131 research outputs found
Quick X-ray microtomography using a laser-driven betatron source
Laser-driven X-ray sources are an emerging alternative to conventional X-ray
tubes and synchrotron sources. We present results on microtomographic X-ray
imaging of a cancellous human bone sample using synchrotron-like betatron
radiation. The source is driven by a 100-TW-class titanium-sapphire laser
system and delivers over X-ray photons per second. Compared to earlier
studies, the acquisition time for an entire tomographic dataset has been
reduced by more than an order of magnitude. Additionally, the reconstruction
quality benefits from the use of statistical iterative reconstruction
techniques. Depending on the desired resolution, tomographies are thereby
acquired within minutes, which is an important milestone towards real-life
applications of laser-plasma X-ray sources
Hyperspectral compressive wavefront sensing
Presented is a novel way to combine snapshot compressive imaging and lateral shearing interferometry in order to capture the spatio-spectral phase of an ultrashort laser pulse in a single shot. A deep unrolling algorithm is utilized for snapshot compressive imaging reconstruction due to its parameter efficiency and superior speed relative to other methods, potentially allowing for online reconstruction. The algorithm’s regularization term is represented using a neural network with 3D convolutional layers to exploit the spatio-spectral correlations that exist in laser wavefronts. Compressed sensing is not typically applied to modulated signals, but we demonstrate its success here. Furthermore, we train a neural network to predict the wavefronts from a lateral shearing interferogram in terms of Zernike polynomials, which again increases the speed of our technique without sacrificing fidelity. This method is supported with simulation-based results. While applied to the example of lateral shearing interferometry, the methods presented here are generally applicable to a wide range of signals, including Shack–Hartmann-type sensors. The results may be of interest beyond the context of laser wavefront characterization, including within quantitative phase imaging
Séparations mécaniques fluide/solide
Licencedécantation gravitaire ; centrifugations (décantation centrifuge et cyclones) ; filtrations (sur support et en profondeur
Observation of laser power amplification in a self-injecting laser wakefield accelerator
We report on the depletion and power amplification of the driving laser pulse in a strongly-driven laser wakefield accelerator. Simultaneous measurement of the transmitted pulse energy and temporal shape indicate an increase in peak power from TW to a maximum of TW after 13 mm of propagation in plasma density of cm. The power amplification is correlated with the injection and acceleration of electrons in the non-linear wakefield. This process is modeled by including localized redshifting and subsequent group delay dispersion at the laser pulse front
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