Design Of Beam-line Of A High-intensity Nanosecond Pulse DD/DT Neutron Generator

Ns pulse neutron generator based on fusion reaction of D(d,n)~3He and T(d,n)~4He has important and special application value in fast neutron nuclear data measurement,neutron physics and neutron application technology.There are few ns pulse neutron generators in China,and the D-Beam current is generally weak and the neutron yield is low,which cannot well meet the current situation of neutron nuclear data measurement,neutron physics and neutron application technology research.Based on the DC beam ZF-400 high current neutron generator being developed by Lanzhou University,this paper plans to design a high current ns pulse beam beamline to generate high current ns pulse neutron beam.The main contents and conclusions of the paper are as follows:Based on the design scheme of ZF-400 DC beam high current neutron generator,the overall structure of ns pulse beam line is proposed.In the design of the beam line,the beam energy is required to be between 200ke V and 400ke V,the DC beam intensity injected into the pulse system is about 5m A,the half-height width of the pulse on the target is less than 2ns,and the beam spot diameter on the target is less than 10mm.Using the self-developed IONB1.0 program and beam envelope simulation,the DC beam line scheme in front of the pulse system is determined.The DC mixed deuterium beam intensity is 15m A.After analysis,the deuterium monatomic ion beam reaches7.5m A.After being collimated by the baffle,the injected beam spot is 10mm,and the injected beam current is greater than 5m A.The design theory and method of sinusoidal scanning chopper and drift tube double gap buncher with pulse beam line key element are studied.On this basis,the preliminary design parameters of the two elements are completed.Using the beam dynamics simulation software TRACK,the transmission state of deuterium beam in pulse system under the condition of beam energy of 400Ke V is simulated.According to the simulation results of beam transmission state,the structural and electrical parameters of chopper and buncher are designed.The parameters of sinusoidal scanning chopper are as follows:1)The length of scanning plate is 200mm;2)The gap between the two plates is 40mm;3)The frequency setting of scanning voltage is 1.6MHz;3)The scanning voltage amplitude is 4k V;5)The drift distance between the scanning plate and the beam selection plate is 50cm;6)The half width of the slit on the beam selector is 6mm in X direction and 1.5mm in Y direction;7)After cutting,the long pulse width is 85ns,the average current intensity of the pulse beam is0.309ma,and the repetition frequency of the cutting beam is 3.2MHz.The parameters of sinusoidal scanning buncher are as follows:1)The length of intermediate electrode is 463.26mm;2)The length of grounding electrode is 100mm;3)The inner diameter of bunching tube is 30mm;4)The bunching gap width is 20mm;5)The bunching voltage amplitude is 80k V;6)The bunching voltage frequency is 6.4MHz.Under this parameter,the drift distance between the buncher and the target is 462cm;7)A group of three element quadrupole lenses is added in the drift section.The pulse half height width on the target is 1.173ns,the bottom width is 2.399ns,and the beam spot diameter in X direction and Y direction on the target is 7.43mm and 7.21mm,which meets the design requirements of pulse beam line.Finally,the cutting and bunching of deuterium beams with different energy are simulated and analyzed.The results show that ns pulses can also be realized under the condition of reduced beam energy.When the energy is 350kev,300ke V and 200ke V,the pulse FWHM on the target can reach 1.631ns,1.727ns and 1.789ns respectively.However,the pulse bottom width is significantly larger than the result of the energy of 400Kev.The reason may be that the relevant parameters of the chopper and buncher have not been fully optimized and matched,and further optimization design is needed.