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Nuclear Activation Techniques for Analysis of Laser Induced Energetic particles – NATALIE

Submission summary

Considerable progress has been made recently in generating electron and proton beams in high intensity (1E19W/cm²) femto-second laser pulse interactions with gaseous or solid targets. Typically 1E12 particles with an exponential-like energy distribution are produced in few picoseconds bunches. The divergence of such beams is of the order of 1E-3 mm mrad. The characterization of these beams is difficult and needs to be improved. Standard detectors are not able to record such a quantity of particles simultaneously, spectrometers have a poor detection solid angle, and track detectors (CR39) or Radio Chromic Films (RFC) can only be used at low particle fluxes. Another method consists in using these beams to induce nuclear reactions leading to β+ emitters of short periods which can be detected with very good signal to noise ratio. This technique has been used successfully in different experiments to characterize laser-accelerated electron and proton beams. The very rapid development of high intensity lasers will provide in a few years very high charged particles fluxes which can be used in different domains: - In nuclear physics we will be able to study nuclear reactions rates and nuclear decays in extreme conditions, as for example in dense plasmas (1E27 charged particles/m3) produced in laser-solid targets interactions or in the presence of very high intensity laser electric fields (1E11 V/cm). - Besides their high intensities these pulsed beams are short (few picoseconds) have excellent emittances and can therefore be injected into large scale ion accelerators. - In plasma physics the proton radiography is used to characterize dense opaque plasmas. The characteristics of the incident lighting up proton beam must be precisely known for the optimal use of this technique. - Medical applications are also possible with these high fluxes of ions easily-produced from tabletop lasers. For instance radioisotopes can be produced in the same way they are from traditional heavy ion cyclotrons. It is hoped that the laser technology will allow the multiplication of the number of production sites. The proximity of the radioactive tracer sources from the patients would allow the medical use of shorter lifetime radioisotopes in smaller quantities. Projects exist which aim at using directly these ion beams to treat diseases by hadrontherapy as it is done with traditional heavy ion accelerators. For all these applications one needs to determine precisely the initial high flux ion beam characteristics. We propose to develop a nuclear-activation-based diagnostic for this purpose. The number of accelerated particles in the beam will be deduced from the number of nuclear reactions induced in a chosen sample of matter. Furthermore, setting in the accelerated ion's pathway a stack of calibrated foils we will reconstruct from the number of reactions induced in each of the foils the initial kinetic energy distribution of the incident particles. To make the induced nuclear reaction easily detectable, we favour reactions leading to the formation of beta+ emitters. To characterize proton beams we will use (p,n) reactions on 63Cu leading to the beta+ emitter 63Zn which has a lifetime of 38 min. To determine the proton spatial distribution we will insert Radio Chromic Films between the copper foils in the stack. The more numerous and thinner copper foils you have in the stack, the better energy resolution you will obtain in the measurement. We therefore want to develop a multi counters beta+ station in order to be able to measure simultaneously the activity of at least 10 foils.

Project coordination

Medhi TARISIEN (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Help of the ANR 150,000 euros
Beginning and duration of the scientific project: - 36 Months

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