Gamma Camera

I have access to several types of used Nuclear Medicine gamma cameras. I've
often entertained the idea to convert one for astro-gamma imaging. I'm not
much of an astronomer but am somewhat knowledgeable with gamma cameras. The
main problem that has always stopped me from pursuing this idea, is the fact
that the large sodium-iodine crystal can fracture if there's an ambient
temperature change of 6 degrees F in 1 hour. Outdoor temperature
fluctuations ... (well I'm sure you understand).
I apologize if this is not the correct NG for my question. Perhaps I can be
directed to a more appropriate one? Thank you.

Cordially,
west

"west" writes:
I have access to several types of used Nuclear Medicine gamma cameras. I've
often entertained the idea to convert one for astro-gamma imaging. I'm not
much of an astronomer but am somewhat knowledgeable with gamma cameras. The
main problem that has always stopped me from pursuing this idea, is the fact
that the large sodium-iodine crystal can fracture if there's an ambient
temperature change of 6 degrees F in 1 hour. Outdoor temperature
fluctuations ... (well I'm sure you understand).
I apologize if this is not the correct NG for my question. Perhaps I can be
directed to a more appropriate one? Thank you.

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.

Craig

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"Craig Markwardt" wrote in message
news

"west" writes:
I have access to several types of used Nuclear Medicine gamma cameras.
I've
often entertained the idea to convert one for astro-gamma imaging. I'm
not
much of an astronomer but am somewhat knowledgeable with gamma cameras.
The
main problem that has always stopped me from pursuing this idea, is the
fact
that the large sodium-iodine crystal can fracture if there's an ambient
temperature change of 6 degrees F in 1 hour. Outdoor temperature
fluctuations ... (well I'm sure you understand).
I apologize if this is not the correct NG for my question. Perhaps I can
be
directed to a more appropriate one? Thank you.

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.

Craig

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Craig B. Markwardt, Ph.D. EMAIL:
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
--------------------------------------------------------------------------

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?

west

Dear west:

"west" wrote in message
m...

"Craig Markwardt" wrote
in message
news
....
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

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?

west



I assume its as Alpha particles, neutrons, long lifetime mesons, and similar
debris of atomic nuclii being smashed apart by extremely high energy EMR.

Google would know, of course.

"west" writes:

"Craig Markwardt" wrote in message
news

"west" writes:
I have access to several types of used Nuclear Medicine gamma cameras. I've
often entertained the idea to convert one for astro-gamma imaging. I'm not
much of an astronomer but am somewhat knowledgeable with gamma cameras. The
main problem that has always stopped me from pursuing this idea, is the fact
that the large sodium-iodine crystal can fracture if there's an ambient
temperature change of 6 degrees F in 1 hour. Outdoor temperature
fluctuations ... (well I'm sure you understand).
I apologize if this is not the correct NG for my question. Perhaps I can be
directed to a more appropriate one? Thank you.

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?

I wasn't actually talking about subtracting background. What I meant
was that gamma-rays from space cannot penetrate the atmosphere deeply
enough to reach sea level. Other radiation like cosmic rays don't
usually penetrate either; they interact in the upper atmosphere, but
they produce high energy particle showers which can reach sea
level.[*] That is usually what is meant by "cosmic rays" on earth.
The sun, supernova remnants, active galaxies are all sources of cosmic
rays.

Craig
[*] - internet search term "cosmic ray shower"

--
--------------------------------------------------------------------------
Craig B. Markwardt, Ph.D. EMAIL:
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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"Craig Markwardt" wrote in message
news

"west" writes:
I have access to several types of used Nuclear Medicine gamma cameras.
I've
often entertained the idea to convert one for astro-gamma imaging. I'm
not
much of an astronomer but am somewhat knowledgeable with gamma cameras.
The
main problem that has always stopped me from pursuing this idea, is the
fact
that the large sodium-iodine crystal can fracture if there's an ambient
temperature change of 6 degrees F in 1 hour. Outdoor temperature
fluctuations ... (well I'm sure you understand).
I apologize if this is not the correct NG for my question. Perhaps I can
be
directed to a more appropriate one? Thank you.

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.

Craig

--
--------------------------------------------------------------------------
Craig B. Markwardt, Ph.D. EMAIL:
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
--------------------------------------------------------------------------

I think I need a refresher in spectrum-frequency. Ham radio signals (HF) are
reflected by the ionosphere. That's how Hams communicated around the world.
However, VHF, UHF, etc., are shorter wavelength signals that penetrate
through all atmospheric layers and are lost in space. Communications is line
of sight only. The highest frequency or shortest wavelength of the spectrum
that I am familiar with is gamma waves. Why can they not penetrate the
earth's atmosphere? Also, what are cosmic rays and how do they compare to
gamma rays? Thank you kindly for any input.
Cordially,
west

Dear west:

"west" wrote in message
...
"Craig Markwardt" wrote
in message
news
....
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.

I think I need a refresher in spectrum-frequency. Ham
radio signals (HF) are reflected by the ionosphere. That's
how Hams communicated around the world. However,
VHF, UHF, etc., are shorter wavelength signals that
penetrate through all atmospheric layers and are lost in
space. Communications is line of sight only. The highest
frequency or shortest wavelength of the spectrum that I
am familiar with is gamma waves.

That is as high as it goes. A "billion years ago", higher energy
photons were called cosmic rays. Today, cosmic rays refer to the
non-photon particles that originate outside our atmosphere.

Why can they not penetrate the
earth's atmosphere?

Activation energy. Below a certain energy, you do not have
enough energy to activate/boost/liberate/expel an electron.
Above this energy, you do. The threshold is just below (above?)
visible light for most common atmospheric gasses. For example,
you cannot see through smoke, but with infrared, you can.

Also, what are cosmic rays and how do they compare to
gamma rays? Thank you kindly for any input.

Cosmic rays are generally high energy protons and the like. Like
this one:
http://www.fourmilab.ch/documents/ohmygodpart.html

David A. Smith

"west" writes:


"Craig Markwardt" wrote in message
news

"west" writes:
I have access to several types of used Nuclear Medicine gamma cameras.
I've
often entertained the idea to convert one for astro-gamma imaging. I'm
not
much of an astronomer but am somewhat knowledgeable with gamma cameras.
The
main problem that has always stopped me from pursuing this idea, is the
fact
that the large sodium-iodine crystal can fracture if there's an ambient
temperature change of 6 degrees F in 1 hour. Outdoor temperature
fluctuations ... (well I'm sure you understand).
I apologize if this is not the correct NG for my question. Perhaps I can
be
directed to a more appropriate one? Thank you.

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.
....
I think I need a refresher in spectrum-frequency. Ham radio signals (HF) are
reflected by the ionosphere. That's how Hams communicated around the world.
However, VHF, UHF, etc., are shorter wavelength signals that penetrate
through all atmospheric layers and are lost in space. Communications is line
of sight only. The highest frequency or shortest wavelength of the spectrum
that I am familiar with is gamma waves. Why can they not penetrate the
earth's atmosphere? Also, what are cosmic rays and how do they compare to
gamma rays? Thank you kindly for any input.

The atmosphere is more complicated than you describe. In certain
wavelength bands the atmosphere is opaque; this is due to the
composition of the atmosphere and the nature of electromagnetic
interactions.

For low energy gamma-rays (E 512 keV) the primary interaction would
be photoelectric absorption. A gamma-ray interacts with an atom and
ejects an electron, thereby losing energy. These reactions proceed
until the gamma ray has lost enough energy that it can no longer eject
any more electrons. The ejected electrons and the recombining ions
can produce IR/optical/UV light. Extremely high energy photons can
also make showers which reach the ground, at least the Cerenkov light
from the electrons does.

The point is that the original gamma ray doesn't make it to the
ground.

Best of luck,
CM

On Wed, 26 Oct 2005 00:00:35 GMT, "west"
etched in cyberspace:

I have access to several types of used Nuclear Medicine gamma cameras. I've
often entertained the idea to convert one for astro-gamma imaging. I'm not
much of an astronomer but am somewhat knowledgeable with gamma cameras. The
main problem that has always stopped me from pursuing this idea, is the fact
that the large sodium-iodine crystal can fracture if there's an ambient
temperature change of 6 degrees F in 1 hour. Outdoor temperature
fluctuations ... (well I'm sure you understand).
I apologize if this is not the correct NG for my question. Perhaps I can be
directed to a more appropriate one? Thank you.

Cordially,
west
Hi West

Why don't you try to run up the camera inside and see what image you
can get out of it.
As the other posters hve said you will be unlikely to get gamma rays
from space, but you may be able to image something even if its not
gamma. Can you change the length of exposure?
If its so sensitive to temperature fluctuation, you had better wait
for overcast outdoor contitions before you take it outside.
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