Ultra-high radiation levels (particle fluence up to 1018 part./cm2 and ionising dose up to 100 MGy), are expected in the next generation of High Energy Physics (HEP) colliders currently under study at CERN. State of the art solid-state devices for radiation and particle measurement (mainly passive devices or silicon-based active sensors) are not capable of integrating such radiation levels, as well as of providing feasible solutions to build online monitoring devices.
The innovative technology investigated in this project consists of thin-film metal structures (5-1000nm range), for which structural, chemical and electrically observable effects occur under ultra-high particle bombardment. As a result, depending on the film thickness and uniformity, on one hand, the resistivity of these structures (made of Copper) was proven to gradually increase according to the integrated neutron and high-energy protonfluence.
However, on the other hand, these sub-micron thin metal layers can also exhibit an instantaneous and permanent increase in their conductivity. Moreover, thin metal films can be effectively used as Secondary Electron Emission (SEE) materials. In this latter application, the integration of multiple metal layers on thin plastic carrier substrates may open the way to ultra-low material budget and high-sensitivity particle beams monitors.The microfabrication of the devices is carried out at the Centre of Micronanotechnology (CMi) of the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Lausanne, Switzerland. Nano-metermetal layers, manufactured by Atomic Layer Deposition (ALD), are provided by the University of Helsinki, Finland.
The first goal of this project is to study in detail the physics/chemical/structural phenomena underlying these observable effects (with simulation studies and experimental measurements) and to optimise the sensitivity of the sensor structures by varying geometrical (thickness, width W, length L) and physical (material) properties of the thin layers. This with the final goal of evolving towards an operative sensor structure. These sensors could find application in several fields where ultra-high particle fluxes are expected, as well as where a particle beam monitoring with extremely-low material budget is required, such as medical, nuclear, energy, industrial (sterilisation, material modification, etc.), radiation test facilities, space, avionics.