> In a message dated 3/29/00 7:22:09 AM Pacific Standard Time,
> [EMAIL PROTECTED] writes:
>
> << I would add
> that if this phenomenon is indeed responsible for the problems were having
> with the profiles, then the tube manufacturers should challenged to address
> the matter. It would appear that a simple shield, with a slot in it,
> between the filament and the anode would solve this (most unpleasant)
> problem. >>
>
> If you crack open a sealed X-ray tube, you will see that " a simple shield,
> with a slot in it, between the filament and the anode" is indeed in place and
> serves as the bias cup for electron focussing. Unlike for open tube systems,
> this bias cannot be regulated independently and is at filament heater
> potential. As the filament ages, it will sag and lose its intended position
> with respect to the cup opening. Defocussing sets in and it seems you cannot
> do much about it with current W-filament technology.
In some older x-ray tubes they used to have two separate filaments.
One could select filament one or two...it was a convenient idea.
Has that idea been abandoned in the latest tubes?
Regards Joe
[EMAIL PROTECTED]
