Laser-wakefield accelerators for high-resolution X-ray imaging of complex microstructures

Abstract

Laser-wakefield accelerators (LWFAs) are high acceleration-gradient plasma-based particle accelerators capable of producing ultra-relativistic electron beams. Within the strong focusing fields of the wakefield, accelerated electrons undergo betatron oscillations, emitting a bright pulse of X-rays with a micrometer-scale source size that may be used for imaging applications. Non-destructive X-ray phase contrast imaging and tomography of heterogeneous materials can provide insight into their processing, structure, and performance. To demonstrate the imaging capability of X-rays from an LWFA we have examined an irregular eutectic in the aluminum-silicon (Al-Si) system. The lamellar spacing of the Al-Si eutectic microstructure is on the order of a few micrometers, thus requiring high spatial resolution. We present comparisons between the sharpness and spatial resolution in phase contrast images of this eutectic alloy obtained v ia X-ray phase contrast imaging at the Swiss Light Source (SLS) synchrotron and X-ray projection microscopy via an LWFA source. An upper bound on the resolving power of 2.7 ± 0.3 μ m of the LWFA source in this experiment was measured. These results indicate that betatron X-rays from laser wakefield acceleration can provide an alternative to conventional synchrotron sources for high resolution imaging of eutectics and, more broadly, complex microstructures.

Exploring phase contrast imaging with a laser-based Kα x-ray source up to relativistic laser intensity

“…This compromise can be balanced by adjusting only one parameter, the laser intensity on target. At low laser intensity, the best x-ray source spatial coherence and the lowest L s / ⊥ L ratios are achieved which offer the highest edge contrast signal enhancement, suitable for applications such as the control of material fabrication processes 22 . On the opposite, at very high laser intensity, faster imaging acquisition can be done thanks to high available x-ray photon flux with a L s / ⊥ L ratio still below unity.…”

“…Between these two alternatives, ultrafast x-ray laser plasma sources appear as good candidates for PCI at a laboratory scale. Among them, x-ray sources provided by laser plasma acceleration such as Betatron [17][18][19][20][21][22][23] and inverse Compton scattering [24][25][26][27] offer potential alternatives thanks to their high brightness and very small source size, making possible the acquisition of an x-ray image in single shot mode. However, they are until now based on laser driven systems with high peak power (>30 TW) 23 difficult to scale up to high repetition rate.…”

Single-Shot Multi-keV X-Ray Absorption Spectroscopy Using an Ultrashort Laser-Wakefield Accelerator Source

“…As the divergence of the x-ray source provides the range of different incident angles upon the crystal spectrometer and the spectral spread of the detector is achieved by satisfying the Bragg condition at different angles, a more divergent beam leads to a wider accessible spectral range. For the high-flux shots the direct filter pack measured a mean critical energy of E crit ¼ 9.9 AE 1.5 keV, and the entire beam contained ð7.2 AE 2.8Þ × 10 5 photons=eV at 5 keV, comparable to the highest x-ray flux observed in previous LWFA measurements [30,38]. The shot-to-shot standard deviation here is combined with the systematic errors in quadrature.…”

“…The strong electric field inside the cavity can subsequently accelerate electrons to GeV energies in just a few centimeters [27,28]. Our LWFA operated using a two-stage gas cell [29,30]. The first stage (3 mm long) was filled with a 98%He þ 2% N 2 gas mix, and the second stage (19.6 mm long) was filled with He.…”

Перспективные Технологии Для Прикладных Резонансных Ускорителей Заряженных Частиц И Примеры Их Использования (Обзор)

“…терного ускорения, отмеченныx в отчете Министерства Энергетики США по стратегии развития перспективных ускорителей [43]: лазерное кильватерное ускорение [44], плазменное кильватерное ускорение [45] и структурное кильватерное ускорение [46]. В таких ускорителях можно потенциально получить огромные значения градиентов поля (до 1 TeV/m [47]), в том числе и для ионов [48].…”