From those operating voltages,60 kV and above... I would expect copious amounts of xrays to be coming through SS walls up to at least 250 mils. It takes approximately 85 to 90 mils of lead to fully attenuate 60 kV Xrays. Tests I ran with 1/8 inch lead sheeting.. showed a peek-through at about 124 kV. Since radiation opacity depends on Z ( the atomic number) you need less lead than Stainless steel.
In one test with a 75 kV ebeam exiting in 1ATM air, Xrays from Bremmstalung (braking radiation) penetrated a 100 mil SS enclosure with enough residual energy to travel a number of feet in air. We had to enclose the chamber in a lead lined cabinet.
If the pressures were low enough to allow tens of kV, particularly about 40 kV, I would think Xray emission might be the most plausible thing to expect.
Thinking about the brilliant glow.. and its slow decline, radiative heat transfer is about all you have at these low pressures. So it would cool slowly.. very slowly...
So the explanation might be in terms of Xrays only... but.. that being said.... why was this the only time it was seen?
Dave Cooper
Created on Saturday, May 26, 2001 2:02 AM EDT by David Cooper