Re: RF Shielding for CRTs

["John Saunderson" <johnsaunderson@hotmail.com>]

I seem to recall an NRPB report from a few years back showing that the dose
to an operator from NORM's in the glass screen of a VDU exceeded the dose
from X-rays by several orders of magnitude.

John Saunderson
johnsaunderson@hotmail.com



----- Original Message -----
From: Langenegger, Armin <alang@allsaintshealthcare.org>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Sent: Tuesday, February 15, 2000 3:11 PM
Subject: RE: RF Shielding for CRTs


>
>
> "Weren't the old vacuum tubes used in TV sets a source of
> x-ray exposure?
> Glen
> glen.vickers@ucm.com"
>
>
> Yes they were. These days the acceleration of the cathode
> electron beam is about 20keV for most color sets. As these electrons
> interact with the phosphor on the TV tube surface they slow down and
produce
> bremstrahlung with a maximum energy of around 20keV. This is in the
> mammography range and most is absorbed by the thick glass of the TV tube.
> Minute amounts will pass through the tube and will be absorbed by the air.
>
> Many old sets had thiner glass on the top and bottom of the
> tubes and I remember many stories about the family cat that lay on top of
> the TV becoming sterile after many years. (Urban Myth?)
>
> But the original question was shielding for RF. I also
> believe that this is not a problem.
>
>
>
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