Alumina ceramics used in microwave systems are susceptible to the multiplication of secondary electron emission on the surface due to the influence of resonation between electrons and RF electrical field, and the detrimental effect of multipactor may be therefore triggered. For the alumina-loaded microwave components, low secondary electron yield (SEY) is urgent to be achieved on the inserted alumina surfaces for mitigating multipactor. In this work, for achieving an ultralow SEY surface of alumina, two recognized low-SEY treatments are combined. For the primary SEY suppression, a series of microstructures were fabricated on the alumina surfaces with various porosity and aspect ratio at hundred-micron scales by infrared laser etching. The microstructure with 52.14% porosity and 1.78 aspect ratio showed an excellent low-SEY property, which could suppress the SEY peak value (δm) of alumina from 2.46 to 1.00. For the secondary SEY suppression, the SEY dependence of TiN coating on sputtering parameters was studied, and the lowest δm of 1.19 was achieved when the gas flow ratio of Ar:N2 was 15:7.5. Whereafter, by depositing TiN ceramic coating onto the laser-etched porous samples, an ultralow SEY, δm equaled 0.69, was achieved on the alumina surfaces. The simulation work revealed the impact of dielectric surface charge on electron multiplication and uncovered the mechanism of using low SEY surfaces to inhibit multipactor. Some coaxial filters with alumina filled were fabricated for verification, the results revealed that the multipactor threshold increased from 125 W to 425 W after applying the TiN-coated porous alumina, and to 650 W after treating another multipactor sensitive area with the same low-SEY process. This work developed an advisable method to sharply reduce SEY, which is of great significance for the multipactor mitigation of the alumina-loaded microwave components.
A trispecific hybrid, MTP (hereafter called tripsazea), was developed from intergeneric crosses involving tetraploid Zea mays (2n = 4x = 40, genome: MMMM), tetraploid Tripsacum dactyloides (2n = 4x = 72, TTTT), and tetraploid Z. perennis (2n = 4x = 40, PPPP). On crossing maize-Tripsacum (2n = 4x = 56, MMTT) with Z. perennis, 37 progenies with varying chromosome numbers (36-74) were obtained, and a special one (i.e., tripsazea) possessing 2n = 74 chromosomes was generated. Tripsazea is perennial and expresses phenotypic characteristics affected by its progenitor parent. Flow cytometry analysis of tripsazea and its parents showed that tripsazea underwent DNA sequence elimination during allohexaploidization. Of all the chromosomes in diakinesis I, 18.42% participated in heterogenetic pairing, including 16.43% between the M- and P-genomes, 1.59% between the M- and T-genomes, and 0.39% in T- and P-genome pairing. Tripsazea is male sterile and partly female fertile. In comparison with previously synthesized trihybrids containing maize, Tripsacum and teosinte, tripsazea has a higher chromosome number, higher seed setting rate, and vegetative propagation ability of stand and stem. However, few trihybrids possess these valuable traits at the same time. The potential of tripsazea is discussed with respect to the deployment of the genetic bridge for maize improvement and forage breeding.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.