The helicon double-layer thruster (HDLT) is a prototype plasma thruster propulsion system that works by injecting gas into an open-ended source tube, where radio frequency AC power produced by an antenna surrounding it electromagnetically ionizes the gas. Within this highly charged plasma, a low-frequency electromagnetic helicon wave is excited by the antenna’s electromagnetic field, further heating the plasma.
Such “magnetic nozzle” thrusters accelerate the plasma they produce to generate thrust for spacecraft, representing a form of electric propulsion with several potential applications in spacecraft design. However, while plasma flows that occur naturally within magnetic fields are often released or “detached”—like when coronal ejections erupt from the Sun—getting plasmas to behave in the same way in the laboratory is more challenging.
Part of the reason for this has to do with the fact that magnetic field lines form closed loops, requiring a mechanism for plasma flow to be detached from the magnetic nozzle in order for thrust to occur. Although ions detach easily on account of their sizable gyro radius, the same can’t be said for magnetized electrons, whose electric fields grab the ions and return them into the thrust structure, thereby nullifying the production of any actual thrust.
Now, researchers with Tohoku University and The Australian National University say they have announced the experimental demonstration of cross-field inward transport of electrons in a magnetic nozzle as a result of magneto-sonic wave excitation. The result appears to be a successful reduction in the divergence of expanding plasmas, as well as the reported neutralization of detaching ions; findings that represent a potential breakthrough in overcoming the longstanding plasma detachment problem.
To read more, click here.