Dragon-i Device Is Light Induced Neutron Source For Neutron Resonance Thermometry Feasibility Study

The temperature measurement using neutron resonance spectrum has many advantages comparing traditional techniques of temperature measurement.This technique can take the shock temperature,because of its short responding time and the penetrating of neutron.But there is no one can study this technique with the absence of high strength white neutron source.To investigate the feasibility of neutron resonance temperature measurement using Dragon-â… ,this paper does many works as follows through MC simulation code MCNP5 and FLUKA:Firstly,the computed neutron production is 1.34×10¹¹ per electron pulse(MCNP5) and 1.55×10¹¹ per electron pulse(FLUKA),according to the electron beam characteristics of now state and using the multi-layer Ta target.The photo-neutron has a continuous energy spectrum with a peak between 0.1MeV and 1MeV,and an isotropy distribution.Its pulse width is 85ns.Secondly,the neutron productions of many materials had been computed with the electron beam characteristics of Dragon-â… ,the results display they are 10¹² magnitudes,and the production of natural uranium and natural thorium are higher than the others.The production of natural uranium can be enhanced with the increasing of target thickness,and approach a saturation at 8cm of the thickness with a value of 7.47×10¹²per electron pulse.Thirdly,the moderation of photo-neutron with three moderators-beryllium,heavy water and paraffin-shows that the optimal thickness of moderators to gain maximum resonance neutron(from leV to 100eV) strength are 10～12cm,12～16cm and 2～2.5cm,respectively. And the broadening of neutron pulse width caused by moderation is from sub-microsecond to microsecond,the broadening of paraffin is one magnitude lower than the others.The optimal thickness of paraffin for neutrons produced by natural uranium is between 2.5cm and 3.0cm.Fourthly,the transmission spectrum of neutrons produced by multi-layer Ta target and 7cm U target penetrating through a 1cm tungsten layer after optimal moderation of paraffin had been simulated,from which the resonance dip of 21.06eV can be seen.But the counts around resonance dip from multi-layer Ta target are from several to several tens n^*cm(-2*)μ^s-1, and it is difficult to measure the resonance dip on experiment.Fortunately,the counts from U target are 5～6×10² n^*cm^-2*μ^s-1,the resonance dip can be measured on experiment.Fifthly,the neutron transmission spectrum of Dragon-â… using 7cm U target and 3cm paraffin moderator passing through the Mo sample had been calculated,according to the sample set used by Los Alamos.The 21.06eV resonance peak of 182W and its broadening trend can be seen,and the counts of Dragon-â… is higher than Los Alamos.Sixthly,the neutron production had been measured using silver activation detector,in order to check up the simulated result.The measured neutron production is around 10¹² per electron pulse,accords with the simulated result.The conclusion can be seen that the Dragon-â… can be used for temperature measurement using neutron resonance spectrum with a 7cm U target and a 3cm paraffin moderator,through the works above.