Development and consideration of compact neutron generator

Summary form only given. Recently, neutron source is in great demand for industrial and medical applications. For example, neutron activation analysis, petroleum exploration, boron neutron capture therapy, luggage screening, cancer treatment, and so on. There are three types of primary sources from which to choose, radioisotopes, nuclear reactors, and accelerator-based neutron source. Radioisotopes are used plenty of industrial applications, but it is not well suitable for applications that require pulsed beam, and they are dangerous of the radiation exposure. Nuclear reactor and particle accelerators are possible to generate a large number of neutrons, but their sizes are large and it needs enormous money. Therefore, we have been engaging in the development of compact and comparatively high yield neutron generator for 3 years. The device is made of stainless cylindrical chamber. The dimensions are approximately 70mm in diameter and 500mm in height. The Pole type anode is made of tungsten, diameter of 2mm and length of 1.5mm. The mesh type cathode is made of tungsten, diameter of 3mm. The system is maintained at a constant pressure of 0.1-10Pa by bleeding deuterium gas into the chamber through a leak valve. A 0-120kV, 0-40mA constant current DC power supply is used to power for the device. When a high voltage applied between electrodes, the glow discharge takes place between them, so that deuterium ions are generated. They are accelerated toward the mesh cath ode and passing through it. Accelerated ions are interacted with atmospheric deuterium nucleus, so that neutron is generated. This interaction is well known D-D nuclear reaction. One of the most important parameters to increase the number of generated neutrons is potential difference between electrodes. Therefore, the break down potential difference dependency of H2 gas pressure was measured and compared with various shapes of electrodes. The device was operating pressure was varied at 0.1-10Pa and 4 types anode were employed. Three pole type anode and plate anode were used, their diameters are 1.0mm, 1.2mm, 2.5mm for pole and area is mm2 for plate. It is found that there is strong dependency between gas pressures and break down potential difference. The potential difference was increased in accordance with decreasing pressure. It was capable of reaching most high potential difference in used plate type anode.