We present the development and characterization of a high-stability, multi-material, multi-thickness tape-drive target for laser-driven acceleration at repetition rates of up to 100 Hz. The tape ...surface position was measured to be stable on the sub-micrometre scale, compatible with the high-numerical aperture focusing geometries required to achieve relativistic intensity interactions with the pulse energy available in current multi-Hz and near-future higher repetition-rate lasers (
$>$
kHz). Long-term drift was characterized at 100 Hz demonstrating suitability for operation over extended periods. The target was continuously operated at up to 5 Hz in a recent experiment for 70,000 shots without intervention by the experimental team, with the exception of tape replacement, producing the largest data-set of relativistically intense laser–solid foil measurements to date. This tape drive provides robust targetry for the generation and study of high-repetition-rate ion beams using next-generation high-power laser systems, also enabling wider applications of laser-driven proton sources.
The objective of our study was to assess the DiversiLab® automated repetitive sequence-based PCR (rep-PCR) system for typing C. albicans and C. glabrata isolates and to compare it with two proven and ...routinely used typing methods. A total of 39 isolates from 11 patients with candidaemia or tissue candidiasis (two to six isolates per patient) were analyzed with three typing methods: DiversiLab® rep-PCR, multilocus sequence typing and multilocus microsatellite typing. DiversiLab® rep-PCR results were consistent with those obtained using the two other typing methods for C. albicans, but not for C. glabrata. Thanks to its simplicity of use, rapidity, standardization and reproducibility, the DiversiLab® rep-PCR system is an interesting tool to investigate C. albicans infections.
Experimental and numerical analysis of the effect of stress–strain heterogeneities (due to elastic anisotropy, grain orientations and interactions) on martensitic transformation are investigated here ...for a Cu-Based SMA multicrystal. The shape and crystallographic orientation of each grain are measured successively by optical microscopy and Electron Back Scattered Diffraction (EBSD) technique. During a tensile loading at room temperature, the displacement field of the free surface is measured by Digital Image Correlation (DIC) with the software CORRELI-Q4 Roux, Hild, 2006; Besnard et al., 2006. The strain field is then derived numerically. A finite element model is designed. The shape of each grain is defined as a subdomain and meshed by three dimensional continuum elements. A behavior law, describing the thermomechanical response of a SMA single crystal, is adopted and implemented into the Abaqus
® finite element code. It is based on a micromechanical approach and takes into account the various possible active martensitic variants. The study shows that the experimental and numerical results are in good agreement. Moreover, the stress state in grains is disturbed by the neighboring grains and this disturbance has a strong influence on the martensite variant activation. Finally, the study shows that the martensitic transformation mainly occurs in localized bands involving the well crystallographic oriented grains with respect to the loading direction.
A machine learning model was created to predict the electron spectrum generated by a GeV-class laser wakefield accelerator. The model was constructed from variational convolutional neural networks, ...which mapped the results of secondary laser and plasma diagnostics to the generated electron spectrum. An ensemble of trained networks was used to predict the electron spectrum and to provide an estimation of the uncertainty of that prediction. It is anticipated that this approach will be useful for inferring the electron spectrum prior to undergoing any process that can alter or destroy the beam. In addition, the model provides insight into the scaling of electron beam properties due to stochastic fluctuations in the laser energy and plasma electron density.
We study the approximation of
min set cover combining ideas and results from polynomial approximation and from exact computation (with non-trivial worst case complexity upper bounds) for
NP-hard ...problems. We design approximation algorithms for
min set cover achieving ratios that cannot be achieved in polynomial time (unless problems in
NP could be solved by slightly super-polynomial algorithms) with worst-case complexity much lower (though super-polynomial) than those of an exact computation.
We report on experimental measurements of energy transfer efficiencies in a GeV-class laser wakefield accelerator. Both the transfer of energy from the laser to the plasma wakefield and from the ...plasma to the accelerated electron beam was diagnosed by simultaneous measurement of the deceleration of laser photons and the acceleration of electrons as a function of plasma length. The extraction efficiency, which we define as the ratio of the energy gained by the electron beam to the energy lost by the self-guided laser mode, was maximized at19±3%by tuning the plasma density and length. The additional information provided by the octave-spanning laser spectrum measurement allows for independent optimization of the plasma efficiency terms, which is required for the key goal of improving the overall efficiency of laser wakefield accelerators.
Wakefields in a cluster plasma Mayr, M. W.; Ceurvorst, L.; Kasim, M. F. ...
Physical review. Accelerators and beams,
11/2019, Letnik:
22, Številka:
11
Journal Article
Recenzirano
Odprti dostop
We report the first comprehensive study of large amplitude Langmuir waves in a plasma of nanometer-scale clusters. Using an oblique angle single-shot frequency domain holography diagnostic, the shape ...of these wakefields is captured for the first time. The wavefronts are observed to curve backwards, in contrast to the forwards curvature of wakefields in uniform plasma. Due to the expansion of the clusters, the first wakefield period is longer than those trailing it. The features of the data are well described by fully relativistic two-dimensional particle-in-cell simulations and by a quasianalytic solution for a one-dimensional, nonlinear wakefield in a cluster plasma.
In cases of malaria, rapid and accurate diagnosis of Plasmodium sp. is essential. In this study three different quantitative, real-time PCR methods were compared with routine methods used for malaria ...diagnosis. A comparative study was conducted prospectively in the laboratories of Montpellier and Nîmes University Hospitals. The methods used for routine diagnostic malaria testing consisted of microscopic examination of Giemsa-stained blood smears and rapid diagnostic tests. Three quantitative real-time PCR methods (qRT-PCR) were tested: qRT-PCR1 amplified a specific sequence on the P. falciparum Cox1 gene, qRT-PCR2 amplified a species-specific region of the multicopy 18S rDNA, and qRT-PCR3 amplified a mitochondrial DNA sequence. Among the 196 blood samples collected, 73 samples were positive in at least one of the five tests. Compared with the routine method, there were no false negatives for P. falciparum diagnosis in either qRT-PCR1 or qRT-PCR3. In all P. ovale, P. vivax and P. malariae infections diagnosed from blood smears, qRT-PCR1 was negative, as expected, whereas qRT-PCR2 and qRT-PCR3 were positive and concordant (simple κ coefficient = 1). One negative sample from microscopy was positive with both qRT-PCR2 and qRT-PCR3. Together, qRT-PCR3 and the combined qRT-PCR1 and qRT-PCR2 were concordant with routine methods for malaria diagnosis (99% and 99.5%, respectively). These three rapid, molecular qRT-PCR methods, used alone or in association, showed excellent results, with high concordance, accuracy and reliability in malaria diagnosis.
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