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We present an experimental and simulation-based investigation of the temporal evolution of light emission from a thin, laser-ionized helium plasma source. We demonstrate an analytic model to calculate the approximate scaling of the time-integrated, on-axis light emission with the initial plasma density and temperature, supported by the experiment, which enhances the understanding of plasma light measurement for plasma wakefield accelerator (PWFA) plasma sources. Our model simulates the plasma density and temperature using a split-step Fourier code and a particle-in-cell code. A fluid simulation is then used to model the plasma and neutral density, and the electron temperature as a function of time and position. We then show the numerical results of the space-and-time-resolved light emission and that collisional excitation is the dominant source of light emission. We validate our model by measuring the light emitted by a laser-ionized plasma using a novel statistical method capable of resolving the nanosecond-scale temporal dynamics of the plasma light using a cost-effective camera with microsecond-scale timing jitter. This method is ideal for deployment in the high radiation environment of a particle accelerator that precludes the use of expensive nanosecond-gated cameras. Our results show that our models can effectively simulate the dynamics of a thin, laser-ionized plasma source. In addition, this work provides a detailed understanding of the plasma light measurement, which is one of the few diagnostic signals available for the direct measurement of PWFA plasma sources.
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This content will become publicly available on December 1, 2025
The impact of electron inertia on collisional laser absorption for high energy density plasmas
High-power lasers are at the forefront of science in many domains. While their fields are still far from reaching the Schwinger limit, they have been used in extreme regimes, to successfully accelerate particles at high energies, or to reproduce phenomena observed in astrophysical settings. However, our understanding of laser–plasma interactions is limited by numerical simulations, which are very expensive to run as short temporal and spatial scales need to be resolved explicitly. Under such circumstances, a non-collisional approach to model laser–plasma interactions becomes numerically expensive. Even a collisional approach, modeling the electrons and ions as independent fluids, is slow in practice. In both cases, the limitation comes from a direct computation of electron motion. In this work, we show how the generalized Ohm's law captures collisional absorption phenomena through the macroscopic interactions of laser fields, electron flows, and ion dynamics. This approach replicates several features usually associated with explicit electron motion, such as cutoff density, reflection, and absorption. As the electron dynamics are now solved implicitly, the spatial and temporal scales of this model fit well between multi-fluid and standard magnetohydrodynamics scales, enabling the study of a new class of problems that would be too expensive to solve numerically with other methods.
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- Award ID(s):
- 1943939
- PAR ID:
- 10588558
- Publisher / Repository:
- American Institue of Physics
- Date Published:
- Journal Name:
- Physics of Plasmas
- Volume:
- 31
- Issue:
- 12
- ISSN:
- 1070-664X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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