New Ceramic Electron Multiplier

The design and performance of a new ceramic envelope electron multiplier are described. The tube uses hemispherically shaped 3/8" diameter dynodes crimped into kovar cups. The dynode assemblies are alternately stacked between high-alumina ceramic rings and brazed into a rugged single piece construction envelope. The structure has an outside diameter of 0. 5 inches with an overall length of 2.75 inches and is capable of withstanding extreme environmental conditions. The tube withstands 100 g shocks for 11 msec duration, random vibration levels of 1.3 g2 /Hz, and can be operated over a temperature range from liquid N2 to 400°C. The electron optics of the discrete dynodes provide optimum interstage electron collection. The single electron pulse height distribution at gains higher than 108 is nearly Gaussian and has a FWHM of approximately 0.6. Complete data on pulse height distribution characteristics is reviewed over the dynamic range of the device. The photon sensitivity of the device will be discussed within the range of 58.3 to 150 nm as well as the adaptability for charged particle conversion below 3 keV. Fatigue characteristics are examined as a function of accumulated counts up to 1012, exposure to controlled atmospheres of dry air, noble gases, and maximum counting rates up to 10 MHz. Applications for these detectors are reviewed, including their projected use in mass spectroscopy experiments on the Apollo 17 mission.