Re: Poulsen arc gap / Magnetic blow-out spark gaps....

In a message dated 10/7/99 5:38:27 AM Central Daylight Time, tesla-at-pupman-dot-com 

<< The large inductance insulates the RF circuit from the DC power
 supply. Apparently, the same (?) inductances formed also an 
 electromagnet with the poles creating a magnetic field at the gap. Why 
 I don't know. >>

See the NBS Circ # 74, pp. 221-223 for a brief discussion of the Poulsen gap.

The magnetic field is applied perpendicular to the arc so the resulting 
vector extinguishes the arc. This allows the source voltage to recharge the 
to start the arc and the cycle starts over. I am not clear where this 
magnetic field originates. As Antonio writes, it may originate in the series 
reactors. How this is timed is a total mystery to me.

 Evidently there is another magnetic field used in the Poulsen to solve the 
problem of cavitation of the electrodes. As the arc burns, the cathode is 
eaten away causing the length of the arc to get longer and increase the time. 
The CW frequency of the Poulsen
never could be controlled. So one technique was to apply a radial magnetic 
field to the
cathode which causes the arc to rotate around the terminal to maintain a flat 
surface. To solve the same cavitation problem, Circ 74 also says that they 
"revolved" the
cathode. That's what the book says: "revolved", not rotated. There are no 
to explain the geometry of all this. 

Fascinating stuff, and a total mystery.

Happy day,
Ralph Zekelman