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

To: tesla-at-pupman-dot-com
Subject: Re: Poulsen arc gap / Magnetic blow-out spark gaps.... (fwd)
From: Tesla List <mod1-at-pupman-dot-com>
Date: Fri, 8 Oct 1999 22:27:45 -0600 (MDT)
Approved: mod1-at-pupman-dot-com



---------- Forwarded message ----------
Date: Fri, 08 Oct 1999 19:03:34 -0400
From: bryan <bryan-at-apexrad-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Poulsen arc gap / Magnetic blow-out spark gaps....

Ralph, All,

This seems like a difficult thing to effectively implement. Knowing a little
(yes, a little knowledge *is* a dangerous thing) about ramping high intensity
magnetic fields, (a la MRI,) it seems that the difficulties presented by the
field oscillation would make the construction a formidable challenge. Even a
spinning electromagnet, acting like a chopper, would seem to have little
advantage over a standard RSG, would it?

Isn't the basic idea the same? To elongate the ion path and thereby increase the
necessary potential across the gap?

Bryan Kaufman


> Original Poster: Parpp807-at-aol-dot-com
>
> In a message dated 10/7/99 5:38:27 AM Central Daylight Time, tesla-at-pupman-dot-com
> writes:
>
> << 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
> cross-product
> vector extinguishes the arc. This allows the source voltage to recharge the
> capacitor
> 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
> (Flatter?)
> 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
> photographs
> to explain the geometry of all this.
>
> Fascinating stuff, and a total mystery.
>
> Happy day,
> Ralph Zekelman