Magnetic fields are seen in every parts of the Universe. But where do they come from? We study plasma processes that results in the formation of such fields.
To understand the dynamics of plasmas we rely on large-scale computational models. We use radiation-hydrodynamics simulations, as well as ab-initio codes to model quantum effects.
The interior of planets and white dwarfs consists of matter at very high density. Which are its properties? Can we measure their viscosity and thermal conductivity?
Electrons at the focus of a high intensity laser can reach enormous accelerations. This mimics Hawking's radiation from a Black Hole horizon. Can we also produce light (pseduo)scalar particles, such as axions?
Cosmic rays arrive on Earth with very high energies. Interstellar shocks and turbulence is believed to produce them. Can we recreate equivalent conditions in the laboratory?
Experiments are performed on a variety of laser facilities, spanning from the largest laser in the world - the National Ignition Facility - to our laser system here in Oxford. We also work with the next generation light sources.
One of the approaches to fusion attempts to compress a fuel pellet using laser beams, whereby the matter is accelerated towards the centre by the rocket effect, which mimics gravity. Thus, this bears similarities with the core-collapse of a star.
Inertial confinement fusion research uses hohlraum (that is, gold tubes) targets to convert laser energy into x-rays. This x-rays are then used to compress a tiny hydrogen-filled capsule placed at its centre.
As a high-power laser is focused on a target, high energy electrons, protons and even positrons are produced. These contribute to the transport of energy from the laser into the matter.
Lasers can deposit a large amount of energy in the matter. At pressures exceeding 1 Mbar, the energy density becomes comparable to that of an electron in the hydrogen atom. Quantum effects must be accounted for - a new state of matter is reached.
Prof Gregori research interests cover laboratory astro-particle physics with high power lasers, dense plasmas as found in interior of stars and planets, and inertial confinement fusion (ICF) energy. He started at Oxford University in October 2007 as as an RCUK Fellow in the Department of Atomic and Laser Physics. In 2012 he became Fellow and Tutor of Physics at Lady Margaret Hall, and in 2013 he was appointed Professor of Physics.
From 2001 to 2005 Prof Gregori worked at the Lawrence Livermore National Laboratory (USA), in the Fast Ignitor Physics group within the ICF Program. He was a post-doctoral researcher from 2001 to 2003 and then appointed as staff scientist. From 2005-2012, Prof Gregori has been holding a senior experimental scientist position at the Rutherford Appleton Laboratory.
He received a Ph.D. and a M.S. from the University of Minnesota (Minneapolis, USA) and a M.S. from the University of Bologna (Italy). In 2007, Prof Gregori's team was awarded a 2007 Daiwa Adrian Prize for its research into ‘High energy density science: new frontiers in plasma physics’. In 2014 Prof Gregori was awarded the Edouard Fabre International Scientific prize for contribution to the physics of inertial fusion and of laser-produced plasmas. Prof Gregori was recipient of the 2019 and 2020 John Dawson Award for Excellence in Plasma Physics by the American Physical Society, and the 2022 Cecelia Payne-Gaposchkin Medal and Prize by the Institute of Physics Physics.
Prof Gregori is fellow of the American Physical Society (USA) and Fellow of the Institute of Physics (UK).
The NIF laser is used to generate a turbulent, magnetised plasma. This mimic the same plasma conditions we find in cluster of galaxies and our goal is to understand how magnetic fields behaves in such systems.
Even if very small compared to NIF, our campus lasers (a 10 J, 10 ns Nd:YAG plus a 50 mJ, 50 fs Ti:Sapphire) are essential for training and preparation for work in the largest systems.
Not just work...having a Christmas dinner in London.
Preparing to load the next target and gathering invaluable data.
A great achievement!