Vacuum-helium-leak-detection method based on carbon-nanotube-based field-emission sensor

A vacuum-helium-leak-detection method based on a carbon-nanotube-based field-emission sensor, which includes a carbon-nanotube-based cathode having a Raman amorphous peak ID/graphite peak IG ratio greater than 1.0 and an electrically conductive anode, the method including steps of:

• (1) performing a Joule-heat degassing process on the carbon-nanotube-based cathode for a time period to with a large field-emission current having a density J0 so that Joule heat makes carbon nanotubes of the cathode release gas that was absorbed on their surfaces previously thus enters the carbon nanotubes into an intrinsic emission state;
• (2) upon completion of the degassing process, setting the field-emission current to an initial, small emission current thereof rapidly, recording an average of values of the field-emission current in a time period t, testing the carbon-nanotube-based cathode for field-emission sensing effect with helium gas at different pressure levels so as to form a sensing characteristic curve of the carbon-nanotube-based field-emission sensor, performing fitting on the sensing characteristic curve so as to obtain an index curve, and converting the different pressure levels of the helium gas into corresponding vacuum leak rates;
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• (3) packaging the carbon-nanotube-based cathode into a vacuum chamber in a system to be detected, performing testing when a helium stream reaches balance, obtaining an average of current variations in the time period t from the testing, comparing the average of the current variations with the index curve obtained in Step (2) so as to determine a vacuum leak rate of the system to be detected.