The Theoretical Simulation And Experimental Test Of Boron-coated Straw-tube Neutron Detectors

With the development of science and technology, neutron detection has beenplaying a more and more important role in fields such as national security, medicalimaging and aerospace. So far,3He is the most popular neutron reaction with its largeneutron capture cross section, which is widely used in thermal neutron detection field asa good neutron absorber. However, the shortage of3He in recent years results in itsincreasing price. Thus, searching for a new alternative of3He neutron detector becomespopular among researchers. The Boron-Coated Straw Tube neutron detector is one ofthe neutron detectors of great concern.Boron coated straw tube is a kind of proportional counter with B4C coated on itsinner surface of the thin substrate. The performances of detection efficiency andposition resolution of the straw tube are mainly studied.With MCNP program and matlab, the detection efficiency of a single straw tubeand different detector array are both simulated. The thickness of B4C and the abundanceof10B are the two factors which mainly influence detection efficiency. Since thethickness of boron layer is limited in a single tube by the range of α and7Li in B4C,detector array is studied for higher total efficiency. The simulation results show themaximum efficiency of a single straw tube can achieve11.303%with4.3μmenrichedB4C and2.997%with4.0μmnatB4C coated. With detector array, more rowsof detectors bring about higher efficiency, with thinner B4C layer needed in each tube.The optimal thicknesses of50rows ofnatB4C andenrichedB4C detector array arerespectively about2μ mand1μ m. Effiency of50%can be reached by50rows ofnatB4C straw tubes or11rows ofenrichedB4C straw tubes.As to the energy deposition of neutron and gamma, matlab is used to model thephysical process. The simulation results give different neutron energy depositionspectra of straw tubes with different thickness of B4C. Meanwhile, the neutron/gammadiscrimination has been studied.The straw tubes are realized and single straw tube was tested for its detectionefficiency and position resolution. With an straw tube coated1.38μ m90%enrichedB4C, the efficiency of the tube can achieve8%and the position resolution of one1μmnatB4C straw tube can reach7.267mm when working with pure argonand under the voltage of730V.