The Design And Preparation Of Field Emission Neutralizer

With the development of space exploration,the requirements for the performance of spacecraft have been gradually improved.As one of the most important parts in the electric propulsion system,the properties improvement of the neutralizer plays an important role in the field of aerospace propulsion.The life,energy consumption,environmental adaptability and emission current must be improved greatly to meet the need of neutralized.The neutralizer based on carbon nanotube field emitters become the mainstream of the present research due to its outstanding over-all properties.The unique feature of the carbon nanotube field emission cathode is simple structure,small size,low power consumption,and no work media storage equipment and-valves.That is very suitable for small or micro-electric propulsion system.However,the carbon nanotube field emission array still has some problems to be solved in the future,such as its low emission current density,poor stability etc.This paper attempts to fabricate the carbon nanotube field emitter based neutrailizer.By microwave plasma chemical vapor phase deposition,good morphology,high emission current of carbon nanotube field emitters was prepared firstly.The electron gun structure was simulated and optimized using electromagnetic field simulation software to meet the requirements of the neutralizer.The main work are as follows:1.Growth of carbon nanotube emitters.After overall process technology was studied,including photolithography,catalyst deposition,MW-PECVD process.Carbon nanotube field emission array with a good morphology and perpendicular to the substrate was prepared successfully,and the current density of 4.5 A/cm2 was reached which meet the need of the neutrailizer.2.Design and optimize the neutralizer's electronic optics system.In order to enable the emitted electrons to be effectively emitted into the space to neutralize the ions which are ejected by the electron thruster,the corresponding neutralizer structure is designed and optimized.At the same time,the electronic optical structure can effectively isolate a large numbers of ions from the ion propulsion,to avoid the ion bombardment field emission cathode array.3.Measurement of field emission properties of neutralizer.The carbon nanotubefield emission array was assembled into a neutralizer structure,and the field emission performance of the neutralizer was tested in high vacuum system.The emission current of the neutralizer is 473 mA.The grid transmission rate is about 60 %.