The invention relates to a microwave driven plasma ion source (1) for ionising a sample to be ionised to sample ions, the microwave driven plasma ion source (1) including a sample intake (6) for inserting the sample from an outside of the microwave driven plasma ion source (1) into an inside (3) of the microwave driven plasma ion source (1); a microwave generator (10) for generating microwaves for generating a plasma (101) from a plasma gas (100); a plasma torch (20) providing a plasma torch orientation direction (29) having an inside (21) for housing (2) a process of generation of the plasma (101) from the plasma gas (100) and for housing a process of ionising the sample to the sample ions by exposing the sample to the plasma (101), wherein the plasma torch (20) comprises a torch outlet (22) for letting out the plasma (101) and the sample ions from the inside (21) of the plasma torch (20) essentially in the plasma torch orientation direction (29) to an outside of the plasma torch (20), the torch outlet (22) having a torch aperture. Furthermore the microwave driven plasma ion source (1, 201) includes a shielding (4) for shielding off the microwaves from passing from the inside (3) of the microwave driven plasma ion source (1) to the outside of the microwave driven plasma ion source (1), wherein the shielding (4) comprises a shielding outlet (5) for letting out the plasma (101) and the sample ions from the inside (3) of the microwave driven plasma ion source (1) essentially in the plasma torch orientation direction (29) to the outside of the microwave driven plasma ion source (1), the shielding outlet (5) having a shielding aperture. Thereby, the shielding outlet (5) is fluidly coupled to the torch outlet (22) for letting out the plasma (101) and the sample ions from the inside (21) of the plasma torch (20) essentially in the plasma torch orientation direction (29) to the outside of the microwave driven plasma ion source (1), wherein a size of the shielding aperture is less than 150%, preferably less than 125%, particular preferably less than 110% of a size of the torch aperture, wherein both the size of the shielding aperture and the size of the torch aperture are measured in units of area.

A plasma thruster comprises a cylindrical discharge channel (1), an injector (4), a RF antenna surrounding the discharge channel (1) and a device (3) for generating an axial static magnetic field in the discharge channel (1). The RF antenna is a cylindrical birdcage antenna (2) formed of several electrically conductive parallel legs (10) connected by two end rings (11) including capacitors (12) between adjacent legs (10) in each case. The two end rings (11) with the capacitors (12) are formed on two printed circuit boards (14) to which the legs (10) are attached, said printed circuit boards (14) having a through opening for the discharge channel (1). The antenna maximizes electrical coupling efficiency and provides resulting electromagnetic fields for quasi-neutral plasma acceleration along with the magnetic field effect provided by the externally applied magnetic field. This plasma thruster allows an easy upscaling or downscaling due to the printed circuit boards and is particularly suitable for low power applications like propulsion for smaller spacecrafts or satellites.

A plasma thruster comprises a cylindrical discharge channel (1), an injector (4), a RF antenna surrounding the discharge channel (1) and a device (3) for generating an axial static magnetic field in the discharge channel (1). The RF antenna is a cylindrical birdcage antenna (2) formed of several electrically conductive parallel legs (10) connected by two end rings (11) including capacitors (12) between adjacent legs (10) in each case. The two end rings (11) with the capacitors (12) are formed on two printed circuit boards (14) to which the legs (10) are attached, said printed circuit boards (14) having a through opening for the discharge channel (1). The antenna maximizes electrical coupling efficiency and provides resulting electromagnetic fields for quasi-neutral plasma acceleration along with the magnetic field effect provided by the externally applied magnetic field. This plasma thruster allows an easy upscaling or downscaling due to the printed circuit boards and is particularly suitable for low power applications like propulsion for smaller spacecrafts or satellites.