Shielding Material

["Bob Westerdale" <Bob.Westerdale@ametek.com>]

Greetings...

I've been asked to recommend an alloy for use in the construction of a 

port cover for a 400 kV Electron Microscope ( TEM).   I usually work with 

low kV systems ( ie < 30 kV)  where material is much less a factor;   This 

high kV Instrument presents a challenge in that:

1.      The part will be cut from a cube about 5" X 5" x 5",  with a 

number of high precision machined features, so that  machinability is a 

serious concern



2.      I'd like to be able to plate the part ( Cu-Ni-Cr) for aesthetics



3.      I need an alloy with the best beam stopping capability I can find. 

 



4.      I cannot make the whole part out of Pb,  as there are some 

structural loads that would not be well served by a mushy material.  ( and 

plating would nearly impossible.)



We've made similar parts in the past out of Leaded brass ( e.g. clock 

brass or marine brass) and in some cases 303 or 304 Stainless,  I'm hoping 

that there might be some more modern materials ( ie tungsten/tantalum or ? 

alloys...)  that might allow for a less massive solution.       Space is 

at a premium,   and I'd like to avoid a prolonged search for ' Unobtanium 

' 



This component will be headed for Germany,  interesting to note that we 

cannot allow any exposed Pb surfaces, for fear of toxicity, and the 

Radiation leakage at 2" must be less than .1 mR/Hr.  (The end-user who 

told me this was chain smoking unfiltered Rothmans in a tiny, unventilated 

room.....  so much for risk perception!)



If anyone has any suggestions/experience I'd be quite grateful!



Thanks,

        Bob Westerdale

        EDAX Inc.

        Mahwah, NJ.