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Help building an digital x-ray system

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LAN_403

Tue Mar 16 2010, 09:22PM

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

New idea, how about teflon or delrin tube, i can machine the tube to fit the bulb then slide a lead jacket to it with an aluminum insert as output window,
would this be a better aproach ?
BTW i know some rectifiers if over driven emit xrays, please look at this picture and let me know if this one could be a better candidate.

klugesmith

Tue Mar 16 2010, 10:38PM

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

I'm no x-ray expert (yet).
Just an old tinkerer with some degrees in Science (from a well-regarded institute of technology).

Among the experts here, Lutz has generally advised to operate x-ray tubes in oil
(an environment for which they were designed ).
Fabio has shown pictures of his rotating-anode tube operated in air (without rotation).

I think few amateur radiographers will ever put as much wear on a tube
as an ordinary week of professional service. Be cognizant of the heat capacity of the tube's
anode and cathode, and the rem / Sievert capacity of your own variously sensitive tissues.

Tue Mar 16 2010, 10:57PM

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

Thanks for your advice, the main concern is arcover, this is why the oil, (the alu filter and lead shield are a MUST) since lead is a metal i guess i need the oil to prevent arcing to the lead shield, correct ?

Proud Mary

Wed Mar 17 2010, 12:44PM

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

Klugesmith wrote ...

I think few amateur radiographers will ever put as much wear on a tube
as an ordinary week of professional service.

This assumes that the amateur's tube was operated within its design ratings by
someone who knew what they were doing.

Wed Mar 17 2010, 01:58PM

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

i doubt any one in this forum does not know what he or sheÂ´s doing.

There might be people like me that know what they want to do and might not know how to doit, or they might even not know how to do it in a safe manner,
but hey, some of us enter these forums to learn not only how to do things, but to learn how to safetly do things.

trust me there are numerous webpages that tell you how to x-ray, but with my almost inexistent knoledge of this type of photon energy i was able to tell it was unsafe.
btw, i build and service laser cutters ranging from 15w all the way to kilowatt machines. and i have self learned this tech by myself, with no school, ( i do have an engineering degree, but not related)

Fabio

Wed Mar 17 2010, 11:19PM

Registered Member #122 Joined: Fri Feb 10 2006, 12:55PM
Location: Milano Italy
Posts: 148

Fabio has shown pictures of his rotating-anode tube operated in air (without rotation).

Yes, but i use either an car induction coil powered by 555+IGBT interrupter or a flyback transformer powered by a small ZVS....... in other words i used a really low power.

i also used a big xray head (with rotating anode and of course with oil) powered by two potential transformer wired in series at about 7 kilowatt but of course the simplest source is a dental head (with integrated HV transformer, just connect it to a timer switch and go directly to mains)

i can also suggest to scale your system to a higher voltages, tin solder is quite dense (and tin/lead one is denser!) so you may need something about 110 to 160kV to get a decent image.

Ciao!
Fabio.

Thu Mar 18 2010, 01:27AM

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

im planning on a ZVS Flyback driver and multiplier stages, i have achived as much as 16inch sparks from such setup, would this be enough ?

i have seen some dental heads on local surplus, these have internal HV transformer in them, but too many wires coming out, how can i hook up to mains, and how to control tube current ?

thanks

Fabio

Thu Mar 18 2010, 07:22PM

Registered Member #122 Joined: Fri Feb 10 2006, 12:55PM
Location: Milano Italy
Posts: 148

most dental head have only two wires + ground and you simply connect them to the mains to emit Xrays, anyhow, some heads nay have one additional wire for current measurement, (wich is usually directly tied to ground or connected to ground with a resistor) and some expensive heads may also have a separate supply for the heater (that could be either directly connected to the heater if the HV transformer is single ended or supplied via an isolation transformer if the HV transformer is centertapped).

i have 7 different xray heads and i played with many other with my friends, all with successful results, so if you buy one heads and take some pics, i can help you in finding the correct connections.

Ciao!
Fabio.

Thu Mar 18 2010, 08:03PM

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

Fabio,
Thanks for this great help offer, i will go to the surplus yard tomorrow and will take some pictures from whatever is available, would you mind looking at the pics and provide an advice on wich one looks better for the task.

Again THANKS!!!

LutzH

Thu Mar 25 2010, 03:06AM

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

Hello:

Sorry for the delay, the insulator enclosure material does not matter from a radiological perspective, unless you get into something like dense Thoria ceramic. Shielding is basically density related more than Atomic #. In other words a sheet of brass which has the same per square foot weight as a sheet of lead will almost be the same, except that the brass will be thicker of course.

Oil or no oil boils down to what will hold the KV being used. Industrial x-ray machines often use SF-6 gas for insulation, to keep the weight down. So use what works, I would stay away from anything black due to the potential carbon black problem already mentioned in another post, I agree with this post completely. The oil does make cooling much more easy in many cases, for cont. use etc.

The .5mm Al filter is only to absorb the soft x-rays which do nothing except burn you, they do not contribute to the image anyway so they are useless for imaging, unless you are doing a flower.

Hope this helps......Lutz

PS: Measure for leaks always :)

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