Photoelectric ion source photocathode regeneration system
AssigneeImplant Sciences Corporation
InventorsS.N. Bunker, Leonid Krasnobaev
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Abstract
An explosive detection system based on an ion mobility spectrometer detects the presence of trace molecules in air. Such instruments require an ion source to ionize the trace molecules. An ion source that does not require a radioactive source to operate can use the photoelectric effect to produce electrons. Such a photoelectric ion source will gradually be contaminated and lose its photoelectron emission properties when operated in the air. The photocathode of the ion source can be automatically regenerated by a heater in thermal communication with the photocathode. The heater may be activated when the photoelectron emission falls below a predetermined value ro may run or cycle continuously.
Claims19
An ion mobility spectrometer, comprising:
- a chamber;
- a photocathode and an anode that provide an electric field within said chamber;
- a source of ultraviolet wavelength photons in optical communication with said photocathode;
- a heater in thermal communication with said photocathode;
- and
- a temperature control system that raises the temperature of the photocathode independent of any other heaters provided with said ion mobility spectrometer, whereby said dedicated heater provides regeneration and cleaning of said photocathode.
A method of operating an ion mobility spectrometer, comprising:
- providing sampling gas flow from an external gas sampling inlet of the ion mobility spectrometer proximal to an ion source;
- providing ultraviolet photons to a photocathode to emit electrons therefrom;
- accelerating electrons emitted from the photocathode using a voltage between an anode and the photocathode in order to produce ions therefrom;
- accelerating ions through a drift tube to a current collector;
- measuring current reaching the current collector;
- and
- raising the temperature of the photocathode independent of any other heaters provided with the ion mobility spectrometer to provide regeneration and cleaning of the photocathode in response to the rate of photoelectron emission falling below a predetermined value.
Dependencies are inferred from the claim text.