In a message dated 6/13/00 12:41:31 AM Eastern Daylight Time, 
david@............. writes:

<<  Mu-metal is a trade name for a nickel alloy (77% Ni,
 14% Fe, 5% Cu, 4% Mo), also known as Permalloy-C and several
 other names as well. "Mu" refers to the Greek letter, which is used
 to indicate magnetic permeability.  >>
        
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Hi David,
    Many thanks for your interesting and valuable information telling us what 
mu-metal really is and how it excludes magnetic fields from an enclosed 
volume. Very interesting stuff.  Sounds like an expensive alloy though, and 
the need to anneal it in a hydrogen atmosphere after fabrication puts it out 
of reach for amateur applications. There is a way around the problems for 
Meredith and others, however. Top of the line oscilloscopes have a mu-metal 
shield around their CRTs (cathode ray tubes). Old tube-type oscilloscopes go 
cheap and are plentiful at Hamfests (ham radio fleamarkets). To find a 
hamfest near you and the weekend it will happen see 
<>. Look for Tektronix, Hewlett Packard or 
any military scopes. They have mu-metal shields around their CRTs but most 
other brands do not. The shield as it is will be annealed and big enough to 
do a pretty good job of hiding your diamagnetic seismograph or other project 
from street traffic and the Earth's magnetic field with its magnetic storms. 
Look for old scopes not in operating condition and offer $5 to $10 and you 
will take home most of them.
Have fun,
Cap

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