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Help building an digital x-ray system

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Steve Conner

Thu Mar 11 2010, 03:37PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yes, I see just another flyback driver here... not a digital X-ray machine...

Fri Mar 12 2010, 02:06AM

Registered Member #2721 Joined: Fri Mar 05 2010, 04:09PM
Location: Guadalajara, Jalisco
Posts: 28

i dont mind matching the horses to the cart or vice versa, but i wiould apreciate some help here, besides the thread title is "Help building an digital x-ray system" and not "look at my digital x-ray system"

available for the project:
1.- the "Just another flyback driver from the pictures above"
2.- the xray tube marked "41605" and flybacks on the picture below
3.- intensifier cassete "CURIX ORTHO FAST" AGFA
4.- Voltage multiplier (tested with the fist flyback left on the picture and gives 12" sparks)

if it does not work for the bga balls at first attempt it can always be improved, but i want it at least to work as a digital xray system.

suggestions anyone ???

Thanks

Proud Mary

Fri Mar 12 2010, 02:35AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

It looks very unsafe and unsound to me, Ed, and the knowledge that you are not even able to calculate yourself the component values of an elementary push-pull circuit is not reassuring.

X-rays are insidious and their effect is cumulative, so I for one don't feel able to help you further with your digital X-ray device.

This is the hand of a Russian youth who did this injury to himself last year while playing with a second-hand X-ray tube, just as you intend to do.

Amputation was narrowly avoided, but cancer could well appear years later...

Fri Mar 12 2010, 02:53AM

Registered Member #2721 Joined: Fri Mar 05 2010, 04:09PM
Location: Guadalajara, Jalisco
Posts: 28

Thanks for your concern,
i do know the extreme dangers of any ionising source of radiation, this is why i want to obseve the images trhu a digital sistem, and also im not planing on xraying myself, im also in the process of purchasing x-ray leak detector to check if the lead is enough.

Thanks

LutzH

Sat Mar 13 2010, 12:52AM

Registered Member #1721 Joined: Sat Sept 27 2008, 08:44PM
Location:
Posts: 136

Hello:

You will need a few additional things like:

A reliable instrument to monitor radiation levels (Not a cold war dosimeter measuring rem!, we called those "dead meters" since they basically measure how dead you already are)

A shielded enclosure first for the tube by itself, and then again, add a second enclosure for the whole assembly, both using lead, or other high atomic number shielding.

A way to measure your MAS (Milliampere /Seconds at a given tube KV)

Always use the lowest KV to get the job done, and Always have at least .5mm -1 mm of Al filtration in the beam, by mounting the Al filter right on the tube output area in a permanent way, so it cannot fall out etc. This will help reduce the chances of your hand looking like the one in the prior posting. There was another case like it in the US, with a student, and an x-ray diffraction machine. He got new skin grafted onto his hand, with his rear end being the skin donor area.

When completed, do an area survey at max power, just to check for any leaks. X-rays can be very cool when used safely, but when not, they tend to produce latent leukemia, and lymphomas. Also shield your thyroid, x-ray induced thyroid CA is very virulent, and it has killed many good folks.

Use as fast of an optical system as you can to record the image from the fluor. screen, or best: Get an old medical image intensifier from an old fluoro setup. If you make your own recording setup, see if you can get an old fast manual lens to fit your dig. camera. The old Nikon 105mm F1.8 lens would be good for this app. for example. For the screen, a Gadolinium fast screen is good, and it has a reasonable match to the avarage CCD detector. It comes in two types: Detail, and Fast. For 95% of applications the fast screen is fine and offers sub mm resolution, something like 5-10 lines / mm.

The size of the focal spot on the x-ray tube makes a big difference also for resolution. An old medical rotating anode setup is perfect, becuase at less then 10 ma, you do not need to spin the anode, and it already comes in a well shielded enclosure to boot. At under 70KV the tube housing lead is enough in most cases, then you only need to shield the beam path, if the housing leakage is low enough.
Take care and be safe :)

Sun Mar 14 2010, 05:39AM

Registered Member #2721 Joined: Fri Mar 05 2010, 04:09PM
Location: Guadalajara, Jalisco
Posts: 28

LutzH, thanks for your advice, and yes, i was almost ready to purchace one of those "dead meters"

already working on the tube shield, it will be layered as follows,

1 tube
2 pvc pipe filled with dielectric oil
3 lead wraping with aperture for output
another pvc pipe
4. aluminum pipe
5 yet another pvc pipe

regarding optical system, i can get an image intensifier at local surplus but i dont have a clue as how to wire it, they have some complete units including cameras.

meanwhile do you know if the intensifier screen from the cassete i have will work with the camera ???

Thanks, for the help, i really apreciate someone who tells you the best aproach to be safe, rather than telling you not to do it.

i love guns and have a great respect for them, and this machine should be treated no diferent than a loaded gun.

BTW, i have 3 kids and i have teached them to know the danger of guns if miss used, while also teaching them how to use and respect a loaded gun.

Again, Thanks

klugesmith

Sun Mar 14 2010, 09:24AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

I've been wondering if ABS plastic would be a better choice than PVC for an x-ray tube enclosure, especially if three pipes are nested.
PVC is 57% chlorine by weight, an element with higher Z than aluminum. I bet it attenuates and scatters x-rays more than the same thickness of bones or teeth.

Sun Mar 14 2010, 01:29PM

Registered Member #2721 Joined: Fri Mar 05 2010, 04:09PM
Location: Guadalajara, Jalisco
Posts: 28

exellent !
great hint, ABS will be

Thanks

klugesmith

Tue Mar 16 2010, 03:58PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

On the other hand, the black color of most ABS pipe is due to pigment.
Would not surprise me if they use carbon black, as is used in tire rubber, for sunlight resistance.
I am planning to do some HV dielectric tests using sharp pinpoint electrodes and a NST,
one of these months, unless you or someone else here gives answers and references.

The other issue is oil resistance of ABS and PVC. Here's one reference from a Google search:

Some DIY tests which I would do, if answers don't come from online research:
1) soak plastic samples in the oil for a few days or months, then check for dimensional swelling or weight gain.
2) soak long, thin samples in oil, then check for increase in flexibility compared to control samples.

The purported (by me) x-ray density of standard PVC pipe could be mitigated by machining to make a thin exit window.

-Rich

[edit] Of course, commercial applications of x-rays to inspect BGA connections invariably use microfocus X-ray tubes, whose source spot is measured in microns.

Compared to a regular x-ray tube (1mm or 2mm spot size), the microfocus source can be much closer to the subject, and get away with much less total x-ray flux, and get significant geometric (projection) magnification. We're looking forward to seeing your results.

Proud Mary

Tue Mar 16 2010, 07:52PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Klugesmith wrote ...

On the other hand, the black color of most ABS pipe is due to pigment.
Would not surprise me if they use carbon black, as is used in tire rubber, for sunlight resistance.
I am planning to do some HV dielectric tests using sharp pinpoint electrodes and a NST,
one of these months, unless you or someone else here gives answers and references.

The other issue is oil resistance of ABS and PVC. Here's one reference from a Google search:

Don't forget x-ray-induced polymer degradation, Rich.

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