Medium power compact sources of electromagnetic radiation in millimeter and sub-millimeter ranges

Abstract

Sources of electromagnetic radiation in THz range with high enough power and wide frequency range are necessary for an increasing number of applications in the technologies and many scientific researches including high data rate communications, remote high resolution imaging, chemical spectroscopy, materials research, deep space research and communications, biomedical diagnostics, radar and remote sensing system, diagnostics of plasma, concealed weapon or threat detection and etc.[1] However, at present a lot of customers are unable to use the advantages of the THz wave applications because of the absence of compact, easy in service sources. Existing gyrotrons are powerful devices but they are huge, expensive and difficult in operation complexes [2]. Another and main technical disadvantage of gyrotrons is narrow frequency range [3]. At the same time both solid state devices and BWOs have low level of output power that is not enough for many applications.In this work the description of developed BWO-Clinotrons of millimeter and sub-millimeter ranges is presented. Experimental results on both formation and transportation of intense electron beam interacting with the space harmonics of slowing wave system show the possibility to increase the output power of THz clinotrons [4]. Second part of this work is dedicated to development of low-voltage CRM which can be used in mentioned applications [5][6][7].One of the main problems of advance of vacuum electron devices based on Cherenkov radiation is THz range lies in a decrease of the efficiency of interaction of an electron beam with a slow wave that in turn reduces the output power. It is caused by the decrease of the height of the area in which the surface wave field is concentrated above the grating on the one hand and the increase of the ohmic losses with the increase of the radiation frequency on the other hand. Also the question of RF output becomes very important with shortening of the operation wavelength in BWO and clinotron. One of the ways to increase the efficiency of the interaction of electron beam with the slow wave is to increase the electron beam current density. For example, at the frequencies above 200 GHz, the current density should be greater than 50 A/cm 2 .However, the use of intense electron beams requires focusing magnetic field providing electron beam pulsation value smaller than the thickness of effective layer of slow wave field. The requirements for both value and distribution of magnetic field become stronger with the increase of the radiation frequency. Thus, to achieve the optimal operation parameters of sub-millimeter clinotrons it is required to provide the value of magnetic field higher than 1 Tesla. At present the progress in rare-earth material technology allows one to design the compact focusing magnetic system as it is shown in fig. 1 [8]. Figure 1. Magnetic field distribution simulated in SuperFish Code (left) and distribution of the longitudinal component of the magnetic field in the magnet bore (right). 359 978-1-4799-1068-7/13/$...