Dear All, As an assignment I have to design a CCD Sensor based FPGA digital Camera. However, the Camera will be exposed to XRAY (It will be placed behind an Imaging Intensifier). Does anybody know how XRAY affects the electronic circuits (The CCD Sensor and the FPGA ). What type of noise should I expect and what should I do to prevent it. Thanks in advance
Can bits be flipped?
Do you need a RadHard FPGA?
Cheers, Jon
How about:
Advice - buy "Space Class" devices. This will probably be from Actel.
A little bit of lead foil goes a long way. Depends on how much XRAY I imagine. Be careful.
Ever consider using a phosphor plate to turn the x-rays into visible light first?
Hi John, I guess that's what the OP means.
X-ray,
Has no effect on the device, except that (eventually) the total dose will accumulate, and the Vt of the devices will begin to shift, and eventually, the device will fail.
This is unlike a CCD, which may register 'hits' and display noise.
Only neutrons, or protons, with LET of 1 Mev have enough energy to create charge clouds, and change bits:
Contact your local Xilinx FAE to find out about X-Ray dose (how long it can "take it.").
At some dose level, that usage becomes ITAR restricted (people use stuff this hard to build nuclear bombs, or operate in the presence of nuclear explosions) so you will no longer be able to buy, or use, such parts, unless the US State Department permits you to do so.
I suspect for your application, our commercial parts are more that "hard" enough.
X-rays, after all, are just photons, and they just do not pack enough energy to affect even the MGTs in our parts, and certainly do not affect the logic and memory.
Austin
Spiel?
X-rays are just wimpy little photons ....
SEUs are caused by cosmic rays (heavy ions, like iron, gold, etc with LET's of > 100 MeV) that create neutron showers with energies beyond
1000 MeV.Austin
Is it internal flash or external flash? If anything, flash would be the weakest link.
I would think an old fashioned tube camera with tube amplifiers would be the most radiation resistant.
CMOS doesn't like X-Rays much. There is a failure mechanism that tends to harden CMOS SRAM bits in one direction. I'm not sure how bad it gets though.
-- Keith
On Thu, 17 Jan 2008 21:14:46 -0500, in sci.electronics.basics, krw gurgled:
THE HORRORS!
Someone need to tell Agilent & Teradyne ASAP. Millions of boards a year are run through their x-ray fault detection systems.
Digital boards quite often with memory.
Vidicon tubes! I haven't seen one of those in a whole lot of years but I'm so happy everythign is CCD now.
Hi,
There are rad-hard CCDs available. There are also rad-hard FPGA's available. Actel uses anti-fuse technology, which is inherently rad- hard. We (fellow engineers and I at my aerospace company) use Actel and Quicklogic FPGAs for space-based applications.
Tom P. =2E
As you did not mention it, perhaps it is yet unknown: The 'NASA office of Logic Design' did quite some studies about the influence of differend kinds of radiation on both off-the-shelf and 'rad hard' types of electronics. Did not see anything on CCDs, but FPGAs seem to be definitely in scope there.
There's loads of information about their results and learned lessons on
Hope this helps, Thiemo
-- Query a PGP key server (e.g. http://www.pgp.net/) for my public key 41068629. Strange sender address? Please see http://www.thiemo.net/misc/list-mail.shtml
There's a heck of a big difference between running a board through an xray machine a few times, and having that board run for a long time being exposed to xrays of uncertain energy while it's operating.
-- Wim Lewis , Seattle, WA, USA. PGP keyID 27F772C1
On Sun, 27 Jan 2008 01:15:36 +0000 (UTC), in sci.electronics.basics, Wim Lewis bloviated:
And just what are those parameters? What level is safe? What level is damaging? Length of time with respect to *energy* level? Frequency domain? Studies to support that data?
Don't leave everyone hanging:
It's OK to leave me hanging. Like most people, I don't care much about the effects of X-rays. My equipment isn't subjected to any significant intensity, because it's not X-rayed while in use, nor is it likely to go into space.
If you're so interested, why not research it yourself?
On Mon, 28 Jan 2008 14:58:32 +0000, in sci.electronics.basics, snipped-for-privacy@btinternet.com bloviated:
Ah, so you didn't quite catch the quite obvious drift of the questions.
Here is a little research for you, look up the term FUD.
Follow that with "saccharine in rodents".
To all it matters to what level of radiation from your source gets to your CCD camera. As a X Product Manager for a X-ray imaging company if we placed the CCD camera behind a intensifier tube -- lots of material between it and the camera a few lens -- we had little problem with noise from the x-ray beam we we producing. We could still detect some x-rays at this point but they were real weak. Now when we put the CCD (Sony) B/W camera in the direct beam path we had issues of noise in the CCD detector. We landed up placing the camera off axis. When we went to a special CCD camera behind a screen and a little glass it was not a bad but could still be seen and needed averaging to get rid of the problems we could see. Hope this helps-- Place the camera off axis if at all possible remember a lot of thing are transperant to x- ray but will reflect light.
Regards Cliff
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