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The balloon-borne and airborne instrument SPECIES (SPECtromètre Infrarouge à lasErs in Situ) recently built in our laboratory will be described. This is a mid-infrared absorption spectrometer, including four channels by coupling Interband or Quantum Cascade Lasers (ICLs or QCLs) to Optical-Feedback Cavity-Enhanced Absorption Spectroscopy (OF-CEAS). Using cavities of 50 cm length, this leads to very high resolution (< 0.005 cm-1) spectra and very long optical paths (> 5 km) and thus, low detection limits for the trace gases to be measured. It can contribute to the detailed description and understanding of the functioning of the free troposphere and stratosphere in terms of composition, chemical reactivity and circulation of air masses by carrying out fast (< 2 s) in-situ measurements of reactive trace gases and greenhouse gases among CO, NOx, CH2O, 12CO2, 13CO2, CH4 and N2O, at very high spatial resolution, i.e. a few meters vertically or hundred meters horizontally. Mini-SPECIES is the lightened version of SPECIES, comprising two lasers coupled to two cavities and reduced electrical power, which allows its integration in aircraft or its operation for long-duration stratospheric balloon flights (> 4 days). High accuracies are obtained when calibration in flight, or at ground before and after the flight, is performed against standards. In addition to providing reference measurements for calibration/validation of space missions, these performances can lead to in-depth characterization of particular atmospheric processes.

Monitoring climate change and stratospheric ozone budget requires accurate knowledge of the abundances of greenhouse gases and ozone depleting substances from the lower troposphere to the stratosphere. An infrared laser absorption spectrometer called SPECIES (acronym for SPECtromètre Infrarouge à lasErs in Situ) has been developed for balloon-borne trace gases measurements.The complete instrument has been validated on the occasion of a flight in August 2021 in the polar region (Kiruna, Sweden) within the frame of the “KLIMAT 2021” campaign managed by CNES for the “MAGIC” project using concomitant balloon and aircraft flights. Results of this flight concerning CH4 and CO2 will be presented.

To understand tropospheric air pollution at regional and global scales, the SPIRIT airborne instrument (SPectromètre Infra-Rouge In situ Toute altitude) was developed and used on aircraft to measure volume mixing ratios of carbon monoxide (CO), an important indicator of air pollution, during the last decade. SPIRIT could provide high-quality CO measurements with 1σ precision of 0.3 ppbv at a time resolution of 1.6 s thanks to the coupling of a quantum cascade laser to a Robert multi-pass cell. It can be operated on different aircraft such as Falcon-20 and ATR-42 from DLR (Germany) and SAFIRE (CNRS-CNES-Météo France). With support from various projects, more than 200 flight hours measurements were conducted over three continents (Europe, Asia, and Africa), including two inter-continental measurements (Europe-Asia and Europe-Africa). Levels of CO and its horizontal and vertical distribution are briefly discussed and compared between different regions/continents. CO generally decreases with altitude except for the measurements in high-latitude regions, indicating the important contribution of long-distance transport to CO levels at high-latitude regions. A 3D trajectory mapped by CO level was plotted for each flight and presented in this study. The database is archived on the AERIS database (https://doi.org/10.25326/440), the French national center for atmospheric observations (Catoire et al., 2023). Besides, it could help to validate model performances and satellite measurements. For instance, the database covers measurements at high-latitude regions (i.e., Kiruna, Sweden, 68° N) where satellite measurements are still challengeable and at low-latitude regions (West Africa and South-East Asia) where in situ data are scarce and satellites need more validation by airborne measurements.

International audience; Following the Hunga Tonga eruption (20.6°S, 175.4°W, mid-January 2022), we present a balloon-borne characterization of the stratospheric aerosol plume one week after its injection (on 23 and 26 January 2022, La Réunion island at 21.1°S, 55.3°E). Satellite observations show that flight (a) took place during the overpass of a denser plume of sulfate aerosols (SA) compared to a more diluted plume during flight. (b) Observations show that the sampled plumes (at around 22, 25 and 19 km altitude, respectively) consist exclusively of very small particles (with radius

To understand tropospheric air pollution at a regional/global scale, the SPIRIT airborne instrument (SPectromètre Infra-Rouge In situ Toute altitude) was developed in 2011 and used on aircraft to measure CO, an important indicator of air pollution, during the last decade. SPIRIT could provide high-quality CO measurements with 1σ precision of 0.3 ppbv at a time resolution of 1.6 s. It can be operated on different aircraft from DLR (Germany) and SAFIRE (CNRS-CNES-Météo France) such as Falcon-20 and ATR-42. With support from various projects, more than 200 flight hours measurements were conducted over three continents (Europe, Asia, Africa), including two inter-continental transect measurements (Europe-Asia and Europe-Africa). Levels of CO and its horizontal and vertical distribution are briefly discussed and compared between different regions/continents. A 3D trajectory mapped by CO level was plotted for each flight and presented in this study. The database containing all the raw data will be archived on the AERIS database (www.aeris-data.fr), the French national center for Earth observation dedicated to the atmosphere. The database can help to understand the horizontal and vertical distribution of CO over different regions and continents. Besides, it can help to validate model performance and satellite measurements. For instance, the database covers measurements at high-latitude regions (i.e., Kiruna, Sweden, 68˚N) where satellite measurements are still a challenge, and at low-latitude regions (West Africa and South-East Asia) where in situ data are scarce and satellites need more validation by airborne measurements.

A three-channel laser absorption spectrometer called SPIRIT (SPectromètre InfraRouge In situ Toute altitude) has been developed for airborne measurements of trace gases in the troposphere and lower stratosphere. More than three different species can be measured simultaneously with high time resolution (each 1.6 s) using three individual CW-DFB-QCLs (Continuous Wave Distributed FeedBack Quantum Cascade Lasers) coupled to a single Robert multipass optical cell. The lasers are operated in a time-multiplexed mode. Absorption of the mid-infrared radiations occur in the cell (2.8 L with effective path lengths of 134 to 151 m) at reduced pressure, with detection achieved using a HgCdTe detector cooled by Stirling cycle. The performances of the instrument are described, in particular precisions of 1, 1 and 3 %, and volume mixing ratio (vmr) sensitivities of 0.4, 6 and 2.4 ppbv are determined at 1.6 s for CO, CH4 and N2O, respectively (at 1σ confidence level). Estimated accuracies without calibration are about 6 %. Dynamic measuring ranges of about four decades are established. The first deployment of SPIRIT was realized aboard the Falcon-20 research aircraft operated by DLR (Deutsches Zentrum für Luft- und Raumfahrt) within the frame of the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) European project in November-December 2011 over Malaysia. The convective outflows from two large convective systems near Borneo Island (6.0° N–115.5° E and 5.5° N–118.5° E) were sampled above 11 km in altitude on 19 November and 9 December, respectively. Correlated enhancements in CO and CH4 vmr were detected when the aircraft crossed the outflow anvil of both systems. These enhancements were interpreted as the fingerprint of transport from the boundary layer up through the convective system and then horizontal advection in the outflow. Using these observations, the fraction of boundary layer air contained in fresh convective outflow was calculated to range between 22 and 31 %, showing the variability of the mixing taking place during convective transport.

The Laser MegaJoule (LMJ), built at CEA/CESTA near Bordeaux, France, will conduct research in the field of plasma physics and inertial confinement fusion. Some of these experiments are designed to produce during less than one nanosecond up to 10 19 neutrons at 14 MeV in indirect drive mode. The 300 m long building that hosts both laser sources and target chamber was designed to confine neutron and gamma fluxes in the experiment hall during a shot. Monte Carlo simulations were performed using a TRIPOLI 4 modelling of the facility to ensure that prompt doses in occupied areas inside the facility that host employees during a shot will be sufficiently low. Although significant radiation levels inside the experiment hall, prompt doses in occupied rooms are limited to a few μSv per shot which is fully compatible with radiation level limits.

The sensitivity of molecular fingerprinting is dramatically improved when the absorbing sample is placed in a high-finesse optical cavity, because the effective path length is increased. When the equidistant lines from a laser frequency comb are simultaneously injected into the cavity over a large spectral range, multiple trace gases may be identified1 within a few milliseconds. However, efficient analysis of the light transmitted through the cavity remains challenging. Here, a novel approach—cavity-enhanced, frequency-comb, Fourier-transform spectroscopy—fully overcomes this difficulty and enables measurement of ultrasensitive, broad-bandwidth, high-resolution spectra within a few tens of microseconds without any need for detector arrays, potentially from the terahertz to ultraviolet regions. Within a period of just 18 µs, we recorded the spectra of the ammonia 1.0 µm overtone bands comprising 1,500 spectral elements and spanning 20 nm, with a resolution of 4.5 GHz and a noise equivalent absorption at 1 s averaging of 1 × 10−10 cm−1 Hz−1/2, thus opening a route to time-resolved spectroscopy of rapidly evolving single events. By combining Fourier transform spectroscopy with two frequency-shifted combs and cavity ring-down spectroscopy, scientists demonstrate a powerful new tool for ultrahigh sensitivity spectroscopy. The scheme can measure broadband, high-resolution spectra in tens of microseconds, does not require detector arrays and may allow tuning from terahertz to ultraviolet frequencies.

For the first plasma diagnostics to be deployed at the Laser Megajoule (LMJ), the Commissariat a l'Energie Atomique (CEA) is developing ultrafast x-ray imaging cameras to analyze spatial and temporal evolution of laser-plasma interaction parameters. These cameras, which operate in the target chamber vacuum, are composed of a one-dimensional (1-D) streak or a two-dimensional (2-D) gated detector, power supply units, control electronic modules, and a charge-coupled device (CCD) readout system. In order to optimize their definition and to ensure easy maintenance, these cameras are packaged inside a hermetically sealed chamber comprised of a pressurized box (air box), which also enable the electronics to operate at atmospheric pressure and provide protection of the camera against the harsh operating environment induced by fluxes of neutrons, x-rays and gamma rays, and electromagnetic radiations. This paper introduces the work led by CEA concerning the development of the air box which integrates the x-ray streak and framing cameras for the first LMJ plasma diagnostics experiments, with regard to the integration and operational constraints of the facility.

This paper gives an overview of works undertaken at CEA/DIF in high speed cinematography, optoelectronic imaging and ultrafast photonics for the needs of the CEA/DAM experimental programs. We have developed a new multichannel velocimeter, and a new probe for shock breakout timing measurements in detonics experiments. A brief description and a recall of their main performances will be made. We have implemented three new optoelectronic imaging systems, in order to observe dynamic scenes in the ranges of 50 - 100 keV and 4 MeV. These systems are described, their main specifications and performances are given. Then we describe our contribution to the ICF program: after recalling the specifications of LIL plasma diagnostics, we describe the features and performances of visible streak tubes, X-ray streak tubes, visible and X-ray framing cameras and the associated systems developed to match these specifications. At last we introduce the subject of components and systems vulnerability in the LMJ target area, the principles identified to mitigate this problem and the first results of studies (image relay, response of streak tube phosphors, MCP image intensifiers and CCDs to fusion neutrons) related to this subject. Results obtained so far are presented.

The Laser Megajoule is the project equivalent in France to the National Ignition Facility project in USA. The laser has been sized to achieve ignition of a small amount of DT and to produce fusion energy in laboratory with a significant gain, by imploding small capsules filled with a DT mixture. The target area has to be designed to contain the maximum threats imposed by large emissions of neutrons, x-rays and debris due to the explosion of the target. We describe the 10 m diameter target chamber. Prediction calculations of the x-ray threats on the debris shields and the first wall are also detailed. We show that the first wall has to be protected by refractive materials and that low porosity plasma-sprayed boron carbide is potentially a good candidate. We also show that high velocity shrapnels generated by neutron, x-ray and ion deposition in the materials close to the target could also be a threat for the target chamber first wall and optics.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

International audience; An ecophysiological growth process model, called INCA, for simulating the growth and development of a young walnut tree (Juglans regia L.) during three or four years, is presented. This tool, currently under development, aims at integrating architectural and physiological knowledge of the processes involved, in order to give a more rational understanding of the pruning operation. The model describes a simple three-dimensional representation of tree crown, solar radiation interception, photosynthesis, respiration, growth and partitioning of assimilates to leaves, stems, branches and roots. It supports the hypothesis that the tree grows as a collection of semiautonomous, interacting organs that compete for resources, based on daily sink strengths and proximity to sources. The actual growth rate of organs is not predetermined by empirical data, but reflects the pattern of available resources. The major driving variables are solar radiation, temperature, topological, geometrical and physiological factors. Outputs are hourly and daily photosynthate production and respiration, daily dimensional growth, starch sorage, biomass production and total number of different types of organ. The user can interact or override any or all of the input variables to examine the effects of such changes on photosynthate production and growth. Within INCA, the tree entities and the surrounding environment are structured in a frame-based representation whereas the processes are coded in a rule-based language. The simulation mechanism is primarilybased on the rule chaining capabilities of an inference engine.; L'article présente un modèle écophysiologique de croissance et développement du noyer. INCA vise à intégrer les connaissances architecturales et physiologiques que l'on a sur le sujet, de manière à optimiser les opérations de taille.

Xenon is a fission product of uranium that must be monitored on line and in real time in the cover gas of a sodium cooled fast neutron reactor (SFR) for safety reasons. In this paper, tunable diode laser absorption spectroscopy is applied to quantify low concentrations of natural xenon in argon. Optical detection is carried out at 12 145 cm−1 (823 nm) from the 6s[3/2]02 Xe electronic metastable state, populated in a low pressure DC glow discharge. Optimal discharge parameters (110 Pa, 1.3 W) were experimentally determined to maximize the laser absorption signal. Measurement stability, argon pressure spectral broadening, isotope quantification, and linearity of the optical measurement with respect to the xenon concentration in the gas sample were carefully investigated. Under optimized experimental conditions, the detection limit of xenon over argon molar ratio is estimated as 60 ± 10 parts per billion at 1 Hz, corresponding to a xenon number density of 1.6 × 109 atoms.cm−3 along the laser beam.

Michelson-less Fourier spectra, comprising 500,000,000 spectral elements spanning 1 nm with 2.3 kHz (7.7 10^-8 cm^-1) resolution, are recorded within 6s. Moving mirror of equivalent interferometers should cover 130 km at 78,000 km/hour velocity.

Laser frequency combs are triggering new powerful approaches to multiplex or parallel spectroscopy aimed at achieving sensitive and accurate detections of multiple molecular species over a broad spectral window. Amongst them, Fourier transform spectroscopy based on the time-domain interferences between two independent frequency combs of slightly different repetition rates has a considerable potential for extremely high resolutions and remarkably short acquisition times. However, up to now, simple set-ups have exhibited limited spectral resolution broadband spectra [1], while high resolution on limited spectral ranges was only achieved with significant effort [2] by using state-of-the-art reference cavities to stabilize the two frequency combs.

Dual-comb Fourier transform spectroscopy with cavity enhancement holds much promise for trace gas sensing. Broadband high resolution spectra of ammonia around 1.0 µm are recorded within 18 µs and a noise-equivalent-absorption of 1 10−10 cm−1Hz−½.

Multipass cells offer a simple manner to enhance the sensitivity of dual-comb Fourier transform spectrometer. 1.5 µm spectra spanning 125 nm and exhibiting a noise-equivalent absorption coefficient of 4·10−9 cm−1Hz−½ are recorded within 63 µs.