Improvements to quasistatic model #26
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* Plasma column can have a different radial extent than simulation box. * Set `edge_order=2` when calculating `nabla_a2`. * Implement new method for computing psi and derivatines at plasma particles. It is now done by interpolating between neighboring values. This ensures that `dr_psi=0` in a uniform plasma. The boundary conditions have also been reformulated. They are now more robust and allow for plasma columns of finite width. * The minimum value of `psi` is now limited to -0.9. Also, the amplitude of dxi_psi and b_theta_bar is now limited to 3. This improves the stability near the blowout peak. * Plasma particles leaving the simulation box are no longer removed. * Plasma particles with too much momentum will be reset to a rest state. This avoids having to remove highly relativistic particles and improves the stability near the blouout peak. * Fixed an inconsistency in the derivatives of particles crossing the axis during the Runge-Kutta push. The sign of the derivatives in now inverted. * Fixed a bug in `update_gamma_and_pz`, where a2 was (incorrectly) being divided by 2. * Implemented bew method for computing b_theta at plasma particles. It is now also based on interpolation and it is more accurate than before. * Fixed a bug when returning a_i and b_i. The wrong value was being removed due to not taking the particle sorting into account.
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This PR contains several improvements to the quasistatic wakefield model. It greatly improves the stability, specially for strongly non-linear wakes where a sharp blowout peak is present. It also allows for plasma columns of finite width, different from that of the simulation box.
Changes
Plasma column can have a different radial extent than simulation box.
Set
edge_order=2when calculatingnabla_a2.Implement new method for computing psi and derivatives at plasma particles. It is now done by interpolating between neighboring values. This ensures that
dr_psi=0in a uniform plasma. The boundary conditions have also been reformulated. They are now more robust and allow for plasma columns of finite width.The minimum value of
psiis now limited to -0.9. Also, the amplitude of dxi_psi and b_theta_bar is now limited to 3. This improves the stability near the blowout peak.Plasma particles leaving the simulation box are no longer removed.
Plasma particles with too much momentum will be reset to a rest state. This avoids having to remove highly relativistic particles and improves the stability near the blowout peak.
Fixed an inconsistency in the derivatives of particles crossing the axis during the Runge-Kutta push. The sign of the derivatives in now inverted.
Fixed a bug in
update_gamma_and_pz, where a2 was (incorrectly) being divided by 2.Implemented new method for computing b_theta at plasma particles. It is now also based on interpolation and it is more accurate than before.
Fixed a bug when returning a_i and b_i. The wrong value was being removed due to not taking the particle sorting into account.
Sample images:
Strong blowout:
Finite-width plasma column:
