Exploring new frontiers in marine radioisotope tracing - adapting to new opportunities and challenges

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Cresswell, T., Metian, M., Fisher, N. S., Charmasson, S., Hansman, R. L., Bam, W., Bock, C., & Swarzenski, P. W. Exploring new frontiers in marine radioisotope tracing - adapting to new opportunities and challenges. Frontiers in Marine Science, 7, (2020): 406, doi:10.3389/fmars.2020.00406.Radioisotopes have been used in earth and environmental sciences for over 150 years and provide unique tools to study environmental processes in great detail from a cellular level through to an oceanic basin scale. These nuclear techniques have been employed to understand coastal and marine ecosystems via laboratory and field studies in terms of how aquatic organisms respond to environmental stressors, including temperature, pH, nutrients, metals, organic anthropogenic contaminants, and biological toxins. Global marine issues, such as ocean warming, deoxygenation, plastic pollution, ocean acidification, increased duration, and intensity of toxic harmful algal blooms (HABs), and coastal contamination are all impacting marine environments, thereby imposing various environmental and economic risks. Being able to reliably assess the condition of coastal and marine ecosystems, and how they may respond to future disturbances, can provide vital information for society in the sustainable management of their marine environments. This paper summarizes the historical use of radiotracers in these systems, describes how existing techniques of radioecological tracing can be developed for specific current environmental issues and provides information on emerging issues that would benefit from current and new radiotracer methods. Current challenges with using radioecological tracers and opportunities are highlighted, as well as opportunities to maximize the application of these methods to greatly increase the ability of environmental managers to conduct evidence-based management of coastal and marine ecosystems.The IAEA is grateful for the support provided to its Environment Laboratories by the Government of the Principality of Monaco. This contribution was made within the framework of the IAEA CRP on “Applied radioecological tracers to assess coastal and marine ecosystem health” (K41019)

Monitoring Photonic Nanojets from Microsphere Arrays by Femtosecond Laser Ablation of Thin Films

3rd International Conference on Nanostructures Self-Assembly (NANOSEA), Cassis, FRANCE, JUN 28-JUL 02, 2010International audienceBy comparing finite-difference time-domain near field simulations and femtosecond laser ablation of thin films, we characterize in three dimensional-space photonic nanojets from microsphere arrays. We demonstrate periodic driving of transparent films with thickness up to 100 nm (onto absorbing substrates) is feasible with 1-mu m diameter silica spheres. Working with larger polystyrene spheres, the apparent increase of the propagation length of the photonic nanojets makes possible to drill films as thick as 500 nm. Interestingly, the lateral width of the produced craters can be maintained below 400 nm evidencing the low divergence of the nanojets. For backside illumination of the arrays, the ablation features are located at the top of the microspheres. We reveal field enhancements in and out the spheres as well as laser energy confinement at the particle substrate interface. The wide variety of features observed in the experiments open routes to fabricating nanomaterials

Periodically structured Silicon substrate by microsphere-assisted laser interactions

Conference on Laser-Based Micro- and Nanopackaging and Assembly VII (LBMP) as a part of LASE Photonics West, San Francisco, CA, FEB 06-07, 2013International audienceLaser near-field enhancements underneath transparent microspheres can be used to locally implement new functionalities in materials. Using this technique, we report micro-and nano-structuration on silicon (Si). The Langmuir-Blodgett (LB) technique is primarily used to realize monolayers of C18 functionalized silica (SiO2) microspheres on a large size area of the substrates. Afterwards, by irradiating the deposited monolayer with single shot UV nanosecond laser pulses in the ablation regime, we demonstrate the formation of dense arrays of craters in silicon substrate. In particular, we describe our works to obtain mono dispersed craters of sub micrometer size using LB technique and taking the fluence and sphere size as variable process parameters. Finite-difference time-domain (FDTD) simulations are presented to estimate the enhancement intensity factor and near-field distribution below the spheres in the experiments

SiO

By illuminating transparent microsphere monolayers with single UV nanosecond laser pulses, we produce arrays of nanopatterns in oxide film on silicon. The reported features reveal the nature of the interaction of the photonic nanojets inside the oxide layer and at the highly absorbing substrate surface depending on the film thickness and the laser pulse energy

22 W average power multiterawatt femtosecond laser chain enabling 1019 W/cm2 at 100 Hz

International audienceWe measure the wavefront distortions of a high peak power ultrashort (23 fs) laser system under high average power load. After 6 min-100 Hz operation of the laser at full average power (> 22 W after compression), the thermally induced wave-front distortions reach a steady state and the far-field profile of the laser beam no longer changes. By means of a deformable mirror located after the vacuum compressor, we apply a static pre-compensation to correct those aberrations allowing us to demonstrate a dramatic improvement of the far-field profile at 100 Hz with the reduction of the residual wavefront distortions below λ/16 before focusing. The applied technique provides 100 Hz operation of the femtosecond laser chain with stable pulse characteristics, corresponding to peak intensity above 10 19 W/cm 2 and average power of 19 W on target, which enables the study of relativistic optics at high repetition rate using a moderate f-number focusing optics (f/4.5)

Organically bound tritium (OBT) and carbon-14 accumulation in the sediments off the mouth of the Rhône river

International audienceWe have studied the recent history of organically bound tritium (OBT) and carbon-14 in suspended organic matter carried by the Rhône from the analysis of two cores collected in the sedimentary cone off the river mouth. Measured OBT and carbon-14 concentrations highlight characteristic anthropogenic traces in the suspended matter of the Rhône, with a peak of tritium and carbon-14 commencing at the start of the 1970s and extending over some 30 years. In spite of the influence of the atmospheric nuclear tests of the 1950s and 1960s, and of the discharges of carbon-14 by the nuclear industries located along the Rhône, carbon-14 levels are low due to the diluting effect of a refractory carbon component very low in carbon-14 present in the coastal sediments. OBT levels are well above the modern background created by the global imprint of bomb-tritium. Detailed study of the impact of the various contribution to the tritium peak indicates that these traces are mostly the result of the sediments in the Rhône being contaminated by past tritium releases by the watchmaking industry in the upper Rhôn

Micro/Nano-Structuration of Silicon using Photonic Nanojet Mechanism

Conference on Lasers and Electro-Optics Europe & International Quantum Electronics Conference (CLEO/Europe-IQEC), Munich, GERMANY, MAY 12-16, 2013International audienceno abstrac

Micro/Nano-Structuration of Silicon using Photonic Nanojet Mechanism

Conference on Lasers and Electro-Optics Europe & International Quantum Electronics Conference (CLEO/Europe-IQEC), Munich, GERMANY, MAY 12-16, 2013International audienceno abstrac

High repetition rate (100 Hz), high peak power, high contrast femtosecond laser chain

High intensity femtosecond laser are now routinely used to produce energetic particles and photons via interaction with solid targets. However, the relatively low conversion efficiency of such processes requires the use of high repetition rate laser to increase the average power of the laser-induced secondary source. Furthermore, for high intensity laser-matter interaction, a high temporal contrast is of primary importance as the presence of a ns ASE pedestal (Amplified Spontaneous Emission) and/or various prepulses may significantly affect the governing interaction processes by creating a pre-plasma on the target surface. We present the characterization of a laser chain based on Ti:Sa technology and CPA technique, which presents unique laser characteristics : a high repetition rate (100 Hz), a high peak power (> 5 TW) and a high contrast ratio (ASE<10(-10)) obtained thanks to a specific design with 3 saturable absorbers inserted in the amplification chain. A deformable mirror placed before the focusing parabolic mirror should allow us to focus the beam almost at the limit of diffraction. In these conditions, peak intensity above 1019W. cm(-2) on target could be achieved at 100 Hz, allowing the study of relativistic optics at a high repetition rate

Tritium and radiocarbon levels in the Rhône river delta and along the French Mediterranean coastline

International audienc