ИСТИНА

The paper is devoted to the feasibility study of photonuclear reactions at photon energies below 10 MeV. Significant results could be obtained, especially on pigmy resonance excitation in soft nuclei measured with real and virtual photons through excitation of spin isomers. The experimental study of low-lying collective excitations of nuclei is now an actual problem, because it allows us to investigate toroidal and compression modes of excitations of nuclei of different multipolarity (M1, M2, E2, etc.), to obtain additional information on the neutron halo in nuclei, to promote the development of microscopic nuclear models. This implies measurements of the total cross sections of photoabsorption, yields and cross sections of photoneutron reactions. Preliminary comparative results obtained with the electron linear accelerator LUE-8 MeV at INR and terawatt femtosecond laser complex of Moscow State University are presented. Mutual use of two different systems provides high accuracy measurements and the development of new technologies. Based on numerical simulation and targeted experiments new methods for the study of photonuclear reactions are under development. Experimental & numerical studies of interaction of femtosecond laser radiation with intensity up to 5х1018 W/cm2 with dense plasma, conducted recently using terawatt femtosecond laser facility at MSU, are discussed. Main stress was on the control of plasma parameters (luminosity in X-ray and gamma ranges, generation of bunches of relativistic electrons and fast multicharged ions) and their optimization by choosing interaction regime and preplasma parameters. The pre-plasma extent was controlled by changing time delay between the pulses and energy density of the nanosecond pulse. We studied two specific set of parameters then electron heating is very efficient and gamma quanta as high as 7-10 MeV appeared at intensities of 2000 PW/cm2. In the last part of the paper we are also considering applicability of our approaches for large scale modern laser installations such as the ELI-NP facility that can be used for efficient production of “monochromatic” gamma beam within sub10 MeV range for nuclear studies not only with stable but also isomeric nuclei.