Re: SEDs and radiation
Re: SEDs and radiation
- Subject: Re: SEDs and radiation
- From: David Scharf <email@hidden>
- Date: Sun, 08 Jan 2006 21:28:49 -0800
Hi Marco,
When an electron of sufficient energy (voltage) "hits" an element, it
generates characteristic X-Rays (a characteristic energy spectrum of
that element)(incidentally, this principal is used for X-Ray analysis).
Energies below 5 or 10KV are not very significant as a health hazard,
especially when hitting lighter elements, and are easily absorbed bu
leaded glass. However higher energies of 20KV - 30KV and above, when
hitting denser elements, generate more energetic X-Rays which can be
penetrating enough to be a hazard if not shielded and absorbed.
Dave Scharf
DAVID SCHARF PHOTOGRAPHY
Scanning Electron Microscopy
Phone 323-666-8657
Fax 323-666-0449
2100 Loma Vista Place
Los Angeles, CA 90039
http://www.scharfphoto.com
http://www.electronmicro.com
Marco Ugolini wrote:
In a message dated 1/8/06 8:34 AM, email@hidden wrote:
Marco,
In CRTs the "harmful" radiation is essentially from two
source:
1- the x-rays generated by high velocity electrons,
accelerated by 30 kV plus voltages, which hit the metal
grid around the phosphors and high density elements in the
phosphors themselves. The larger the tube, the higher is
the voltage required, and the higher the voltage, the
higher is the x-ray energy. A thick (heavy, think Sony
WEGA) leaded glass is used in these tubes to absorb most
of the radiation.
2- low frequency electro-magnetic produced by the
deflection coils. This is, also mostly, filtered by
suitable metallic shields.
The operating voltages in SED display are around 10 kV,
the electrons are much better confined (no spill on shadow
mask), and there are no magnetic deflection coils. Because
of this, the "harmfull" radiation level should be much
lower, and not be as dependant on display size.
Hi Danny.
Thank you for your explanation.
Do I understand this correctly to mean that there is still a certain level
of X-ray-type radiation, however low-level, involved in SED technologies?
Incidentally, do LCDs actually produce no radiation at all?
Thank you.
--------------
Marco Ugolini
Mill Valley, CA
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