I went to a veterinarian clinic recently. They had an x-ray machine on a table and a very small partition to block a computer. What effects can the electromagnetic radiation have on the computer’s hardware and software? Is it right to assume that a clinical x-ray machine’s effects on a computer are different than an airport one’s? The computer did have a wireless card and I was not surprised that they told me that they routinely have to reset their wireless connection. But would it add permanent effects?
Not sure if this is the main or even a significant issue, but the idea of “radiation hardening” (that is, making something resistant to radiation effects) is important in semiconductor manufacturing.
In the acute sense, radiation can upset a computer because a high energy photon screaming through a semiconducting junction can cause it to conduct momentarily when it wasn’t supposed to. In an extreme case, CCD imaging chips for low light pictures record so many cosmic rays that the software you use with them has a variety of cosmic ray filters you can adjust to your needs.
In the cronic sense, radiation damage can build up in things and change their behavior. I think I remember that a long term radiation effect in optical materials such as glass (and some optical glass is, or was, made with uranium) is yellowing. I don’t know specific problems in semiconductors but would expect there could be some.
Microprocessors that control smart weaponry, or microprocessors for satellites that don’t have the protection of the earth’s atmosphere, are two examples of thoroughly radiation hardened products.
There is a very, very small risk of damage due to the X-rays. Even background (ionizing) radiation can cause a bit to flip on a memory chip. But the odds are quite low.
The “real” problem with airport X-ray machines are the magnetic fields from all the electronics involved. The longer your laptop spends on the belt, the worse. But still fairly low odds.
Just keep in mind that consumer devices are made with the cheapest possible components that can be bubble-gummed together. Multiply lots of people times low odds, divide by low quality and you still get a few people a day who lose some data.
First off this is not a consumer product but a clinical X-ray machine. I doubt it was “bubble-gummed” together. Assume that it is no different than one you would find in a hospital. Second, won’t the x-ray machine emit higher levels of electromagnetic radiation than an airport x-ray machine?
Umm, I was talking about the computer being made of low quality components.
But then I do seem to have had an off night posting…
From what I remember, x-rays can flip bits and generally do funky things with electrons, possibly making a 0 turn into a 1. Randomly flipping bits isn’t very healthy for a computer. They tend to crash when you do that. Also, x-rays can cause atoms to move around a bit in the silicon, which eventually can destroy the semiconductors properties.
For short exposure, like going through airport security, there’s not much to worry about, but long term exposure (like sitting next to an operating x-ray machine 24/7) is probably going to ruin the semiconductors if the exposure level is great enough. I don’t know how much exposure the computer is really going to get though. I would hope not much, because there are probably people that work in that area too.
Ahem. Imaging equipment repair technician here. Yes, I’m an X-ray repairman.
I’m not sure what computer you are talking about – was the computer part of the x-ray system? Was it set up in the control booth, or stashed behind some other partition?
Modern imaging equipment is moving away from film-based x-rays, so computers are not uncommon in and around x-ray machines. Furthermore, even x-ray machines built in the 80’s had extensive electronic technology – including in the collimator, right under the tube.
No special shielding is used, other than to protect the patient and staff, and as required by federal law (CFR 21). In fact, specialty equipment to detect the x-rays are required by repair staff, and these devices require fairly large amounts of radiation input for accurate results. Basically, modern electronics seem to be fairly immune to diagnostic x-rays.
I routinely place my my pager, cellphone, or other electronic device in the x-ray beam while repairing a device, because the various materials make a good test phantom.
I know of no instances where electronics were damaged or affected by x-rays in any way. I’m not discounting the possibility, but I don’t think it’s a concern.
Memory chips that rely on stored charges, like EPROMs (Erasable Programmable Read Only Memory), can be erased by exposure to x-rays. They are normally erased by exposing the silicon chip to a strong UV light source. This causes the stored charges to dissipate.
Interesting replies. Danalan, this is a film-based x-ray machine. The computer is indepenedent of the machine and is in its place due to convience. And by partition i mean a regular wall (no extra shielding). The computer is very buggy and I’m still not sure if it is due to the x-rays or that it is an old and crappy computer. (Now i see what you were talking about, ftg ).
It’s far more likely that power issues caused by the x-ray machine are the source of the computer problems.
X-ray generators develop very high voltage, low amperage, short duration electrical pulses to drive the x-ray tube, thus make x-rays. Typical exposures would be 60,000 to 100,000 volts (60 Kv - 100 Kv) at .2 - .6 amps (200 milli-amps or mA - 600 mA), for .25 seconds.
This usually causes ‘sags’ in the electrical supply for the machine. Many small installations are not hooked up to sufficiently robust supplies, so the sags can be very damaging to equipment. There are ways to fix this, but perhaps the best bet is to put a quality UPS on the computer.
Also, mks57 – I’m going to have to request a cite.
See eprom
This message thread:
http://www.vanderbilt.edu/radsafe/9603/msg00170.html
is more indicative of the levels of x-radiation required to erase eproms – and in any case your cite states that the substrate was physically damaged by the radiation.
How about this compromise: I admit, eproms are erasable with x-rays. Such erasure occurs only at high radiation doses, so high in fact that the radiation can physically damage the device.
However, diagnostic x-ray machines are not normally capable of this type of exposure, or at least not used as such beyond maximum load testing.
As certain industrial x-rays, and any radiation therapy device, are quite capable of damaging at least eprom electronics, inordinate care should be taken in exposing electronic devices to the primary radiation beam.
EPROM chips aren’t used in computers anymore, I haven’t seen one since the days of the 486. They’ve been replaced by EEPROMs, which are erased electrically rather than via UV flashing. Someone else will have to comment on whether EEPROMs are more or less radiation sensitive than EPROMs.
Back in the day, parity checking and ECC were much more necessary and widely implemented for system memory. The reason was that the ceramic packaging of the silicon chips contained traces of uranium and other impurities, resulting in frequent bit-flips as the the silicon chips themselves were bombarded with alpha particles. Since better quality control measures were instituted, this ceased to be a problem. Today, the average computer experiences a bit-flip in system memory due to cosmic rays once every six months as its only radiation problem. These advances in memory reliability are what made ECC a useless extravagance for all but the most mission critical servers.
EPROMs are still widely used in many embedded computer systems. Just because they are not used in the latest desktop PC, doesn’t mean that they don’t exist. Embedded computer systems often use “old technology” for reasons of cost, simplicity, compatibility and reliability. You might be surprised at the number of embedded computers that are based on ancient CPU designs such as the Z-80, an 8-bit processor that runs at 4 MHz.
I think you are overly optimistic about the quality of memory and the quality of memory subsystems. Alpha particles are not the only cause of soft and hard errors in DRAM. IMHO, any computer manufacturer that does not design in parity checking or ECC is bordering on negligence. I’ve wasted many hours troubleshooting computers with subtle memory problems that were very difficult to diagnose. The cost of adding parity checking or ECC is small compared to the costs of dealing with a computer system that randomly crashes or corrupts its data.
I also fix medical imaging systems for a living. If the computer is properly shielded (ie the case is on the system) and it is not directly in the beam of the X-ray, the radiation shouldn’t be causing any problems. I do a lot of work on Computed Radiography systems and I’ve never seen a problem on the computers in the same room with the X-ray equipment. Now whoever brought up the power issues could be correct. If the computer system is not on a decent UPS and it is running on the same circuit as the X-ray machine (I think this is very unlikely, but possible) it could cause problems. My guess is that the computer probably needs preventive maintenance, has caught a virus/trojan horse, etc.
The one major issue you see from hospital and medical areas on computers are the effects of an MRI on a computer monitor. It will bend the crap out of the image. It a lot of fun when hospitals poorly shield an MRI room and put a Radiologist reading room on the other side of the wall. Whenever you fire up the MRI the doctor will get very angry, or will be going for coffee, but he won’t be reading images.
Mike