Time delay of the hard X-ray and neutron emission at PF 1000 facility

Abstract

The PF 1000 plasma focus device with deuterium as filling gas is used for the study of hard X-rays and neutrons (originated from D-D fusion reactions). The time of generation and energy distribution of neutrons were determined using the time-of-flight method and MC simulations. The hard X-ray and neutron signals have usually two pulses: the first at the minimum of current derivative and the second 120 ÷ 170 ns later. An experimentally observed asymmetry of neutron pulses detected with scintillation detectors in axial z-direction downstream and upstream is explored by simple model in which each of both neutron pulses is decomposed into two components: the asymmetry one with energy above 2.45 MeV downstream and the symmetry one with the maximum of 2.45 MeV. In this article we describe in detail the shot No. 5566. The asymmetry component has energy downstream 2.55 ÷ 2.85 MeV (the first peak) or/and 2.70 ÷ 3.00 MeV (the second peak). The symmetric component in the energy range 2.2 ÷ 2.7 MeV is generated a few tens ns after the asymmetric one and it contains a lower part 25 ÷ 35 % of neutrons. In this presented shot the onset of neutrons was observed before the onset of hard X-rays. This fact declares the possibility of acceleration of a fraction of the fast energy deuterons before the fast electrons.