Laser-produced continua for absorption spectroscopy in the VUV and XUV

Recent work has shown that with appropriate targets, laser-produced plasmas provide clean essentially linefree continua suitable for absorption spectroscopy from 40 to 2000 Å. A systematic study of the continua emitted by the elements from samarium to ytterbium is reported, and their use in absorption spectroscopy is demonstrated. The temporal profiles of the continuum pulses at different wavelengths are studied with a photomultiplier system and are found to have essentially the same halfwidths as the pulse from the exciting Q-switched ruby laser (~25 nsec). Pulse heights are shown to be reproducible to 15% or better. Ambient gases, at least at pressures up to several Torr, do not affect the emission mechanism. A comparison with other continuum sources at XUV wavelengths (i.e., BRV, synchrotron) is made, and possible future developments are outlined

Electric field and discharge properties of single and multiple arrangement of Pulsed Atmospheric Plasma Streams

International audienceIn this study, one focuses on the diagnostic of single and multiple pulsed atmospheric plasma streams (PAPS) with the investigation of electric field (EF). The authors will present the results of EF strength obtained with two different methods. The first technique is a custom made electro optic sensor based on the Pockels effect, allowing for recording simultaneously two orthogonal components of the EF vector, time and spaced resolved. The second method uses Stark polarization emission spectroscopy of the He I line at 492.19 nm. Depending on the experimental conditions, both methods will be either complementary or compared with each other. The outcomes will bring information about the reliability of each methods and are of high interest for the validation of numerical simulation results

Electric field characterization of plasma gun and multi-jet plasma arrays

Invited oralInternational audienceRoom temperature Pulsed Atmospheric Plasma Streams (PAPS) have already demonstrated their unique potential in biology and medicine. Lately, the validation of multi-jet plasmas resulting from metallic and dielectric assemblies-containing many orifices-plugged to a single Plasma Gun (PG) and operating at moderate feed gas flow rate (from hundreds to thousands standard cubic centimeters) has been demonstrated [1]. This technological improvement enhances the credibility of plasma jets to treat large areas and volumes being beneficial in biomedical and recently in agriculture applications. Although the role of reactive oxygen and nitrogen species (RONS) produced by plasma is currently under many investigations, the simultaneous contribution of intense pulsed electric fields (EF) in the activation of biological mechanisms still remains unclear. Therefore, in this work, the authors focus on the characterization of EF in PAPS applied to the treatment of cells and culture medium. EF maps [2] time and space resolved have been recorded with an electro optic sensors [3] and contribute to the interpretation of biological responses, e.g. electroporation, electropermeabilization and the impacts on cell viability. The controlled propagation of multi-jet plasmas depends on the nature of the assemblies and is observed by time resolved iCCD imaging as shown in Fig. 1 and Fig. 2. While the metallic one allows for simultaneous ignitions of multiple PAPS, the dielectric one leads to a controlled splitting of the PG ionization wave, inducing a propagation delay between each orifice. Effects of multi-jet plasmas on the hydrodynamic of the gas are studied together via fast-schlieren imaging and by EF characterization. The outcome of this work will be of significant interest towards the use of multiple jets in plasma treated cells, agriculture and biomedical applications. XD is supported with the grant INEL/Région Centre Val de Loire

Australian wildfires cause the largest stratospheric warming since Pinatubo and extends the lifetime of the Antarctic ozone hole.

This is the final version. Available from Nature Research via the DOI in this record.Data availability Observational and model data is available from the Centre for Environmental Data Analysis archive (CEDA) catalogue (https://archive.ceda.ac.uk/), project reference: NE/S00212X/1. MSU/AMSU data are produced by Remote Sensing Systems and sponsored by NASA (data are available at www.remss.com). Assistance in analyzing the data is available by contacting the corresponding author.Global mean lower stratosphere temperatures rose abruptly in January 2020 reaching values not experienced since the early 1990s. Anomalously high lower stratospheric temperatures were recorded for 4 months at highly statistically significant levels. Here, we use a combination of satellite and surface-based remote sensing observations to derive a time-series of stratospheric biomass burning aerosol optical depths originating from intense SouthEastern Australian wildfires and use these aerosol optical depths in a state-of-the-art climate model. We show that the S.E. Australian wildfires are the cause of this lower stratospheric warming. We also investigate the radiatively-driven dynamical response to the observed stratospheric ozone perturbation and find a significant strengthening of the springtime Antarctic polar vortex suggesting that biomass burning aerosols play a significant role in the observed anomalous longevity of the ozone hole in 2020.Natural Environment Research Council (NERC)Natural Environment Research CouncilMet Office Hadley Centre Climate ProgrammeUKR

Including ash in UKESM1 model simulations of the Raikoke volcanic eruption reveals improved agreement with observations

In June 2019 the Raikoke volcano, located in the Kuril Islands northeast of the Japanese archipelago, erupted explosively and emitted approximately 1.5 Tg ± 0.2 Tg of SO2 and 0.4–1.8 Tg of ash into the upper troposphere and lower stratosphere. Volcanic ash is usually neglected in modelling stratospheric climate changes since larger particles have generally been considered to be short-lived particles in terms of their stratospheric lifetime. However, recent studies have shown that the coagulation of mixed particles with ash and sulfate is necessary to model the evolution of aerosol size distribution more accurately. We perform simulations using a nudged version of the UK Earth System Model (UKESM1) that includes a detailed two-moment aerosol microphysical scheme for modelling the oxidation of sulfur dioxide (SO2) to sulfate aerosol and the detailed evolution of aerosol microphysics in the stratosphere. We compare the model with a wide range of observational data. The current observational network, including satellites, surface-based lidars, and high-altitude sun photometers means that smaller-scale eruptions such as Raikoke provide unprecedented detail of the evolution of volcanic plumes and processes, but there are significant differences in the evolution of the plume detected using the various satellite retrievals. These differences stem from fundamental differences in detection methods between, e.g. lidar and limb-sounding measurement techniques and the associated differences in detection limits and the geographical areas where robust retrievals are possible. This study highlights that, despite the problems in developing robust and consistent observational constraints, the balance of evidence suggests that including ash in the model emission scheme provides a more accurate simulation of the evolution of the volcanic plume within UKESM1.</p