Stabilized field electron emitter using ballast resistance.

What is it about?

We have developed x-ray irradiation systems using field-electrons, which were emitted from carbon nanofibers. The field-electron emission (FE) was usually known to be unstable, and so ballast resistance (BR) was used to stabilize the field emission. However, fundamental principle of the stabilization using the BR was not sufficiently understood. The stabilization by the BR has been extensively studied using resistances of 1< R < 1500 MΩ at electron current of 1 < I < 100 μA. The current and voltage stabilities ε(R) = ΔI(R)/I and η(R) =ΔV(R)/V, where V is electron extracting voltage, were interpreted by employing a dynamical impedance z of the FE emitter. The optimum current and extracting voltage stabilities of ε(R) ~ 0.002 and η(R) ~ 0.001 were maintained around R ~ 10 MΩ and I ~ 80 μA. These were sufficient stabilities for actual operations.

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Why is it important?

During the x-ray irradiation, intensity of x-ray must be as stable as possible. To achieve the stable x-ray irradiation, the FE electron has to be sufficiently stable. Therefore, the electron emitter must be operated at the optimum condition.

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