🚀 go-pugleaf

In article <15387.2b4d8179@ohstpy.mps.ohio-state.edu> 
edharris@ohstpy.mps.ohio-state.edu writes:
> I put in a beaker of water and tried adjusting the amount of power by
>varying the amount of water.
>
>Unfortunately though, if you put in too much water, it seems to kill the
>plasma. If you back off a bit on the amount of water, then the plasma/gas combo
>is still too hot. It behaves in an either/or manner: either too much power, or
>no plasma! Maybe there is a way to overcome this problem.
>
>Since I had nothing to loose, I tried John's suggestion of lowering the value
>of the capacitor in series with the magnetron. So far, this works, but I'm not
>sure if the magnetron is being damaged in some way. 

You probably have not read my last reply to John.  Changing the capacitor
WILL likely damage the magnetron.  But since this is a form of vacuum tube,
it tends to fail more gracefully than solid-state devices.  I would mainly
expect you to get very much shorter life from the magnetron, perhaps tens of
hours rather than hundreds or thousands.  But this is just a guess.

Remember that the plasmas also have negative resistance properties.  A home
microwave oven is a multimode cavity.  Most commercial systems use single-mode
resonant cavities when they want precise control.  That little fan-blade like
thing in your oven (which may be hidden under a plastic cover) is not a fan
but a "stirrer" to deflect the microwaves from the waveguide and cause them
to sweep the oven cavity in an attempt to get uniform heating of food.  I would
guess that the problems you are seeing are due to times when your plasma is in
the full field of the oven.  You might need to distribute smaller containers
of water throughout the oven to make things more uniform.  A possibility is
to wrap the plasma chamber with Teflon tubing in which you have flowing water.

Use a small diameter tubing; certainly no larger than 1/4 " OD.  If you know
how to make "waveguide beyond cutoff" openings into the cavity, you can go as
large as 1/2" OD thick-wall tubing.  Remember that the water has a high
dielectric constant and thus the water filled waveguide has a much lower cutoff
frequency than does air filled guide.  If you do not understand what I am
talking about here, email me.  It is easy to hurt yourself by microwave leakage
from the oven if you go drilling holes in the oven to run the tubing and do
things wrong.  Safety first!
					Barry
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|  ___  ________  |    Dr. Barry L. Ornitz          WA4VZQ
| |  / /        | |    Eastman Chemical Company
| | / /         | |    ECC Research Laboratories, Engineering Research Div.
| |< < K O D A K| |    Process Instrumentation Research Laboratory
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| |__\ \________| |    Kingsport, TN  37662  (615/229-4904, FAX 615/229-4558)
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