Accurate electron beam phase-space theory for ionization-injection schemes driven by laser pulses. (7th December 2022)

• Record Type: Journal Article
• Authors: Tomassini, Paolo; Massimo, Francesco; Labate, Luca; Gizzi, Leonida A.
• Is Part Of: High power laser science and engineering. Volume 10(2022)
• Publication Date: 2022-12-07
• Subjects: 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 pulses; High power lasers -- Periodicals; 621.366
• DOI: 10.1017/hpl.2021.56
• Languages: English
• ISSNs: 2095-4719

Abstract

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 ${\mathrm{Kr}}^{8^{+}\to {10}^{+}}$ and ${\mathrm{Ar}}^{8^{+}\to {10}^{+}}$, 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.