Next steps in research on laser driven ion acceleration in Saclay
Relying on a rich set of human resources, technical expertise and equipment, we are going to implement an ambitious program of research.
a) Energy scaling laws
Most of the existing models wich are supposed to give scaling laws about proton beams main features (maximum energy, number of accelerated particles) seem better suited to high-energy and "long" duration (~ ps) laser pulses. This is explained by the fact that these models mainly go by data acquired in experiments carried out on such facilities. However, we can understand the interest, mainly economic, for future laser facilities to achieve very high levels of intensity but using a very short pulse duration and relatively little energy. As a consequence, it becomes important to check and modify existing laws scale to better fit them to this kind of interaction regime. This is what we propose to do by studying the influence of pulse duration and the intensity of illumination on the maximum energy and on the spectral distribution of protons.
b) Nano-structured targets
Recent experiments in Saclay showed the coupling efficiency increase potential of micro and nano-structured targets. Boosted by our results, we will extend the exploration of this research field using targets with characteristics better suited to our interaction parameters. Moreover, we will also study the emission of electron bunches we observed using targets showing a regular periodic grating-like pattern on the laser exposed surface.
c) The ALPS project
As a logical continuation of the ANR project “GOSPEL”, ended in 2012, ALPS project is in the framework of the SAPHIR project (see below), to which our team takes part. This strategic industrial innovation project, a collaboration between industrial and academic partners, aims to define the necessary scientific and technological building blocks for the realization of a protontherapy device using a laser driven proton source. Three main research objectives are pursued:
- Development of scaling laws for proton energies of different laser intensities up to the ultra-relativistic regime, I> 1021 W cm-2, in order to build a laser ion source of medical interest;
- Getting a deepen insight into the knowledge of the fundamental aspects of laser-generated plasmas, to identify and control the more suitable acceleration paths for practical use of the produced ion beams;
- Quantifying the effects that a dose deposited by laser-accelerated particles have on biological samples, aiming to confirm or deny their usefulness for proton therapy.
The CEA / DAM-IDF and the LOA (project leader) are the other partners of the project.
d) The PROPAGATE project
The PROPAGATE project aims to perform a systematic experimental study of the basic laser-absorption mechanism on atomic clusters as a function of the cluster average size, the electron density and the laser parameters (energy, pulse length, contrast ratio…) in order to measure the absolute rates of particle production. PROPAGATE has built a strong interdisciplinary collaboration between chemists with an expertise in nano-object production processes, who will provide also the characterisation of these nano-objects, atomic physicists, who will build the spray source necessary for the introduction of the nano – objects into the laser reaction chamber, nuclear physicists for the neutron and high-energy particle detection, laser plasma physicists and astrophysicists. The experimental activity will be held on the ECLIPSE laser at CELIA and on the UHI100 TW laser system in Saclay.
e) Ions energy transfer to matter
Laser accelerated ion bunches emittance and duration are orders of magnitude smaller than bunches one can get using a conventional accelerator. We have shown that the shot to shot reproducibility can rise up to 5% RMS using UHC laser pulses. All these features make laser accelerated ions the perfect device to study the energy deposition in matter over extremely short time scales, in particular through pump-probe experiments. Such information is of primary interest for the development of numerical models of induced fluorescence in matter by ionizing particles. This research program is carried out in collaboration with the CEA / IRAMIS / Nanosciences et Innovation pour les Matériaux la Biomédecine et l'Energie (NIMBE).
f) Laser accelerated protons for protontherapy: the SAPHIR consortium
Among all the possible applications of these proton bunches, the most interesting from a social point of view is, by far, the possibility of using them for cancer treatment. In this context, the aim of SAPPHIRE consortium is to study the feasibility of a laser-generated source expected to be more compact, flexible and chip than existing facilities based on standard compact proton accelerators. This project, which recently received the enthusiastic support of OSEO, gathers partners of recognized competence in the world of research and business: the LOA, CEA-DAM, Amplitude Technologies, Institute Gustave Roussy, the Curie Institute, the Orsay Proton Therapy Center, Propulse sas, Imagine Optic and Dosisoft.