Localizing transient acoustic signals has a dual interest. It may contribute to area surveillance. It also constitutes a protection against snipers. For these reasons, acoustic localization systems have been developed and satisfactorily evaluated in open outdoor environments. In urban environments though, the ground surface and the surrounding buildings strongly modulate the acoustic propagation, through reflection, masking and/or diffraction of the signal. These modulations dramatically degrade the performance of standard systems for acoustic localization. The challenge is to conceive and develop an innovative system which can integrate the complex propagation features caused by urban environments. The French-German Research Institute Saint-Louis (ISL) has developed a preliminary acoustic localization system, based on the concept of time reversal. The principle is to measure the transient signal at various locations in the urban environment, reverse the chronology of signals, and simulate the propagation of the reversed signals within the synthetic urban environment. The maximum interference gives the source position. The system has been satisfactorily tested in idealized frameworks. The tests also pointed the necessity of a more exhaustive and efficient description of signal propagation in the urban environment. The LORETA project (LOcalisation par Retournement Temporel Acoustique) is a research initiative with balanced contributions from the ISL and the Laboratoire de Mécanique des Fluides et d’Acoustique (LMFA). The general purpose of the project is to pursue the development and evaluation of the time-reversal localization system. The project is based on 59 months of work and lasts 30 months. It will gather the theoretical, modelling and experimental skills of six permanent researchers and a post-doc. A first, upstream research goal is to document the propagation of transient sounds in the presence of obstacles and ground effects. Indoor acoustic measurements will be coupled to a Schlieren imaging system. The observations will be compared to an up-to-date numerical modelling of the sound propagation in the time domain. Outdoor propagation measurements will also be performed. The so-formed dataset may be distributed. The second research task is aimed at developing and testing reduced numerical solutions in order to simulate sound propagation in the localization system. Existing models will be compared with the observational data acquired in the upstream research task. The evaluation will account for reliability and computational request. The selected solutions will be integrated in the sound propagation model used for localization. The model will be evaluated in a reference outdoor, urban scenario. The third research task is to quantify the performance of the time-reversal localization system within the above reference scenario. Specifically, we will investigate the performance sensitivity to (i) modulations of sound propagation induced by the atmosphere, (ii) the location and number of deployed acoustic sensors, and (iii) the refinement of the sound propagation model relative to the computational request. Finally, specific dissemination and exploitation initiatives are proposed toward the scientific and technical communities involved with the outdoor sound propagation and the localization of acoustic sources such as gun shots. With these dual purposes and with the innovative scientific goals, the proposed research project particularly fits with the scientific objectives of the ASTRID call.

The goal of the SUPREMATIE project consists in investigating the possibility of priming high explosives by the decomposition of nanothermites. Nanothermites are versatile energetic compositions which are prepared by mixing nanoparticles of metallic oxides and a reducing metal. The mixture can be performed either by dispersing nanopowders in a liquid or by a chemical coating process. The energy released per unit volume by the combustion of thermites is higher than the one of most explosives. Classical thermites are made of micrometric particles. Their decomposition rates are slow and are responsible for their small combustion power. Conversely, nanothermites possess decomposition rates which are close to those of explosives. The power released by the combustion of nanothermites seems to be high enough to induce the deflagration -or even the detonation- of high explosives. The explosives that will be studied to validate the concept are: the pentrite (PETN), the hexogen (RDX) and the hexanitrohexaazaisowurtzitane (CL-20). The priming of the explosives will be studied by using the aluminothermic reaction of nanothermites which have been identified by the experimental characterization as the most reactive (e.g. WO3/Al; CuO/Al; Bi2O3/Al…) Up to now, the priming of high explosives is performed by the detonation of primary explosives such as metallic azides or fulminates (Ag, Pb, Hg), or the perchlorates of nitrogen complexes of transition metals (BNCP). The use of nanothermites for this purpose is a novel concept. Nanothermites have the advantage of being very stable along time and far less sensitive to thermal and impact stresses than primary explosives. Furthermore, nanothermites have extremely reproducible reactive properties and can be activated by mixing processes just before being ignited. The demonstration of the fact that high explosives could be primed by nanothermites should open new horizons in the field of pyrotechnic security, due to the relative -or absolute- flegmatisation of the most sensitive components of pyrotechnic chains. In addition, the chemicals used to formulate nanothermites can be chosen in order to minimize the toxicity of the nanothermite and of its combustion products. These aspects are all the more important as the use of explosives for civilian purposes will considerably increase in the coming years. Many fields of human activity are concerned: civilian security; spatial, automotive pyrotechnics; fireworks; demolition of concrete structures; natural resources extraction; treatment of nuclear waste and novel applications in electronics or medicine. The validation of the concept proposed in this project could lead to dual applications corresponding to well-defined needs. The last step of the project will consist to study the integration of {nanothermite + explosive} systems in 9 mm bullets used by homeland security services. These high energy ammunitions will significantly improve the defensive response ability of the law enforcement officers against criminals armed with assault weapons.

Current pulsed power supplies (PPS) for applications as high magnetic field generation, electromagnetic forming or electromagnetic launchers are typically based on capacitive storage and therefore very bulky. In order to integrate a pulsed power generator in a mobile system, it is necessary to reduce the size and weight of such a generator. Due to its higher energy density compared to capacitors, inductive storage offers the possibility of remarkable size reduction. This proposal deals with an inductive XRAM generator which can be used to generate high power pulses at low inductive loads. The concept of an XRAM generator is to charge several inductances in series and discharged them in parallel to a load. By this, a limited charging current can be multiplied. In this project, the ISL and the LNCMIpropose the setup of a 1 MJ XRAM generator in order to demonstrate the feasibility of this PPS for high energy/high power applications. The XRAM principle was successfully tested in earlier works at ISL with different setups. Now, this generator will be tested in combination with Li-ion batteries as primary energy source and a medium caliber railgun as load. Railgun experiments with supply currents up to 800 kA will be compared to experiments from the past which were performed with capacitor banks. Based on the experimental results, we will design a multiple megajoule XRAM generator for a railgun artillery system which will be able to launch projectiles with a mass of 5 kg to a distance of 200 km. The goal of this project is to verify the compactness of an inductive system with current multiplication compared to a capacitor based PPS and to show that such system can be mobile by size and weight estimation.

The whole range of the electromagnetic spectrum gives access to a wide variety of characterization and imaging techniques to study the physical and chemical properties of matter at different size and timescales. But due to the lack of suitable lasers sources or efficient detectors, the entire range is not covered. The middle infrared (midIR) remains one of the last frontier between 2 and 8 µm, where ultrashort, intense and coherent sources are not optimized. Yet, the development of broadband, widely tunable and intense midIR sources in the 2-12 µm is of great importance not only for basic research but also for applications in medicine, defense and security in band I (0,5-2,5 µm), II (3-5,5 µm). Depending on the targeted application, a greater emphasis is given to the high energy, the bandwidth or the tunability: since midIR spans over most of the vibrational and rotational spectra of molecules, it is well-suited for hyperspectral imaging, or atmospheric gas sensing with LIDAR. Nevertheless, the rarity of midIR-emitting lasers material makes it difficult to efficiently produce ultrashort lasers in this range. To reach this frequency domain, the available near infrared lasers (Ti:Sa, Yb) are converted with non-linear techniques. However, these methods suffers from limitations due to the strong midIR absorption of the common crystals, the high pump absorption by the crystals transparent in the midIR (AgGaS2 and other chalcogenides, ZGP, CSP) pumped with near infrared laser, and the multiphoton absorption of the pump at wavelength 1 kHz) subpicosecond source emitting at 2 µm. Its hybrid fiber-solid architecture is compact and robust, and suitable for integration. These features are of high interest for both academic and industrial applications. The energy will be further increased up to 30-40 mJ, adapted for the generation of intense secondary radiations with with both civil and defense applications. It is particularly well suited for XUV generation up to keV energy, but also for efficient pumping generation of an exceptionally large range midIR wavelengths via optical parametric amplification in nonlinear crystals. Depending on the application (civil or defense), either an intense ultrashort (few cycle) radiation, or an ultrabroad bandwidth (1 to 3 octaves), or else a broadly tunable narrowband spectrum will cover midIR band II.

The aim of the project proposed by Bertin Technologies, CEA and ISL is to develop a system to assist in the detection, recognition and identification of threats in the visible and infrared domains. The algorithm developed during this project is intended to be embedded in optronic systems used in the battlefield. It will therefore be subject to material and energy frugality constraints. The proposed approach will rely on artificial intelligence solutions based on deep neural networks. This technology is very promising for detection, recognition and identification applications. However, it requires supervised learning with a lot of annotated data representative of the usecases, which is difficult to obtain for military applications, as well as a high computing power during use. ISL, CEA and Bertin Technologies will bring their expertise to bear in data acquisition, AI training and optimisation, hardware integration and optronics to overcome the three technical hurdles of learning from a frugal dataset, joint exploitation of visible and infrared data, and frugality in computing power. A demonstration model based on Bertin Technologies' existing optronic solutions will be produced in order to validate the solution developed. This project is in line with French and European strategies to pursue research efforts in the field of AI, which has major economic and strategic implications. From a military point of view, it addresses strong tactical and operational challenges, in particular for surveillance, reconnaissance, identification and intelligence gathering applications. Embedded in optronic systems, artificial intelligence can facilitate the processing of information transmitted by sensors, limit the risks of human error, facilitate rapid decision-making and optimize the consumption of sensor batteries. Threat detection, recognition and identification functions are also of interest in civilian areas, particularly in the surveillance of sensitive areas (ports, borders) or industrial sites, as well as self driving cars.