Experimental investigation of size broadening of a Kα x-ray source produced by high intensity laser pulses

The size of a hard Kα x-ray source ($${\mathrm{E}}_{{\rm{K}}_{\rm{\alpha }}}$$ E K α = 17.48 keV) produced by a high intensity femtosecond laser interacting with a solid molybdenum target is experimentally investigated for a wide range of laser intensity (I ~ 1017–2.8 × 1019 W/cm2) and for four values of the temporal contrast ratio (6.7 × 107 < CR < 3.3 × 1010). Results point out the size enlargement of the x-ray source with the increase of laser intensity and with the deterioration of temporal contrast. It amounts up to sixteen times the laser spot size at the highest laser intensity and for the lowest temporal contrast ratio. Using hydrodynamic simulations, we evaluate the density scale length of the pre-plasma L/λ just before the main pulse peak. This allows us to show that a direct correlation with the laser absorption mechanisms is not relevant to explain the large size broadening. By varying the thickness of the molybdenum target down to 4 µm, the impact of hot electron scattering inside the solid is also proved irrelevant to explain the evolution of both the x-ray source size and the Kα photon number. We deduce that the most probable mechanism yielding to the broadening of the source size is linked to the creation of surface electromagnetic fields which confine the hot electrons at the solid surface. This assumption is supported by dedicated experiments where the evolution of the size enlargement of the x-ray source is carefully studied as a function of the laser focal spot size for the highest contrast ratio.

Characterization of Energetic Protons Generated in the ShenGuang-II UP Petawatt Laser Interactions with Foil Targets

The characterization of energetic protons generated in the ShenGuang-II UP petawatt laser interactions with foil targets has been systematically studied. The proton energy spectra and angular distributions are measured with a radiochromic film stack. It shows that the proton energy spectra have a Boltzmann distribution with temperature of about 2.8 MeV and cutoff energy of about 20 MeV. The divergence angles of protons vary from 10° to 60°, dependent on the proton energy. The proton source size and location are investigated via the proton point-projection mesh imaging. The proton virtual sources are found to locate tens to hundreds of microns in front of the foil target, depending on the proton energies. A Monte Carlo simulation estimates the diameter of the virtual proton source to be about 12 μm for the protons with energy of 16.8 MeV, which is much smaller than the laser focus size of about 50 μm. The spatial resolution of the 16.8 MeV proton imaging is quantified with the point spread function to be about 15 μm, which is consistent with the proton virtual source size. These results will be important for the users conducting experiments with the protons as a backlighting source on the ShenGuang-II UP petawatt laser.

Process Mining of Disease Trajectories: A Literature Review

Disease trajectories model patterns of disease over time and can be mined by extracting diagnosis codes from electronic health records (EHR). Process mining provides a mature set of methods and tools that has been used to mine care pathways using event data from EHRs and could be applied to disease trajectories. This paper presents a literature review on process mining related to mining disease trajectories using EHRs. Our review identified 156 papers of potential interest but only four papers which directly applied process mining to disease trajectory modelling. These four papers are presented in detail covering data source, size, selection criteria, selections of the process mining algorithms, trajectory definition strategies, model visualisations, and the methods of evaluation. The literature review lays the foundations for further research leveraging the established benefits of process mining for the emerging data mining of disease trajectories.

Extragalactic Radio Sources: Jet/Lobe Internal Pressure and Consequences

In this work, we use analytical methods to describe expansion of Extragalactic Radio Sources (EGRS). Result shows that source size expansion depends on the following parameters: age of the source, lobe internal pressure, ambient medium density, and angle of observation. Moreover, from the analyses, we have shown that the obtained results, and , suggestively implies that and . This shows that since , jet internal pressure exceeds the lobe’s internal pressure. Therefore, for a typical EGRS, this simply indicates that ambient medium density is higher in the jet region than in the region of the lobe. This is expected since the ambient density thins out from the central core to the region where lobe is located. It is in consonance with the notion that for large extended EGRS, lobes are located outside the host galaxies rather than within the host galaxies. Moreover, we can conclude from these results that compact steep spectrum sources have denser ambient medium than their more extended counterparts.

On nuclear coalescence in small interacting systems

The formation of light nuclei can be described as the coalescence of clusters of nucleons into nuclei. In the case of small interacting systems, such as dark matter and $$e^+e^-$$ e + e - annihilations or pp collisions, the coalescence condition is often imposed only in momentum space and hence the size of the interaction region is neglected. On the other hand, in most coalescence models used for heavy ion collisions, the coalescence probability is controlled mainly by the size of the interaction region, while two-nucleon momentum correlations are either neglected or treated as collective flow. Recent experimental data from pp collisions at LHC have been interpreted as evidence for such collective behaviour, even in small interacting systems. We argue that these data are naturally explained in the framework of conventional QCD inspired event generators when both two-nucleon momentum correlations and the size of the hadronic emission volume are taken into account. To include both effects, we employ a per-event coalescence model based on the Wigner function representation of the produced nuclei states. This model reproduces well the source size for baryon emission and the coalescence factor $$B_2$$ B 2 measured recently by the ALICE collaboration in pp collisions.

Parametric simulation studies on the wave propagation of solar radio emission: the source size, duration, and position

&lt;p&gt;&lt;span&gt;The solar atmosphere is fluctuated and highly refractive for low frequency waves (&lt;300MHz), the observed features of solar radio sources have indicated the existence of complex propagation effects. The propagation effect has two major parts: refraction and scattering, these two parts have combined influence on the observed source size and position of radio imaging and temporal-frequency features in the radio spectroscopy.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;We present a parametric simulation for the propagation effect of the radio wave from solar radio bursts, with the method of parametric simulation, we can build connections between the solar atmosphere plasma condition and the observed radio source properties. By comparing the simulation results with the observed source size and property we estimated the scattering rate and the degree of anisotropic of the background electron, and from the simulation results we propose a possible explanation for the co-spatial phenomena of the fundamental wave and harmonic wave in single frequency.&lt;/p&gt;

LOFAR Imaging of the Solar Corona during the 2015 March 20 Solar Eclipse

&lt;p&gt;The solar corona is a highly-structured plasma which can reach temperatures of more than 2 MK. At low frequencies (decimetric and metric wavelengths), scattering and refraction of electromagnetic waves are thought to considerably increase the imaged radio source sizes (up to a few arcminutes). However, exactly how source size relates to scattering due to turbulence is still subject to investigation. The theoretical predictions relating source broadening to propagation effects have not been fully confirmed by observations, due to the rarity of high spatial resolution observations of the solar corona at low frequencies. Here, the LOw Frequency ARray (LOFAR) was used to observe the solar corona at 120&amp;#8211;180 MHz using baselines of up to 3.5 km (corresponding to a resolution of 1&amp;#8211;2&amp;#8217;) during the partial solar eclipse of 2015 March 20. A lunar de-occultation technique was used to achieve higher spatial resolution (0.6&amp;#8217;) than that attainable via standard interferometric imaging (2.4&amp;#8217;). This provides a means of studying the contribution of scattering to apparent source size broadening. This study shows that the de-occultation technique can reveal a more structured quiet corona that is not resolved from standard imaging, implying scattering may be overestimated in this region when using standard imaging techniques. However, an active region source was measured to be 4&amp;#8217; using both de-occultation and standard imaging. This may be explained by increased scattering of radio waves by turbulent density fluctuations in active regions, which is more severe than in the quiet Sun.&lt;/p&gt;&lt;p&gt;&lt;br&gt;&lt;br&gt;&lt;/p&gt;