High-resolution phase-contrast imaging of biological specimens using a stable betatron X-ray source in the multiple-exposure mode

Abstract

Phase-contrast imaging using X-ray sources with high spatial coherence is an emerging tool in biology and material science. Much of this research is being done using large synchrotron facilities or relatively low-flux microfocus X-ray tubes. An alternative high-flux, ultra-short and high-spatial-coherence table-top X-ray source based on betatron motions of electrons in laser wakefield accelerators has the promise to produce high quality images. In previous phase-contrast imaging studies with betatron sources, single-exposure images with a spatial resolution of 6–70 μ m were reported by using large-scale laser systems (60–200 TW). Furthermore, images obtained with multiple exposures tended to have a reduced contrast and resolution due to the shot-to-shot fluctuations. In this article, we demonstrate that a highly stable multiple-exposure betatron source, with an effective average source size of 5 μ m, photon number and pointing jitters of <5% and spectral fluctuation of <10%, can be obtained by utilizing ionization injection in pure nitrogen plasma using a 30–40 TW laser. Using this source, high quality phase-contrast images of biological specimens with a 5- μ m resolution are obtained for the first time. This work shows a way for the application of high resolution phase-contrast imaging with stable betatron sources using modest power, high repetition-rate lasers.

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

“…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.…”

Laser-driven x-ray and proton micro-source and application to simultaneous single-shot bi-modal radiographic imaging

“…Betatron radiation is per default a broadband source with small source sizes (~μm), and small divergence angles (~mrad). This usually requires multi-shot stitching of images in order to capture objects of a meaningful size (e.g., few mm) 49 or large distances. Thomson scattering using laser wakefield accelerators can produce quasimonochromatic photon beams, with a small source size at potentially higher photon energies.…”

Phase-contrast imaging with laser-plasma-accelerator betatron sources

“…This effect has been commented on in recent manuscripts, such as Ref. [ 10 ], but no quantative description has been provided to this point. As a simplified model, we approximate this effect by considering the betatron source to be M discrete emission point sources lined up in a row, each with distance R 1,M from the sample, and each with photon flux distribution…”

“…Betatron motion of electrons inside the laser-plasma accelerator, 1 resulting in the emission of betatron X-rays, has been extensively reported on in high-profile papers over recent years. [2][3][4][5][6][7][8][9][10][11] The betatron spectrum has an intrinsically broad bandwidth, extending up to the critical photon energy E c , before dropping off exponentially. E c scales 3 with the electron Lorentz factor γ, the plasma density n 0 , and the transverse beam size r b , as E c [eV ] = 5×10 −21 γ 2 n 0 [cm −3 ]r b [µm].…”