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Electric propulsion is now a successful method for primary propulsion of deep space long duration missions and for geosynchronous satellite attitude control. The Closed Drift Thruster, also called Hall Thruster or SPT (Stationary Plasma Thruster) was primarily conceived in USSR (the ancient Soviet Union) and since then, it has been developed by space agencies, space research institutes and industries in several countries such as France, USA, Israel, Russian Federation and Brazil. In this work, we present the main features of the Permanent Magnet Hall Thruster (PMHT) developed at the Plasma Laboratory of the University of Brasilia. This project is supported by the Brazilian Space Agency program for universities named UNIESPAÇO. The idea of using an array of permanent magnets, instead of an electromagnet, to produce a radial magnetic field inside the plasma channel of the thruster is very significant. It allows the development of a Hall Thruster with power consumption low enough to be used in small and medium size satellites. The description of a new vacuum chamber built to test the second prototype of the PMHT (PHALL II) is given. PHALL II has an aluminum plasma chamber and is smaller with 15 cm diameter and will contain rare earth magnets. We show the plasma density and temperature space profiles inside and outside the thruster channel. Ion temperature measurements based on the Doppler broadening of spectral lines and ion energy measurements are also shown. Based on the measured plasma parameters, we construct an aptitude figure of the PMHT. It contains the specific impulse, total thrust, propellant flow rate and power consumption necessary for satellites orbit raising and attitude control. Based on previous studies of geosynchronous satellite orbit positioning, we perform numerical simulations of satellite orbit raising from an altitude of 700 km to 36000 km using a PMHT operating in the 100mN -500 mN thrust range. In order to perform these calculations integration techniques were used. The main simulation parameters were orbit raising time, fuel mass, total satellite mass, thrust and exhaust velocity. We conclude comparing our results with results obtained with known space missions performed with Hall Thrusters.

Sterilization refers to any process that effectively kills or eliminates transmissible agents (such as fungi, bacteria, viruses, prions, spore forms, etc.) from a surface, equipment, foods, medications, or biological culture media. In general, surgical instruments and medications that enter an already sterile part of the body (such as the blood, or beneath the skin) must have a high sterility assurance level (SAL). In order to reach this SAL, several sterilization agents have been applied: heat, steam under pressure, radiation, electron beam, and chemical products. However, none of the sterilization methods available has a universal application, and the choice of the ideal technique depends on the physical and chemical properties of the materials that are going to be sterilized. The use of non-thermal plasmas on sterilization has been recognized as a successful technology for it congregates safety, effectiveness and quickness. In this work, we present some results of a plasma source developed at the Plasma Laboratory of the University of Brasilia for sterilization procedures at atmospheric pressure. We used ordinary air and Argon as the precursor gases. Our apparatus consists of two coaxial cylindrical tubes with different radii connected to a high voltage power source. The plasma characterization was made with spectroscopic analysis, Langmuir probes and indirect measurements, such as the discharge current. The validation of the procedure was made with the Bacillus subtilis' and the Bacillus stearothermophilus' spores and vegetative cells. We counted the viable cells after the exposure to the plasma with the pour plate technique. We also used scanning electron microscopy images to investigate the interaction of the plasma with the sterile material packages available at hospitals, in order to evaluate the compatibility of our device with the products used nowadays. Finally, we studied the biocide mechanisms of the plasma and related the inactivation of the microorganisms to their interactions with the ultraviolet radiation emitted by the plasma, with the free radicals in the plasma, and to etching processes.978-1-4244-2636-2/09/$25.00 ©2009 IEEE

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