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Field Reversed Configurations

Confinement of Energetic Fusion Particles in FRC Reactors H. E. Ferrari and R. Farengo Centro Atómico Bariloche and Instituto Balseiro, 8400 Bariloche, RN, Argentina. Field Reversed Configurations. Elongated compact toroids with negligible toroidal field.

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Field Reversed Configurations

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  1. Confinement of Energetic Fusion Particles in FRC ReactorsH. E. Ferrari and R. FarengoCentro Atómico Bariloche and Instituto Balseiro, 8400 Bariloche, RN, Argentina

  2. Field Reversed Configurations • Elongated compact toroids with negligible toroidal field. • Very high b (b~1), could use advanced fuels (i. e. D-He3) • Formation: Field reversed q-pinch Rotating magnetic fields (RMF) Spheromak merging • Sustainment: Fusion born charged particles Rotating magnetic fields (RMF) Neutral beam injection

  3. This work • Study the dynamics of protons and a particles in D-He3 and D-T FRC reactors. • Calculate the power deposited on each species and the current generated. • Monte Carlo code follows the exact particle trajectories (no gyro-averaging) including stopping and difussion: • Equilibrium (fixed), from Grad-Shafranov equation:

  4. D-He3 FRC reactor Equilibrium parameters from ARTEMIS proposal: rs=1.12 m, ℓs=17 m, Te=Ti=87.5 keV, fD=0.5, fHe=0.25

  5. Proton orbits

  6. Proton orbits • There are more “positive” than “negative” current particles. • With collisions “negative” current particles are lost sooner. • Hollow equilibria have a larger fraction of negative current particles.

  7. Effect of difussion • It has been argued that velocity space diffusion should not be important due to the high energy of the protons. • Adding diffusion increases the size of the accessible region and negative current particles get lost rapidly.

  8. Current and deposited power • Significant proton current, similar to the proposed value. • Protons deposit their power on the electrons, a particles on the ions. • The equilibrium with the highest fusion power has the lowest current and deposited power. • Poor proton confinement results in high required tE.

  9. Current and deposited power Proton power a particle power Proton current

  10. Effect of external toroidal field • Can a toroidal field improve proton confinement? • Studied the effect of a “vacuum” toroidal field. • Sharp drop in current and deposited power at low toroidal field due to increased losses through the ends. • At high toroidal field deposited power increases but current decreases.

  11. Effect of a rotating magnetic field • A transverse RMF, used to drive current, can degrade particle confinement. • The RMF is characterized by its amplitude, frequency and penetration depth (d=0.1 rs). Proton power Proton current Proton current and deposited power decrease but there are no sharp resonances as in NBI.

  12. D-T reactor • Small, recently proposed low fusion power reactor EM: magnetic mirrors added to reduce axial particle losses. The a particle orbits present similar features as those shown for protons but their mean free path is shorter.

  13. a-particle orbits

  14. Current and deposited power • Large fraction of power deposited but small current. • Power deposited mostly on electrons (4:1). • Increasing the density, and magnetic field, increases the fraction of power deposited in the plasma. • Adding magnetic mirrors increases the fraction of deposited power.

  15. Spatial distribution of deposited a particle power

  16. Neutral Beam Injection • Particle sources replaced by NB. • Ionization package added to the code. • Beam ions can rotate in the same sense as the current, or in the opposite, depending on the position and velocity they have when ionize (Pq). • Very low efficiency for the D-He3 reactor at reasonable energies (Eb≤2 MeV). • Good efficiency for D-T reactor, ~128 kA/A at 1 MeV.

  17. Beam ion orbits “Positive” “Negative”

  18. Efficiency for D-T Reactor

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