# Thomson backscattering in combined uniform magnetic and envelope modulating circularly-polarized laser fields

## TL;DR

This paper investigates Thomson backscattering in combined magnetic and laser fields with envelope modulation, revealing fundamental laws that enable control and enhancement of radiation spectra for advanced technological applications.

## Contribution

It analytically uncovers scale invariance laws governing radiation spectra in complex laser-magnetic field interactions, enabling precise tuning and energy enhancement of emitted radiation.

## Key findings

- Radiation energy scales with the sixth power of the motion constant.
- Spectral shape remains unchanged when frequencies are scaled simultaneously.
- Maximum radiation harmonic can be tuned without altering amplitude.

## Abstract

The Thomson backscattering spectra in combined uniform magnetic and cosine-envelope circularly-polarized laser fields are studied in detail. With an introduction of the envelope modulation, the radiation spectra exhibit high complexity attributed to the strong nonlinear interactions. On the other hand, four fundamental laws related to the scale invariance of the radiation spectra are analytically revealed and numerically validated. They are the laws for the radiation energy as the $6$th power of the motion constant exactly, also as the approximate negative $6$th power with respect to the initial axial momentum and laser intensity in a certain of conditions, respectively, and finally an important self-similar law, i.e., when the circular laser frequency, the envelope modulation frequency, and the modified cyclotron frequency are simultaneously increased by a factor, the radiation energy will be increased by the second power of that factor without changing the shape of the spectrum. With the application of these laws, especially the last one, a much higher radiation energy can be obtained and the harmonic at which the maximum radiation occurs can be precisely tuned without changing its amplitude. These findings provide a possible way to advance radiation technology in many fields such as medicine, communications, astrophysics, and security.