Numerical Simulation Research On Influence Factors Of Cryogenic Target Temperature

Inertial confinement nuclear fusion(ICF)will be a kind of new energy source in the future,while cryogenic freezing target is the ideal target for ICF.In order to achieve the successful ignition of laser inertial confinement nuclear fusion.It is required to form a uniform and smooth deuterium tritium(DT)ice layer.The quality of the ice layer mainly depends on the thermal environment around the capsule.So we must control the temperature field around the capsule.In this paper,we take the National Ignition Facility Project(NIF)as a prototype.The influencing factors of temperature field uniformity and problems of temperature control were studied by Fluent.The structure of the temperature sensor is studied.The results show that although the temperature sensor has a certain influence on the temperature field of the capsule,the temperature fluctuation is only 0.02 m K,which is negligible.The effects of the structure and layout of the heater on the temperature field are studied.The results of numerical simulation show that the uniformity of the temperature field will be improved when the external auxiliary heating is added.When the heat flux of upper heater is 600W/m2 and heat flux of the lower heater is 700W/m2,temperature field would be most uniform.At this time,the gas velocity was also reduced to a minimum of 0.516 mm/s.The temperature distribution of the ultra low temperature cold-chain was studied.The results show that the time required to cool from the cooling-head to the target is about 40 s.As the cold source conduction takes time,the temperature of the capsule will first increase and then decrease,and finally become balance.The thermal resistance between the silicon cooling arm and the aluminum sleeve is analyzed.We found that the temperature of the target increases with the increase of the thermal resistance,and the maximum temperature difference between the inner and outer surfaces of the frozen target is increased.As the gas velocity in the hohlraum increases,the maximum temperature variation of cryotarget surface increased.The effects of uniform and non-uniform ice layer on the temperature field were studied.We found that in the case of uniform ice layer,with the increase of ice layer thickness,the maximum temperature difference of the capsule inner surface increases.The greater the decay heat of the uniform ice layer,the temperature difference of capsule inner and outer surfaces is increased.For non-uniform ice layer,the horizontal deviation of the ice layer will cause greater damage to the uniformity of the temperature field.We can optimize the vertical offset ice layer by adding auxiliary heating.But the radial offset can not use this method.