X-Ray machines - Technology and use in Hobby Electronics.

[Fraser]

Question
Is an X-Ray machine useful for electronics or is it just a geek toy?

Answer
There is no simple answer as much depends upon the electronic engineer’s needs and experience.

Question
Is X-Ray safe to use?

Answer
Yes and No...... Yes if used correctly, no if misused. There is NO 'safe' dose of X-Ray radiation.  Exposure to ionizing radiation should kept as low as possible and below the agreed safety thresholds for users of such equipment. Ionizing radiation can cause cell deformities, radiation burns and potentially cancer.

Still interested? Then read on for more on this topic......

1. What can an X-Ray machine offer the engineer? In short, the ability to see the unseen.
An X-Ray machine of suitable power effectively makes solid objects transparent so that the user may see what resides within the DUT. Typical cases in electronics would be nondestructive visibility of hidden case screws and clips, hidden components within potting compound, internal  parts within sealed modules and copper tracks within multi-layer PCB's  or under IC's. In industry X-Ray is also used to inspect the quality of solder balls under BGA devices. This requires high magnification however. The only limitation on seeing through opaque objects with X-Ray is the power of the beam used as that and the imaged material density determines the penetration depth.

2. What types of X-Ray equipment are available to the public?
X-Ray is ionizing radiation that can cause harm to life, be it human or other. As such there are definite rules to be followed when using X-Ray producing equipment, even at low tube drive voltages. For this reason some thought is needed with regard to what X-Ray equipment is best used by the everyday user rather than a licenced industrial operator.

a) Open site medical X-Ray and suspect package inspection equipment.
Open site X-Ray can be dangerous as it requires the operator to ensure that no one, including themselves, is in the X-Ray beam or subject to high levels of reflected X-Ray energy. There is typically no physical containment of the area between the X-Ray generator, the DUT and the imaging system. As such it is possible for irradiation to occur if used incorrectly. There are significant legal implications if a person believes that they were irradiated by the user of the equipment. Examples of this type of equipment are: Dental X-Ray heads, Golden X-Ray inspection X-Ray generators and LIXI Scope medical triage X-Ray used for fast limb damage assessments.

b) Controlled space X-Ray equipment.
A classic example of a controlled space X-Ray is a Hospital X-Ray facility where health and safety measures are built in to the room design and protective screens are present for the operator. Such facilities may still contain exposed X-Ray generators but their activation occurs at a safe distance and targeting is carefully monitored throughout the imaging process. The processes and controls make such equipment safer to use than open site X-Ray. To a degree, dental X-Ray may be similar but the Generator heads can be free floating for flexibility of use. This is where the risk of unintentional irradiation lies.

c) Cabinet X-Ray equipment
Cabinet X-Ray equipment is likely to be the safest of the available X-Ray imaging options as the controlled space is reduced to the area directly around the Generator, DUT and imaging system. Provided the cabinet is not damaged there is no reason for X-Ray to escape its confines and so the risk of irradiation is minimal. Cabinet systems often do not require the operator to be licenced or X-Ray dose monitored. This is in recognition of their intrinsic safety. Common cabinet type X-Ray equipment’s are X-Ray Mail scanners and medical biopsy/research X-Ray equipment. A semi cabinet equipment known to most of us is the conveyor belt baggage scanners found at airports etc. These are still intrinsically safe when used correctly but a fool may still irradiate parts of their body that are passed into the 'tunnel' whilst the X-Ray Generator is activated. This makes it less safe than a full cabinet design but process mitigates the risk adequately.

d) Home built X-Ray equipment
Home built X-Ray generators have the potential to be lethal and very unsafe for the user. Before considering building an X-Ray Generator or such equipment, the wise DIY enthusiast ensures that they are in possession of adequate safety knowledge and design principles. The risks are not just in containment of the emitted X-Ray but also the high voltages and currents associated with common X-Ray tubes. Death or serious injury can result from a poorly built X-Ray Generator. Not a DIY project that I can recommend for the beginner entering into the world of X-Ray imaging. The builder must build a safe EHT power supply, contain and cool the X-Ray tube, Shape the X-Ray beam, control the output power and screen the user from X-Ray, both on beam and reflected.

3. Are there different types of X-Ray?
Yes there are two major types of X-Ray energy. Soft and Hard. Soft X-Ray is produced at low anode voltages such as 10KV. The X-Ray beam has very low penetration capability and that may make people think it safer than Hard X-Ray. This is not the case however. Remember there is no 'safe' dose of ionizing radiation. Soft X-Ray is stopped as it passes through human or animal tissues. It is totally absorbed by the tissues cells with potential damaging effects on them. Soft X-Ray is not great for imaging even low density DUT's and is often filtered out using an Aluminium plate in Medical X-Ray equipment. It provides no image enhancement yet increases the patients X-Ray dose significantly. Do not think of soft X-Ray as 'Safe' even at lower levels of power. Hard X-Ray is produced at higher anode voltages of say 25kV and above. The anode of large medical X-Ray equipment’s often uses anode voltages of more than 120kV. Hard X-Ray tends to punch through human tissue with less potential harm to the cells than soft X-Ray. Hard X-Ray provides the images that we know and love at airport security etc. It punches through many different densities of DUT depending upon the Anode voltage that is being used.

4. What specifications are important when looking for an X-Ray machine?
Much will depend upon your intended uses for the unit but here are some comments:

a) Open, controlled space or cabinet solution. I recommend a cabinet solution for reasons of intrinsic safety and often no need for X-ray dosimeter monitoring by your national radiological service.

b) X-Ray Tube types. There are different X-Ray tube types for different applications. There needs and performance differs. Conventional X-Ray rubes operate at high anode voltages and the target has a relatively large spot size. Such tubes are not great doe high resolution imaging. Micro-focus tubes normally operate at lower anode voltages of less than 100KV and so beam penetration is often inferior to that of conventional X-Ray tubes. More KV = more penetration. They have a very small target spot size which provides excellent high resolution imaging. To protect the target Micro-focus tubes may have low operating currents. Do not be tempted to increase the current above the manufacturer’s specification. Damage will result. Like many things in life there can be a choice between brute force with deep penetration and precision directed energy with less penetration. The choice is often dependent upon the user’s needs. In the case of a baggage X-Ray machine, high resolution comes second to penetration capability to see through various dense materials such as metal cans etc. A biopsy medical X-Ray needs a more delicate touch with lower need for penetration but great need for image resolution and clarity. This is why a biopsy X-Ray runs a Micro-focus tube and high resolution diode array camera.

5. What penetration can be expected of conventional and Micro-focus X-Ray tubes?
Penetration is very dependent upon the DUT material density, KeV of the X-Ray beam and the sensitivity of the imaging system behind the DUT. as a very rough idea of what to expect. A conventional >120KV X-Ray generator can provide good penetration in many metals such as aluminium, steel, copper, brass etc. Higher KV is needs for higher density materials. Micro-focus tubes run at <100KV and this limits their penetration capability. Do not expect good penetration in steel or brass. Penetration in less dense metals such as aluminium and copper is good. Baggage X-Ray machines with image enhancement fitted can image through 25mm of steel! A 35KV Micro-focus cannot image through 2mm of steel. Very much horses for courses.

6. What X-Ray imaging systems exist and which is best for the hobbyist user?
Conventional X-Ray imaging uses X-Ray sensitive fil that is sandwiched between scintillator plates in a cassette of varying sizes. The Film reacts to X-Ray exposure and the scintillator plates produce visible light that enhances the image produced. High resolution images use just the X-Ray sensitive film as the result is a crisper image. The problem with the film type imaging is the need to develop it much like conventional film. Not very hobbyist friendly. A scintillator plate behaves like the film in that it produces an image but is exists only whilst the X-Ray is present on its surface. Polaroid used to produce film cassettes that contained a scintillator plats that illuminated a monochrome instant film. The exposed film was processed in the same way as conventional Polaroid instant film. Such a system was simple but expensive to use. Now pretty much obsolete. New technologies have developed. Scintillator plates are still in use but they are now viewed by optical cameras and high resolution diode array detectors. The digital age has come to X-Ray imaging. A digital cassette is now used that contains the imaging array and all electronics to store the array output. A dedicated machine then downloads the data from the cassette for processing. Such a system is very expensive and not normally suitable for the hobbyist.  I recommend using a scintillator plate with digital camera or diode array imaging technique. It offers many benefits to the hobbyist. Even a Digital SLR on a slow shutter can produce images from a scintillator plate. Scintillator plates may be purchased on ebay or medical X-Ray film cassettes may be purchased and the two scintillator plates removed from them.

7. What did I buy and from where?
I have regular access to an industrial X-Ray machine. Sadly I will lose access to such equipment when I take early retirement in February 2015. I wanted to find a basic X-Ray imaging system that would allow me to see concealed screws and clips in equipment cases, components concealed in potting and also PCB tracks inside PCB's. I do a lot of PCB reverse engineering and multi-layer PCB's have always been a challenge. I also fancy doing some artistic X-Ray work..... Ever seen an insect or flower in the X-Ray image domain? It can be interesting to play with such if the equipment is capable of high resolution images.

I decided that a compromise solution that might just be adequate for my needs was a Todd Research or similar X-Ray mail scanner. The resolution is lacking but penetration is pretty good. The common use of a relatively low resolution optical camera viewing a scintillator plate limits performance. The higher levels of X-Ray that these machines produce does have an issue for many users..... The equipment makes use of much lead shielding and so they are VERY heavy to transport and move around the lab. Definitely not portable equipment.

By chance whilst on ebay I stumbled upon a medical X-Ray cabinet solution that is designed for Biopsy and even electronics imaging. The unit is called a Faxitron MX-20 and utilizes a 50KV micro-focus X-Ray tube and a sensitive diode array digital camera that drives a dedicated imaging card in a PC running Windows 2000 Pro. The tube is only run at a maximum of 35KV which does limit penetration but the high resolution imaging and digital image capture capability won me over. Penetration is not always the most important specification. An added benefit of the MX-20 is that it is intrinsically safe to use and its low KV on the Tube Anode reduced the need for screening. The MX-20 needs only a twin skin steel case to contain the ionizing radiation. No lead shielding means that it is relatively light at 70Kg. The MX-20 comes in two major versions. Conventional film/digital cassette and high resolution digital camera array.  Sub versions of the Digital camera equipped unit provide different diode array sizes to suit the intended task and cost constraints of the customer.  I purchased two Faxitron MX-20 units, one is without the digital imaging capability and the other is equipped with the full Monty 2048 x 2048 pixel  100mm x 100mm high resolution diode array camera. Both units use the identical X-Ray generator that forms the top 4 inches of the cabinet and is removable. If the digital MX-20 suffers a tube or EHT failure I will just transplant the other unit’s top section onto the digital cabinet. I should have a decent X-Ray capability for many years to come.
Another owner of an MX-20 (Digital) was without the required PC and interface card. He decided to reverse engineer the unit in an attempt to extract imaging from the camera. He has a web page showing some internal images of the MX-20 that I hope you will find interesting.

http://photonics.engr.uga.edu/xray_imager/index.html

I will not repeat the images here as the web pages are an interesting read. The Faxitron is a lovely piece of kit that is well suited to X-Ray imaging of microelectronics but it does not have the penetration to image through steel screening cans.

So is an X-Ray machine a necessity in the modern electronics lab or workshop or just a Geek toy? In my opinion it is neither. For those with a need for seeing inside sealed or potted items, it can be invaluable. Reverse engineering is also assisted by such technology as hidden traces become clearly visible. Is it a toy.... no, definitely not a toy as it has safety implications and is not very geeky toy like anyway. As Mike has said in communications over these units.... they are a nice to have rather than a necessity. I agree but recommend that if, like me, you stumble upon a suitable system, you consider buying it.

For information my Faxitron MX-20 cabinet is a 2005 unit that is still around in many bio labs around the world. It cost $22,000 for the cabinet and an extra $25,000 for the digital camera imaging option (inc computer, interface and software).

http://www.faxitron.com/life-sciences-ndt/products/mx-20.html

I paid GBP250 for the standard film MX-20 and GBP1000 for the Digital Camera equipped MX-20 unit that included all hardware, P4 3GHz ASUS computer, interface, software and LCD 17" monitor. Not an insignificant sum, but well worth the investment for me in my electronic activities.
I shall upload some images in due course and will be happy to answer questions on X-Ray technology.

Aurora

[Fraser]

Faxitron MX-20 images

[Fraser]

Faxitron MX-20 images

[Precipice]

That's quite wonderful, and I'm envious! I've been accumulating parts for a homebuild (PSU, emitting valve, since I'm in no great hurry, scintillation film, and because of jobs I've done, I've got a lot of HD CMOS camera chips that I can crack the glass off and press bits of film onto, to see if direct coupling is possible, for high res work).
(I take it your prices on the MX-20 stuff weren't repeatable? I'd abandon homebuilt like a shot, for that price!)

Is there any chance of a slanted shot to show some BGA balls and their soldering?

[Alex Eisenhut]

Wish I had the space and money to tinker around with stuff like this. When I wanted a piece x-rayed, I sent it off to a lab.

[Fraser]

@precipice,

Sadly the two units I purchased were the only ones the sellers had. Different sellers but both local to me. It was just meant to be    Both sellers said they have had the MX-20 before but most come with no hard disk due to DPA. You now know someone with a copy of the software though 

Keep an eye out on ebay.co.uk and DOT Med. The sellers are dealers in ex lab and hospital equipment that they buy from auctions around the country. Having looked at the Win2000 event logs my unit has had very little use since 2005. 30 or so days of use !

Prior to this purchase I was considering building a simple X-Ray source and, like you, bought the required main parts. I bought some BS7W low voltage X-Ray tubes from Ukraine and some scinterllator plates from Russia. The BS7W is an interesting tube that only requires 15KV across it to produce decent X-Ray output. Take a look here if you are not already aware of this tube:

 http://www.hardhack.org.au/xraydtt

http://www.hardhack.org.au/crystallography

The beam has a 5 degree divergence upon exit from the tube target. Sounds about right for very small images such as in X-Ray Microscopy, or larger images if the DUT is placed around 1m from the tube !

I bought a pair at around GBP50 each as they will become unobtainium once the sellers stock is exhausted. They are far easier to use than a conventional high voltage tube and have better output than an old TV EHT rectifier valve. I may sell my BS7-W's if anyone wants them as my Faxitron will serve my needs fine.

Aurora

[IanB]

When you say "not an insignificant sum", are you referring to the £250? If so, I am surprised. That seems to me a like the kind of sum you might spend on an electronic toy like a camera or a computer. It doesn't seem like a heavy sum.

I did a quick scan of your introductory post, but I didn't immediately see the answer to a question many may have. Could X-rays damage the item being imaged? Like for instance, could they induce voltages in delicate circuits or corrupt flash memory data?

[Fraser]

@IanB,

I was referring to the cost of the Digital MX-20 at GBP1000. It is true that I can afford such a price, but hobbyists budgets can be limited and I made the statement in recognition of such  I personally consider my purchases to be bargains and I am a very happy bunny 

With regard to damaging electronics with X-Ray, I can make the following real world comments

1. In production quality control and inspection it is not unusual to find a specilaist microfocus X-Ray machine that is capable of in excess of 200 KV across the the cathode & anode. These machines are used to inspect the balls on BGA chips for presence, poor shape, cracking and bridging. I have seen sensitive BGA chips inspected at in excess of 160KV and no damage has been considered likely.

2. I personally have inspected sensitive electronic equipment, including high speed computers, with pulsed X-Ray with an output of up to 300KeV. I have yet to induce a fault in such equipment.

3. X-Ray imaging is not advisable on electronics that is powered and operating. That is just common sense.

4. Never X-Ray in an explosive atmosphere !

5. I believe much testing has been done on sensitive memory chips to determine the damage level for memory cells. I have no doubt that corruption could occur with very high levels of X-Ray passing through the die but I have not seen it in my 27 year career in the field. Airport X-Ray should not corrupt memory cells and the fact that all laptops get X-Rayed these days at airports suggests that this is indeed the case.

6. I HAVE seen an electret microphone destroyed by significant and repetitive exposure to X-Ray of around 160KeV. The static charge was removed from the plate and so it was no longer an electret mic.The Mic was tested around 20 times at approx 120 to 160KeV. That is pretty high levels of exposure !

So have I personally seen ANY evidence of damage to memory cells or sensitive microprocessors by normal X-Ray imaging. Nope no sign of any issues at all. I am not saying that you cannot damage such devices with X-Ray but I suspect the KeV would have to be very high to do so. HOWEVER, anything that holds a static charge is succeptible to damage. Old 'Stephen' radiation monitors use a static charged Quartz filament as the radiation detector. The ionizing radiation discharges the charge on the filament in a predictable manner and this gives the dose reading over time.

Do I have any worries about 35KV tube anode X-Ray illumination of a sensitive chip... no concern at all. 160KV anode voltage...I am still not concerned about damage.

Aurora

[IanB]

@IanB,

I was referring to the cost of the Digital MX-20 at GBP1000. It is true that I can afford such a price, but hobbyists budgets can be limited and I made the statement in recognition of such  I personally consider my purchases to be bargains and I am a very happy bunny 

Oh, I missed the £1000 bit. My mistake 

You are correct, that starts to become a significant sum...

[ixfd64]

Interesting "patients" you've got there.

[Fraser]

Ionizing Radiation damage to electronics is discussed here:

http://www.erai.com/presentations/Training%20Track%206/Radiation%20Damage%20on%20Electronic%20Components-Creative%20Electron.pdf

http://www.spansion.com/Support/Application%20Notes/X-ray_inspection_on_flash_AN.pdf

The Spansion comment on flash memory makes very interesting reading. It would appear that X-Ray below 9KeV is more damaging to the memory cell charge than higher KeV levels.

Aurora

[mikeselectricstuff]

Something that in my (brief research) a while ago wasn't clear. Obviously this is very country dependent, but in the UK what are the legalites of using X-ray equipment?

As far as I could establish (UK)  :

There don't appear to be any restrictions on ownership of x-ray equipment, nor any system for registration - ISTR reading that in some countries (US? Canada?) all x-ray kit must (in theory) be registered and any transfer notified. The place I got the baggage X-ray from, who regularly deals with this stuff,  was quite keen to take a note of the generator serial number and the purchaser's address - I don't recall if he asked for a disclaimer. 

Use in conjunction with a business or where there are employees comes under the Ionising radiations Regulations 1999. What is not clear is whether any aspects of this apply in a hobbyist scenario -   The regs make frequent use of the term "employer" but I couldn't make out if this meant in a workplace context or as in "employing ionising radiation"
 
Is there any distinction/exemption  between  open sources (e.g. medical/dental) and closed ones (mailroom, baggage etc.)?

Of course the  no.1 thing is to try to keep under the radar.. I know that at least one UK amateur x-rayer had a visit from someone - all was OK in that case, but was just wondering what the actual legal position was.

Incidentally Ben Krasnow got some heat from his homemade CT and backscatter setups, but again they seem to have taken a pragmatic approach, last reported as  "Don't use it til it's all shielded and we'll come along & certify it for you"


 

[mikeselectricstuff]

BTW on teh subject of x-ray effect on electronics, this is an interesting appnote on the effects on Intersil's voltage reference devices that use an analogue floating gate
www.intersil.com/data/an/an1533.pdf

[EEVblog]

2nd hand units of any decent capability (these days that means digital output) are rare as hens teeth here in Australia.

[Fraser]

@Mike,

A good question and one that I cannot answer except to provide the following comment:

1. Any employer who requires staff to use non(ooops!) ionising radiation is duty bound under law to protect those employees from harm. As such the employer must have a nominated non ionising radiation adviser available. That person must attend a training course at what was NRPB (UK). The employer is also required to detail the equipment that will be used by the employees. Some equipment is intrinsically safe with screening and interlocks etc, some is open site and considered potentially harmful. In the case of intrinsically safe equipment such as mail room scanners, the employer DOES NOT need to have the employees Dosimeter badged but the machine must be inspected for leakage on an annual basis by a qualified person. This is often the service company that supports the equipment. Equipment that produces open site X-Ray or that is very powerful in nature invokes user monitoring regulations where the users are dosimeter badged and given annual health checks by a doctor. I came under that heading and my annual radiation dose was carefully monitored. I even had to take my badge with me when being X-Rayed in Hospital. What was NRPB (I forget what it calls itself now) provides advice to employers and employees on Radiation related matters. Harwell run the dosimeter monitoring service.

2. The ownership of an electric X-Ray producing equipment is legal in the UK without registration. Manufacturers are VERY careful about who has access to X-Ray machines as they are concerned regarding liability in the case of an accident. We used to place Mail Scanners beyond easy use by cutting the mains cable and removing the control boards. These days the manufacturer insists on removing the X-Ray generator and sending it for correct disposal. This may be to avoid amateur tinkering with what is after all a dangerous piece of equipment if used improperly. It is not radioactive waste.

3. Ownership of Radioactive isotopes, as used in some X-Ray appliances such as the Lixi Scope is a complicated matter. The isotopes, though small, must be transported in line with all manner of regulations and packing requirements. The Iodine isotope has a half life of only 6 months so the user must arrange for replacement at regular intervals via approved means.That is GBP5000 a time ! Ownership of a radioactive isotope is not recommended outside accepted institutions as there is fear of dirty IED's these days. I recommend against buying ANYTHING that states that it contains a radioactive isotope. Some are VERY nasty indeed. The only exception would be ionising chamber fire detectors but they are less common these days anyway.

4. Is it legal to use an intrinsically safe X-Ray cabinet as a hobbyist ? I honestly have no idea but common sense makes me think that provided it has not been modified and is being used only by the owner in accordance with the manufacturers instructions, there should not be a problem. In my case I have teh advantage of having been officially trained in non ionizing radiation and its hazards. As such I am less likely to do something daft    My unit runs with a maximum voltage across the X-Ray tube of 35KVp. The penetration capability of the KeV that it produces is so low as to be easily attenuated by my garage walls and doors. Fall off with distance also means that I am not able to irradiate my neighbours even if I wanted to !  Now if I owned a much more powerful Industrial X-Ray machine that could produce significant KeV, I would be nervous on two counts. 1. Am I safe from its emissions. 2. Am I breaking any laws by using it without regular site checks and formal Non ionizing radiation surveys ?

5. Equipment that is not legal to use is normally placed beyond use by the service agents when it is decommissioned. I see no evidence of such activity with low output X-Ray systems that are often seen for sale, but then maybe, just like us, no one really knows the law surrounding ownership and use of such equipment as part of a hobby.

6.  Those thinking of experimenting with X-Ray do need to consider the legalities of such in their country. As Mike states, if you are sensible you will probably be OK but remember that Non Ionizing radiation is not healthy for you or others so health and safety organisations can get a bit worried about DIY equipment !  BE WARNED Guiger Muller tube based non ionizing radiation meters do not have a linear response to X-Ray and most do not provide a useful reading below around 40KeV. They are counters so if they do not trigger on say 35KeV you will be unaware of a risk ! Scintillator based meters are required for lower KeV's.

Aurora

[amyk]

You mean ionising and not non-ionising, right?

Because almost everyone probably already owns a very powerful non-ionising radiation device.

[Fraser]

Mike hasn't mentioned it but he did an excellent tear down of a mail scanner a while ago.



That is a more powerful unit than mine as it has to punch through all manner of objects and is used by staff so fine tuning of images if not an option in many cases.

The unit appears to be a Todd Research model as its internals look familiar to me. As you will see, it uses a cctv like camera technology that is viewing the Scinterllator plate. This was a technology that appealed as it was cheaper than large diode detector arrays and associated processing.

Mike's unit was the sort of thing I was hunting for when I found the Faxitron MX-20. In the end the MX-20 suits my needs better.

For those thinking of experimenting with X-Ray imaging using a CMOS or CCD camera, be aware taht you need a lead glass plate in front of the imaging chip  or camera lens in order to avoid 'sparklies' caused by the X-Ray beam hitting the sensitive detectors on the chip. Remember, X-Rays are Photon based !

Aurora

[mikeselectricstuff]

2nd hand units of any decent capability (these days that means digital output) are rare as hens teeth here in Australia.

Digital stuff is rare and expensive everywhere unless you are extremely lucky like Aurora, but the combination of a DSLR and a screen can be a reasonable substitute to avoid messy film processing. 

1. Any employer who requires staff to use non ionising radiation is...

Surely X-rays are ionising radiation...?

It is not radioactive waste.

But best to remove any radiation warning stickers before carting the lead off to the scrappie to avoid them getting spooked..

And probably not a good idea to chuck a beryllium windowed tube in the bin...

[Fraser]

Its late and brain is fading....yep I meant Ionising and not non-ionising 

However I have used some pretty scary NON-Ionising radiation emitters as well 

Radar isn't too healthy if misused.

[mikeselectricstuff]

For those thinking of experimenting with X-Ray imaging using a CMOS or CCD camera, be aware taht you need a lead glass plate in front of the imaging chip  or camera lens in order to avoid 'sparklies' caused by the X-Ray beam hitting the sensitive detectors on the chip. Remember, X-Rays are Photon based !

Or use a mirror, as in the mailroom unit.
Another option may be to point the camera at the plate from the same side as the x-ray, so you're not getting x-rays directed at the camera.

Incidentally there is another type of detector I've seen a couple of types of on  ebay, which exposes a "magic" storage screen material, and then afterwards scans it using a red (I think) laser and photomultiplier to read out the latent image.   

[mikeselectricstuff]

2nd hand units of any decent capability (these days that means digital output) are rare as hens teeth here in Australia.

And it appears you'd need a license...
http://www.health.vic.gov.au/radiation/businesses.htm

Though there are a few dental units on Oz Ebay

[Fraser]

In case anyone in the UK wants to read the HSE regs, they are to be found here:

http://www.legislation.gov.uk/uksi/1999/3232/contents/made

I also found the dental regulations for dentists but it basically said to comply with the above regs.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/337178/misc_pub_DentalGuidanceNotes.pdf

I comply on the X-Ray containment, interlocks, key control and access control so I believe I pass the basic requirements of use. I am not about to employ anybody or run demonstrations to visitors so my conscience is clear 

Aurora

[Fraser]

I briefly mentioned the issues surrounding radioactive isotopes used for X-Ray and medical therapies.

Some time ago I read of a stolen isotope that ended up contaminating 100's of people and killing four. Its a very nasty example of how dangerous certain isotopes can be:

http://en.wikipedia.org/wiki/Goi%C3%A2nia_accident

If it says Isotope.....walk away.

If its a large dew drop shaped steel object on a strong stand and the 'window' is open........ run away as quickly and as far as you can    Such units contain powerful (deadly) X-Ray source Isotopes for imaging thick steel as found in oil rig production. I remember a company went bust and when the owners of the industrial unit arrived to regain possession they got more than they bargained for. The defunct company used a large isotope for X-Ray work on steel tubes. It was still in the unit sat awaiting some poor fool to open its exit window. Fortunately someone recognised it. The bill for its disposal was massive as specialist facilities are needed to extract and store the isotope.

Aurora

[IanB]

The bill for its disposal was massive as specialist facilities are needed to extract and store the isotope.

Nah, you just give it to the NNL at Sellafield and say "Here you go chaps, your problem!"

What are they going to do, give it back and say "No, thank you"?

[Fraser]

Sadly no one does anything for nothing in the UK these days....they would just send you the fat bill and pursue you for its payment to the grave