🚀 go-pugleaf

In <31MAY199510210133@orion.cmc.uab.edu> mann@orion.cmc.uab.edu (RANDY
P. MANN) writes: 
>
>An engineer asked me a question today that I couldn't answer
completly.
>He asked: Why can't we start the generators at full power?  
>The only answer that I could think of was the damage that would be
caused 
>to the filament. 
>
>My question to the net is:
> What other problems would be associated with starting up at full
power?
> Is it possible to start at full power?
> What is the highest power that we could start with?
>

Randy -

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.

I would be surprised if the generator could be damaged by turning it on
too quickly.  You might want to ask the manufacturer about that.  

To power up, you could start at something like 30 kV 15 mA, and bring
it up over a period of about ten minutes.  But this has always been a
subject for debate, and I don't know of anyone who has actually studied
this.  The lifetime of an X-ray tube seems to be dependent on certain
quirks of its manufacturing, and there's a lot of variability.  That's
probably one reason why manufacturers don't usually warantee them for
very long.  

By the way, you don't want to run your tube at its full power rating. 
I would recommend not going above 80%.  

- Paul Wolf