In a plasma of sufficient size and density, photons emitted within the system have a probability of being reabsorbed and reemitted multiple times-a phenomenon known in astrophysics as resonant ...scattering. This effect alters the ratio of optically thick to optically thin lines, depending on the plasma geometry and viewing angle, and has significant implications for the spectra observed in a number of astrophysical scenarios, but has not previously been studied in a controlled laboratory plasma. We demonstrate the effect in the x-ray spectra emitted by cylindrical plasmas generated by high power laser irradiation, and the results confirm the geometrical interpretation of resonant scattering.
Compression is an essential component of achieving high gain in inertial confinement fusion. However, increasing compression with crystalline ablator-based implosions had not succeeded up to now, ...attributed to increased hydrodynamic instability growth. We present experimental results demonstrating record high compression of stagnated fuel in indirectly driven implosions that use a high-density carbon ablator at the National Ignition Facility (NIF) Spaeth et al., Fusion Sci. Technol. 69, 25 (2016) by the use of a modified drive pulse (and capsule design). Specifically, the SQ-n design Clark et al., Phys. Plasmas 29, 052710 (2022) replaces the second and the third shock phase with a more gently ramped rise designed to reduce in-flight fuel adiabat and instability growth at both the ablation front and the ablator-DT fuel interface and hence promote increased compression. Comparing the results from a large set of experiments, we show that SQ-n achieves ≈ 15%–30% higher compression than prior designs, a finding that may chart a path toward increased compression and higher gain at the NIF Abu-Shawareb et al., Phys. Rev. Lett. 129, 075001 (2022)..
•A novel Helicobacter sp. was identified in wild Gopher tortoises (Gopherus polyphemus) with rhinitis.•Phylogenetic analysis shows that this organism and other previously characterized Helicobacter ...from tortoises form a clade.•Two qPCR diagnostic assays for the gyrA and groEL genes were developed, cross-validated, and used to survey tortoises.•Mortality of tortoises significantly correlated with higher Helicobacter loads detected by qPCR (P = 0.028).
The genus Helicobacter includes spiral-shaped bacteria in the phylum Proteobacteria, class Epsilonproteobacteria, order Campylobacteriales, that have been associated with disease in animals, including reptiles. Three wild gopher tortoise (Gopherus polyphemus) index cases presented between 2012 and 2019 with nasal discharge, lethargy, and weight loss. Cytological examination of nasal discharge from all 3 tortoises identified marked heterophilic and mild histiocytic rhinitis with abundant extracellular and phagocytized spiral shaped bacteria that stained positive with Warthin-Starry stain. Polymerase chain reaction (PCR) and sequencing of the 16S rRNA gene revealed this to be a novel Helicobacter species. Two tortoises died despite treatment attempts, and the third was moribund and was euthanized. Histological examination of the nasal mucosa (n = 3) showed granulocytic to lymphocytic rhinitis with variable mucosal hyperplasia, erosion, and ulceration; Warthin-Starry staining highlighted the presence of spiral bacteria in the untreated tortoise. Genus-specific primers were designed, and the gyrA and groEL genes were amplified by PCR and sequenced. Phylogenetic analysis shows that this organism and other previously characterized Helicobacter from tortoises form a clade. Development and cross-validation of two qPCR diagnostic assays for the gyrA and groEL genes showed significant correlation of the results of two assays (P < 0.0001). These assays were used to survey nasal wash samples from 31 rehabilitating gopher tortoises. Mortality of tortoises significantly correlated with higher Helicobacter loads detected by qPCR (P = 0.028). Appropriate quarantine protocols for tortoises during rehabilitation should consider this organism. Upper respiratory disease in tortoises may involve complex microbial ecology; factors beyond Mycoplasmopsis (Mycoplasma) agassizii should be taken into account.
An inertial fusion implosion on the National Ignition Facility, conducted on August 8, 2021 (N210808), recently produced more than a megajoule of fusion yield and passed Lawson's criterion for ...ignition Phys. Rev. Lett. 129, 075001 (2022). Here we describe the experimental improvements that enabled N210808 and present the first experimental measurements from an igniting plasma in the laboratory. Ignition metrics like the product of hot-spot energy and pressure squared, in the absence of self-heating, increased by ~ 35%, leading to record values and an enhancement from previous experiments in the hot-spot energy (~ 3×), pressure (~ 2×), and mass (~ 2×). These results are consistent with self-heating dominating other power balance terms. The burn rate increases by an order of magnitude after peak compression, and the hot-spot conditions show clear evidence for burn propagation into the dense fuel surrounding the hot spot. These novel dynamics and thermodynamic properties have never been observed on prior inertial fusion experiments.
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