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

TL;DR

This study demonstrates laboratory observation of collective beam-plasma instabilities in a relativistic electron-positron pair plasma, providing experimental validation for models relevant to astrophysical phenomena.

Contribution

First laboratory measurement of collective behavior in a relativistic pair plasma, validating particle-in-cell simulations and astrophysical models.

Findings

Magnetic-field amplification observed due to beam-plasma instability

Measured magnetic fields agree with simulation predictions

Demonstrates feasibility of laboratory astrophysics experiments

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.