Abstract
IN an earlier communication1, I have described the possibility of using an electron multiplier, based on the secondary emission principle, for the detection of individual electrons by cooling the multiplier for the purpose of suppressing the thermal emission in liquid air. I stated there that this method of counting individual electrons does not necessarily require the use of liquid air, provided multiplying electrodes, with fairly great secondary emission factor and sufficiently high work function are used. There is a large discrepancy in the data of various papers published on the subject of work function and secondary emission of a surface. Experiments had to be carried out to determine whether a surface satisfying our requirements could be found, and we found the following surface satisfactory from the above point of view:
Very thin layers of barium oxide on a nickel base activated by the method normally used for oxidecoated cathodes will easily give a multiplication factor of T = 2·5, with a primary electron velocity of 200 volts. A multiplication of about 10,000 times was achieved in a ten-stage multiplier. The thermionic emission (at room temperature) and field emission of the active surfaces in this multiplier are negligible.
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Bay, Z., NATURE, 141, 287 (1938).
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BAY, Z. Electron Multiplier as an Electron Counting Device. Nature 141, 1011 (1938). https://doi.org/10.1038/1411011a0
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DOI: https://doi.org/10.1038/1411011a0
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