Single-frequency reflection characterisation of shock tube excited plasma

• Published in: AIP advances Vol. 7; no. 8; pp. 085115 - 085115-8
• Main Authors: Tian, Jing, Tang, Pu, Ma, Ping, Li, Lutong, Li, Ruiming, He, Ziyuan, Chen, Bo
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01-08-2017; AIP Publishing LLC
• Subjects: Blackout; Computer simulation; Electron density; Genetic algorithms; High speed; Plasma; Plasma sheaths; Reflectance; Reflection
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/1.4996450

Plasma has been of great interest to engineers and scientists during the past few decades
due to its wide applications. Besides, the plasma-sheath-caused lose of communication
(i.e. re-entry blackout) that happens when a spacecraft re-enters the earth atmosphere is
still a problem to be solved. The microwave characterisation of shock tube excited plasma
has been an important method for exploring the transmission and reflection of microwave
signals in plasma. The existing frequency sweep or multi-frequency technologies are not
desirable for the characterisation of high-speed time-varying plasma generated in shock
tubes. Hence, in this paper a novel signal-frequency approach is proposed to measure both
electron density and collision frequency of plasma in shock tube. As frequency sweep is
not required in this method, it is extremely suitable for characterising the shock tube
excited high-speed time-varying plasma. The genetic algorithm is applied to extract
electron density and collision frequency from the reflection coefficient. Simulation
results demonstrate excellent accuracy for electron density within
1
0
10
∼
1
0
12

c
m
−
3
and collision frequency within
5
×
1
0
10
∼
1
0
12

H
z
. This work paves the way for a fast and compact microwave
reflection measurement of shock tube generated plasma.