CapAAVSO@....... wrote:

> In a message dated 6/11/00 1:38:07 PM Eastern Daylight Time,
> mlamb1@.......... writes:
>
> << With enough shielding, then it may
>  show somewhat more seismic signals, both here or in the country. >>
>
> ------------------------------------------------------------------------------
> -----
> Hi Meredith,
>     I have a couple of square feet of 1/32 thick mu-metal. Tell me how much
> you need to shield your seismometer's magnets and I'll cut off a piece and
> send it to you. It will be interesting to see what shielding it can do. I'll
> need your postal mailing address though.

Hi Casper,

Wow....thats very generious of you on the mu-metal offer.  I'am
hesitant here simply because of the sheer tentative size of the
shield I'am considering.  I think its quite different than a
magnetometers
relatively close-in shielding in that, with the levitated magnet, the
simple magnetic attraction between the shield material and the magnet
will need more distance and hence a huge sized
shield/container/cylinder, with both ends covered.  Presently I'am
considering using a simple thick cardboard 12" in diameter tube that
will be cut to 15" in height (or length), and stood on end to cover the
frame and sit on the base plate.  Even with this over the frame the
distance to the magnet will be roughly 5.5" at its closest, and it could
be still a no go, but all I can do is try that for now.   So....its no
small amount of magnetic shielding material that will be needed overall.

Am planning on going the salvage route on permalloy/mu-metal.  This
is going to be selected and specific "old" torroid foil coils made by
Arnold Engineering, or other material which have been proven to range
from "good" to "super" stuff.  Bob Lamb, my brother has already donated
a quanity of super type material, which I hope will at least cover one
unit shield (I'd like 2....ha, for the other direction of E-W
possibly).  Although its thin tape like stuff, it should help or work to
a unknown degree.  Time will tell eventually of the success or failure
in this approach.  Additional layers are possible to apply in this
approach, with whatever is available, with a 1/16" to 1/8" separation
between layers.

I do have a appreciation of the big cost of the mu-metal material, and
in particular to the thickness you mentioned.....its about like buying
gold ....very, very expensive stuff.

 << Have to confess my ignorance....what does the AAVSO stand

> for in your email address?  Your full name?  Any web site?
> Curiosity of course.>>
>     AAVSO stands for American Association of Variable Star Observers. AAVSO
> has a solar division that publishes a monthly Solar Bulletin. The current May
> issue of the Bulletin has a recording of the big magnetic storm of 24 May. It
> was made with a homemade torsion-pendulum magnetometer. There are also
> complete instructions how to build a flux gate magnetometer for a little over
> $50. These include the schematic, a circuit board layout, parts list and two
> pages describing how the flux gate works. If you, or anyone else, would like
> a copy, just send me a self addressed envelope at my address below and I'll
> be glad to send a copy.

Actually there is quite a number of PSN email recipients that are also
interested in astronomy and/or other sciences.  The torsion-pendulum
magnetometer almost....sounds like it could be along the line of Roger
Bakers design article in the Amateur Scientist section of Scientific
American, of (?) January 1999, not withstanding another model?

As far a a neodymium magnet attached to a thread/string, I'd
wonder whether a stronger gauss magnet like a grade R45 (~14.2K)
would be of any added benefit over a "standard" neo magnet of
some (R30)~ 12-13K (potential)gauss field magnet?  Seems like it
would boost the sensitivity somewhat.  Just a thought to ponder.
Actually; for anyone interested...Forcefield/Wondermagnet does
have afew R45 magnets left (1/4" diameter by 1" long, with the
poles on each half of the rod diameter,lengthwise), item #16.  This is
the same magnet I use in the diamagnetic seismometer/aka, "pulse
magnetometer".....ha.  See:
 
http://www.wondermagnet.com/dev/magnets.html

>
> Casper H. Hossfield
> PO Box 23
> New Milford, NY 10959
>

Take care, Meredith Lamb

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