As in HERF gun: a device that can disrupt the normal operation of digital equipment such as computers and navigational equipment by directing High Energy Radio Frequency energy at them.
Principles Behind HERF (High Energy Radio Frequency) Bursts:
The general idea is to set up an L-R-C circuit and destabilize it. For example, we know the change in emf (E) is related to the ke quantities (L = indcutance, R = resistance, C = capacitance) by:
L (d^2 I(t) / dt^2) + R (dI(t) / dt) + I(t)/ C = dE(t)/ dt
where I(t), and E(t) are time-variable
Under suitable conditions (cf. Spicer, 'Solar Physics', v53, p. 305, 1977) it is possible to induce a voltage 'spike' which is the equivalent of a HERF burst. In his Fig. 4, Spicer shows a profile of such a burst, generated using an ST-tokamak.
Of course, ST-tokamaks are not needed to accomplish this. It is fairly well known that *all* electrical circuits containing an inductance (L) are intrinsically explosive (cf. Alfven, 'Cosmic Plasma', p. 34, Dordrecht-Reidel, 1981).
Thus, if such a circuit is somehow disrupted, there is an explosive release of magnetic energy, of order:
W = 0.5 LI^2
Where L is the inductance (say of the inducting coil in the circuit) and I is the current. Say, for example, that L = 10 H (10 Henries) and I = 20A, then:
W = 0.5 (10H) (20A)^2 = 2000 J (Joules)
This is a fair amount of energy.
In practical HERF circuits one would incorporate a 'double layer' say by using a capacitor across which some maximum value of voltage V(D) might be applied. As the current is made to exceed a threshold value I(D), a voltage drop V(D) occurs across the capacitor up to the current I(ex) when it explodes and disrupts the current (cf. Alfven, ibid.).
When switched on, the current increases at rate:
dI/dt = (V(b) - R I/ L)
(V(b) is intrinsic emf of circuit)
Without the 'double layer' (capacitor) it reaches saturation at:
I(s) = V(b)/ R
If I(D) < I(s) uts rate of increase for I > I(D) is given by:
dI/dt = [V(b) - V(D) - RI]/ L
The current will tend towards a saturation value:
I(s)' = [V(b) - V(D)]/ R
If I(ex) < I(s)' the double layer will explode before saturation value is reached.
The explosion will generate a high energy radio frequency pulse.
This pulse, if proximate enough to an electronic device (i.e. computer) will render it inoperable.