X-ray susceptiblity

[Patrick Spohrer]

Pete,

Did I just have bad luck or are the plane flights overseas to blame? Would a led Bag help? What would you do?

-patrick

[Mike Rehmus]

At 35,000 feet, gamma is fairly strong since one is above a lot of the earth's atmosphere.

gamma/xrays are ionizing radiation and anything that will ionize will cause cancer, semi-conductor damage, etc. X-Ray lasers are just super-sources of ionizing radiation.

Unless you have a neutron field, it is almost impossible to get the Alphas and betas near a CCD in a camera.

Been there (Nuclear Power) still glow faintly.

[Andre De Clercq]

Gamma radiations are not ionizing in practical life. They are electromagnetic waves (like radiowaves) which could introduce ionization effects at very high energy levels, much higher than the cosmic levels even in the stratosphere (far above 35000feet). Even at still much higher medical diagnostic levels where gamma radiation is used to see through the body, there is no significant ionization involved. What damages electronic devices are the particle based (I called it alpha and beta families ) emissions. Those particles are generated by radioactive materials (nuclear plants, nuclear bombs/weapons..)and in our cosmos. Only particle based "radiation" can destruct the cristal lattices in CCD imagers and microelectronic devices in general, not by ionization, but by (very) local heat when releasing their energy.

[Mike Rehmus]

In the Nuclear Power industry (and the U.S. Navy) they are considered strong contributors to whole body ionizing radiation dosages. In fact, when the reactor is shut down, they are, unless something is contaminated, the only source of radiation.

Alpha and Beta particles are indeed strongly charged particles but they cannot get inside to do anything to the semiconductors Even a sheet of paper will stop them. So unless someone sprinkles them like fairy dust directly onto a CCD after stripping off the inert covers over the CCDs, they are very improbable candidates.

[Pete Bauer]

Gamma and xrays don't reach the lower atmosphere, for all practical purposes:

http://imagers.gsfc.nasa.gov/ems/gamma.html

Lead shielding won't help during those polar route flights and may actually cause more secondary radiation -- when a high energy particle like GCR, hits it.

With rare exception, where we humans take our cameras (excepting, for example, astronauts and nuclear tech workers), any damage caused by radiation of these various types is just too rare and random to worry about. Sometimes, no doubt, a CCD hit is actually due to an unlucky high energy particle (and even less likely, EM radiation like gamma or xray) but other causes including slight manufacturing defects and whatnot are undoubtedly more likely causes...though in any given instance, it is unlikely that one would know the actual cause. Can airport xray machines damage high speed film? Yes. Your camcorder? I really would doubt it. Flying over the poles? Hmmm, possible, but in any one trip it would still seem pretty unlikely.

We all like to describe the world around us in absolute terms...black is black, white is white and betwixt the two no gray to be seen. But our universe is made up of the gray stuff of mathematical probabilities.

[Andre De Clercq]

Like I already mentioned, heavy particles(wrongly mentioned as alpha particles) are known as causes for CCD defects Gamma ray are not involved in CCD degradation.. See:
http://www.fullcircleresearch.com/Ra...hardening.html
http://en.wikipedia.org/wiki/Radiation_hardening
A lot more is available about microelectronic "device hardening", so I will not spent more time to inform some people about CCD defects.

[Pete Bauer]

Thanks for the links, Andre. Good stuff and a quick read. Recommended to all following this thread!

[Mike Rehmus]

Very interesting, professor. I learn new things (or relearn) them all the time.

[Patrick Spohrer]

Thanks Pete :)

[Lamar Lamb]

Hey Mike, are you an ex Navy Nuke? Ex-Submarine ELT here. I then worked as an HP Tech at Plant Hatch for 14 years and now am in Operations.

[Mike Rehmus]

Yes, RC Div, Swordfish & Robert E. Lee

[Lamar Lamb]

Andre,
How do you explain our plant's camera degradation in purley gamma radiation fields? I have spent most of my adult life working in the field of Health Physics and have been on the pratical side of gamma, beta, nuetron, and alpha radiation trying to minimize their negative effects. If what you say is true then how do you explain how an ion chamber measures gamma radiation? And the definition of Roentgen? Gamma and X-Rays are both electromagnetic radiation, just different energy levels. They are both ionizing radiation.

[Lamar Lamb]

I could tell..... :-) Guardfish here.

Originally Posted by Mike Rehmus

Yes, RC Div, Swordfish & Robert E. Lee

[Andre De Clercq]

Lamar, maybe don't fully understand your questions. What did I write what countradicts Geiger counter behaviour? Gasses get easely (slightly) ionized in gamma radiation environments, and of course in nuclear plants gamma rays are also around. On the CCD deterioration (death pix) I already mentioned the known reasons (particale inpact). The only other things known in microelectronics and gamma radiation is some shift in MOS transistor properties (not a defect) if the TID (total ionizing doze) is sufficiently high. Also in floating gate microelectronic devices (e.g. flash memory) there is a memory loss risk at high doses. Roentgen rays (only historic value) relate to the first discovery of radioactivity (alpha beta and gamma rays...nuetrons were not yet "discovered" at that time). Today X-ray is related to (mostly) electronically generated gamma rays. In a nuclear plant (as you certainly know) it's a matter of controlled bombardements of uramium by nuetrons. In the "dangerous" zones, neutron are not fully screened off and it is still possible now and then they travel around and cause CCD death pixels.

[Lamar Lamb]

Perhaps I didn't understand your statements but it seemed as if you were saying that ccds would not be affected by gamma / x-rays because they were not ionizing radiation. This is not true. My field concentrates mainly on the biological effects of radiation. I have not studied much about the effects of radiation on electronics but I work with radioactive material and radiation every day. I know where it comes from, how it behaves, and how it interacts with matter. I know that we see ccd degradation in our cameras that are exposed to purely gamma fields. No measurable neutron dose rates in these areas. No Beta or alpha radiation present and neither would present a problem if it were because it would be shielded by the environmental housings. Alpha particles won't even penetrate the dead layer of skin on your body so how, if they were present, could they present a problem to a ccd buried deep in a camera body.

Regarding ion chambers, they are different from Geiger-Mueller tubes. They rely on the same basic principle of ionization occurring in the detector but with ion chambers you can measure the actual energy deposited in that chamber where as with a Geiger-Mueller tube you can only measure interactions (ionization events).

Roentgen is a non-SI measure of radiation here in the US. Like Sv are used there, we use Rem, Rad, and Roentgen. My reference to the roentgen was to emphasize that it is a unit that was used to measure x-ray radiation levels and its original definition is: “That amount of x-ray radiation that will deposit 1 erg of energy in one gram of dry air.” So how could you characterize x-rays as being non-ionizing when this unit of measure was originated to measure them?

I might add that in my experience you must be careful about believing or trusting sources on the web. I have seen many false statements regarding radiation and its effects from seemingly reliable sources. Just today I saw a site that states, and I quote, "there are currently no SI units for measuring radiation." Wonder where that guy has been.................

Originally Posted by Andre De Clercq

Lamar, maybe don't fully understand your questions. What did I write what countradicts Geiger counter behaviour? Gasses get easely (slightly) ionized in gamma radiation environments, and of course in nuclear plants gamma rays are also around. On the CCD deterioration (death pix) I already mentioned the known reasons (particale inpact). The only other things known in microelectronics and gamma radiation is some shift in MOS transistor properties (not a defect) if the TID (total ionizing doze) is sufficiently high. Also in floating gate microelectronic devices (e.g. flash memory) there is a memory loss risk at high doses. Roentgen rays (only historic value) relate to the first discovery of radioactivity (alpha beta and gamma rays...nuetrons were not yet "discovered" at that time). Today X-ray is related to (mostly) electronically generated gamma rays. In a nuclear plant (as you certainly know) it's a matter of controlled bombardements of uramium by nuetrons. In the "dangerous" zones, neutron are not fully screened off and it is still possible now and then they travel around and cause CCD death pixels.