10.5: Development of THz gyrotrons with pulse solenoids for detecting concealed radioactive materials

This paper describes the first steps in the development of high-power THz-range gyrotrons with pulsed solenoids for remote detection of concealed radioactive materials. We first discuss the detection concept based on focusing high-power THz wave beams in small spots where the wave electric field amplitude exceeds the threshold required for initiating the breakdown. The specific feature of this concept in the case of using the THz radiation is a small volume in which the electromagnetic energy is localized. As a rule, in the absence of gamma rays causing additional ionization there should be initially no free electrons in this volume to initiate the discharge. Thus, the fact that the breakdown takes place in this volume immediately after the THz source is turned on will indicate that there is an additional source of ionization (such as radioactive materials). In the paper, we report first results on the study of air ionization by concealed radioactive materials and the first results of the design of a 670 GHz gyrotron. First estimates show that the gyrotron efficiency can be in the range of 20–25% and the gyrotron power can exceed 100 kW.