Study on secondary electron suppression in compact D-D neutron generator

A compact D-D neutron generator, with a peak neutron yield of D-D reactions up to 2.48x10(8)n/s is being developed at Lanzhou University in China for application in real-time neutron activation analysis. During tests, the problem of back acceleration of secondary electrons liberated from the neutron production target by deuterium ions bombardment was encountered. In this study, an electric field method and a magnetic field method for suppressing secondary electrons are designed and experimentally investigated. The experimental results show that the electric field method is superior to the magnetic field method. Effective suppression of the secondary electrons can be achieved via electrostatic suppression when the bias voltage between the target and the extraction-accelerating electrode is >204V. Furthermore, the secondary electron emission coefficient for the mixed deuterium ion (D-1(+), D-2(+), and D-3(+)) impacting on molybdenum is estimated. In the deuterium energy range of 80-120keV, the estimated secondary electron emission coefficients are approximately 5-5.5 for the mixed deuterium ion glancing incidence of 45 degrees and approximately 3.5-3.9 for the mixed deuterium ion normal incidence.