Comment on `On quantum effects in spontaneous emission by a relativistic electron beam in an undulator' by G. Geloni, V. Kocharyan and E. Saldin (arXiv:1202.0691)

TL;DR

This paper defends a previous quantum model of spontaneous emission in relativistic electron beams, arguing that the criticism claiming the model's quantum regime prediction is unphysical is unfounded.

Contribution

It clarifies and defends the validity of a quantum regime model for electron momentum evolution in spontaneous emission, countering prior criticisms.

Findings

The criticism of the quantum regime model is unfounded.

The model accurately predicts discrete momentum group evolution.

The quantum description is physically consistent.

Abstract

In arXiv:1202.0691, Geloni et al. criticise our recent work describing the spontaneous emission by a relativistic, undulating electron beam. In particular they claim that our prediction of a quantum regime in which evolution of the electron momentum distribution occurs as a sequential population of discrete momentum groups rather than in terms of a drift-diffusion process is unphysical and artificial. We show that the criticism of our model contained in arXiv:1202.0691 is unfounded.