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FLASH News - FLASH: The First Soft X-ray FEL Operating Two Undulator Beamlines Simultaneously
No full textSwitching between 'identical cathode laser systems' in real life - Symptoms and empirical performance
No full textProtosiphonorhinus patrickmuelleri gen. et sp. nov., the first fossil member of the sucking millipede family Siphonorhinidae (Colobognatha, Siphonophorida) described from Cretaceous Myanmar amber
No full textMillipedes (Diplopoda) are an abundant group of fossilized terrestrial arthropods throughout the Palaeozoic Era. However, there is a gap in the Mesozoic Period with only slightly more than a dozen fossils known, until more recent fossil records – mainly from Cenozoic Dominican and Baltic ambers – became available. Here, we describe a millipede of the family Siphonorhinidae from Myanmar amber, a species-poor group, comprising just six extant genera, disjunctly distributed in Southeast Asia, South Africa, Madagascar, Chile and California. Micro-computed tomography (µ-CT) enabled detailed visualizations of essential elements for description, including the tergites, legs, head, antenna, and notably the gonopods. The new genus shares some characteristics with species of the extant genus Siphonorhinus Pocock, 1894. Protosiphonorhinus patrickmuelleri gen. et sp. nov. differs from extant species of the family mainly in the shape of the antenna, tergites, and anterior gonopods. A recently described fossil species of Siphonophorida from Myanmar amber was erroneously assigned to the family Siphonorhinidae. We transfer it to the family Siphonophoridae, as Siphonophora globosa (Su, Cai & Huang, 2024) comb. nov. The description of the new genus and the reinterpretation of the previously described fossil Siphonorhinidae allows for a rejection of a hypothesis of bradytely within the Siphonorhinidae from the mid-Cretaceous to the present day
Ultrahigh-pressure crystallographic passage towards metallic hydrogen
No full textThe structural evolution of molecular hydrogen H2 under multi-megabar compression and its relation to atomic metallic hydrogen is a key unsolved problem in condensed-matter physics. Although dozens of crystal structures have been proposed by theory1,2,3,4, only one, the simple hexagonal-close-packed (hcp) structure of only spherical disordered H2, has been previously confirmed in experiments5. Through advancing nano-focused synchrotron X-ray probes, here we report the observation of the transition from hcp H2 to a post-hcp structure with a six-fold larger supercell at pressures above 212 GPa, indicating the change of spherical H2 to various ordered configurations. Theoretical calculations based on our XRD results found a time-averaged structure model in the space group with alternating layers of spherically disordered H2 and new graphene-like layers consisting of H2 trimers (H6) formed by the association of three H2 molecules. This supercell has not been reported by any previous theoretical study for the post-hcp phase, but is close to a number of theoretical models with mixed-layer structures. The evidence of a structural transition beyond hcp establishes the trend of H2 molecular association towards polymerization at extreme pressures, giving clues about the nature of the molecular-to-atomic transition of metallic hydrogen. Considering the spectroscopic behaviours that show strong vibrational and bending peaks of H2 up to 400 GPa, it would be prudent to speculate the continuation of hydrogen molecular polymerization up to its metallization
Investigating the Reductive Phosphatization Reaction Pathway in the Synthesis of Transition Metal Phosphates: A Case Study on Titanium Phosphates
No full textReductive phosphatization is an original synthesis approach to the formation of transition metal phosphates (TMPs). The approach enables the synthesis of known TMPs, but also new compounds, especially with transition metals in a low-valent state. However, to exploit the enormous potential of this synthesis method, it is necessary to identify and characterize all of the potential intermediates and final synthesis products. Here, we report on in situ synchrotron X-ray powder diffraction experiments to unravel the temperature-dependent formation pathway of TMPs using TiO–NHHPO as an example. The pathway consists of several consecutive steps, including the melting of NHHPO, which acts as a reducing agent and a reaction medium. A reduction in the ratio of TiO to NHHPO decelerates the reaction and causes increased impurity formation. The hypophosphite melt reduces Ti4+ in TiO to Ti, and a previously unknown compound, denoted as Ti(III)po with chemical composition (NH)HTi(HPO), is formed. In a subsequent step, (NH)HTi(HPO) reacts in a polycondensation reaction to form monoclinic NHTiPO, denoted as Ti(III)p in our earlier work
Dark sector searches with the CMS experiment
No full textAstrophysical observations provide compelling evidence for gravitationally interacting dark matter in the universe that cannot be explained by the standard model of particle physics. The extraordinary amount of data from the CERN LHC presents a unique opportunity to shed light on the nature of dark matter at unprecedented collision energies. This Report comprehensively reviews the most recent searches with the CMS experiment for particles and interactions belonging to a dark sector and for dark-sector mediators. Models with invisible massive particles are probed by searches for signatures of missing transverse momentum recoiling against visible standard model particles. Searches for mediators are also conducted via fully visible final states. The results of these searches are compared with those obtained from direct-detection experiments. Searches for alternative scenarios predicting more complex dark sectors with multiple new particles and new forces are also presented. Many of these models include long-lived particles, which could manifest themselves with striking unconventional signatures with relatively small amounts of background. Searches for such particles are discussed and their impact on dark-sector scenarios is evaluated. Many results and interpretations have been newly obtained for this Report
FLASHlab@PITZ: Prooxidant and apoptotic effects of ultra-high dose rate electron irradiation in vitro
No full textThe FLASHlab@PITZ R&D platform at DESY offers a wide range of dose rates, from clinical levels (0.05 Gy/s) to ultra-high dose rates (HDR) of up to 1014 Gy/s, using a 22 MeV electron beam. This flexibility enables studies in both conventional (LDR) radiotherapy and HDR therapy, supporting research into safer and more effective cancer treatments
First Search for Dark Photon Dark Matter with a MADMAX Prototype
No full textWe report the first result from a dark photon dark matter search in the mass range from 78.62 to 83.95 μeV/ with a dielectric haloscope prototype for madmax (Magnetized Disc and Mirror Axion eXperiment). Putative dark photons would convert to detectable photons within a stack consisting of three sapphire disks and a mirror. The emitted power of this system is received by an antenna and successively digitized using a low-noise receiver. No significant signal attributable to dark photons has been observed above the expected background. Assuming unpolarized dark photon dark matter with a local density of _=0.3 GeV cm we exclude a dark photon to photon mixing parameter >2.7 ×10 over the full mass range and >1.1 ×10 at a mass of 80.57 μeV/ with a 95% confidence level. This is the first physics result from a madmax prototype and exceeds previous constraints on in this mass range by up to almost three orders of magnitude
Enabling electron-energy-loss spectroscopy at very high energy losses: An opportunity to obtain x-ray absorption spectroscopy–like information using an electron microscope
No full textElectron-energy-loss spectroscopy (EELS) with an electron microscope and X-ray absorption spectroscopy (XAS) with a synchrotron are techniques for material characterization, both of which are based on exciting core electrons. Both techniques have a similar energy resolution, but while the spatial resolution of EELS can drop to atomic scales, the spatial resolution of XAS is typically limited to micrometer scales. Yet, XAS is commonly the preferred technique for analysis of the extended fine structure of ionization edges, mainly thanks to the excellent signal-to-noise ratio and the large range of ionization energies (from ∼5 to ∼40 keV) that can be probed at synchrotron end stations. In contrast, EELS is traditionally limited to ionization energies of ≲2 keV because electrons in the beam that lose more than 2 keV will be too distant from the operating energy of the electron microscope. Chromatic effects in the postsamplelenses allow only some of such energy-loss electrons to reach the EELS detector, as the latter electrons will either suffer from being strongly defocused or will not make it to the detector at all. In this paper, we present results from our novel Iliad EELS spectrometer, which offers a greatly increased range of ionization energies up to 30 keV. We achieve this vast increase by carefully controlling the optics of our electron microscope and carefully matching the optics of our EELS spectrometer to it, such that all the chromatic effects are removed or compensated. We exemplify its performance by recording EELS nearedge fine structure (ELNES) of the Zr L-edges at 2.3 keV, extended fine structure EELS (EXELFS) of Cu K-edge at ∼9 keV, and EELS of the Mo K-edge at 20 keV and Sb K-edge at ∼30 keV. We benchmark our data against near-edge and extended fine structure X-ray absorption (XANES and EXAFS) data, and we quantitatively analyze the Cu K-edge EXELFS, demonstrating the capability to determine elementspecific bond lengths and to distinguish different oxidation states such as metallic Cu, CuO, or CuO on asubmicrometer scale