Accurate electron beam phase-space theory for ionization-injection schemes driven by laser pulses
Authors: Tomassini Paolo; Massimo Francesco; Labate Luca; Gizzi Leonida A.
Autors Affiliation: INO CNR, Intense Laser Irradiat Lab, Via Moruzzi 1, Pisa, Italy; ELI NP, Magurele, Ilfov, Romania; EA, USR 3441, Maison Simulat, Gif Sur Yvette, France; Ist Nazl Fis Nucl, Sect Pisa, Pisa, Italy.
Abstract: After the introduction of the ionization-injection scheme in laser wake field acceleration and of related high-quality electron beam generation methods, such as two-color and resonant multi-pulse ionization injection (ReMPI), the theory of thermal emittance has been used to predict the beam normalized emittance obtainable with those schemes. We recast and extend such a theory, including both higher order terms in the polynomial laser field expansion and non-polynomial corrections due to the onset of saturation effects on a single cycle. Also, a very accurate model for predicting the cycle-averaged distribution of the extracted electrons, including saturation and multi-process events, is proposed and tested. We show that our theory is very accurate for the selected processes of Kr8+-> 10+ and Ar8+-> 10+ resulting in a maximum error below 1%, even in a deep-saturation regime. The accurate prediction of the beam phase-space can be implemented, for example, in laser-envelope or hybrid particle-in-cell (PIC)/fluid codes, to correctly mimic the cycle-averaged momentum distribution without the need for resolving the intra-cycle dynamics. We introduce further spatial averaging, obtaining expressions for the whole-beam emittance fitting with simulations in a saturated regime, too. Finally, a PIC simulation for a laser wakefield acceleration injector in the ReMPI configuration is discussed.
Journal/Review: HIGH POWER LASER SCIENCE AND ENGINEERING
Volume: 10 Pages from: e15-1 to: e15-16
More Information: The authors acknowledge the financial contribution from the CNR funded Italian Research Network ELI-Italy (D.M. No. 631 08.08.2016) and from the EU Horizon 2020 Research and Innovation Program under Grant Agreement No. 653782 EuPRAXIA. The authors also wish to thank the engineers of the LLR HPC clusters and of the cluster Ruche in the Moulon Mesocentre for computer resources and help.KeyWords: field theory ionization; high-quality electron beams; ionization injection; laser wakefield acceleration; laser-plasma acceleration; resonant multi-pulse ionization injection; tunnel ionization; two-color ionization; ultraintense laser pulsesDOI: 10.1017/hpl.2021.56