I thought it might be interesting to try a more rapid succession of pulses. This was realized with an IRF510 MOSFET, instead of a relay. The MOSFET is controlled by a square wave generator. Frequency can be adjusted between 1 to 10 kHz. Because the switching device is closed for a much shorter period of time than in the last circuit, the inductance must be considerably less -- about six orders of magnitude. Here were are using a 40 uH inductor, instead of 20 Henrys.
You can experiment with larger amounts of inductance and lower frequencies of square wave.
The 555 Square Wave Generator circuit is based on the design shown in the MC1455 Datasheet. Page 6, Figure 17, Astable Circuit. You can also try a PWM if you want to make something more sophisticated. https://www.petervis.com/GCSE_Design_and_Technology_Electronic_Products/555-pwm-circuit/555-pwm-circuit.html
Like the previous setup, the whole circuit is charged negatively with respect to Earth ground. The 18v battery serves this purpose. The Coulomb Potential of the pipe is varied with respect to time, but it always remains negative. The magnitude of the Coulomb Potential varies, but its sign does not change. The sign is always negative.
Time variations of the Coulomb Potential of a negatively charged pipe are complemented by something which looks like the Riemann Surface of the imaginary part of the Natural Logarithm of z. It looks like a corkscrewing flat ribbon coming down into the pipe. It is rotating in such a way that it appears to be screwing downwards into the pipe. But it does not come out the other end. It goes into the Other Space.
A spike contains all frequencies Think of a bell. If you wack it with a stick, it will ring. If you go up to the bell, and slowly push on it with your stick, then slowly pull the stick away, it's not going to make much sound!
The Integral of sin(x) from 0 to 2Pi equals zero, because the positive parts of the wave cancel out the negative parts.
That is why you must keep the Coulomb Potential negative, and not let it swing positive.
The integral of sin(x) - 18 from zero to 2Pi is non-zero, because the whole wave lives under the x-axis.
$$ \int_0^{2\pi} {\sin(x) - 18} $$ $$ \int_0^{2\pi} {\sin(x)} - \int_0^{2\pi} {18} $$ $$ \left( \cos(2\pi) - cos(0) \right) - \left( 18(2\pi) - 18(0) \right) $$ $$ 1 - 1 - 36\pi $$ $$ -36\pi $$
When the Coulomb Potential varies with respect to time, but it always stays negative, then you actually get something. The -18 represents the negative bias voltage between the circuit and Earth ground.