Demonstration of the synchrotron-type spectrum of laser-produced Betatron radiation

TL;DR

This paper precisely measures the spectrum of Betatron X-ray radiation from laser-plasma accelerators, confirming its synchrotron nature and opening new avenues for time-resolved X-ray applications.

Contribution

It provides the first high-resolution, single-shot spectral measurement of Betatron radiation, validating its synchrotron-type spectrum with theoretical agreement.

Findings

Spectra measured from 8 to 21 keV with high resolution

Confirmed synchrotron-type spectral shape of Betatron radiation

Critical energy determined as 5.6 keV with low uncertainty

Abstract

Betatron X-ray radiation in laser-plasma accelerators is produced when electrons are accelerated and wiggled in the laser-wakefield cavity. This femtosecond source, producing intense X-ray beams in the multi kiloelectronvolt range has been observed at different interaction regime using high power laser from 10 to 100 TW. However, none of the spectral measurement performed were at sufficient resolution, bandwidth and signal to noise ratio to precisely determine the shape of spectra with a single laser shot in order to avoid shot to shot fluctuations. In this letter, the Betatron radiation produced using a 80 TW laser is characterized by using a single photon counting method. We measure in single shot spectra from 8 to 21 keV with a resolution better than 350 eV. The results obtained are in excellent agreement with theoretical predictions and demonstrate the synchrotron type nature of this radiation mechanism. The critical energy is found to be Ec = 5.6 \pm 1 keV for our experimental conditions. In addition, the features of the source at this energy range open novel perspectives for applications in time-resolved X-ray science.