It is well-known that a neutron detector is a detector that is capable of detecting neutrons. Neutrons do not have charges, which results in no ionization or excitation, so typical detectors cannot detect neutrons directly. The neutron detector conducts measurement by utilizing secondary particles generated in the reaction (including nuclear reaction, nuclear fission or nuclear recoil) between neutrons and some atomic nuclei contained in the detector.
The most common neutron detector in the prior art is a 3He neutron detector, such as, a 3He proportional counter tube neutron detector. The detection principle of the 3He neutron detector is based on nuclear reaction, the process of which is shown as follows:3He+n→1H+3+765 KeV  (1)
The reaction product is charged particles of protons and tritons. Reaction energy generated in the reaction caused by thermal neutrons is distributed between protons and tritons. Protons and tritons work within a proportional counter tube which uses 3He gas as working gas. When protons and tritons pass through the gas, they undergo ionization collision with 3He gas so that the molecules of the 3He gas are ionized and loss some energy to form a large number of ion pairs (electrons and positive ions). The 3He neutron detector, as a gas detector, is applied a high positive voltage on its central anode wire, and an electrical field is therefore formed between the anode wire and the tube wall of an outer shell. Under the action of an external electrical field, the electrons and positive ions drift towards positive and negative electrodes, respectively, wherein electrons drift towards the anode wire, and wherein the positive ions drift towards a cathode wall and are collected by the electrodes.
The 3He neutron detector usually has a co-axial cylindrical structure, wherein the anode wire is located on the longitudinal central axis of the cylindrical tube wall serving as a cathode.
The 3He neutron detector has the stable and ripe performance, and is widely applicable and popular in the fields of scientific researches, anti-terrorism and safety inspection. However, the global annual output of 3He gas is not increased, which causes the supply of 3He gas extremely scarce. Therefore, the key search and development in the art is to find a cost-effective product that can replace the 3He neutron detector.
It is thus desirable to replace the 3He neutron detector with the proportional counter tube neutron detector coated with boron on the inner tube wall. Such a boron-coated neutron detector is much cheaper than the 3He neutron detector. However, the boron-coated neutron detector has the neutron counting rate which is only about one tenth of that of the 3He neutron detector of the same size, and therefore has the poor detection efficiency.
Such a boron-coated neutron detector can be further improved to obtain a highly effective, relatively cheap neutron detector.