An accurate and efficient laser-envelope solver for the modeling of laser-plasma accelerators

Abstract

Detailed and reliable numerical modeling of laser-plasma accelerators, where a short and intense laser pulse interacts with an underdense plasma over distances of up to a meter, is a formidably challenging task. This is due to the great disparity among the length scales involved in the modeling, ranging from the micron scale of the laser wavelength to the meter scale of the total laser-plasma interaction length. The use of the time-averaged ponderomotive force approximation, where the laser pulse is described by means of its envelope, enables efficient modeling of laser-plasma accelerators by removing the need to model the details of electron motion at the laser wavelength scale. Furthermore, it allows simulations in cylindrical geometry which captures relevant 3D physics at 2D computational cost. A key element of any code based on the time-averaged ponderomotive force approximation is the laser envelope solver. In this paper we present the accurate and efficient envelope solver used in the code INF&RNO (INtegrated Fluid & paRticle simulatioN cOde). The features of the INF&RNO laser solver enable an accurate description of the laser pulse evolution deep into depletion even at a reasonably low resolution, resulting in significant computational speed-ups.

Emittance preservation in plasma-based accelerators with ion motion

“…The dashed black line is the theoretical result Eq. (19). The theoretical result is in good agreement with modeling for n b;0 =n 0 ≲ 2000 (corresponding to Γ ≲ 1).…”

“…Red dots are the simulation results, the black dashed line is the theoretical prediction Eq. (19). All the other bunch and plasma parameters are the same as in Fig.…”

“…We provide, for any arbitrary bunch shape, analytic expressions for the transverse wake in the bunch region, and we compute the final (i.e., after phasespace mixing) bunch emittance. Analytical results, valid in the nonrelativistic ion motion regime where the induced ion density perturbation, δn i ¼ n i − n i;0 (n i;0 ¼ n 0 =Z i being the unperturbed ion density and n i the ion density including ion motion effects), satisfies δn i =n i;0 ≲ 1, are compared to fully nonlinear and self-consistent particle-in-cell (PIC) simulations performed with the code INF&RNO [18,19]. Finally, we derived a class of initial beam distributions that are exact equilibrium solutions, enabling ion motion without emittance growth.…”

Comparative study of active plasma lenses in high-quality electron accelerator transport lines

“…17, the theoretical degradation is compared with modeling results obtained with the 2D-cylindrical particle-in-cell (PIC) code INF&RNO (using the quasi-static modality). 45,46 The following parameters, relevant to the LPA FEL application, 15 were used: L APL ¼ 2.9 cm, R APL ¼ 500 lm, h 0 ¼ 1 mrad, 250 MeV energy, n0 ¼ 0.49 lm, L b ¼ 2 lm, I b ¼ 4.5 kA (30 pC), I APL ¼ 750 A, and L drift ¼ 9.3 cm (thus r r ¼ 93 lm and beam density n b0 ¼ 1.7 Â 10 15 cm -3 ). One can observe in Fig.…”

Petawatt Laser Guiding and Electron Beam Acceleration to 8 GeV in a Laser-Heated Capillary Discharge Waveguide

“…This effect is exploited here by using laser pulses of length 8 ns that undergo considerable self-guiding during the pulse rise-time. MHD simulations performed using the multi-dimensional code MARPLE (Magnetically Accelerated Radiative PLasma Explorer) [23], with additional modules from inf&rno [24,25] to calculate the heater laser pulse propagation, showed that although the front of the heater pulse was mismatched to the plasma channel, later temporal slices of the pulse could be propagated with less than 10 % change in spot size.…”