## 3 Development Strategy of a HPT Based on MEIC Plasma Reactor
The material was chosen specifically to minimize its inductive load, thereby reducing power losses;
* A multi-dipole cusp magnetic confinement system composed of eight plate-shaped neodymium iron boron (NdFeB) magnets (PMs) of 38 EH grade with gold plating, arranged near the m = +1 mode antenna, capable of producing an external magnetic field strength of 800 G. The PMs are radially magnetized;
* A solenoid-free MN represented by a ring-shaped NdFeB PM of 38 EH with gold plating (Ni-Cu-Ni-Au) to extend its Curie point limit;
* A primary structure and positioning system, consisting of a magnetic support, stiffening rods and stiffeners, all fabricated from aluminum. Figure 4: Cooper-based half-wavelength right helical (HWRH) antenna used to excite helicon waves within the MEICP reactor. Figure 3: CAD rendering of the Helicon Plasma Thruster Breadboard Model (HPT-BM). The proposed HWRH antenna, presented in Figure 4, is designed to excite the right-hand circularly polarized \((m=+1)\) mode of the helicon dispersion relation, thereby ensuring the highest possible density within the MEICP reactor. The currents applied to the HWRH antenna generate an RF magnetic field within the MEICP reactor of the Helicon Plasma Thruster, which induces an RF electric field parallel to the externally applied magnetic field \(B_{0}\). This electric field drives electrons along the direction of \(B_{0}\), establishing the necessary space charge distribution to mitigate the axial component of the electric field [57]. However, the perpendicular electrostatic field produced by this space charge is not neutralized, as the multi-cusp magnetic field configuration effectively confines electrons in the perpendicular direction. This perpendicular electric field efficiently couples with the helicon wave's space charge field in the perpendicular direction. This perpendicular electric field efficiently couples with the helicon wave's space charge field, enhancing the overall efficiency of the plasma system. The magnetic system is a critical component of the HPT, serving the following multiple functions: it enables the excitation of helicon waves, minimizes plasma losses to the internal thruster walls, and generates the external MN necessary for supersonic plasma expansion. To develop a competitive cathodeless EP system based on the MEICP reactor, a magnetic field configuration using permanent magnets (PMs) is proposed, optimized for both plasma generation and acceleration. The use of NdFe8 permanent magnets with gold plating (Ni-Cu-Ni-Au) results in a simpler and more lightweight thruster unit, capable of generating the required magnetic field in space with limited electric power [64; 65; 66], while also extending the operational temperature range due to the higher Curie point. The magnetic confinement system of the MEICP reactor consists of a set of eight PM bars, each measuring 70 mm in length, 10 mm in width, and 5 mm in thickness, with radial inward magnetization. As depicted in Figure 5b, this configuration creates a cusp magnetic confinement structure with a magnetic field intensity of 800 G.  
The magnetic system along the reactor axis can be adjusted by varying the distance between the two sets of PMs. The multi-cusp magnetic configuration minimizes particle losses to the ionization chamber walls, thereby increasing plasma density and improving plasma uniformity [67; 68]. Utilizing a non-uniform magnetic field, such as a converging-diverging magnetic nozzle or a magnetic cusp located near the RF antenna [69], may further enhance thrust performance. In this helicon plasma source, utilizing the non-uniform magnetic field could enable more efficient plasma production. To enhance thrust performance, it is crucial to maintain higher plasma pressure upstream of the magnetic nozzle. Thereby, the outlet section diameter of the ionization chamber was reduced to 10 mm.