On the sensitivity of terahertz gyrotron based systems for remote detection of concealed radioactive materials

Abstract

This paper analyzes some features of systems intended to remotely detect concealed radioactive materials by using a focused THz radiation. This concept is based on possibility to focus high-power THz radiation in a small spot where the wave field exceeds the breakdown threshold. However, in the absence of any sources of ionization, the probability to have in this breakdown-prone volume any seed electrons is very low. Thus, high breakdown rate in a series of THz pulses will indicate the presence of concealed radioactive materials in the vicinity of a focused wave beam. The goal of the present paper is to determine by using the statistical theory THz pulse duration required for reliable initiation of the discharge. Then, the detectable mass of the radioactive material is determined as the function of distance and of the THz wave power and pulse duration. Lastly, possible benefits from using pulse compressors, which shorten the pulse duration but increase the wave power and, hence, the breakdown-prone volume, are analyzed. It is shown that the use of pulse compressors can significantly improve the sensitivity of THz gyrotron based systems for remote detection of concealed radioactive materials.

Experimental investigation of powerful 0.67 THz gyrotron with a pulsed solenoid for remote detection of concealed radioactive materials

“…The temporal evolution of plasma in such breakdowns will be analyzed in the subsequent work. Possible benefits from using pulse compressors, which shorten the pulse duration but increase the wave power and, hence, the breakdown-prone volume, were analyzed [10]. It is shown that the use of pulse compressors can significantly improve the sensitivity of the system.…”

A possibility of remote detection of air breakdown in a focal spot of microwave beam using reflected signal

“…1 and 2). In previous studies [2,3] it was shown that at a higher frequency the discharge evolution is associated with continuous propagation of the ionization front, whereas at a lower frequency this evolution is associated with quasi-periodic jumps of the ionization front. The continuous propagation of the ionization front is accompanied by smooth evolution of the reflection coefficient (Fig.…”

“…The breakdown delay time, as well as the plasma parameters, is sensitive to existence of radioactive materials which can ionize air producing thereby seed electrons in the vicinity of the breakdown prone volume [1][2][3]. Therefore a study of the breakdown evolution can give some particular information about the closeness of radioactive materials to the focal spot of high power microwave beam [3,4].…”

A 670 GHz gyrotron with record power and efficiency

“…Corresponding conditions were analyzed elsewhere. [16][17][18] In particular, it was shown that an attractive option would be a 670 GHz gyrotron delivering the power above 200 kW in 10-20 ms long pulses. The choice of the frequency was determined by two factors.…”