Emre Turkoz

2-D Electromagnetic and Fluid Models for Inductively Coupled Plasma for RF Ion Thruster Performance Evaluation

A numerical model for the inductively coupled plasma in radio frequency (RF) ion thruster discharge chamber is developed to evaluate the plasma parameters for a 2-D axisymetric domain. The spatial distributions of various plasma parameters are obtained. The ion thruster performance is evaluated by calculating the discharge loss per ion for different deposited RF power values. The geometry of RIT-15LP is applied as the thruster configuration and the results are shown to have the same tendency as presented in the literature. The results of this paper proved that above a certain RF power deposition into the discharge chamber, there is a tradeoff between the thrust obtained from the ion engine and the discharge loss per ion.

Prototype design and manufacturing method of an 8 cm diameter RF ion thruster

Among the various types of plasma thrusters developed over the last few decades for in-space propulsion applications of satellites and spacecrafts, Hall effect thrusters and ion engines are the most studied ones. The work at Bogazici University is concentrated on radio frequency ion thrusters. In this paper the design and manufacturing methods of the BURFIT-80 (Bogazici University Radio Frequency Ion Thruster-80) are explained. The BURFIT-80 is an experimental ion thruster and will be tested in the vacuum chamber at Bogazici University. The Ion Thruster has a cylindrical discharge chamber having an inner diameter and outer of diameter of 80 mm and 88 mm respectively, with a length of 72 mm. A double grid system with 91 holes is implemented. Preliminary calculations suggest that the thruster will generate thrust in the range of 2 to 6 mN. A discussion on material selection and manufacturing methods is presented for the production of the prototype.

Optimization of radio-frequency ion thruster discharge chamber using an analytical model

The radio frequency ion thruster is an impulse generator to be used in space missions. It is a plasma based generator which utilizes electrostatic field between grids to accelerate the ionized gas out of the thruster to generate thrust. An analytical model is used to optimize the geometry of the discharge chamber which contains the inductively coupled plasma. The model is implemented and verified with existing thrusters and the results of the optimization process are presented. The results of our optimization routine validate the recent trend in radio frequency thruster design, which promotes hemispherical discharge chambers.

2D Fluid Model for Axisymmetric RF Ion Thruster Cylindrical Discharge Chamber

Radio-Frequency (RF) ion thrusters are impulse generators to be used at in-space applications. Inductively coupled plasma (ICP) is generated by using electromagnetic heating through the utilization of a number of axisymmetric coils in the discharge chamber of an RF ion thruster. A numerical model is built to investigate the underlying physics of the ICP in RF ion thrusters. The model solves the Maxwell‘s equations through magnetic vector potential equation and assumes that the ICP can be assumed to obey the continuum approach. Approximations are applied to the equations of motion for electrons, ions and neutrals to facilitate the simulations. Finite volume method for compressible gases is adapted for the ICP and results show the same tendency as previous models and experiments.

AETHER: A simulation platform for inductively coupled plasma

Abstract An in-house code is developed to simulate the inductively coupled plasma (ICP). The model comprises the fluid, electromagnetic and transformer submodels. Fluid equations are solved to evaluate the plasma flow parameters, including the plasma and neutral densities, ion and neutral velocities, electron flux, electron temperature, and electric potential. The model relies on the ambipolar approximation and offers the evaluation of plasma parameters without solving the sheath region. The electromagnetic model handles the calculation of the electric and magnetic fields using the magnetic vector potential. The transformer model captures the effect of the matching circuit utilized in laboratory experiments for RF power deposition. The continuity and momentum equations are solved using finite volume method. The energy, electric potential, and magnetic vector potential equations are solved using finite difference method. The resulting linear systems of equations are solved with iterative solvers including Jacobi and GMRES. The code is written using the C++ programming language, it works in parallel and has graphical user interface. The model is applied to study ICP characteristics of a plasma confined within a cylindrical chamber with dielectric walls for two different power deposition cases. The results obtained from the developed model are verified using the plasma module of COMSOL Multiphysics. The model is also applied to a plasma source configuration, and it is demonstrated that there is an overall increase in the plasma potential when current is extracted from ICP with a biased wall electrode.

Design and thermal analysis of the insert region heater of a lanthanum hexaboride hollow cathode

Several space electric propulsion devices, such as ion engines and Hall effect thrusters, use hollow cathodes as the electron sources for providing the necessary electrons for the ionization of the propellant and to neutralize the ion beam leaving the thruster. Most of the hollow cathodes used in space applications have used Barium-oxide impregnated Tungsten (BaO-W) inserts as the thermionic emission material due to its low work function. However, recent studies have shown the advantages of using Lanthanum-hexaboride (LaB6) insert material as the thermionic emission source. However, due to its higher work function, the LaB6 inserts have to be heated to a much higher temperature compared to the BaO-W inserts. In this paper, design and thermal analysis of the heater of a prototype hollow cathode with an LaB6 insert as the thermionic emission material is presented. The built hollow cathode will be used as a neutralizer electron source for BURFIT-80, an 80 mm diameter laboratory RF ion thruster running on Xenon propellant.

A Study of Ion Thruster Optics through Particle Simulations and Evaluation of the Near Plume Plasma Properties

A three-dimensional hybrid PIC-DSMC code is developed to simulate the physics of ion optics between an accelerator and a screen grid that are placed at the end of the discharge chamber of an ion thruster. Ions and neutrals are both represented with macro particles that have dierent weights. Electric potential is evaluated from the Gauss’ Law that takes the form of the Poisson’s equation, where the right hand side includes the net charge density evaluated at the computational grid nodes. The solution domain is a 30 o slice in cylindrical coordinates with symmetry boundary conditions at the radial and azimuthal boundaries. Macro particles are tracked with the Leapfrog algorithm. DSMC collisions are implemented for heavy species. A parametric study is performed to nd the grid conguration that yields the best performance.

Design of the retarding potential analyzer to be used with BURFIT-80 Ion thruster and validation using PIC-DSMC code

For better integration of plasma thrusters into spacecraft and satellites, potential damaging effects of impinging high energy ions on the spacecraft surfaces should be taken into consideration. For analyzing the plume plasma in this regard, retarding potential analyzers (RPA) are used in electric propulsion as one of the most fundamental and widely used diagnostics tools. RPA determines the ion energy distribution of plume plasma which is in the downstream of a thruster. This paper reports on a successful design process of an RPA to be used with BURFIT-80 ion thruster. An in-house developed hybrid Particle-In-Cell Direct Simulation Monte Carlo (PIC-DSMC) code, which is previously applied for ion thruster grid region is implemented to simulate the flow in the RPA. Results are used to validate the effective operation of the RPA. Potential distributions in the RPA are investigated and the calculated currents collected by the collector is compared with an existing experimental study.