US 12,140,126 B2
Plasma thruster with birdcage antenna
Francesco Romano, Stuttgart (DE); Yung-An Chan, Stuttgart (DE); Georg Herdrich, Esslingen (DE); and Stefanos Fasoulas, Stuttgart (DE)
Assigned to Universität Stuttgart, Stuttgart (DE)
Filed by Universität Stuttgart, Stuttgart (DE)
Filed on Dec. 8, 2022, as Appl. No. 18/077,291.
Claims priority of application No. 21213628 (EP), filed on Dec. 10, 2021.
Prior Publication US 2023/0182929 A1, Jun. 15, 2023
Int. Cl. F03H 1/00 (2006.01); G01R 33/34 (2006.01); H05H 1/54 (2006.01); B33Y 80/00 (2015.01)
CPC F03H 1/0081 (2013.01) [G01R 33/34076 (2013.01); H05H 1/54 (2013.01); B33Y 80/00 (2014.12); F03H 1/0093 (2013.01); H05H 2245/00 (2013.01)] 5 Claims
OG exemplary drawing
 
1. A plasma thruster comprising:
a cylindrical discharge channel (1) having an inlet for a propellant and an outlet,
an injector (4) for injecting the propellant through the inlet into the cylindrical discharge channel (1),
an RF antenna surrounding the cylindrical discharge channel (1), said RF antenna when fed with RF power generating electromagnetic fields that ionize the propellant forming a plasma (8) in the cylindrical discharge channel (1) that is then ejected through the outlet to generate thrust,
a magnetic field generator (3) for generating an axial static magnetic field in the cylindrical discharge channel (1), said axial static magnetic field providing boundary conditions for formation of helicon waves within the plasma (8), as well as providing a magnetic nozzle effect at the outlet for quasi-neutral plasma acceleration, wherein
the RF-antenna is a cylindrical birdcage antenna (2) formed of a number of electrically conductive parallel legs (10) connected by two end rings (11) on each side, said two end rings (11) comprising one or several capacitors (12) between adjacent legs (10) among the number of electrically conductive parallel legs in each case, said one or several capacitors (12) defining a resonance frequency of the cylindrical birdcage antenna (2), and
the injector (4) is made of an electrically conductive material and mounted movably along a cylinder axis of the cylindrical birdcage antenna (2) for fine tuning of the resonance frequency,
wherein the two end rings (11) with the one or several capacitors (12) are soldered on two printed circuit boards (14) to which the number of electrically conductive parallel legs (10) are attached, said two printed circuit boards (14) having a through opening for the cylindrical discharge channel (1), wherein the number of electrically conductive parallel legs (10) comprise feet (13) for fastening on both ends of each of the number of electrically conductive parallel legs, and the two printed circuit boards (14) on which the one or several capacitors (12) are soldered, are placed on isolating flanges (15) to which the number of electrically conductive parallel legs (10) are fixed by means of screws and nuts (17) through holes in the feet (13), in the two printed circuit boards (14) and in the isolating flanges (15).