Plasma light dynamics and measurement techniques of a plasma-based accelerator plasma source*

We present a study on helium plasma afterglow light dynamics in a plasma wakefield accelerator (PWFA) plasma source, employing both experimental and simulation methods. We first model the plasma formation using a split-step Fourier code and a particle-in-cell (PIC) code, followed by a simulation of the plasma expansion dynamics via a fluid code. We then create a simple model to estimate the time-resolved photon emission density from the plasma, considering electron-impacted collisional excitation and electron-ion recombination. The results reveal that the electron-impacted collisional excitation events dominate the light emission process. In addition, we devise an innovative statistical analysis method capable of capturing the nanosecond-scale temporal dynamics of plasma light using a cost-effective CMOS camera with microsecond-scale integration and timing jitter. This approach is broadly applicable and ideal for high-radiation settings, such as PWFA experimental environments. Our results show good agreement between the experimental data and simulations. Finally, we demonstrate an analytic formula for a PWFA-like plasma source’s time-integrated peak plasma light density, an easily accessible measurement in PWFA experiments.