Abstract
Overmoded slow-wave structure (SWS) plays an important role in developing the performance of Cerenkov oscillators at the millimeter-wave range. To investigate the effect of SWS size on power capacity as well as the problem of mode competition, the properties of the resonance modes in an overmoded SWS are focused on. Based on the mode selection method of enhancing the field of TM 01 and keeping the field of TM 02 mode steady, the output results for SWSs with various sizes are studied. Consequently, the size of SWS is reasonably determined, which can provide an effective beam-wave interaction process and the purified output mode. Moreover, the study on electron's movement in the diode area under the magnetic field of 0.8 T is conducted and then the value of the overmoded ratio α is finally confirmed as 2.5 to guarantee a lossless transportation of the electron beam. Verified by the particle-in-cell (PIC) simulations, the optimized structure shows a good capability of improving the output power and purifying the output mode.
Highlights
As one of the most promising high power microwave (HPM) generators, Cerenkov oscillator has shown great advantages in providing high output power, good tunability and compact structure [1]–[4]
(a), the colored solid-spots on TM02 represent the non-synchronous points that have the same frequencies with the synchronous operating points on TM01. These points on TM02 are mainly caused by the discontinuous waveguide and the size of waveguide has an obvious influence on the nonsynchronous points on TM02
Reasonably choosing the size of slow-wave structure (SWS) is the basis of designing an overmoded Ka-band Cerenkov oscillator
Summary
As one of the most promising high power microwave (HPM) generators, Cerenkov oscillator has shown great advantages in providing high output power, good tunability and compact structure [1]–[4]. The overmoded structure is helpful in improving the output power, especially for the devices operating over the millimeter-wave ranges. S. Li et al.: Influence of SWS Size on Mode Purification in an Overmoded Ka-Band Cerenkov Oscillator. In the optimized overmoded SWS, the output power is improved and the issue of mode competition is effectively solved. PERFORMANCE OF THE MODES IN THE OVER-MODED SWSS WITH VARIOUS SIZES As shown in Fig., the profile of SWS that contains a rectangular ripple and a semicircular head is preferred here because of its high power handling capacity [10].
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