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Electron cyclotron resonance ion thruster (ECRIT) with a diameter of 2 cm has the characteristics of no hot cathode and high specific impulse, which is suitable for the air-breathing electric propulsion system. In order to adapt to the atmospheric composition characteristics of nitrogen and oxygen in low orbit, the computational and experimental research on the performance of the ECRIT ion sourse with nitrogen propellant is an important basis for analyzing the feasibility of applying ECRIT to the air-breathing electric propulsion system. In this paper, the global model of the nitrogen ECRIT ion source with a diameter of 2 cm is established to calculate its performance. Then, the computational results are compared with the experimental results to analyze the difference. The research results show that when the input power of the ion source is 8 W and the gas flow rate is 2 ml/min, the computational and experimental results of the extracted ion beam current and thrust reach the maximum with the extracted beam current of 16.2 and 12.5 mA and the thrust of 476.6 and 368 μN, respectively. When the input power is 8 W and the gas flow rate is 0.6 ml/min, the computational and experimental results of the specific impulse are 2 095.8 and 1 855.6 s, both reaching the maximum value. The relative errors between the computational and experimental results of the extracted ion beam current, thrust and specific impulse all range from 2% to 32%. When the input power and gas flow rate used are 8 W and 1 ml/min in calculation, and 8 W and 0.8 ml/min in experiment, the ion source is on the optimal operating state. At this situation, the computational and experimental propellant utilization efficiencies with 17.8% and 16.2% respectively are high, and the ion energy loss with 443.9 and 596.2 W/A respectively is low.

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Electron cyclotron resonance ion thruster (ECRIT) with a diameter of 10 cm can operate on multiple types of gases and it is feasible to be applied to air-breathing electric propulsion systems. The study on the neutralizer of the ECRIT running on nitrogen gas is the basis for the study on the ECRIT running on nitrogen-oxygen mixed gas. When the ECR neutralizer of typical 10 cm ECRIT running on xenon gas runs on nitrogen gas, the extracted electron current is reduced, because ions tend to drift out of the neutralizer, due to the lower molecular weight of nitrogen. The typical neutralizer is no longer suitable to run on nitrogen gas. In this paper, based on the 10cm typical ECR neutralizer, in order to inhibit ion drift out of the neutralizer and improve the performance of electron extraction, a bipolar ECR neutralizer suitable to run on nitrogen gas is experimentally studied. The results show that under the conditions of gas mass flow rate of 0.04mg/s and input power of 10W, the anode voltage required by the typical ECR neutralizer running on nitrogen gas is 150V when the extracted electron current is 134mA. However, the bipolar ECR neutralizer requires only 50V anode voltage, which decreases by about 67%. When the anode voltage is 40V, the power loss of the typical ECR neutralizer is 1204.82W/A, while the power loss of the bipolar ECR neutralizer is 95.23W/A, which is about 8.3% of the former. The ion shielding effect of the bipolar ECR neutralizer running on nitrogen gas is remarkable and the electron extraction performance is improved.

The electron cyclotron resonance (ECR) neutralizer is an important part of the micro ECR ion thruster. The electrons extracted from the neutralizer are used to neutralize the ions extracted from the ECR ion source, thereby avoiding the surface charges accumulating on the spacecraft, and the behaviour of electron extraction affects the overall performance of the thruster. In order to investigate the electron extraction through the orifices of the micro ECR neutralizer, a two-dimensional particle-in-cell with Monte Carlo collision (PIC/MCC) model is established in this work. The effects of different magnetic circuits on the electron extraction of the neutralizer and the influence of different cavity lengths on the wall current loss are studied through numerical simulation. The effects of different magnetic circuit structures on the electron extraction and wall current loss of the neutralizer are studied. The calculation results show that the position of the ECR layer and the magnetic flux lines near the extraction orifices are very important for the electron extraction performance of the neutralizer. When the ECR layer is located upstream of the antenna, electrons are easily lost in migration and diffusion motion, and the energy required for the electrons to cross the potential well before the extraction hole is higher. If more magnetic flux lines pass parallelly through the extraction orifices, the neutralizer requires a small voltage to extract the same electron current. When the ECR layer is cut by the antenna or is located downstream of antenna, more electrons may migrate along the magnetic flux lines to the vicinity of the extraction orifices, thereby reducing the voltage of collector plate. The effects of different cavity lengths on the extraction of electrons under the same magnetic circuit structure are studied. It is found that increasing the length of the cavity allows more parallel-axis magnetic flux lines to pass through the extraction holes to avoid electron loss on the surface of the extraction plate, and thus increasing the extraction electron current. The research results conduce to designing a reasonable neutralizer magnetic circuit and cavity size.