Comment on "Feasibility of an electron-based crystalline undulator"

TL;DR

This paper critically evaluates a proposed electron-based crystalline undulator, demonstrating its infeasibility under previous assumptions and proposing a feasible alternative with different parameters based on new simulations.

Contribution

It refutes prior claims about the feasibility of electron-based crystal undulators and introduces a new, more realistic design supported by initial simulations.

Findings

Previous scheme has K >> 1, destroying photon interference

Electron dechanneling length was overestimated, reducing feasible periods

A feasible electron-based crystal wiggler can operate with K=10 and N=2

Abstract

Tabrizi et al. [physics/0701342] discuss the feasibility of an electron-based crystal undulator (e-CU) by planar channeling of 50 GeV electrons through a periodically bent crystal. We show that their scheme is not feasible. First, their undulator parameter is K >> 1 always, which destroys photon interference. Second, they overestimate the electron dechanneling length in e-CU by an order of magnitude, which shortens the number N of e-CU periods from 5-15 (as they hope) to just 1-2. This kills their e-CU concept again. We made first simulation of electron channeling in undulated crystal and conclude that an electron-based crystal wiggler is feasible with wiggler strength K=10 and number of periods N=2.