Tom, W8JI wrote:
"Many people vizualize current in a small loading inductor as starting
at one end and traveling through the conductor turn-by-turn.

That`s how the experts say the coul in a TWT works, and it is no
different from other coils.

RF energy travels in waves which induce currents on conductors in their
paths which in turn induce more waves.

Energy has no choice but to follow the conductor. It is nonsense to say
this is not the means used by energy traveling through an inductor while
riding on its surface due to skin effect. The energy follows the
conductor wrapping its way around the form fron start to finish.

Energy hits the speed limit of physics if it can at 300,000,000 meters
per second. but
its interaction with any conductor slows it depending on the
characteristics of the conductor guiding it.

An inductor reduces the group velocity (actual energy velocity) of any
wave traveling along its surface. The group velocity is always less than
the velocity of light (300,000,000 m/sec.). Phase velocity may exceed
the velocity of light but only to the extent that the actual group
velocity is slower than the velocity of light.

An inductor reduces the group velocity of a wave traveling upn is
surface.Inductors are also known as "retardation coils".

The RF`s changing current generates waves. In an inductor, it ideally
lags voltage across that inductor (as a circuiy element) by 90-degrees.
Time represented by a 90-degree delay can be calculated by: velocity =
frequency x wavelength. 90-degrees is 1/4-wavelength.

It is possible to measure the delay of a circuit but when your
measurement seems to violate the laws of physics it`s more likely your
measurement was flawed than you have discovered any new physics.

Tight coupling does not speed transfer of energy through a coil. TWT
coils are tightly coupled. Remember, the coil does not allow current to
change instantly. Lenz`s law prevails. Current lag enforces a delay.

Tom also wrote on "Welcome to W8JI.com":
"An inductor delays the flow of current in relationship to applied
voltages as the magnetic field inside the coil expands. Voltage
increases before current starts to flow. This phase relationship berween
voltage and current is often confused with time delay in the inductor."

I`m done with my critique only because I`m out of time.

Best regards, Richard Harrison, KB5WZI