(e,2e) & related processes

An (e,2e) experiment is the measurement of an electron impact ionisation process where both the exiting electrons are detected in coincidence. It is a measurement almost at the limit of what is quantum mechanically knowable and its description presents a substantial challenge to theory. There are at least two very good reasons for studying (e,2e) and related processes. The first is that only now is an understanding of the dynamics of the collision process beginning to emerge, the range and sophistication of the present experiments allows one to identify kinematical regimes where delicate and subtle effects can be observed and where present theories can be stretched to their limit. The second is that the multiple coincidence technique offers the possibility of an analytic tool that could be used to probe the structure of the target, be it atom, molecule, thin film or surface. These goals are not independent, of course, since the latter objective cannot be achieved unless we know enough about the dynamics of the ionisation process to be able to correct for kinematical effects.

Major Projects Under Way:

• Coulomb few body effects in Atomic Collisions
• Ionisation processes with two active target electrons
• Excitation/Ionisation, Autoionisation
• Photo double ionisation
• Inner shell ionisation at relativistic energies
• (e,2e) with Spin Polarized Electrons
• (e,2e) on Bulk Matter
• Fragmentation processes using a range of projectiles: electron, photon and multi-charged ions

Helium Bubbles

Helium bubbles have been observed in the fuel containers used in fission reactors. The nickel nuclei in the containers absorb neutrons from the nuclear reaction and decay to produce alpha particles. The alpha particles combine with electrons from the metal to produce helium atoms which collect to form helium bubbles. The effect of helium bubbles on the strength of the fuel containers clearly needs to be investigated. In particular, a reliable estimate of the pressure inside the bubbles is required. The pressure can be calculated from the equation of state for helium if the density of helium inside the bubbles is known.

Major Projects Under Way:

• Including the effects of electron delocalization into the calculations
• Obtain an equation of state