Deposition Behavior And Irradiation Damage Of Complex Mixed Particle Beams In The Zirconium Deuterate Target Film

At present,high intensity-short pulse neutron generators based on vacuum arc ion source with deuterium electrode have attracted extensive attention.It has played an important role in neutron transient gamma spectra measurement and pulse neutron-neutron detection technology.The vacuum arc ion source with deuterium electrode will produce complex particle beams,including various valence states of metal ions,deuterium ions and metal vapor.When the neutron generator works,the complex particle beams interact with the deuterium(tritium)target,which seriously affects the stability and operating lifetime of the target.In this paper,the deposition behavior and irradiation damage of complex mixed particle beams in the zirconium deuterate target film are studied.Besides,the effect of different particle beams on the neutron performance of the zirconium deuterate target film is also studied.The physical mechanism of the damage effects on various particles is revealed,which provides experimental evidence for evaluating the stability of the zirconium deuterate target film performance.The major research achievements of this work are as follows:1)A physical model for the interaction between pulsed ion beam and film materials is established.The internal temperature-stress fields of the zirconium deuterate target film irradiated by ion beams under different parameters were obtained.The simulation results show that the surface temperature of the target film changes sharply with the pulse loading time of the pulse ion beam,and it reaches the peak value at the end of the pulse.The variation of the surface thermal-stress vs time curve is consistent with the variation of the temperature vs time curve.There is a stress jump at the interface between film and substrate,which indicates that the interface between film and substrate is susceptible to thermal stress.Therefore,there is a trend that film is easy to peel off the substrate.The thermal damage and thermal stress damage of metal ions are more serious than the deuterium ions.Therefore,in the neutron generator,the control of the metal ions proportion is very important for improving the local thermal effect and thermal stress of the deuterium target.2)The irradiation damage mechanism and effect of zirconium deuterate target film implanting by metal titanium ion are studied.The diffusion and distribution of deuterium atoms and titanium atoms in the zirconium deuterate film,and the damage mechanism of the film surface defects are discussed respectively.Finally,the neutron yield performance of zirconium deuterate films is studied.The results show that the thickness of the whole film will be reduced due to the strong sputtering effect of metal ions.However,after high dose of titanium ion implantation,a balance of the deuterium distribution on the surface of the zirconium deuterate film can be reached due to the sputtering effect.The irradiation damage zone on the surface of the zirconium deuterate film is generated by the irradiation of titanium ions.The defects in the irradiated zone are attributed to the collision scattering of the incident ions.The deuterium desorption are occurred in the damaged surface of the zirconium deuterate film,resulting in a decline of the surface deuterium concentration.The D-D reaction neutron yield is closely related to the deuterium distribution on the surface of the zirconium deuterate target film.With the increase of the irradiation dose of metal titanium ions,the neutron yield decreases significantly,the decline is about 12%.Finally,the neutron yield tends to be stable.3)The irradiation damage mechanism and effect of zirconium deuterate target film implanting by high dose deuterium ion are studied.The diffusion and distribution of deuterium atoms in the zirconium deuterate film,and the damage mechanism of the film surface defects are discussed respectively.Finally,the neutron yield performance of zirconium deuterate films is studied.The results show that deuterium atoms will recombine to form deuterium molecules in the deposition region of the film after high dose deuterium ion implantation.When the deuterium molecules aggregate to a certain degree,deuterium molecules(deuterium gas)will erupt outward and destroy the film,forming the craters on the surface of the film.A large amount of deuterium ion implantation will lead to a super-stoichiometry phenomenon(deuterium:zirconium =2:1).This is a proof that the deuterium atoms recombine to form deuterium molecules and deuterium molecules cannot escape outwards.After deuterium ion irradiation,the deuterium atom in the deposited region of the zirconium deuterate film will diffuse into the low deuterium concentration region.Finally,the deuterium content reaches equilibrium in the bulk of zirconium deuterate,and the deuterium content in the zirconium deuterate film is not less than the content before irradiation.This phenomenon indicates that the zirconium deuterate film has a self-healing effect after deuterium ion implantation,which is derived from the pinning effect of the defect on the deuterium atom.Two different types of irradiation damage mechanisms will be produced in zirconium deuterate film after a large dose deuterium ion irradiation.One of mechanisms is that the small size vacancy defects are formed on the collision scattering area based on collision scattering.The other is that large void defects are formed due to the accumulation of deuterium bubbles in the ion deposition area.The defects produced by high dose deuterium ion implantation and the variation of deuterium concentration in the deposition area have little effect on the neutron yield performance,while the surface physical damage for the film caused by high dose deuterium ion implantation is serious.There are two effective ways to improve the neutron yield performance of the zirconium deuterate film under high dose deuterium irradiation.One method is to improve the mechanical property and the resistance irradiation damage performance of thin films.The other is to discharge deuterium atoms in deuterium targets by low temperature annealing for many times.4)The neutron yield and stability of zirconium deuterate target film that deposited by metal titanium vapor are studied.The diffusion and distribution of deuterium atoms in the zirconium deuterate film and the neutron yield performances of the zirconium deuteron film are discussed.The results show that a titanium thin film layer is attached to the surface of the zirconium deuterate film by the vapor deposition of metal titanium.There is certain diffusion and infiltration between the titanium thin film layer and zirconium deuterate target film,due to the boundary between them is not clear.At the same time,there is a remarkable phenomenon that deuterium atoms likely diffuse into the titanium thin film layer.The influence of titanium vapor on the neutron yield is very large.This is due to the metal vapor deposition will change the distribution of deuterium atoms in the surface of zirconium deuterate target film.There are two effective ways to improve the neutron yield performance of the zirconium deuterate target film under the metal vapor deposition.Firstly,it is to reduce the amount of metal vapor produced by the ion source.Secondly,it is suitable to increase the target temperature to promote the diffusion of the deuterium atom onto the titanium layer surface.