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<DIV><FONT size=2> The lamp o-ring for the XLA is Beckman part
number 961564, o-ring, Strobe Lamp Face - to - Lamp assy. The material is listed
as Kalrez, and is NOT vacuum greased. </FONT></DIV>
<DIV><FONT size=2>The other little o-ring on the outside is 961565, o-ring, Lamp
Assy - to - Monochromator Mount, and is also Kalrez, and not
greased.</FONT></DIV>
<DIV><FONT size=2> All the other o-rings in the XLA are
Buna-N, and are greased with silicone vacuum grease (except the PMT
Seal).</FONT></DIV>
<DIV> <FONT size=2>Dirty, worn, or dry (no vacuum
grease) o-rings can cause wavelength repeatability problems, and radial
position problems, as the shafts to the inside of the chamber are sealed by
these o-rings. </FONT></DIV>
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<DIV><FONT size=2>John Gunther</FONT></DIV>
<DIV><FONT size=2>Lab Performance Specialists</FONT></DIV>
<DIV><FONT size=2>Rocky Mountain Operations</FONT></DIV></DIV></BODY></HTML>