Laboratory astroparticle physics

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.

Abstract:

The generation of dense electron-positron pair beams in the laboratory can enable direct tests of theoretical models of γ-ray bursts and active galactic nuclei. We have successfully achieved this using ultrarelativistic protons accelerated by the Super Proton Synchrotron at (CERN). In the first application of this experimental platform, the stability of the pair beam is studied as it propagates through a meter-length plasma, analogous to TeV γ-ray-induced pair cascades in the intergalactic medium. It has been argued that pair beam instabilities disrupt the cascade, thus accounting for the observed lack of reprocessed GeV emission from TeV blazars. If true, this would remove the need for a moderate strength intergalactic magnetic field to explain the observations. We find that the pair beam instability is suppressed if the beam is not perfectly collimated or monochromatic, hence the lower limit to the intergalactic magnetic field inferred from γ-ray observations of blazars is robust.