ENSURE is a research project for the investigation of innovative techniques of particle acceleration.
But, what are accelerated particles used for? What are their main industrial and societal applications?
High-energy particle beams are currently exploited in many different scientific fields both for technological applications and fundamental research, such as:
- medical technology: radiotherapy (e.g. oncological hadrontherapy) and isotope production for medical purposes (e.g. PET and SPECT);
- nuclear and materials engineering: inertial confinement nuclear fusion, materials characterization (for example ion beam analysis e.g. for cultural heritage preservation and neutron imaging e.g. for cargo containers scanning), materials irradiation;
- basic science: particle physics, generation and use of synchrotron radiation, warm dense matter production, diagnostic of electromagnetic fields.
Different, well-established techniques for particle acceleration exist that are currently exploited in the so-called conventional accelerators such as linear accelerators, synchrotrones and cyclotrones. However, conventional accelerators have certain limits, among which are reduced flexibility, substantial radioprotection concerns and large scale, high cost facilities.
A new approach may be possible thanks to the development of novel laser systems able to deliver pulses with extremely high powers and extremely short durations. Upon the interaction with such laser pulses, matter turns into a “non-ordinary” state of aggregation: the plasma state. This kind of interaction gives rise to the strongest electric fields ever generated in a laboratory (thousands of billions of volts per meter) that ultimately lead to the acceleration of charged particles – in particular protons and other ions – with high energies and in very short distances (few microns), as artistically depicted in the figure below.
As opposed to conventional accelerators, laser-based particle acceleration is potentially more flexible, comes with less radioprotection concerns and requires smaller and cheaper facilities. Nowadays many efforts in the scientific community are focused on various issues and challenges that need to be faced to actually build and use laser-particle accelerators.
One interesting feature is that the acceleration process may be controlled and optimized using particular nanostructured materials with special properties that no ordinary material has. These complex materials are produced exploiting different techniques of materials science and are called nanofoams because of their porosity (see the image below!).
The most important characteristic that makes nanofoams interesting for laser-driven ion acceleration is their extremely low average density, which can reach values as low as a few times the density of air (they are so porous that air actually occupies most of the foam volume). According to plasma physics, this low density value allows for a better absorption of the laser energy. Besides, the ion emission requires the presence of a high-density solid material. Hence the development of the Double Layer Target (DLT) concept, in which a low-density layer is coupled with a thin solid layer from which the ions are emitted (along the direction of the laser).
The ENSURE project investigates both theoretically and experimentally the fundamental physical processes at play together with the potential applications related to these topics, where major advances are still needed. Numerical simulation and theoretical studies are employed to shed insights into the acceleration process, providing a guideline for the experimental activity. Optimized targets are then designed, produced and characterized, exploiting (and refining) advanced material science techniques, to be finally tested in particle acceleration experimental campaigns. The investigation of potential and promising applications can then be carried out, exploiting the knowledge and insight previously obtained. Because many different fields of expertise are involved, ENSURE addresses its goals by bringing together – into one single team – nuclear engineering, materials science, laser technology , plasma physics, nanotechnology and also computer science.