The potential of fiber-based sensors to monitor the fluence of atmospheric neutrons is evaluated ... more The potential of fiber-based sensors to monitor the fluence of atmospheric neutrons is evaluated through accelerated tests at the TRIUMF Neutron Facility (TNF) (BC, Canada), offering a flux approximatively 109 higher than the reference spectrum observed under standard conditions in New York City, USA. The radiation-induced attenuation (RIA) at 1625 nm of a phosphorus-doped radiation sensitive optical fiber is shown to linearly increase with neutron fluence, allowing an in situ and easy monitoring of the neutron flux and fluence at this facility. Furthermore, our experiments show that the fiber response remains sensitive to the ionization processes, at least up to a fluence of 7.1 × 1011 n cm−², as its radiation sensitivity coefficient (~3.36 dB km−1 Gy−1) under neutron exposure remains very similar to the one measured under X-rays (~3.8 dB km−1 Gy−1) at the same wavelength. The presented results open the way to the development of a point-like or even a distributed dosimeter for natu...
Spacecraft charging issues related to GEO concern all dielectric surfaces susceptible to charge t... more Spacecraft charging issues related to GEO concern all dielectric surfaces susceptible to charge to significant voltages because of the space environment. Testing materials helps defining margins and keeping a good level of confidence on spacecraft resistance to damaging effects. Another aspect of spacecraft charging analysis relies on numerical simulation. Several tools aims at calculating surface charging in harsh environments, in the energy range of some to hundreds of keV, produced by geomagnetic sub storms. Main codes include: NASCAP, SPIS, MUSCAT and Coulomb-2. They use different numerical and sometimes physical models and cross checking their results is a progress need to get better confidence in simulations performed by spacecraft prime manufacturers. The objective of this paper is to simulate different GEO spacecraft configurations with NASCAP and SPIS and to compare the results, both in terms of absolute and differential potentials. The first section corresponds to SCATHA spacecraft. The second part of this paper presents efforts to model a modern telecom spacecraft. Lastly, we conclude on the reliability of the simulations performed and possible rooms for modelling amelioration.
ABSTRACT Version 5.1 of Spacecraft Plasma Interaction Software (SPIS) has been recently released ... more ABSTRACT Version 5.1 of Spacecraft Plasma Interaction Software (SPIS) has been recently released and is freely available for download to the whole community. It is the outcome of European Space Agency studies, SPIS-Geostationary Earth Orbit (GEO) and SPIS-SCI, and several contributions from the Spacecraft Plasma Interaction Network in Europe community members. It also relies on a Centre national d’études spatiales-sponsored activity to identify user needs of the industry for charging analysis. SPIS is now used in a much wider scope of applications than initially expected, from mission definition to in-flight scientific measurements analysis. The first version of a new modernized generation SPIS 5.1 aims to address these new issues and challenges in spacecraft surface interaction modeling, including spacecraft charging of commercial missions in Medium Earth Orbit/GEO. For this, SPIS 5.1 offers a simplified user interface and introduces new state-of-the-art software technologies.
47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, 2009
For a few years, active airflow control by plasma actuator has been enriched by a comprehensive l... more For a few years, active airflow control by plasma actuator has been enriched by a comprehensive literature focused on the analysis of the discharge interaction with the surrounding airflow as on its potential industrial applications. Flow around flat plate, airfoil model, turbine blades, cylinder have been extensively studied. In this paper, plasma actuators are used to control the jet exhausting from a circular pipe (internal diameter of 50 mm) equipped with a small-angle diffuser (α=22°). Two plasma actuators are placed in opposite position at the wall of the diffuser. The electrode arrangement produces a counter-flow action on the initial region of the free turbulent shear layer. PIV measurements are used to characterize the time-averaged flow fields for baseline and controlled airjet at a primary airjet velocity of 20 m/s (Re D =64.000). The control strategy involves actuation by two dielectric barrier discharges operating in phase (axisymmetric excitation mode) and with a π/2 angle phase (flapping excitation mode). The time-averaged results indicate that axisymmetric actuation fails to enhance the mixing in the jet wake. Streamlines and spatial POD modes reveals that actuation acts on the vortex organization but the imparted energy is too weak to alter the far field region. This differs from the obtained results with flapping excitation. In this case, the potential core is largely shortened, the jet spreading is enlarged and the vortex dynamic is strongly affected by the actuation. In particular, results demonstrate that a significant mixing enhancement is performed when the actuation is in flapping mode at a normalized frequency St=0.1.
The aim of the present work is to demonstrate the versatility of surface discharges for airflow c... more The aim of the present work is to demonstrate the versatility of surface discharges for airflow control in realflight atmospheric conditions. The effects of the air pressure on the electromechanical properties of a single dielectric barrier discharge (DBD) are investigated experimentally in a vacuum chamber. This work shows that the pressure significantly modifies the DBD behaviour without affecting its ability to generate an electric wind suitable for various aeronautics applications. At low pressure (down to 0.2 atm) a considerable plasma extension is observed. Hence two DBD configurations have been tested. Many velocity profiles have been measured in both x and y directions. These local values greatly help the understanding of the EHD conversion compared to balance measurements that only give access to the global force production. Indeed, our results show that the mass flow rate and the induced electric wind velocity exhibit different behaviours when the pressure is decreased. Despite the drop of the mass flow rate imparted to the gas below 0.4 atm it is remarkable that the surrounding fluid velocity rises with decreasing pressure if the grounded electrode is sufficiently long. This is of major importance in the perspective of airfoil separation control or other applications based on boundary layer manipulation.
The properties of a pulsed radio frequency capacitive discharge are investigated at atmospheric p... more The properties of a pulsed radio frequency capacitive discharge are investigated at atmospheric pressure in argon. The discharge can operate in two different modes: a homogeneous glow discharge or turn into filaments. By pulsing the 13.56 MHz generator both the filamentary and the glow modes can be selected depending on the pulse width and period. For a 5 µs pulse width (∼70 RF cycles in the pulse), short pulse periods (less than 100 µs) result in a filamentary discharge while long pulse periods (greater than 1 ms) result in a glow discharge.
The electrical properties of a gliding arc operating in air at atmospheric pressure are studied t... more The electrical properties of a gliding arc operating in air at atmospheric pressure are studied to evaluate its possible applications to flow control. The electromechanical behaviour of the discharge travelling at 4 m s −1 along diverging electrodes in a static magnetic field is analysed in detail. Two different methods are proposed to evaluate the velocity of the arc. An initial estimation is based on the arc current evolution during its transit and additional information is gained from fast digital imaging with a CCD camera. The displacement of the arc observed with short exposure time corroborates the electrical measurement and also exhibits the existence of luminous points on the cathode that can slow down the arc motion. In addition, a particle image velocimetry system is used to investigate the interaction between the gliding arc and the surrounding air. The displacement of the low current glidarc creates a low velocity convection (around 0.2 m s −1 ) in the gas and also generate faster structures up to 1 m s −1 directly in front of the discharge. These electromechanical effects could be used to manipulate the boundary layer region of various aerodynamic shapes.
A new collisional-radiative model for atmospheric-pressure low-temperature argon discharges is pr... more A new collisional-radiative model for atmospheric-pressure low-temperature argon discharges is proposed, which illustrates the significant effect of electron density on the excited atom population distribution. This makes it possible to determine the electron density from the intensity ratio of emission lines of excited atoms. Results of this new method in several types of atmospheric-pressure discharges are found to be in agreement with those of the Stark broadening method and the electric model over a wide electron density range 10 11 -10 16 cm −3 .
Teflon Fluorinated Ethylene Propylene (FEP), used as thermal blankets on satellites, has a specif... more Teflon Fluorinated Ethylene Propylene (FEP), used as thermal blankets on satellites, has a specific electrical behavior under space ionizing environment. Charging behaviors of this dielectric material, under electron beam irradiation, is of special interest for future spacecraft needs. Hence, ground experimental parameters have been adjusted in order to distinguish between the different physical mechanisms that steers FEP charging potential. The effect of incident electron spectrum, electric field, and dose rate has been investigated through surface potential measurements during and after the irradiation process. The experimental results especially reveal that charging potential evolution as a function of time is not strongly dependent upon the electron spectrum and the electric field but varies noticeably with dose rate. These results have been analyzed in the light of a physical model that takes into account ionization, trapping/detrapping, and recombination mechanisms for negative and positive charges.
A characterization method for surface charging analysis on insulators submitted to electron irrad... more A characterization method for surface charging analysis on insulators submitted to electron irradiation has been developed. This method, based on the use of two Kelvin probes (KPs), provides details on the transit time motion for injection of both holes and electrons. It can also be used to assess the isotropy of lateral electrical conduction on the sample. The feasibility of this method was tested on fluorinated ethylene propylene (Teflon® FEP) samples. It was found that central electron injection induces rapid surface charge spreading, in contrast to injection of holes. An electrical anisotropic behaviour of the sample was also detected.
The radiation-induced conductivity of some polymers was described mainly in literature by a compe... more The radiation-induced conductivity of some polymers was described mainly in literature by a competition between ionization, trapping/detrapping, and recombination processes or by radiation assisted ageing mechanisms. Our aim is to revise the effect of the aforementioned mechanisms on the complex evolution of Teflon V R FEP under space representative ionizing radiation. Through the definition of a new experimental protocol, revealing the effect of radiation dose and relaxation time, we have been able to demonstrate that the trapping/recombination model devised in this study agrees correctly with the observed experimental phenomenology at qualitative level and allows describing very well the evolution of radiation induced conductivity with irradiation time (or received radiation dose). According to this model, the complex behavior observed on Teflon V R FEP may be basically ascribed to the competition between electron/hole pairs generation and recombination: electrons are deeply trapped and act as recombination centers for free holes. Relaxation effects have been characterized through successive irradiations steps and have been again well described with the defined model at qualitative level: recombination centers created by the irradiation induce long term alteration on the electric properties, especially the effective bulk conductivity. One-month relaxation does not allow a complete recovery of the material initial charging behavior. V C 2014 AIP Publishing LLC. [http://dx.
A physical flashover (FO) simulator has been developed by ONERA/DESP and CNES. The objective of t... more A physical flashover (FO) simulator has been developed by ONERA/DESP and CNES. The objective of this simulator is to represent the missing cells when testing small coupons in the laboratory. The aim of this paper is to present the results of a parametric study which has been performed on a sample constituted by a solar-array coupon made of six cells
Dedicated experimental facilities have been developed at ONERA and CNES (Toulouse, France) for th... more Dedicated experimental facilities have been developed at ONERA and CNES (Toulouse, France) for the electrical qualification of space used materials and the extraction of the different physical parameters steering their charging behaviour under electron irradiation. These facilities allow working in a large energy range between few eV up to several MeV, a large temperature range (down to -150°C and up to 600°C depending on the facility) and at high vacuum level. This paper aims at presenting the technical characteristics of these different facilities.
The potential of fiber-based sensors to monitor the fluence of atmospheric neutrons is evaluated ... more The potential of fiber-based sensors to monitor the fluence of atmospheric neutrons is evaluated through accelerated tests at the TRIUMF Neutron Facility (TNF) (BC, Canada), offering a flux approximatively 109 higher than the reference spectrum observed under standard conditions in New York City, USA. The radiation-induced attenuation (RIA) at 1625 nm of a phosphorus-doped radiation sensitive optical fiber is shown to linearly increase with neutron fluence, allowing an in situ and easy monitoring of the neutron flux and fluence at this facility. Furthermore, our experiments show that the fiber response remains sensitive to the ionization processes, at least up to a fluence of 7.1 × 1011 n cm−², as its radiation sensitivity coefficient (~3.36 dB km−1 Gy−1) under neutron exposure remains very similar to the one measured under X-rays (~3.8 dB km−1 Gy−1) at the same wavelength. The presented results open the way to the development of a point-like or even a distributed dosimeter for natu...
Spacecraft charging issues related to GEO concern all dielectric surfaces susceptible to charge t... more Spacecraft charging issues related to GEO concern all dielectric surfaces susceptible to charge to significant voltages because of the space environment. Testing materials helps defining margins and keeping a good level of confidence on spacecraft resistance to damaging effects. Another aspect of spacecraft charging analysis relies on numerical simulation. Several tools aims at calculating surface charging in harsh environments, in the energy range of some to hundreds of keV, produced by geomagnetic sub storms. Main codes include: NASCAP, SPIS, MUSCAT and Coulomb-2. They use different numerical and sometimes physical models and cross checking their results is a progress need to get better confidence in simulations performed by spacecraft prime manufacturers. The objective of this paper is to simulate different GEO spacecraft configurations with NASCAP and SPIS and to compare the results, both in terms of absolute and differential potentials. The first section corresponds to SCATHA spacecraft. The second part of this paper presents efforts to model a modern telecom spacecraft. Lastly, we conclude on the reliability of the simulations performed and possible rooms for modelling amelioration.
ABSTRACT Version 5.1 of Spacecraft Plasma Interaction Software (SPIS) has been recently released ... more ABSTRACT Version 5.1 of Spacecraft Plasma Interaction Software (SPIS) has been recently released and is freely available for download to the whole community. It is the outcome of European Space Agency studies, SPIS-Geostationary Earth Orbit (GEO) and SPIS-SCI, and several contributions from the Spacecraft Plasma Interaction Network in Europe community members. It also relies on a Centre national d’études spatiales-sponsored activity to identify user needs of the industry for charging analysis. SPIS is now used in a much wider scope of applications than initially expected, from mission definition to in-flight scientific measurements analysis. The first version of a new modernized generation SPIS 5.1 aims to address these new issues and challenges in spacecraft surface interaction modeling, including spacecraft charging of commercial missions in Medium Earth Orbit/GEO. For this, SPIS 5.1 offers a simplified user interface and introduces new state-of-the-art software technologies.
47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, 2009
For a few years, active airflow control by plasma actuator has been enriched by a comprehensive l... more For a few years, active airflow control by plasma actuator has been enriched by a comprehensive literature focused on the analysis of the discharge interaction with the surrounding airflow as on its potential industrial applications. Flow around flat plate, airfoil model, turbine blades, cylinder have been extensively studied. In this paper, plasma actuators are used to control the jet exhausting from a circular pipe (internal diameter of 50 mm) equipped with a small-angle diffuser (α=22°). Two plasma actuators are placed in opposite position at the wall of the diffuser. The electrode arrangement produces a counter-flow action on the initial region of the free turbulent shear layer. PIV measurements are used to characterize the time-averaged flow fields for baseline and controlled airjet at a primary airjet velocity of 20 m/s (Re D =64.000). The control strategy involves actuation by two dielectric barrier discharges operating in phase (axisymmetric excitation mode) and with a π/2 angle phase (flapping excitation mode). The time-averaged results indicate that axisymmetric actuation fails to enhance the mixing in the jet wake. Streamlines and spatial POD modes reveals that actuation acts on the vortex organization but the imparted energy is too weak to alter the far field region. This differs from the obtained results with flapping excitation. In this case, the potential core is largely shortened, the jet spreading is enlarged and the vortex dynamic is strongly affected by the actuation. In particular, results demonstrate that a significant mixing enhancement is performed when the actuation is in flapping mode at a normalized frequency St=0.1.
The aim of the present work is to demonstrate the versatility of surface discharges for airflow c... more The aim of the present work is to demonstrate the versatility of surface discharges for airflow control in realflight atmospheric conditions. The effects of the air pressure on the electromechanical properties of a single dielectric barrier discharge (DBD) are investigated experimentally in a vacuum chamber. This work shows that the pressure significantly modifies the DBD behaviour without affecting its ability to generate an electric wind suitable for various aeronautics applications. At low pressure (down to 0.2 atm) a considerable plasma extension is observed. Hence two DBD configurations have been tested. Many velocity profiles have been measured in both x and y directions. These local values greatly help the understanding of the EHD conversion compared to balance measurements that only give access to the global force production. Indeed, our results show that the mass flow rate and the induced electric wind velocity exhibit different behaviours when the pressure is decreased. Despite the drop of the mass flow rate imparted to the gas below 0.4 atm it is remarkable that the surrounding fluid velocity rises with decreasing pressure if the grounded electrode is sufficiently long. This is of major importance in the perspective of airfoil separation control or other applications based on boundary layer manipulation.
The properties of a pulsed radio frequency capacitive discharge are investigated at atmospheric p... more The properties of a pulsed radio frequency capacitive discharge are investigated at atmospheric pressure in argon. The discharge can operate in two different modes: a homogeneous glow discharge or turn into filaments. By pulsing the 13.56 MHz generator both the filamentary and the glow modes can be selected depending on the pulse width and period. For a 5 µs pulse width (∼70 RF cycles in the pulse), short pulse periods (less than 100 µs) result in a filamentary discharge while long pulse periods (greater than 1 ms) result in a glow discharge.
The electrical properties of a gliding arc operating in air at atmospheric pressure are studied t... more The electrical properties of a gliding arc operating in air at atmospheric pressure are studied to evaluate its possible applications to flow control. The electromechanical behaviour of the discharge travelling at 4 m s −1 along diverging electrodes in a static magnetic field is analysed in detail. Two different methods are proposed to evaluate the velocity of the arc. An initial estimation is based on the arc current evolution during its transit and additional information is gained from fast digital imaging with a CCD camera. The displacement of the arc observed with short exposure time corroborates the electrical measurement and also exhibits the existence of luminous points on the cathode that can slow down the arc motion. In addition, a particle image velocimetry system is used to investigate the interaction between the gliding arc and the surrounding air. The displacement of the low current glidarc creates a low velocity convection (around 0.2 m s −1 ) in the gas and also generate faster structures up to 1 m s −1 directly in front of the discharge. These electromechanical effects could be used to manipulate the boundary layer region of various aerodynamic shapes.
A new collisional-radiative model for atmospheric-pressure low-temperature argon discharges is pr... more A new collisional-radiative model for atmospheric-pressure low-temperature argon discharges is proposed, which illustrates the significant effect of electron density on the excited atom population distribution. This makes it possible to determine the electron density from the intensity ratio of emission lines of excited atoms. Results of this new method in several types of atmospheric-pressure discharges are found to be in agreement with those of the Stark broadening method and the electric model over a wide electron density range 10 11 -10 16 cm −3 .
Teflon Fluorinated Ethylene Propylene (FEP), used as thermal blankets on satellites, has a specif... more Teflon Fluorinated Ethylene Propylene (FEP), used as thermal blankets on satellites, has a specific electrical behavior under space ionizing environment. Charging behaviors of this dielectric material, under electron beam irradiation, is of special interest for future spacecraft needs. Hence, ground experimental parameters have been adjusted in order to distinguish between the different physical mechanisms that steers FEP charging potential. The effect of incident electron spectrum, electric field, and dose rate has been investigated through surface potential measurements during and after the irradiation process. The experimental results especially reveal that charging potential evolution as a function of time is not strongly dependent upon the electron spectrum and the electric field but varies noticeably with dose rate. These results have been analyzed in the light of a physical model that takes into account ionization, trapping/detrapping, and recombination mechanisms for negative and positive charges.
A characterization method for surface charging analysis on insulators submitted to electron irrad... more A characterization method for surface charging analysis on insulators submitted to electron irradiation has been developed. This method, based on the use of two Kelvin probes (KPs), provides details on the transit time motion for injection of both holes and electrons. It can also be used to assess the isotropy of lateral electrical conduction on the sample. The feasibility of this method was tested on fluorinated ethylene propylene (Teflon® FEP) samples. It was found that central electron injection induces rapid surface charge spreading, in contrast to injection of holes. An electrical anisotropic behaviour of the sample was also detected.
The radiation-induced conductivity of some polymers was described mainly in literature by a compe... more The radiation-induced conductivity of some polymers was described mainly in literature by a competition between ionization, trapping/detrapping, and recombination processes or by radiation assisted ageing mechanisms. Our aim is to revise the effect of the aforementioned mechanisms on the complex evolution of Teflon V R FEP under space representative ionizing radiation. Through the definition of a new experimental protocol, revealing the effect of radiation dose and relaxation time, we have been able to demonstrate that the trapping/recombination model devised in this study agrees correctly with the observed experimental phenomenology at qualitative level and allows describing very well the evolution of radiation induced conductivity with irradiation time (or received radiation dose). According to this model, the complex behavior observed on Teflon V R FEP may be basically ascribed to the competition between electron/hole pairs generation and recombination: electrons are deeply trapped and act as recombination centers for free holes. Relaxation effects have been characterized through successive irradiations steps and have been again well described with the defined model at qualitative level: recombination centers created by the irradiation induce long term alteration on the electric properties, especially the effective bulk conductivity. One-month relaxation does not allow a complete recovery of the material initial charging behavior. V C 2014 AIP Publishing LLC. [http://dx.
A physical flashover (FO) simulator has been developed by ONERA/DESP and CNES. The objective of t... more A physical flashover (FO) simulator has been developed by ONERA/DESP and CNES. The objective of this simulator is to represent the missing cells when testing small coupons in the laboratory. The aim of this paper is to present the results of a parametric study which has been performed on a sample constituted by a solar-array coupon made of six cells
Dedicated experimental facilities have been developed at ONERA and CNES (Toulouse, France) for th... more Dedicated experimental facilities have been developed at ONERA and CNES (Toulouse, France) for the electrical qualification of space used materials and the extraction of the different physical parameters steering their charging behaviour under electron irradiation. These facilities allow working in a large energy range between few eV up to several MeV, a large temperature range (down to -150°C and up to 600°C depending on the facility) and at high vacuum level. This paper aims at presenting the technical characteristics of these different facilities.
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Papers by Nicolas Balcon