Cosmic Rays

[Jim Tittle]

In an attempt to cope with insomnia, I'm reading the new PMW-F3 manual. On page 134, I found this:

"Although the CMOS image sensors are produced with high-precision technologies, fine white flecks may be generated on the screen in rare cases, caused by cosmic rays, etc."

COSMIC RAYS!!!

I already wear my tinfoil hat whenever I leave the house, but now I'm going to have to make one for the camera, too. Life is getting very complicated.

[Don Parrish]

I remember an old myth that being in a airliner at altitude reduced the amount of protective atmosphere and the sensors could be damaged, at least I think it was a myth.

[Jim Tittle]

When I get a good take, I'm going to be sure to ask my AC to check the gate for Cosmic Rays.

[Jim Michael]

Originally Posted by Don Parrish

I remember an old myth that being in a airliner at altitude reduced the amount of protective atmosphere and the sensors could be damaged, at least I think it was a myth.

It's no myth that you are exposed to higher doses of radiation than you are on the ground. About equivalent to an x-ray on a 5 hour flight.

[Erik Phairas]

Yes and bananas are fairly radioactive as well. Enough so to set off detectors set up for people trying to smuggle uranium. If you eat one a day for a year you have definitely increased your chances of getting cancer. You know what that means right? Keep them away from my camera! :)

[Alister Chapman]

Originally Posted by Don Parrish

I remember an old myth that being in a airliner at altitude reduced the amount of protective atmosphere and the sensors could be damaged, at least I think it was a myth.

It's no myth, it's very true and well known that cosmic rays are more damaging at high altitudes. The atmosphere acts as an absorber and reduces the amount of the damaging particles from reaching the ground. Look at any video camera on the ISS or space shuttle and it will be plastered with white flecks. If you fly long haul with CCD cameras a lot the chances are that you will encounter this problem from time to time. The same cosmic rays can also corrupt memory cells in flash media and computer RAM. It's not normally an issue with a computer as it will normally have some form of error checking, but potentially it could corrupt footage on a flash memory card such as an SxS card. I have not seen any reports of this, but it should be considered, just in case. It's even been speculated that Toyota's problems with cars randomly accelerating has been caused by cosmic rays flipping data bits in the controllers for the engine.

[Jim Tittle]

Hopefully, someone at Zacuto is reading this thread and working on some sort of lead shield that will mitigate this problem. Bright yellow. Banana yellow.

[Alister Chapman]

Lead does not stop cosmic rays. Hydrogen absorbs them (or something like that) which is why the atmosphere reduces thier effect. There's an extended thread on this here: http://www.dvinfo.net/forum/home-awa...revention.html

[Brian McKenna]

i had a replacement harddrive reading out jumbled data once. phoned tech-support and after ruling out a number of causes they suggested that relatively high sunspot activity could be the cause.
...turned out to be a bad cable.

[Carlos Molina]

Originally Posted by Alister Chapman

It's even been speculated that Toyota's problems with cars randomly accelerating has been caused by cosmic rays flipping data bits in the controllers for the engine.

Alister, I just read that this hypothesis was disconfirmed. A recent report by NASA and the National Highway Traffic Safety Administration claimed that the unintended acceleration in Toyota vehicles was rooted in mechanical flaws rather than electronic defects. The report found "no causes for the unintended acceleration incidents other than sticking accelerator pedals and floor mats that jammed the pedals down." Those were the causes Toyota had identified. NASA studied whether electromagnetic interference may have caused unintended acceleration, which may be linked to 89 deaths in 71 crashes since 2000, according to the safety agency. NASA investigators used Chrysler Group LLC's test facility in Michigan for its vehicle testing work, and bombarded vehicles with electromagnetic radiation to test the potential effects on the car's circuitry.

Toyota problems were mechanical, study says

[Alan Emery]

Kind of a fun topic.

Primary cosmic rays -- the type we most often hear about are actually not "rays" they originate as particles: mostly protons (nearly 90%) helium nuclei (9%) and electrons (1%) and some other smaller parts. Because the particles are magnetically charged, much of the cosmic "rays" are deflected before they get to the atmosphere. They get concentrated at the poles because they follow the magnetic fields and we sometimes see the effect as aurora borealis or australis.

When cosmic ray particles do hit the atmosphere they collide mostly with nitrogen and oxygen and break up into lots of smaller unstable particles that quickly decay into "muons"; very tiny particles that don't interact with the atmosphere very much so can often reach the earth and because they are small and moving fast, they can penetrate a little way into the earth. Because muons are ionizing radiation they can hit and affect a computer chip (in a camera or in a computer). A computer might get hit once every several years and the induced error in the past was minor enough it was not really noticeable. However as the chips get smaller and more tightly packed with microprocessors and supercomputers are built to have many processors, the frequency of hits on the supercomputer could be 10-20 cosmic ray hits per week -- enough to be a problem. It is real enough that Intel is working on a cosmic ray detector (basically searcing for electrical spikes and eliminating the calculations since the cosmic strike and redoing the calculation).

I don't know if the chips in cameras or our typical computers are really very vulnerable (unless you happen to own a Cray), but it is within the realm of possible. Cosmic ray particles are detected in experiments (normally undertaken in space or high altitude from ballons so there is no interference from the atmosphere) by exposing plastic sheets, then bringing them back and "etching" them using sodium hydroxide which dissolves along the path of damage faster than undamaged plastic. So by extension it is also possible to damage plastic parts of a camera including sensors. The chances of significant visible damage are really small -- but theoretically present.

As I say, it is a fun topic.

Alan

[Jim Tittle]

Tossed and turned all night. Wife said I was mumbling in my sleep. Something about "rays". Ate a banana this morning and felt better.

[Brian McKenna]

...the CCDs on NASA's Solar Dynamics Observatory seem to be doing just fine...

[Jim Michael]

Thanks for the reminder. Bought some bananas today and took a reading. Nothing above background. Didn't peel it so could be some alphas hiding in there, but I kind of doubt it.

[Pete Bauer]

K40 gives off beta, not alpha. The amount of radiation is only "high" in that it is the largest single source of naturally occurring radiation exposure for most people.

Jim, even though the tin foil hat is a definite fashion statement, you might want to hand it down to your least favorite sibling or "friend" because as Alan pointed out "cosmic rays" -- or more correctly galactic cosmic radiation -- are high Z (very energetic) particles and when they strike metals produce a lot of secondary radiation that can actually be more damaging to pink flesh than the original particle. GCR is very difficult to shield, but fortunately the earth's magnetic field and atmosphere together do a great job of it so very, very few (still not "none") make it to our filming locations.