Re: Gamma Camera
- From: "N:dlzc D:aol T:com \(dlzc\)" <N: dlzc1 D:cox T:net@xxxxxxxxxx>
- Date: Wed, 26 Oct 2005 06:20:33 -0700
Dear west:
"west" <westley@xxxxxxxxxxxxxxx> wrote in message
news:aZJ7f.213568$p_1.38930@xxxxxxxxxxxxxxxxxxxxxxxxxx
>
> "Craig Markwardt" <craigmnet@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote
> in message
> news:on7jc1nkq5.fsf@xxxxxxxxxxxxxxxxxxxxxxx
....
>> Your main problem will be that extraterrestrial gamma
>> rays do not penetrate the atmosphere to sea level.
>> That's why most gamma-ray (and X-ray) instruments
>> are launched into space, or at least lofted by high
>> altitude balloon.
>
> Thanks for the reply, Craig. Understood. It has
> always been a struggle to accurately subtract
> background radiation from the total, which at times
> can be significant . This has always been known
> as "background cosmic radiation." Do you know
> what type of radiation this is?
Natural background radiation. If you live in a river delta (eg.
Bangladesh) the natural background can produce higher than is
allowed as an industrial radiation dose by the various radiation
regulating bodies. The reason that river deltas are like this,
is because very heavy metals tend to settle out when water speed
drops.
Terrestrial sources of gamma radiation are quite common.
Granite, potassium (which we cannot live without), even some lead
isotopes. There was even a Co-60 pencil (from a scrapped medical
device) that got smelted into a load of rebar... all of which was
located and destroyed.
Most of what you measure at the surface of the Earth, comes from
the Earth. And people.
David A. Smith
.
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- Gamma Camera
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