Download Study of accelerated channel wall`s sputtering in Hall

Study of accelerated channel wall’s sputtering in Hall thruster
1
Li Yan1, Ping-yang Wang1*, Yang-Hua Ou1, Xiao-Lu Kang2
School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
2
Shanghai Institute of Space Propulsion, Shanghai 200233, China
keyword：Sputtering yield；Hall thruster；Accelerated channel; hybrid PIC method
Hall thrusters are widely used in space propulsion applications due to their high specific
impulse, high thrust efficiency, and high thrust density. The thrusters experience sputter
erosion of the insulator channel, which is the primary factor that limits thruster lifetime. An
important area of Hall thruster research is to understand the erosion and assess thruster
lifetime, for which the sputtering yield is studied in this paper. Hybrid PIC method is used for
calculation of the flow field inside the hall thruster, which sputtering yield of wall material is
got through experiment.
Hybrid PIC method is used for calculation of the flow field inside the hall thruster. The model
considers the ionization process, self-consistent of electromagnetic field and the interaction
between particles and wall. Computing speed is increased through the incensement of ionic
quality and permittivity. Simulation result is consistent with the experimental results, which
verifies the correctness of the model.
There is a lot of research about the sputtering yield of single atomic material by xenon ion,
and a series of formula is deduced. But few experimental data have been taken on the absolute
sputter yield of compound by xenon ions, especially in the energy ranges that concern Hall
thrusters. Typical Hall thrusters operate at a 300 V discharge voltage, leading to single ions
having a maximum energy of 300eV. According to hall thruster, American Yalin, etc
measured the sputtering yield of BN by 300ev xenon ion which is normal incidence. And
Elovikov measured h - BN and r - BN sputtering yield on 0-400ev xenon ion normal
incidence respectively. BNSiO2 is used in SPT-70 ， which is the object of our study.
Experiment of BNSiO2’s sputtering is operated. As shown in figure 1,it is the whole
equipment, which include Vacuum chamber, power supply system, Xe supply system and so
on. Vacuum chamber used in experiment is 2.5 m diameter. Large diameter chamber can
reduced sputtering material deposition on sample surface. The SPT-70 works as sputter ion
source. It provides different incidence angles of ion. In addition to the ion source, sample
fixed bracket and ion energy measuring system are also needed. Result is showed as figure 2.
(1) Windows; (2) Low temperature diffusion pump; (3)
The position of target material; (4) Vacuum chamber; (5)
Ion source; (6) Experimental ceramic sample; (7) PPU;
(8) Ignition console;(9) Control computer;(10) Data
acquisition system; (11) Xenon gas bottle; (12) Support
Figure 1 experimental study system
Fig.2The angular dependence of the normalized sputter
yield
Results of sputtering yield of BN-SiO2 are used in Hall thruster. Flow field in Hall thruster is
calculated. results are shown in figure 3-6.
10
100h
300h
600h
6241h
8
Radial distance eroded / mm
Radial distance eroded / mm
10
6
4
2
0
100h
300h
600h
4040h
8
6
4
2
0
0
1
2
3
0
1
2
Axial distance from thruster exit / mm
Fig.3 Insulating layer outline variation rules when
the anode voltage is 250V
4
5
6
7
8
9
10
11
12
Fig.4 Insulating layer outline variation rules when
the anode voltage is 400V
10
10
100h
300h
600h
3236h
8
Radial distance eroded / mm
Radial distance eroded / mm
3
Axial distance from thruster exit / mm
6
4
2
0
100h
300h
600h
3236h
8
6
4
2
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Axial distance from thruster exit / mm
Fig.5 Insulating layer outline variation rules when
the anode voltage is 500V
0
1
2
3
4
5
6
7
8
9
10
11 12
13 14
15
Axial distance from thruster exit / mm
Fig.6Insulating layer outline variation rules when
the anode voltage is 600V