Recent Progress in the Theory of the Crystalline Undulator

TL;DR

This paper reviews recent advances in the theory of crystalline undulators, highlighting new simulation tools, experimental conditions for observing undulator effects at lower energies, and the superior performance of positron-based devices.

Contribution

It introduces a new Monte Carlo simulation code and demonstrates the potential of crystalline undulators with shorter bending periods and amplitudes, surpassing previous designs.

Findings

Energy below 1 GeV suffices to observe undulator effects.

Shorter bending periods enhance undulator radiation.

Positron beams produce higher intensity and lower background.

Abstract

If an ultrarelativistic charged particle channels inside a single crystal with periodically bent crystallographic planes, it emits hard electromagnetic radiation of the undulator type. Due to similarity of its physical principles to the ordinary (magnetic) undulator, such a device is termed as the crystalline undulator. Recent development of a new Monte Carlo code ChaS made possible a detailed simulation of particle channeling and radiation emission in periodically bent crystals. According to recent findings, energy of the electron beam below 1 GeV is sufficient to observe the undulator effect in a periodically bent crystal. Even more exciting results were obtained for a crystalline undulator whose bending period is shorter than the period of the channeling oscillations and the bending amplitude is smaller than the width of the planar channel. Such a crystalline undulator is far superior to what was proposed previously. It allows for a large effective number of undulator periods. Therefore, it is predicted to emit intense undulator radiation in the forward direction. A narrow undulator peak is seen for both positron and electron beams. Using positrons is, however, more desirable because in this case the intensity of the undulator radiation is higher while the background is lower.