Comment on 'Simulation of ultra-relativistic electrons and positrons channeling in crystals with MBN Explorer'

TL;DR

This paper defends the snapshot model in crystal channeling simulations against criticisms, demonstrating its validity and agreement with experimental data, and clarifies misconceptions about scattering and dechanneling length predictions.

Contribution

The paper provides a detailed rebuttal to criticisms of the snapshot model, confirming its accuracy and effectiveness in simulating ultrarelativistic particle channeling in crystals.

Findings

The snapshot model's mean scattering angle aligns with alternative models.

Incoherent scattering by electrons is negligible for light projectiles.

The snapshot model accurately predicts dechanneling lengths consistent with experiments.

Abstract

The snapshot model of crystal atoms was implemented in the Monte Carlo code ChaS (Channeling Simulator) and is being successfully used for simulation of ultrarelativistic particle channeling. The model was criticized by Sushko et al. (J. Comp. Phys. 252 (2013) 404-418) who claim that it overestimates the mean scattering angle in a single projectile-atom collision. As a matter of fact, no evidence that would support this claim can be found in the mentioned publication. Moreover, the snapshot model and the model suggested by Sushko et al. yield essentially the same value of the mean scattering angle. Contrary to the claim of Sushko et al., the target electrons can be considered as fixed-position scatterer, corrections due to their finite mass and nonzero initial velocity have a negligible impact on the channeling of light projectiles (electrons and positrons). In contrast to the snapshot model, the model preferred by Sushko et al. does not take into account incoherent scattering of the projectile by crystal electrons. This explains why the two models predict different values of the dechanneling length. The claim that the snapshot model underestimates the dechanneling length is unfounded. In actual fact, this model is in good agreement with experimental data.