School of Physics, University of Exeter, Exeter EX4 4QL, United Kingdom pos Анотація:
Received March 13, 2018, published online August 28, 2018
The angular distributing of energy density of “phonon sheet” at it propagation in superfluid 4He at length of impulse about 300 ns is investigated. The availability of flat top on angular dependences of phonon signal is explained by formation of «hot» area in the central region of sheet and process of creation of high energy phonons in this area. The saturation of the width of the flat top for impulse near-by 300 ns is explained by realization of the long pulse regime.