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RE: another reaction to the Pittsburg TMI "study"
I think that the design and function of CRT and x-ray tubes play into this
discussion. CRTs are designed to allow a stream of low-energy electrons to
strike a phosphor screen, which converts the electron energy to be converted
to light. Fluorescence occurs a low ev energies. The x-rays that result
are from characteristic x-rays from the phosphor materials and the glass.
X-ray tubes are designed to convert high energy electrons to high energy
bremsstrahlung photon radiation. The Be window in medical x-ray tubes
reduce the low energy x-rays that would contribute to the skin dose
-- John
John Jacobus, MS
Certified Health Physicist
3050 Traymore Lane
Bowie, MD 20715-2024
E-mail: jenday1@email.msn.com (H)
-----Original Message-----
From: Ted de Castro [mailto:tdc@XRAYTED.COM]
Sent: Monday, November 04, 2002 2:44 PM
To: Stephen Mecca
Cc: Bjorn Cedervall; radsafe@list.vanderbilt.edu
Subject: Re: another reaction to the Pittsburg TMI "study"
Yes - that is what I was commenting on as well. While a x-ray tube is
glass and has a vacuum as well - it usually has a small thinner section
as a window or even other material like Be for these lower energies.
Beyond that x-ray tubes tend to be an inherently stronger cylindrical
design. CRT's on the other hand have a very large flat face which
requires considerable thickness to support the vacuum and even more so
to hold the face flat and to do so against a disadvantageous geometry.
I would invite you to check the most definitive article I have seen on
the subject:
"Low-background Radiation Measurements on Video Display Terminals"
Health Physics VOl 46 no 2 pp 413 - 417, 1984.
There is really nothing in that article that does not apply to today's
CRT's.
. . .
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