Generation of neutral and high-density electron-positron pair plasmas in the laboratory.

Gianluca Sarri ,K Krushelnick,S Kar,G Grittani,L O Silva,D Doria,W Schumaker,J M Cole,T Dzelzainis,A Di Piazza,S P D Mangles,L A Gizzi,S Kuschel,M Vargas,Z Najmudin,Nitin Shukla ,D R Symes ,Jorge Vieira ,Christoph H Keitel ,Kristjan Põder ,Brian Reville ,Alexander Thomas ,Matthew Zepf

doi:10.1038/ncomms7747

Abstract

Electron–positron pair plasmas represent a unique state of matter, whereby there exists an intrinsic and complete symmetry between negatively charged (matter) and positively charged (antimatter) particles. These plasmas play a fundamental role in the dynamics of ultra-massive astrophysical objects and are believed to be associated with the emission of ultra-bright gamma-ray bursts. Despite extensive theoretical modelling, our knowledge of this state of matter is still speculative, owing to the extreme difficulty in recreating neutral matter–antimatter plasmas in the laboratory. Here we show that, by using a compact laser-driven setup, ion-free electron–positron plasmas with unique characteristics can be produced. Their charge neutrality (same amount of matter and antimatter), high-density and small divergence finally open up the possibility of studying electron–positron plasmas in controlled laboratory experiments.

Highlights

Electron–positron pair plasmas represent a unique state of matter, whereby there exists an intrinsic and complete symmetry between negatively charged and positively charged particles
These and other questions could be addressed by ad hoc laboratory experiments; the extreme difficulty in generating e À /e þ populations that are dense enough to permit collective behaviour[11,12] is still preventing laboratory studies and the properties of this peculiar state of matter are only inferred from the indirect interpretation of its radiative signatures and from matching numerical models
These charaÀcteristics, together with tÁhe charge neutrality, small divergence yeÀ =eþ % 10 À 20 mrad, and high average Lorentz factor open up the possibility of studying the dynamics of e À /e þ plasmas in a controlled laboratory environment

Summary

Introduction

Electron–positron pair plasmas represent a unique state of matter, whereby there exists an intrinsic and complete symmetry between negatively charged (matter) and positively charged (antimatter) particles. Despite the intrinsic interest of these results, the low percentage of positrons in the electron–positron beam (of the order, if not o10%) and the low-density reported (collision-less skin depth much greater than the beam size, forbidding plasmalike behaviour) prevent their application to the laboratory study of e À /e þ plasmas All these previous experimental attempts have not been able to generate e À /e þ beams that present charge neutrality and a plasma-like behaviour, both fundamental prerequisites for the laboratory study of this state of matter[14]. These charaÀcteristics, together with tÁhe charge neutrality, small divergence yeÀ =eþ % 10 À 20 mrad , and high average Lorentz factor (gAVE15 with a power-law spectral distribution, comparable to what observed in astrophysical jets22) open up the possibility of studying the dynamics of e À /e þ plasmas in a controlled laboratory environment

Methods

Results

Conclusion