Ion beam neutralization and properties of plasmas from low power ring cusp ion thrusters

Abstract

The design and operation modes of a small, low power ion plasma thruster and the properties of the emitted plasma plumes are discussed. The ion beam is extracted from a primary plasma produced by a stationary low pressure electric discharge where the ion production rate is essentially determined by the discharge current. The experiments evidence that the electron neutralization current controls the space charge levels of the outgoing ion current and also influences the spatial properties of emitted plasmas. The electron plasma density increases with the discharge and the electron neutralization currents, while decreases as the plasma plume expands. However, the corresponding electron temperatures decrease when the electron neutralization currents increments. The collisional origin of this electron cooling effect is excluded because of the large collisional mean free paths involved. Then, these electron energy losses during the neutralization of the ion beam would be caused by more subtle physical mechanisms than collisions. The experimental results are compared with previous numerical simulations and similar phenomena found in other experiments.

Propagator integral method for plasma physics kinetic equations with practical applications

“…The density of particles reaches a higher value for negative positions, while is reduced for x > 0.1, respect to the case without force. This effect is qualitatively similar to what happens in the acceleration grid of an ion thruster [99,100], where, due to the intense electric field, generated by means of polarised grids, the ions are exhausted at high speed to generate thrust and the electrons are slowed down to keep them inside the discharge chamber and contribute to the ionization process.…”

“…This reference voltage can be easily modified before starting the measurement process. Even when this circuit is not unique and other options exist in the literature [137], this scheme has been tested in previous works [99,100,141], providing good results and its verification or possible improvements are out of this thesis scope.…”

“…In the experimental setup employed to obtain the results presented below in this section, the plasma was generated by means of a ring cusp ion thruster, operated with an argon gas flow, as that described in [99,100]. The density and temperature ranges of the electrons in the cold plasmas involved were n e = 10 7 -10 8 cm −3 and T e = (0.75-1.25) eV, respectively.…”

“…The modelisation of this interaction is usually established by models that may not capture all microscopic processes involved, specially in Weakly Ionized Plasmas (WIP) for which the inclusion of a dense heavy cold neutral species hinders the development of models [137][138][139]. Our research group is interested in the use of these probes to analyse the plasma generated in our low temperature laboratory [99,100,152], making this topic of main interest.…”

Emissive Langmuir probes in the strong emission regime for the determination of the plasma properties

“…The plasmas were produced by means of a ring cusp ion plasma thruster described in [12], which was operated as a plasma source. This device produces plasmas with electron densities of n e ~ 0.1-8 x 10 8 cirr 3 and electron temperatures between T e ~ 1-2 eV.…”