Experimental investigations of fast-proton production in a picosecond laser plasma |
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Authors: | V S Belyaev A P Matafonov S M Ribakov V P Danilov V P Krainov V S Lisitsa V P Andrianov G N Ignatyev and A S Rusitski |
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Institution: | (1) Engineering Division, Brown University, Providence, RI 02912, USA |
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Abstract: | Results of experimental investigations of fast-proton production in a laser plasma are presented for the case where the intensity
of laser radiation at the targets is 2 × 1018 W/cm2. Three processes of fast-proton acceleration in laser plasma are investigated: (1) the acceleration of protons from the front
surface toward the laser pulse, (ii) the acceleration of protons from the front surface of the target toward its interior,
and (iii) the acceleration of protons from the rear foil surface in the outward direction. The activation procedure and CR-39
tracker detectors featuring a set of various-thickness aluminum filters were used to record fast protons. It turned out that
the proton-acceleration process is the most efficient in the case of proton acceleration from the rear foil surface in the
outward direction. Experimental results revealed that about N
p
= 107 protons of energy in the region E
p
> 1.9 MeV that are accelerated from the target surface toward a laser ray, N
p
= 4× 107 protons of energy in the region E
p
> 1.9 MeV that are accelerated fromthe front surface of the target toward its interior, and N
p
= 4×108 protons of energy in the region E
p
> 1.9 MeV that are accelerated from the rear foil surface in the outward direction are generated at a laser-radiation intensity
of 2 × 1018 W/cm2 at the surface of aluminum, copper, and titanium targets. Experimental investigations aimed at optimizing the process of
proton acceleration from the rear surface of aluminum foils were performed by varying the foil thickness over the range between
1 and 100 μm. The results of these experiments showed that there is an optimum foil thickness of 10 μm, in which case protons
of maximum energy 5 MeV are generated. |
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Keywords: | |
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