PSN-L Email List Message

Subject: Re: Another mu-metal/permalloy question (and magnetometer note)
From: meredith lamb mlamb1@..........
Date: Tue, 13 Jun 2000 21:54:03 -0700

ChrisAtUpw@....... wrote:

>     If you had two concentric spheres, you would be able to apply a higher
> external magnetic field before it started to penetrate the inner sphere.
>     For your apparatus, I think you need an outer shield of Permalloy etc. to
> reduce the effect of the low external fields and an internal shield to screen
> the Permalloy from the core magnets. This shield might be silicon iron or you
> might get away with mild steel. You might need two layers.
>     Hope this qualitative description helps.
>     Chris Chapman

Chris, David, Al and all,

Many thanks for the email replys to my original question, I've
picked up your thoughts on it, and think I have a sufficient
understanding now.

Lacking alot of lab equipment for all this, about all I can do
is perhaps apply some ribbon permalloy material to a shield
and observe over time.  With time I hope to have a second
diamagnetic machine on line, and with both pointed in the
same direction, one could be unshielded, and then a more
visual comparison could be made with the SDR recording
and perhaps additionally to a regular coil/magnet as the
prospective "ideal".  The most practical approach is too add
layers if needed.


With reference to a magnetometer which uses a "string" and
a magnet, its possible to use acouple layers of diamagnetic
graphite with the magnet simply levitating in between (a
regular diamagnetic stand, with overhead magnets).  Of
course it might need a reflective first surface mirror on a end
of the single or multiple cluster of magnets for output (or other
transducer means).  Providing the graphite is diamagnetic
enough and their is a stable temperature environment, and its
far enough away from metallic/magnetic influences, it might
suffer less temperature effects than is found possibly with a
support "string" in the type previously mentioned.  If the east
-west orientation is desired, than another magnet could be
placed nearby.  A normal diamagnetic "stand" or machine is
sensitive to temperature; but its in the vertical plane.  I never
tried this with my material in the city environment, and of
course the goal was make a seismometer, so I added
diamagnetic side "wedges" of graphite to limit its normal
North-South or magnetic attraction to household items.

Thanks again for all the generious help, from you all.

Meredith Lamb


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Larry Cochrane <cochrane@..............>