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Abstract:

Radiation reaction, the force experienced by an accelerated charge due to radiation emission, has long been the subject of extensive theoretical and experimental research. Experimental verification of a quantum, strong-field description of radiation reaction is fundamentally important, and has wide-ranging implications for astrophysics, laser-driven particle acceleration, next-generation particle colliders and inverse-Compton photon sources for medical and industrial applications. However, the difficulty of accessing regimes where strong field and quantum effects dominate inhibited previous efforts to observe quantum radiation reaction in charged particle dynamics with high significance. We report a high significance ( > 5σ) observation of strong-field radiation reaction on electron spectra where quantum effects are substantial. We obtain quantitative, strong evidence favouring the quantum-continuous and quantum-stochastic models over the classical model; the quantum models perform comparably. The lower electron energy losses predicted by the quantum models account for their improved performance. Model comparison was performed using a novel Bayesian framework, which has widespread utility for laser-particle collision experiments, including those utilising conventional accelerators, where some collision parameters cannot be measured directly.

Abstract:

We study a novel device for generating a high speed rotating plasma. The device weakly ionises and accelerates a hydrogen gas in a co-axial cylindrical chamber via the perpendicular configuration of electrodes with a magnetic field generated by a superconducting magnetic. It has been hypothesised that extreme velocities and plasma particle compression could be achieved under this configuration1 . This work develops a rigorous theoretical model of the bulk plasma dynamics under steady state centrifugal operation. By exploiting the axisymmetry of the system, and from application of problem-specific governing assumptions, a steady state 1D model for the rotational dynamics of the bulk plasma is derived. From here, we present fully analytical solutions for the radial profiles of the MHD model: [azimuthal velocity, particle densities, pressure] and a semi-analytical solution for electric potential. Tables of selfconsistent plasma parameters are computed to provide a comprehensive characterisation of the bulk plasma state. The model is able to determine the peak velocities and plasma compression, and permits parametric studies to elucidate the complex and non-linear relationships between operational device settings and the achieved steady state plasma state condition. The new theoretical solutions therefore provide necessary insights into the viability of the novel device for high energy-density plasma applications.

Abstract:

Understanding dense matter hydrodynamics is critical for predicting plasma behavior in environments relevant to laser-driven inertial confinement fusion. Traditional diagnostic sources face limitations in brightness, spatiotemporal resolution, and in their ability to detect relevant electromagnetic fields. In this work, we present a dual-probe, multi-messenger laser wakefield accelerator platform combining ultrafast X-rays and relativistic electron beams at 1 Hz, to interrogate a free-flowing water target in vacuum, heated by an intense 200 ps laser pulse. This scheme enables high-repetition-rate tracking the evolution of the interaction using both particle types. Betatron X-rays reveal a cylindrically symmetric shock compression morphology assisted by low-density vapor, resembling foam-layer-assisted fusion targets. The synchronized electron beam detects time-evolving electromagnetic fields, uncovering charge separation and ion species differentiation during plasma expansion - phenomena not captured by photons or hydrodynamic simulations. We show that combining both probes provides complementary insights spanning kinetic to hydrodynamic regimes, highlighting the need for hybrid physics models to accurately predict fusion-relevant plasma behavior.