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Multipactor effect is an electronic avalanche which can happen in vacuum. It is the result of a synchronism between the radio frequency (RF) wave and the electron emission [1]. This phenomena particularly affects particle accelerators [2], radio frequency (RF) devices of fusion reactors [3] and spacecraft telecommunication payloads [4]. Multipactor can be described theoretically [5] for geometries such as parallel plate situations or rectangular waveguide. But it became quickly necessary to use Monte Carlo simulations due to the number of parameters influencing on multipactor dynamics [6] and to introduce more detailed inputs. Particle in cell (PIC) method aims to follow macro particles in the position and velocity phase in interaction with a field of force. This method is used in commercial softwares (Spark 3D, CST, HFSS,...) [7] that are commonly utilized inn espace industry. Their main goal is the calculation of multipactor power threshold which is the minimal electromagnetic(EM) power for which multipactor happen. Today, dielectrics are more and more used in RF devices onboard satellites to reduce the dimensions and the weight of the microwave-components. But the effects of dielectrics on multipactor are still not well understood. Therefore, high RF power margins are applied on such devices including dielectrics. Reduce this margin requires to identify and treat critical sections where multipactor occurs. Coves et al [8] have modeled the multipactor discharge in parallel-plate dielectric waveguide and demonstrated that under certain circumstances the static field generated by the multipactor turns-off the electron avalanche. More recently theoretical works [9] have shown that in parallel-plate geometry with small gap the multipactor power threshold varies as function of the applied DC electric field. In the case of dielectric presence, complexity of multipactor effect is coupled to dynamic charge of dielectric. This situation requires a better understanding of the numerical method used in the simulation of the multipactor phenomenon. In this contribution we present an open source 3D mutipactor simulation software. It is able to model multipactor in metallic devices and in situations where dielectric materials are used and influences the multipactor avalanche. We will consider the multipactor avalanche in combination to dynamic dielectrics charging. In this contribution, we present the results of such a code called SPIS-multipactor as it is based on SPIS numerical core [10]. First SPIS-multipactor numerical core is presented. The results of this code was then benchmarked with CST and SPARK 3D codes in a waveguide developed in the framework of Everest Project [11]. Finally, space charge saturation phenomena in the vacuum is investigated, the link between multipactor and dielectric charging dynamics will also be discussed.

Secondary electron emission often appears as a parasitic physical process in systems that either use electrons of a few hundred eV, or that can evolve in an environment where low energy electrons are present [1]. In certain cases, by an avalanche phenomenon, electrons can multiply to a level that can disturb the functioning of sensitive equipments (multipactor) [1] or lead to catastrophic effects such as corona discharges. Multipacting is an issue for space systems that undergo electrons trapped in the earth radiation belts [2]. The satellite’s power chain is particularly sensitive to this physical mechanism. In this context, the risk associated with the electron secondary emission can be mitigated by surface treatments [3] of the walls of the Radio Frequency (RF) devices. The Total Electron Emission Yield (TEY) is closely dependent to the surface state and to the nature of the coating deposited on the material. For instance, the chemical state of the surface is modified by the irradiation in a way that the TEY can be reduced. It is known that irradiations can polymerize organic molecules present at the surface of the material and fix on it a layer of graphite. Since graphite has a low emission yield, the presence of a layer of a few nanometres thick is sufficient to drive and reduce the TEY [4]. This has been shown experimentally [4], but, few numerical simulations of such behaviour have already been performed. The objective of the work presented here, is to study numerically the impact of thin carbon layers of different thicknesses, on the SEY of Ag and Cu substrates, using Monte Carlo simulations [5-[8].

Thruster plume simulations often use a hybrid approach, modeling ions as particles and electrons as a fluid. Nevertheless, the definition of the pressure law in the fluid transport of electrons can be quite challenging. In this paper, the consequence of the pressure law assumption on plasma plume simulation results is deeply analyzed. To validate our approach, modeling outcomes must be compared with experimental results. This has been done through comparisons between simulation results and in-flight data taken from the Retarding Potential Analyzers (RPA) placed on the solar arrays on the Russian geostationary telecommunication satellite Express-A #3. The RPA allows the measurements of ion current at different distances and field of view configurations with regard to the thrusters. In this paper, a new method to couple plasma simulation to an RPA analytical model is presented. It enables to couple a plasma simulation to an advanced analytical RPA probe model, taking into account the effects of misoriented RPA. Results demonstrate that the electron pressure law can significantly affect primary ion trajectories. The results are compared to Express-A RPA data., Les simulations de panache de propulseur utilisent souvent une approche hybride, modélisant les ions comme des particules et les électrons comme un fluide. Néanmoins, la définition de la loi de pression dans le transport fluide des électrons peut être assez difficile. Dans cet article, la conséquence de l'hypothèse de la loi de pression sur les résultats de la simulation du panache de plasma est analysée en profondeur. Pour valider notre approche, les résultats de la modélisation doivent être comparés aux résultats expérimentaux. Cela a été fait grâce à des comparaisons entre les résultats de simulation et les données en vol tirées des analyseurs de potentiel retardateur (RPA) placés sur les panneaux solaires du satellite de télécommunication géostationnaire russe Express-A #3. Le RPA permet les mesures de courant ionique à différentes distances et configurations de champ de vision par rapport aux propulseurs. Dans cet article, une nouvelle méthode pour coupler la simulation de plasma à un modèle analytique RPA est présentée. Il permet de coupler une simulation plasma à un modèle de sonde RPA analytique avancé, prenant en compte les effets d'une RPA mal orientée. Les résultats démontrent que la loi de pression électronique peut affecter de manière significative les trajectoires des ions primaires. Les résultats sont comparés aux données Express-A RPA.

International audience; This paper presents a novel approach used to test surface material charging under electron flux representative of space conditions below 400 keV. A series of severe environments for surface charging at geosynchronous orbit is extracted from Van Allen Probes data and compared to previous Los Alamos National Laboratory measurements. Middle Earth orbit data presented in this paper does not show major differences with respect to geosynchronous orbit data when looking at electron fluxes integrated above 10 keV. Most differences occur below 10 keV. The experimental protocol used to test material properties consists in adapting the electron flux to worst-case conditions. It is shown that the material properties required to predict electrostatic discharges occurrence must be measured with such an adaptive ground setup.

International audience; The AMBRE experiment onboard the ocean topography mapper JASON-3 aims at measuring auroral particle precipitation using two top-hat analyzers for electrons and ions in the 20 eV-28 keV energy range. The JASON-3 spacecraft that has a nearly circular orbit at an altitude of 1336 km with an inclination of 66◦ , at times probes the equatorward part of the auroral oval in a nearly tangentially manner upon leaving the outer radiation belt. In this region of space, during periods of enhanced geomagnetic activity with small or moderate storms, AMBRE detected recurrent ion bands/micro-injections with energies in the 200 eV-28 keV range and which exhibit clear time of flight dispersions. Ray tracing using single trajectory computations suggests that these ions are launched from a source located in the 8000-12000 km altitudinal range and subsequently propagate downward toward the ionosphere. More radial orbits show that the ion bands are detected inside the diffuse auroral zone up to the encounter of auroral arcs. Such observations of dispersed downflowing ions are new and we argue that these structures are produced by localized wave-particle interactions.

Primary discharge occurs on solar arrays due to their interaction with the space plasma. A solar cell may suffer degradation of electrical performance if the primary discharge occurs at the cell edge. To estimate the power generated at the end of life, it is necessary to study the details of solar cell degradation. However, throughout the world, primary discharge has not been recognized as a cause of solar cell degradation. There is now an international collaboration among institutions in Japan, France, and the United States toward a common international standardization of solar array electrostatic discharge test methods. Round-robin tests were carried out as part of this collaborative research. Laboratory experiments were performed at the same time in three institutions using the same test method and identical solar cells. Solar cell degradation was confirmed at all three institutions. It was found that a multijunction solar cell is more susceptible to damage from primary discharge than a crystalline silicon solar cell. Throughout the round-robin tests, discharge has been shown to be a significant cause of solar cell degradation.

第6回宇宙環境シンポジウム (2009年2月29日-30日. 北九州国際会議場), 6th Spacecraft Enivironment Symposium (February 29-30, 2009. Kitakyushu International Conference Center), 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0064542007, レポート番号: JAXA-SP-09-006

Experiments simulating charging on a geostationary orbit were done in laboratory on a large solar array coupon (592 x 1,333 mm) in order to characterize electrostatic discharges. Such discharges were triggered by inverted voltage gradient situation produced on the coupon biased at - 5,000V by using an electron beam striking the sample. Current probes monitored blow-off and flashover currents produced by electrostatic discharges and showed that almost all the energy stored on the cover-glasses can participate to the flashover discharge. Surface potential measurements performed before and after electrostatic discharges, show neutralization area where the differential voltage between the cover glass surface and the coupon decreased from + 1,000 V to + 200 V. The size of the neutralization zone varied with the discharges: while some discharges produce neutralization on a limited surface, other can produce neutralization all over the coupon., 資料番号: AA0049206042, レポート番号: JAXA-SP-05-001E

For telecommunication satellites, RF equipment switching can lead to coaxial cables electrically floating. In a geostationary orbit, space environment can charge floating cables to potentials as high as some tens of volts. With switches, the charge stored on the core flow out and the generated current can trigger interference or damages on MOS transistors. This paper deals with experimental results at electrostatic behavior level for such cables under electron irradiation. Two coaxial cables used in satellites (an overshield brand of seven coaxial cables and a cable connected to a switch) are irradiated by an electron beam source simulating geostationary orbit equivalent energy range and flux intensity. During these experiments, we monitored the current collection and the voltage gained on core and/or cables shielding after their irradiation in order to evaluate the probable occurrence of an electrostatic discharge., 資料番号: AA0049206031, レポート番号: JAXA-SP-05-001E

In this paper, we propose a quasi-neutral model with non-vanishing current describing the expansion of a plasma in an inter-cellular gap on a satellite solar array. Moreover, an electric arc cathode spot model is proposed in order to give suitable boundary conditions for the expansion model., 資料番号: AA0049206063, レポート番号: JAXA-SP-05-001E

The validation of new solar cell for geostationary satellite application sets the problem of arcing between solar cells triggered by electrostatic discharges (ESD(sup 1)). The main difficulty of a ground test is to properly simulate the transient behavior of one string from the first microsecond of an electrostatic discharge and to take into account all the energy stored on a panel that would be released during hundreds of microseconds. The test set-up to use, with all the physical data we need to take into account, to properly simulate the response of the string to an ESD, is presented in this paper. Since the power losses on the Tempo and Panamsat satellites attributed to electrostatic discharges in 1997 (15 percent of the power in three months), the international scientific community has looked into the problem of sustain arc on solar array. It was therefore necessary to draw up a discharge theory, with a sequencing of events, by taking into account the energy available at the moment of discharge on the satellite presented at the 7th SCTC as on this energy depends the amplitude of the primary discharge, and therefore the associated thermal effect, which totally conditions the arc. On the other hand, manufacturers, now encountering problems of electrostatic nature on satellites (section losses on high voltage solar arrays), present the problem in terms of efficient solutions. Manufacturers and laboratories still test solar array samples with their own assembly configurations which, for a single sample, can either be disastrous or have not the slightest effect. Indeed, depending on whether the energy developed in the primary discharge comes from a capacitor of 100 pF or one of 1 micro-F, the result with regards to the direct effects of the primary discharge and the sustained arc risk will be completely different. To test solar array samples a priori in the confinement of an enclosed vacuum, it is necessary to define a laboratory test set-up, which represents what the solar array comes across in the geostationary orbit. To finalize this test set-up, we had to know the error made when using a 4 cells sample instead of a real large solar array in terms of primary discharge representativity, available energy stored, and electrical response of the simulating circuit. This paper will present electrical circuit needed to be representative of the flight configuration. It will explain how to make your own test set-up depending on the solar cells you want to use. This test set-up take into account the energy stored in the coverglass and the way it has to be released. The solar array test set-up is proposed by CNES in the frame of the ECSS for the European standardization. It does not take in consideration any commercial aspects or feasibility by such-and-such manufacturers. So one could imagine disagreements even oppositions to those propositions whom all are based on pure technical aspects. Although, the draft proposed is based on seven years of experiments, last one of which was shared with Japan to set basis of an universal standardization., 資料番号: AA0049206048, レポート番号: JAXA-SP-05-001E

Due to their dielectric nature and under the effect of the different forms of radiation encountered in space, dielectrics accumulate electrical charges up to the point where electrostatic discharges may occur. To prevent and avoid harmful interference due to discharges, their behavior under irradiation must therefore be investigated in the laboratory before they are used in space applications. A current and widely used practice is to submit the tested materials to the bombardment of monoenergetic electron beams. Such a practice ignores the presence in space of a spectrum of electrons with energies reaching several MeV, and leads solely to surface charging and surface potentials generally higher than those really induced in space. The new approach consists in using in laboratory an electron source as similar as possible to the one existing in orbit. This paper describes the result obtained in the SIRENE facility, which was developed for simulating the spatial geostationary or MEO environment during great geomagnetic activity comparatively with monoenergetic irradiation. The range of available electrons in SIRENE goes from 10 to 400 keV. It points out the effect of the radiated induced conductivity. This paper provides results obtained on classical dielectrics as Teflon, Kapton and Duroid of different thickness under mono and multi-energetic irradiation at ambient temperature and at - 150 C. This paper showed also that even in the case of very low flux of high energy electrons, the surface voltage measured remains deeply affected. Based on those results the usual habit to use monoenergetic irradiation for qualification of space dielectrics should be reconsidered. For example surface voltage obtained of Teflon is lower than the one obtained on Kapton under the same irradiation condition., 資料番号: AA0049206008, レポート番号: JAXA-SP-05-001E

8th Spacecraft Charging Technology Conference(October 20-24,2003), Huntsville, Alabama, 資料番号: ARDS030518000