Rapid start of oscillations in a magnetron with a "transparent" cathode

We report on the improvement of conditions for the rapid start of oscillations in magnetrons by increasing the amplitude of the operating wave that is responsible for the capture of electrons into spokes. This amplitude increase is achieved by using a hollow cathode with longitudinal strips removed, thereby making the cathode transparent to the wave electric field with azimuthal polarization. In addition, an optimal choice of the number and position of cathode strips provide favorable prebunching of the electron flow over the cathode for fast excitation of the operating mode. Particle-in-cell simulations of the A6 magnetron demonstrate these advantages of this novel cathode.     

N-alkylation of nitriles—III: Heterocyclizations by aminolysis of nitrilium salts: Imidazoles,4-oxoquinazolines and 4-quinolones

Several heterocyclizations have been carried out by aminolysis of nitrilium salts with aminoesters or propargyl amine. The aminolysis with norvaline methyl ester gave a 5-hydroxyimidazole derivative 8. With a β-aminoester such as methyl anthranilate, the amidinoesters 10 first obtained cyclized to 4-oxo-quinazolines 11. With a N-t-butyl substituted amidine ester 13, the ring closure occurred on the carbon α to the amidine giving a 2-amino-4-quinolone 14. It is only by refluxing in a strong base such as potassium t-butanolate in t-butunol that the oxoquinazoline 15 is obtained. Another type of ring closure occurred when the nitrilium salt was treated with propargylamine: the propargylamidine 16 formed was converted during the working up in the imidazole derivative 17.