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At 20PW (400J in 20fs) we will approach peak intensities of around 10²³Wcm^-2, this is where we start to enter the regime where Quantum Electrodynamics (QED) processes become significant in laser-mat​ter interactions, as well as where we stretch previously studied phenomena into uncharted territory. There will be many scientific opportunities for users coming to the upgraded facility, but we anticipate that there are six major areas where these opportunities lie:

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1. Fundamental Plasma Physics: There are many areas of plasma physics where understanding is incomplete.  The combination of 20PW with VOPPEL and the long-pulse beamlines will create a facility that can address many different aspects of plasma physics.  Advances in fundamental plasma physics will benefit many things ranging from astrophysics, through to fusion and novel industrial imaging techniques.
2. The QED Regime:  It is thought that the 20PW laser will allow users to explore the regime where QED processes become important, such as the production of electron-positron pairs, and it may allow users to probe the physics of pair plasmas.  It may also allow users to probe the completeness of fundamental physical theory in areas such as non-perturbative QED, radiation reactions, and photon-photon interactions.
3. New Physics?: Many scientists are interested in looking for physics beyond that present in the Standard Model, and it has been proposed that ultra-intense lasers could play a role in this search.  Examples of this include the search for hypothetical low-mass particles such as axions, or looking to observe Unruh radiation (an analogue of Hawking radiation for accelerating observers).
4. Matter Under Extreme Conditions:  The combination of lasers will allow the creation and diagnosis of matter at extreme densities and pressures.  This area of study is important for certain avenues of fusion research, the understanding of exoplanets and gas giants, and for investigating the possibility of generating novel metastable materials.
   
5. The Physics of Astrophysics: Over several years, the pursuit of 'laboratory astrophysics' with lasers has been an ever expanding area.  The upgraded facility will expand the range of potential 'lab astro' experiments and it is thought that topics such as magnetic field generation and turbulent amplification, and astrophysical particle acceleration might be addressed.  If copious pairs can be produced then it may even be possible to probe the physics of objects such as gamma-ray bursts.
6. The Appliance of Science: The increase in intensity at 20PW will most likely enhance the performance of electron, ion, and photon generation to new heights.  This will widen opportunities to apply these laser-driven sources to technological and industrial problems.  As fusion is entering a period where there is increasing industrial interest, this could create an important diagnostic for probing inertial fusion schemes, which could be highly beneficial to the UK fusion community.