Small Penning Ion Source Neutron Tube Ion Optical System

The neutron generator is a kind of neutron source that has been widely applied in many areas. It produces 2.5 MeV (D-D) or 14 MeV (D-T) neutron. Ion source, Ion optics system and target are important parts of a neutron tube. Ions, which are generated in the ion source, are extracted and focused or dispersed by the ion optics system, finally impinge the target and produce neutrons. It is the ion optics system that determines the transfer characteristic of beam, and ultimately affects the neutron yield, stability and life of the neutron tube. Hence, the research work of ion optics system is a necessarily part in the neutron tube design.The principle of beam optics is reviewed first in this paper. The transfer characteristics of ion beam of axisymmetric static lens and some simple lens are described in phase space with transfer matrix. The equation of enveloping curve of beam is deducted, and the influence of space charge on beam transfer is discussed simply. Especially, the characteristics of ion optics system of neutron tube and its effect on the performance of neutron tube are introduced. The aperture-film mode is used to simplify the ion optics system of neuron tube, and to calculate its transfer matrix.The working mechanism of Penning ion source is studied by analyzing factors which effect on Penning discharge. Electron temperature and plasma density of Penning ion source, when air pressure is 1×10-3Pa, anode potential is 1400V, is measured in double probe experiment. The software IGUN is used to calculate and simulate the transfer characteristic of beam in ion optics system of a small Penning ion source-neutron tube. The emittances, focusing characteristics and beam spots of different electric parameters, different plasma densities are calculated. The result of x-ray measurement on surface of a used tritium target shows the distribution of beam that impinged on surface of the tritium target comply with the distribution of beam of under-focus.Neutron tubes of different uses ask for different beams. Therefore, ion optics system also has corresponding changes. Designing of associated a particle detectors neutron tube and high yield neutron tube are discussed in detail, and gain some advice for designing neutron tube.