Hall Thruster & Hollow Cathode
The small hollow cathode we use has a maximum outer diameter of 14 mm, a maximum outer diameter of 37 mm and a maximum length of 43 mm. It adopts barium tungsten emitter and resistance heating ignition mode.
We use an external anode plate and a hollow cathode to form a current loop. The external anode and the hollow cathode are both mounted on a one-dimensional displacement platform, and the external anode plate is placed downstream of the hollow cathode, with the initial distance between the anode plate and the contact pole being 40mm. The position between the external anode plate and the hollow cathode can be changed by driving the displacement platform to observe the change of the hollow cathode discharge parameters.
Before the hollow cathode is ignited, it is necessary to activate the exhaust gas to eliminate the impurity gas adsorbed in the hollow cathode material, so as to avoid contamination of the hollow cathode. The activation process uses current heating. The heating current is gradually increased from 0A to 4.2A at a rate of 0.5A per ten minutes, followed by hollow cathode ignition. It has been verified by many experiments that the hollow cathode can be reliably ignited at a Xe gas flow rate of 4 sccm and an ignition voltage of 200 V. The different flow conditions are adjusted, and the hollow cathodes operate in a bright spot pattern, a feather pattern, and a diffuse pattern, respectively.
100 Watt Magnetically Shielded Hall Thruster
Lifespan of low power Hall thrusters is restrained by severe erosion caused by higher surface to volume ratio and thinner ceramic channel walls. Applications of magnetic shielding in kilowatt class Hall thrusters enlighten the design of low power Hall thruster. In our work, we introduced the magnetic shielding concept into the design of a 100W Hall thruster (MSHT) and implemented that using permanent magnets.
Preliminary tests of MSHT were conducted. MSHT worked stably at discharge power ranging from 13 to 263W. Partial magnetic shielding could be proved by comparison between shielded and unshielded walls after test for tens of minutes, which could reduce interaction between the plasma and the discharge channel walls.
Thrust ranging from 2.9 mN to 10.8 mN was recorded employing a self-developed torsional thrust stand in performance tests. Anode specific impulse values varied between 729s and 1576s during all the tests. Anode efficiency higher than 30% was achieved for mass flow rate of 0.5-0.7mg/s with the highest efficiency reaching 37.8%. An additional anode was adopted to solve the barrier of ignition caused by high magnetic field.
kW class Hall thruster test
Since December 11st, 2016, JLPP has been conducting an 8000-hours-lifetime researching experiment on HET-80, which was developed by Shanghai Academy of Space Propulsion. The experiment reached a success on April 25th, 2018, and HET-80 has worked for 8241 hours in total. During the experiment, the thrust and the beam diagnosis of HET-80 was measured and detected. The experiment validated that the lifetime, performance and reliability of HET-80 during the mission period can meet our expected standards.
Benefited from the powerful and reliable DTJ-2.5 vacuum system of JLPP, our experiment spent only 60% of time compared to domestic counterparts to reach the success in the case of low failure rate. Meanwhile, we used on-line calibration electromagnetic-feedback micro-thrust stand and variable beam diagnosis equipment (including RPA, Faraday and Langmuir probes) to successfully monitor the evolution of thruster thrust and beam characteristics during the entire lifetime test.
In the process of completing this work, our team broke through many technical obstacles and established a set of high-reliability electric propulsion measurement and diagnosis systems with independent intellectual property rights.
 Guangchuan Zhang, Junxue Ren, Yiwei Jiang, Chao Lu, Haibin Tang, Kan Xie, Haoxiang Yuan, and Xinyu Yang. "Design and Experiments of a 100 Watt Magnetically Shielded Hall Thruster", 2018 Joint Propulsion Conference, AIAA Propulsion and Energy Forum (AIAA 2018-4587), https://doi.org/10.2514/6.2018-4587
 张广川, 刘鹏, 曹帅, 程佳兵, 姜逸伟 等. HET-80 霍尔推力器寿命试验前 4000h 试验结果. 第十三届中国电推进技术学术研讨会, 北京, 2017
 曹帅, 任军学, 张广川 等. HET-80霍尔推力器推力测试研究. 第十二届中国电推进技术学术研讨会, 哈尔滨, 2016
 曹帅, 王宣，任军学 等. HET-80霍尔推力器8000小时寿命试验研究. 第十四届中国电推进技术学术研讨会, 长沙, 2018