XXIV. Erfahrungsaustausch Oberflächentechnologie mit Plasma- und Ionenstrahlprozessen. Mühlleithen / Vogtland

Transcription

1 UNIVERSITY OF APPLIED SCIENCES XXIV. Erfahrungsaustausch Oberflächentechnologie mit Plasma- und Ionenstrahlprozessen Mühlleithen / Vogtland Status Report: Numerical 3D Ion Extraction Code incorporated self-consistently into a Model of a Radio-Frequency Ion Thruster 1

2 Table of Contents Model of a Radio-Frequency Ion Thruster (by Dr. Volkmar) Planned expansion Chosen approach First results (not validated) Outlook 2

3 Table of Contents Model of a Radio-Frequency Ion Thruster (by Dr. Volkmar) Planned expansion Chosen approach First results (not validated) Outlook 3

4 Self-consistent RF ion thruster model System and boundary definition Output Coil System: U coil S coil, P coil, Q coil m 0 Extraction System: m i, m n I coil I beam, P beam v i, v n, F U scr Efficiency: μ e, μ m U acc 4

5 Self-consistent RF ion thruster model Core modules Charge conservation model Electron temperatur Energy conservation model Ionisation degree Mass conservation model Pressure Self consistency: The output of each model affect the remaining models 5

6 Self-consistent RF ion thruster model Results RIM4, 2D-Modell, heuristic density profile, temperature: 150 C, extraction current: 10mA, propellant: xenon, mass flow: 1 sscm, frequency: 2 MHz 6

7 Table of Contents Model of a Radio-Frequency Ion Thruster (by Dr. Volkmar) Planned expansion Chosen approach First results (not validated) Outlook 7

8 Planned expansion Currently: Analytical plasma extraction model New: Numerical plasma extraction model Plasma limitation I extraction = v b n i A T s v b : Bohm velocity n i : Ion density at the sheath s T: Grid transparency A: extraction surface Modified Child-Langmuir Law Transparency (plasma meniscus) Thrust (consideration of divergence) Grid currents (overcrossing and direct impingement) 8

9 Table of Contents Model of a Radio-Frequency Ion Thruster (by Dr. Volkmar) Planned expansion Chosen approach First results (not validated) Outlook 9

10 Chosen approach Collisionless electrostatic particle-in-cell (PIC) 3D Simulation of non symmetrical grid structures In time domain Simulation of DC and AC-grid-voltages Ions: Considered as particles Elektrons: Assumed to be in thermal equilibrium φ (r) = ρ i+ρ e ε 0 ; ρ e = en e o exp e k B T e φ (r) φ 0 possible collision Finite-difference methods (FDM) Φ i,j,k+1 particle Voxel for geometric modelling Φ i,j+1,k Φ i 1,j,k Φ i,j,k Φ i+1,j,k Φ i,j 1,k Φ i,j 1,k 10

11 Table of Contents Model of a Radio-Frequency Ion Thruster (by Dr. Volkmar) Planned expansion Chosen approach First results (not validated) Outlook 11

12 First results System and boundary definition 4 φ Sheath = V φ Screen = 900 V φ accel = 50 V φ decel = 0 V φ = 0 V Symmetrical boundarys Reflection of particles E t = 0 r Screen = 1.9 mm r accel = 1.2 mm r decel = 1.9 mm Discretization h = x = y = z = mm N = = 651, 664 Points T = 1 ns Plasma boundary n e (x=0) = 2.913E+16 #/m³ T e = 2.97 ev n i(x=0) = n e(x=0) v b = 1,476 m/s 12

13 First results Comment from : In the original presentation a video was shown 13

14 First results 14

15 First results 15

16 First results 16

17 Table of Contents Model of a Radio-Frequency Ion Thruster (by Dr. Volkmar) Planned expansion Chosen approach First results (not validated) Outlook 17

18 Outlook Outlook: Validation Numerical Efficiency Multidimensional Newton's method Multigrid or Preconditioned biconjugate gradient stabilized method Optimised Multicore Performance Incorporation in RF Ion Thruster Model 18

19 THANK YOUR FOR YOUR ATTENTION ANY QUESTIONS? 19

20 First results System and boundary definition φ Sheath = V φ Screen = 900 V φ accel = 50 V φ decel = 0 V φ = 0 V 2 r Screen = 1.9 mm r accel = 1.2 mm r decel = 1.9 mm Symmetrical boundarys Reflection of particles E t = 0 Discretization: h = x = y = z = mm N = = 275, 704 Points T = 1 ns Plasma boundary: n e (x=0) = 2.913E+16 #/m³ T e = 2.97 ev n i(x=0) = n e(x=0) v b = 1,476 m/s 20