Speaker
Description
The bubble regime of drive plasma wakefields is notoriously difficult from an analytical perspective due to the inapplicability of standard fluid theory and perturbative approaches. The most widely used model was developed by Lu et al. [1] and extended for improved accuracy near the rear of the bubble by Dalichaouch et al. [2], this approach gave a 2nd order ODE for the ‘bubble radius’ with one or more phenomenological free parameters and initial conditions determined by PIC simulation data. Taking inspiration for the Lu-type model, we have developed a self-consistent theoretical framework that gives a relatively small closed set of ODE’s for the wake which has a direct correspondence to the kinetic quasistatic theory used in highly accurate PIC codes such as QPAD. This framework is ideal for use with standard ML libraries for rapid parameter scans and optimization. The approach is based on constructing the effective Lagrangian for only the radial coordinates of the plasma electrons by integrating out the fields. The fields can be recovered from the solution for the trajectories. The Lagrangian-based approach has the advantage that it allows for construction of further reduced models using constraint forces and generalized coordinates. The connection to the ‘energy conserving’ delta-sheath theory of Golovanov et al. [3] is given. Comparison of the wakes is also given. This work is supported by DOE under grants, DE-SC0025612 and DESC0010064.
References:
[1] W. Lu et al., Phys. Plasmas 13, 056709 (2006).
[2] T. N. Dalichaouch et al., Phys. Plasmas 28, 063103 (2021).
[3] A. Golovanov et al., Phys. Rev. Lett. 130, 105001 (2023).
| Working group | WG1 |
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