Magnetic gap experiment (was RE: Magnetic quenching.)

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Original poster: Marco.Denicolai-at-tellabs-dot-com 

Hi Dave,

 > I used standard brass brazing rods with flux.

Being a beginner too, I suppose you mean the usual rods used for
plumbing with copper pipes, right?

 > At first I was thinking the magnets were squeezing the spark, but that
 > couldn't be true since all the magnetic flux is oriented in
 > one direction.
 > It must be that the electrons themselves are forced to become
 > polarized such
 > that their north pole is facing the south pole magnet and the
 > south pole of
 > the electron is facing the north pole magnet.  Each electron
 > would then have
 > its angular momentum equally aligned in the same plane, more
 > or less.  This
 > in turn would cause the spark to spread out in a plane.

Well, the explanation is simply very old plain physics. A charged
particle moving perpendicular to a magnetic field will experience a
force which is (again) perpendicular to both its movement and the field
(right hand law). This means, in your setup, the magnetic field is
vertical, the electrons move from one electrode to the other. They will
experience a force that will deviate them to the left or to the right.
As you are working with AC you will see a "discharge plane" vertically
squeezed, like two flat rain drops back-to-back. The electrons will
curve away from the electrode axis and will be the most far from it in
correspondence of the gap center. Getting nearer to the destination
electrode, the eletrical field force will win and they will re-join the
electrode axis.
More erudite please correct me :)

Yesterday night I (sort of) replicated your experiment. Just two steel
bolts, two magnetron magnets, a 8000 kV NST and a variac. I really saw
the flame squeezed into a flat double drop, flattened on a plane
parallel to the magnet faces. As my setup was so poor, warming was
affecting my measurements. I could not notice any difference in the
quenching voltage but I did clearly notice one in the threshold one. No
doubt, with magnets in place the threshold voltage was LOWER!

Then I clamped the two magnets so that their field was in opposition. I
got the impression that the threshold voltage was lowered even further.
The flame now looked really scattered, extending over the bolts end. If
you imagine the right hand law I described above and the magnetic flux
line, you'll see that now electrons are literally thrown away from the
electrode axis.

Corona also sounded different. With no magnets it was a 50 Hz constant
hissing, with magnets it was a unconstant crackling, starting at a lower
voltage (say at variac 200 VAC instead of 220 VAC).

Why and how the magnets facilitate quenching is still to be seen...

 >I don't suppose it is very important what the rod is made from.  I just
 >happened to have thoriated tungsten rod handy.  Perhaps brass rod will
work
 >fine?

Sure, it doesn't matter. I just need to make a spark gap for Thor and
thought tungsten balls would be great.

Best Regards

P.S. You should try too with an opposing magnetic field, as you have got
more magnets than I have and report on your impressions and
measurements.