Can inductors with toroid core be used as a High frequency excitation source. In other words can these coils induce a fast current pulse into a bare conductor ?
(To idealize the problem, let's assume the core permeability is constant)
Thank you for your answers
Hi Nadir, if combined with a fast switching transistor, and provided that "high frequency" means some 100 kHz, then the answer is: Yes. One way to do it is basically similar to ignition systems for combustion engines.
If you are looking for pulse durations of only a few nanoseconds or even less: I'm afraid the inherent capacitance of coils on cores would be too high. Together with the inductivity of the coil, this capacitance forms a resonant circuit. The basic idea of ignition systems is to store energy in the inductor, and to release it within a short interval, accompanied by high voltage. But the length of the interval cannot be below about 1 / (2 * resonance frequency).
To achieve resonance frequencies of some GHz the core material should not be ferrite but ceramic.
It is important to remind that the choice of a suitable core material is intimately connected with the power losses in the core.
Thank you all for your answers,
@Joerg Fricke : Do you mean that the energy released will propagate or only diffuse in the surroundings ?
If one terminal of the inductance is connected to a conductor, during switching off the current through the inductance, the energy will propagate along the surface of the conductor and be partly turned into radiation. The ratio of radiated energy to energy released by the inductance depends mainly on the shape of the conductor and its dimensions relative to the wavelengths of the main part of the power spectrum. But since in turn the power spectrum is affected by shape and dimensions of the conductor, this seems to me a case best suited for simulation. If the shape isn't a simple one (e. g. not just a piece of straight wire) then the same is true for the question of directivity.
Whether the radiated energy propagates with energy density proportional to the square of the distance to the conductor (= no energy loss) or mainly dissipates within a short distance, depends on the medium in which the propagation takes place: For example, in vacuum or dry air there is virtually no dissipation while the dissipation in dense fog or water depends on the wavelength.
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