Investigating radiatively driven, magnetized plasmas with a university scale pulsed-power generator
Physics of Plasmas AIP Publishing 29:4 (2022) 042107
Abstract:
We present first results from a novel experimental platform that is able to access physics relevant to topics including indirect-drive magnetized inertial confinement fusion, laser energy deposition, various topics in atomic physics, and laboratory astrophysics (for example, the penetration of B-fields into high energy density plasmas). This platform uses the x rays from a wire array Z-pinch to irradiate a silicon target, producing an outflow of ablated plasma. The ablated plasma expands into ambient, dynamically significant B-fields (∼5 T), which are supported by the current flowing through the Z-pinch. The outflows have a well-defined (quasi-1D) morphology, enabling the study of fundamental processes typically only available in more complex, integrated schemes. Experiments were fielded on the MAGPIE pulsed-power generator (1.4 MA, 240 ns rise time). On this machine, a wire array Z-pinch produces an x-ray pulse carrying a total energy of ∼15 kJ over ∼30 ns. This equates to an average brightness temperature of around 10 eV on-target.
Strong suppression of heat conduction in a laboratory replica of galaxy-cluster turbulent plasmas
Science Advances 8, 10 (2022)
Abstract:
In conventional gases and plasmas, it is known that heat fluxes are proportional to temperature gradients, with collisions between particles mediating energy flow from hotter to colder regions and the coefficient of thermal conduction given by Spitzer’s theory. However, this theory breaks down in magnetized, turbulent, weakly collisional plasmas, although modifications are difficult to predict from first principles due to the complex, multiscale nature of the problem. Understanding heat transport is important in astrophysical plasmas such as those in galaxy clusters, where observed temperature profiles are explicable only in the presence of a strong suppression of heat conduction compared to Spitzer’s theory. To address this problem, we have created a replica of such a system in a laser laboratory experiment. Our data show a reduction of heat transport by two orders of magnitude or more, leading to large temperature variations on small spatial scales (as is seen in cluster plasmas).
Femtosecond Diffraction and Dynamic High Pressure Science
(2022)
Light-shining-through-wall axion detection experiments with a stimulating laser
Physical Review D - Particles, Fields, Gravitation and Cosmology American Physical Society 105 (2022) 035031
Abstract:
The collision of two real photons can result in the emission of axions. We investigate the performance of a modified light-shining-through-wall (LSW) axion search aiming to overcome the large signal suppression for axion masses ma ≥ 1 eV. We propose to utilize a third beam to stimulate the reconversion of axions into a measurable signal. We thereby find that with currently available high-power laser facilities we expect bounds at axion masses between 0.5–6 eV reaching gaγγ ≥ 10−7 GeV−1. Combining the use of optical lasers with currently operating x-ray free electron lasers, we extend the mass range to 10–100 eV.
Slip competition and rotation suppression in tantalum and copper during dynamic uniaxial compression
(2022)