic pair jet

Abstract

We report on a measurement of collective behavior in a relativistic electron-positron pair plasma produced in the laboratory. Using the Fireball platform at CERN's HiRadMat facility, 440 GeV protons were used to generate an ultra-relativistic, charge-neutral electron-positron pair beam that propagated through an ambient RF discharge plasma. Magnetic-field amplification due to a beam-plasma instability was diagnosed using a high-sensitivity Faraday-rotation probe, supported by detailed characterization of the diagnostic impulse response. The measured path-integrated magnetic field agrees quantitatively with predictions from particle-in-cell simulations. The results provide a critical benchmark for models of relativistic beam-plasma interactions in astrophysical contexts such as blazar jets and pulsar-wind nebulae.
Paper Structure (1 section, 5 equations, 4 figures)

This paper contains 1 section, 5 equations, 4 figures.

Table of Contents

  1. Acknowledgments

Figures (4)

  • Figure 1: (a) Diagram of the Fireball experimental setup, showing the pair-generation target, inductive-mode RF plasma discharge, and Faraday-rotation diagnostic probe. The system was driven by the 440GeV proton beam from the Super Proton Synchrotron at HiRadMat (CERN), delivering a peak intensity of $3\times 10^{11}$ protons per pulse. The beam had a Gaussian transverse profile with 1mm standard deviation and a Gaussian temporal profile of approximately 250ps duration. (b) Spectra / average divergence for the residual primaries and dominant secondary species produced by the target. These data are from FLUKA (Monte Carlo) simulations and were validated against the experimental measurements reported in Ref. Arrowsmith2024. (c) Profile of electron density in the RF discharge (ambient) plasma, based on Langmuir-probe measurements reported in Ref. Arrowsmith2023.
  • Figure 2: (a) Diagram of the Faraday-rotation diagnostic. (b) Measured Faraday signal in an offline sensitivity characterization (c) Impulse response function (IRF) of the Thorlabs PDB435A photodioides used in the Faraday setup, normalized so that $\int\tau(t) dt = 1$.
  • Figure 3: Particle-in-cell simulation results. (a) Magnetic field map at the Faraday probe's axial position, with the size and position of the terbium gallium garnet and the alumina re-entrant tube shown to scale. (b) Path-integrated magnetic field at the probe's position calculated from the simulation, fitted to a Gaussian profile.
  • Figure 4: Measured Faraday-rotation data for extractions with the plasma on (bottom panel) and with the plasma off (top panel) are shown. The plasma off data are compared to results from FLUKA Monte Carlo simulations, whereas the plasma-on data are compared to results from OSIRIS simulations. For the plasma on case, the best-fit Gaussian, convolved with the impulse response (Fig. \ref{['fig:faraday']}c), is also shown. For the experimental data, the shaded band corresponds to the standard deviation across three consecutive repeats.