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The experimental results on the initiation of various (γ, n) and (p, n) nuclear reactions in the picosecond laser plasma are presented. It is demonstrated that the following (γ, n) and (p, n) nuclear reactions can be initiated at a laser intensity of 2 × 1018 W/cm2 with the threshold energies of γ-quanta ranging from 1.67 to 7.56 MeV and the threshold energies of protons ranging from 1.88 to 5 MeV: 9Be(γ, n)2α, 181Ta(γ, n)180Ta, 7Li(p, n)7Be, 63Cu(p, n)63Zn, 48Ti(p, n)48V. The method based on the detection of fast neutrons using the 3He counters is employed for the measurement of the number of the initiated (γ, n) and (p, n) nuclear reactions. The measured yield of the (γ, n) and (p, n) nuclear reactions ranges from 5 × 101 to 105 reactions per laser pulse.

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.

The results of experiments devoted to studying the excitation of the promising nuclear fusion reactions 6Li(d, α)4He, 3He(d, p)4He, 11B(p, 3α), and 7Li(p, α)4He, along with the standard reaction D(d, n)3He, in picosecond laser plasmas are presented. For the first time, it was shown that these reactions may proceed at a moderate laser-radiation intensity of 2 × 1018 W/cm2, the respective yield being 2 × 103 to 105 per laser pulse. A brief survey of the main processes responsible for the generation of fast electrons and fast ions (protons) at the front surface of the target and for the excitation of nuclear fusion reactions is given. The calculated and experimental results on the yield from nuclear fusion reactions in picosecond laser plasmas are compared. The possibilities for optimizing the yield from the promising fusion reactions excited in femto- and picosecond laser plasmas are discussed.

The results of experiments devoted to studying the generation of MeV photons and protons in picosecond laser plasmas at a laser beam intensity of 1018 W/cm2 on Be, Ta, LiF and H7Li targets are presented. Nuclear reactions (γ, n) and (p, n) were used to detect MeV photons and protons. The number of MeV photons and protons generated in laser plasmas was found from the measured neutron yield. Possibilities of particle acceleration due to the formation of pinch structures in laser plasmas are discussed. Calculated and experimental results are compared.

Experimental results on the effect of picosecond and nanosecond prepulses on the neutron yield in laser picosecond plasma on the surface of solid (CD2)n targets at a laser intensity of 1018 W/cm2 are presented. It is demonstrated that the picosecond (nanosecond) prepulse decreases the neutron yield at a laser prepulse intensity of higher than 1013 (1012) W/cm2. The estimates indicate three possible mechanisms for the realization of the observed effect: stimulated Mandelstam-Brillouin scattering of the main pulse by the preplasma, channels of the generation of fast ions, and their possible deceleration in the preplasma. The results of calculations are compared with the experimental data.

Experimental data on neutron production in a plasma generated on a Be target by a picosecond laser of intensity 2 x 10{sup 18} W/cm{sup 2} are presented. In contrast to previous measurements, a Ta converter is not used in this study to generate {gamma} rays. The neutron yield is equal to 2 x 10{sup 3} over a solid angle of 4{pi} steradians per laser pulse. A simultaneous measurement of the maximum energy of hard x rays gave E{sub {gamma}}{sub max} {approx} 6 MeV, the number of these photons being 5 x 10{sup 8} over an angle of 4{pi} steradians per laser pulse. The energy distributions of fast electrons and photons are estimated theoretically.