Copper-catalyzed ring-opening trifluoromethylthiolation/trifluoromethylselenolation of cyclopropanols with TsSCF3 or Se-(trifluoromethyl) 4-methoxybenzenesulfonoselenoate.

We report a ring-opening trifluoromethylthiolation of cyclopropanols with TsSCF3 by using Cu(OAc)2 as the catalyst. Moreover, by using this strategy, the trifluoromethylselenolation of cyclopropanols with Se-(trifluoromethyl) 4-methoxybenzenesulfonoselenoate to access ß-SeCF3-substituted carbonyl compounds is achieved for the first time. The broad substrate scope, readily accessible reagents and cheap catalyst make this protocol an alternative and efficient method for the synthesis of ß-SCF3-substituted or ß-SeCF3-substituted carbonyl compounds.

A high efficiency and high power L-band relativistic magnetron with all-cavity extraction.

Relativistic magnetron (RM) is a promising high-power microwave source, whose advantages include high efficiency, high power, and compact configuration. Enhancing power efficiency and output power are the most important two development directions for RM. Based on the two targets, a high efficiency and high power RM is presented and investigated numerically and experimentally in this paper. When the diode voltage is 485 kV, the beam current is 6.9 kA, and the magnetic field is 0.34 T, and high power microwave is generated with the power of 1.35 GW, frequency of 1.47 GHz, and power efficiency of 40.3% in the experiments.

Design of a tunable turnstile mode converter for high-power microwave applications.

This study investigates the frequency tunability of a coaxial transverse electromagnetic mode (TEM)-linear-polarized TE11 mode tunable turnstile mode converter (TTMC) for high-power microwave applications using a combination of simulation and experiment. In the proposed structure, the sliding folded waveguide can be moved radially to meet the requirement of linear polarization, and the matching structure is designed to eliminate the undesired reflection. The simulation shows that the conversion efficiency of the TTMC can reach over 99% in the frequency range of 1.45-2.35 GHz, corresponding to a frequency tuning bandwidth of about 47.4%. Moreover, the TTMC can maintain a continuous high conversion efficiency at different frequency points by changing the tuning mechanism. The experimental investigation shows that the TTMC can convert the coaxial TEM mode into a circular waveguide TE11 mode with a conversion efficiency of above 95% in the frequency range of 1.55-2.35 GHz. The experimental measurements agree well with the simulation results, implying feasibility of the TTMC design and its superior performance.

Visible-Light-Promoted Selenocyanation of Cyclobutanone Oxime Esters Using Potassium Selenocyanate.

We report the visible-light-promoted selenocyanation of cyclobutanone oxime esters using potassium selenocyanate in the presence of a fac-Ir(ppy)3 catalyst for the first time. Because of the mild conditions employed and use of readily accessible potassium selenocyanate, this method is an effective and green strategy for the synthesis of cyano and selenocyano bifunctional substituted alkanes.

Metal-Free Trifluoromethylthiolation of Arylazo Sulfones.

A visible-light-driven protocol for the synthesis of aryl trifluoromethyl thioethers under photocatalyst- and metal-free conditions has been pursued. The procedure exploits the peculiar properties of arylazo sulfones (having electron-rich or electron-poor substituents on the (hetero)aromatic ring) as photochemical precursors of aryl radicals and S-trifluoromethyl arylsulfonothioates as easy-to-handle trifluoromethylthiolating agents.

Performance improvement of a magnetically insulated transmission line oscillator with a carbon fiber array cathode.

A carbon fiber array cathode (CFAC) was presented and tested in a magnetically insulated transmission line oscillator (MILO) in earlier papers; however, the performance of this cathode was not as good as the traditional polymer velvet cathode, and the nonuniform fibers' distribution on the cathode surface was postulated as the culprit for this. In this paper, this CFAC has been carefully reprocessed, and the performance is improved (efficiency increases from ∼12% to ∼16%) and reaches a level that is as good as the velvet cathode, which means that this CFAC provides a promising substitute for the polymer velvet cathode in MILO.

Influence of voltage rise time on operation frequency in magnetically insulated transmission line oscillator.

In the experiments of a magnetically insulated transmission line oscillator (MILO), the initiatory microwave frequency is slightly higher than the stable microwave frequency. This paper investigates the influence of the front edge of the voltage on microwave frequency. The theoretical analysis shows that the MILO operates at the 2π mode in the initiatory stage; therefore, the microwave frequency is determined by the single slow wave structure (SWS) cavity. During the stable operation, the MILO works at the π mode and the microwave frequency is decided by the structure parameters of the resonant cavity chain. It is a fact that the resonant frequency of a single SWS cavity is higher than that of the resonant cavity chain, so the reason why the initiatory microwave frequency is slightly higher than the stable microwave frequency can be explained. The simulation results agree with the theoretical results.