Plasma scale length and quantum electrodynamics effects on particle acceleration at extreme laser plasmas

Abstract

In this work, simulations of multipetawatt lasers at irradiances ${\sim }10^{23} \ \mathrm {W}\ \mathrm {cm}^{-2}$ , striking solid targets and implementing two-dimensional particle-in-cell code was used to study particle acceleration. Preformed plasma at the front surface of a solid target increases both the efficiency of particle acceleration and the reached maximum energy by the accelerated charged particles via nonlinear plasma processes. Here, we have investigated the preformed plasma scale length effects on particle acceleration in the presence and absence of nonlinear quantum electrodynamic (QED) effects, including quantum radiation reaction and multiphoton Breit–Wheeler pair production, which become important at irradiances ${\sim } 10^{23}\ \mathrm {W}\ \mathrm {cm}^{-2}$ . Our results show that QED effects help particles gain higher energies with the presence of preformed plasma. In the results for all cases, preplasma leads to more efficient laser absorption and produces more energetic charged particles, as expected. In the case where QED is included, however, physical mechanisms changed and generated secondary particles ( $\gamma$ -rays and positrons) reversing this trend. That is, the hot electrons cool down due to QED effects, while ions gain more energy due to different acceleration methods. It is found that more energetic $\gamma$ -rays and positrons are created with increasing scale length due to high laser conversion efficiency ( ${\sim }$ 24 % for $\gamma$ -rays and $\sim$ 4 % for positrons at $L = 7\ \mathrm {\mu }\textrm {m}$ scale length), which affects the ion and electron acceleration mechanisms. It is also observed that the QED effect reduces the collimation of angular distribution of accelerated ions because the dominant ion acceleration mechanism is changing when QED is involved in the process.

Study of particle acceleration by Laguerre–Gaussian ultra intense laser plasma interactions

“…Another popular topic is proton acceleration in NCD plasmas. It has been shown that protons can be accelerated efficiently with an optimum focusing point and plasma density [32] and that quantum electrodynamics (QED) has a strong effect on particle acceleration due to plasma opacity [33]. A recent study of proton acceleration in NCD plasmas using an LG and a fundamental Gaussian laser pulse showed that the proton beam is accelerated by the charge separation field, and reaches energies of 100 MeV, which is around 3.5 times higher than that of a normal Gaussian laser pulse.…”

Light-to-Plasma Momentum Transfer

“…Light pressure can accelerate electrons in laser-plasmas to high energies that are useful for many applications [7][8][9][10][11]. Electrons accelerated by light pressure may be used as a heating source for fusion ignition when the electrons or co-moving ions are injected into laser-compressed deuterium/tritium [12][13][14]. The interaction of light with electrons in the conduction band of solids can be modeled as light-plasma interactions.…”