An improved magnetron which is capable of elongating the life span of the magnetron, reducing the fabrication cost, and enhancing the performance of the system without using a filament in the conventional art, which includes a center lead, an upper end shield engaged to an upper portion of the center...http://www.google.com.hk/patents/US6005347?utm_source=gb-gplus-share專利 US6005347 - Cathode for a magnetron having primary and secondary electron emitters
