Atomic Physics

The multi PW short pulse beams will allow direct heating of solid material to keV temperatures (~107Kelvin). Coupling the long pulse beams with the multi-PW short pulse beams will allow matter to be compressed to densities in excess of 100 g/cm3 (roughly ten times the density of lead) and subsequently heated to keV temperatures.

The behaviour of the electronic states of matter under such conditions is very uncertain, requiring experimental data to test the validity of state-of-the-art atomic physics models.  In particular, the opacity (an important quantity in radiation transfer) can be determined from emission and absorption spectroscopy of tracer layers buried in the material which give measurements of density and temperature. Detailed knowledge of radiation transfer is required for problems ranging from the behaviour of our Sun to the creation of planetary nebulae.

Cats Eye Nebula

A wider parameter space can be accessed by using targets with densities lower than solid. This is important in the study of more exotic astrophysical phenomena such as quasi-stellar-objects (QSO), where the key parameter is the relative dominance of radiation over other forms of energy. We require measurements of the distribution of ionisation in photoionised plasma with very high xi (>100 erg cm s-1), where xi is a commonly used parameter that defines the photoionisation state in plasma.   Such states can be accessed using doped low-density foams inside a radiation cavity.   This is to be compared to the best measurements to date (using the Z-machine at SNLA, where xi =20 erg cm s-1 was achieved).

Driving experiments with the output from an ignition capsule from HiPER will allow even more extreme conditions. It is suggested to use the output from a high-gain target to heat a slab of solid density material to 5 keV and accelerate the target. At the same time, a high magnetic field could be generated using some of the remaining PW beams, whilst using others to diagnose the system with proton beams and high energy photons.

Similarly, the output from a high-gain target could be used to drive a photoionisation plasma experiment. Calculations predict xi >1000 erg cm s-1 which is as high as is believed to exist anywhere in the Universe.