X-ray machine finally done! / Projects / Forums

Forums

4hv.org :: Forums :: Projects

« Previous topic | Next topic »

X-ray machine finally done!

1 2 3 4 next

Move Thread

LAN_403

Freitsu

Wed Dec 15 2010, 09:51AM

Registered Member #3147 Joined: Sun Aug 29 2010, 10:53AM
Location: Finland
Posts: 56

Finally I've finished my x-ray setup, and here are the results. (well, there's still some tinkering to be done)

The x-ray tube is a dental coolidge tube, it's specs are 70kV at 2mA. That's about all I know about it.

I've been running this tube with an ordinary flyback outputting max 30kV, until I decided to try and build a CW multiplier for it to get up to 70kV.
X-ray tube and multiplier had to be dropped in oil to prevent flashovers due to the high voltage, my choice of oil was sunflower oil, and it works pretty nicely!

I choose to drive the multiplier with an AC flyback (the brand Grundig seems to have these in some of their 28"+ TVs). Currently it's being driven with a 555+mosfet but that might change to ZVS in the future.

As you all can see I've used ALOT of hotglue to seal the x-ray tube + multiplier, and so far I haven't had any oil-leaks...

An ordinary transformer + current limiting resistor is used to drive the filament on the tube, I have plans to change this into a rheostat if I can find one that is suitable and cheap.

Things to do next on this machine is make a better cameraholder because now it's just hanging from thin ironwire attached to the small lid on top. And ofcourse experiment with camera exposure time etc.
When testing for leaks with a geiger counter I couldn't detect any so this would indicate it's pretty safe to operate, though I would like to get my hands on some kind of dosimeter to be even more safe and reassured.

Details on the CW multiplier:
It's 3-stage, using 12 pcs 1nF 30kV ceramic disc capacitor, 4 per stage (2 parallelled) and 12 pcs of 20kV 100ns diodes (2 in series so they will withstand 40kV)
I got capacitors and diodes from ebay. Here are the links for anyone that's interested: (it took 1 week to get my stuff from china!)

<- Diodes

<- Capacitors

Testing multiplier before soldering it to x-ray tube

I had to strap x-ray tube to a smaller plastic tube so it wouldn't just bounce around inside the final casing with the multiplier

Tube+multiplier in plastic tube before being filled with oil and sealed

Everything in place!

Notice the little lid, to that I have attached thin iron wires that is holding the camera!

Geigercounter.

My cellphone, I'm not happy with this, you can hardly see any details at all, does anyone have any tips on how to get this better?

Flashlight.

High voltage diode

Flyback, I'm not so happy with this one eighter. I SHOULD get better results since the x-rays seem to penetrate the windings pretty good!

X-ray tube.

Wolfram

Wed Dec 15 2010, 11:17AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Well done, I like the way you've made the enclosed x-ray generator.

I know this method has potential for much sharper x-ray pictures. If you want to improve the x-ray images, I have a few tips for you. Firstly, what camera are you using, and are you sure it was focused right for this picture? Also, what type of x-ray cassette did you take the screen from?

Anders M.

Freitsu

Wed Dec 15 2010, 12:27PM

Registered Member #3147 Joined: Sun Aug 29 2010, 10:53AM
Location: Finland
Posts: 56

Thanks Anders!

The radiograph that I took is waay out of focus, I just wanted to get a picture to show here with this new setup. Focus was set to 10cm and the exposure time is 2 sec.

I have to experiment with diffrent settings on my camera, I will update this thread with pics.

It's a Dimage Z10 camera. X-ray casette is kodak lanex regular (that's all info I have of it). A mammography screen would be much better...

radhoo

Wed Dec 15 2010, 12:36PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

Congrats on your first results!

The oil will affect the hot glue. I used it for the same purpose, then decided to check the resistance of hot glue to oils, and I found out the hot glue not only dissolves in oil, but it will be taken off the surfaces it initially adheres. You should cover the hot-glue with a layer of epoxy asap, to avoid the possible oil leakage mess.

please post complete details on your multiplier (stages/components ratings), are you using a limiting resistor between the multiplier and the tube?

Freitsu

Wed Dec 15 2010, 01:01PM

Registered Member #3147 Joined: Sun Aug 29 2010, 10:53AM
Location: Finland
Posts: 56

Thanks for the warning radhoo! I will cover that extra pipe that I added with epoxy to prevent oil-disaster. If it ever decides that it want to leak oil, the box will atleast contain the oil.

No current limiting resistor is needed, it takes whatever it needs.

I updated OP to answer your question...

Fabio

Wed Dec 15 2010, 01:11PM

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

i suggest a simple (but effective) way to get a perfect focus without turning on the rays:

just put some kind of image (for example a page ripped off from a newspaper) on the fluorescent screen, insert a flashlight to illuminate the image and close the box, now you can manually set the focus for the best result and remove the image and the flashlight.

Ciao!
Fabio.

Freitsu

Thu Dec 16 2010, 09:19AM

Registered Member #3147 Joined: Sun Aug 29 2010, 10:53AM
Location: Finland
Posts: 56

I got the focus set pretty good, but somehow the radiographs get blurry anyway...

OP updated with more radiographs!

Patrick

Thu Dec 16 2010, 09:28AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Wow! Nice! That flyback pic isnt so bad... that might be as good as it gets for low density materials like plastic, which the blurry parts of the pic are.

Freitsu

Thu Dec 16 2010, 09:32AM

Registered Member #3147 Joined: Sun Aug 29 2010, 10:53AM
Location: Finland
Posts: 56

Patrick wrote ...

Wow! Nice! That flyback pic isnt so bad... that might be as good as it gets for low density materials like plastic, which the blurry parts of the pic are.

It might be so, however that phone picture should be way more sharper, maybe it's the screen's fault that you can't see any details... It kinda looks like I've taken picture in dirty water..

Patrick

Thu Dec 16 2010, 09:58AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Freitsu wrote ...

It might be so, however that phone picture should be way more sharper, maybe it's the screen's fault that you can't see any details... It kinda looks like I've taken picture in dirty water..

Have you taken that phone apart yet? maybe it has a lot of steel or copper flashing/shielding. I know my USB o-scope has copper spary-paint on the inside of the plastic cover.

1 2 3 4 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob