🚀 go-pugleaf

Paul Wolf (paulwolf@ix.netcom.com) wrote:
[original post snipped]
: The problem with powering up too fast is that it places thermal
: stresses on the seals of the X-ray tube.  An X-ray tube gets really
: hot, you wouldn't be able to hold it in your hand after it's been on
: for a while.  I'm not sure of the exact mechanism, but rapid thermal
: cycling eventually makes X-ray tubes gassy.

Dear Paul,
	Repeated temperature cycling induces micro-cracks in the envelope of
the tube.  BTW, the same is true of both incandescant and fluorescent light
bulbs and of mercury vapor (and other spectrometer) lamps.  If one can arrange
to leave the bulb on and do one's work in one continuous time period, one can 
greatly extend the life of the bulb.  An example from my own work was the use
of a 1 kW mercury lamp, rated life 100 hrs, for 400 hrs (~three weeks of 24
hr/d experiments!), after which the bulb was still working (we retired it 
rather than risk the lamp housing by turning it back on).
				Yours,
				Bill Tivol