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X-Ray Chicken Wing Inspector

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LAN_403

EEYORE

Tue Dec 22 2009, 06:45PM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

Hello all,
I decided to start a project thread. I am going to be building an X-ray machine to view chicken wings. (To make sure they are okay before I eat them).

Okay, well that is just an excuse to make an X-ray machine I guess.

So right now, I have been playing with the mini focus tubes being sold here and have found that higher voltages seem to produce brighter images. Maybe I am mistaken and its the rise in current (from raising the voltage) that is causing the brighter images. (I am using one of the homemade fluoroscopes).

I plan to buy a real x-ray tube that can withstand higher voltages and current for hopefully better results. (Those drumsticks have some thick bones!).

I am in the process of rounding up some stuff for a HVDC PS. I plan to use a flyback xfmr and either build a CW multiplier or use my TV tripler (if 30kV turns out to be plenty for x-ray images).

So, what is your advice? Stick with lower voltages but beef up the current? Or go for say a 60kV DC multipler with doorknob capacitors and such. Oh yea, Id love to stay away from oil!

EDIT: Planned x-ray tube:

MAtt

Proud Mary

Tue Dec 22 2009, 08:44PM

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

First things first! You'll have to invest in a dosimeter and adequate shielding before producing any X-rays, won't you? A GM counter is wholly unsuitable for this kind of work, because while it can detect the presence of some ionizing radiation, it provides no information whatever on fluence - the radiative flux integrated over time.

EEYORE

Tue Dec 22 2009, 08:52PM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

Hello,
Im guessing an old quartz CDV dosiometer isnt going to cut it, is it?

They are the little tubes that you charge and then leave near a radiation source. I think they were intended for gamma raditation.

Shielding, yes! I saw that hand picture and I dont like it! I have alot of lead sheet sitting around here. My plans would be to stick the x-ray tube inside a PVC pipe and wrap the lead sheeting around the outside. (For ease) A small hole can be drilled where the x-rays are to be emitted. The tube I have in mind has lead sheilding already, but it seems that there is no such thing as TOO MUCH lead!

How about something to absorb soft x-rays? They seem useless for all but burns. Aluminum sheeting maybe?
Matt

Proud Mary

Tue Dec 22 2009, 09:58PM

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

EEYORE wrote ...

Hello,
Im guessing an old quartz CDV dosiometer isnt going to cut it, is it?

Quartz Fibre Dosimeters are very handy for measuring the beam itself, but not for personnel protection outside of a Cherobyl event.

As for attentuating soft rays, not much below 10-15keV will get through the glass of the tube, travel through the air, and still have enough energy to be detected by ordinary means.

Aluminium filters will attenuate much of the long-wavelength braking radiation, and lead to better resolution and contrast in your images.
When you get into the subject, you can use combinations of target elements and filters to create selective bandpass filters .

Remember that X-rays are reflected and scattered by walls and so on, so simply placing a lead shield between yourself and the source will not do.

And lastly, don't forget that the dose immediately in front of the X-ray port can easily be 20 or 30 Gy/sec, so serious burns will result if you put your hand in the way of the beam for even a second.

Zeus

Wed Dec 23 2009, 12:01AM

Registered Member #2316 Joined: Tue Aug 25 2009, 03:04AM
Location: Bendigo, Australia
Posts: 107

Can I ask, are you planning to line up the tube with a raw chicken wing and do a long exposure.

EEYORE

Wed Dec 23 2009, 12:19AM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

Hello,
So is it safe to assume that high voltages and low currents will still work fine regardless of the x-ray tube? The one I plan on sniping looks to be just an anode, heater+cathode type.

I am assuming that low currents will be much safer and still be quite interesting? As for reflected x-rays, I assume you are refering to x-rays that reflect off the target that I am exposing? I could always build a little exposure chamber (lead lined) that allows the tube output window in one way and my fluoroscope to fit in the other way with the object in between. How does that sound?

I have some quartz dosimeters that I can use for now to figure how much radiation I am dealing with.

Am I getting safer?

As for the chicken wings...I plan to expose them long enough to cook them before eating. Also need to look through them to make sure there are no tricks going on before even considering them for dinner. I am a bit odd like that.

Matt

RogerInOhio

Wed Dec 23 2009, 12:52AM

Registered Member #1034 Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154

If the bones don't show up in the X-rays it means that the chickens being raised in the factory farms aren't getting enough calcium in their diet. That is another important thing to look for.

Roger

LutzH

Wed Dec 23 2009, 01:10AM

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

Hello:

As you know you can change two factors, KV and ma, well three if you include time, but for fluoroscopy this does not apply, unless you are calculating how close you are to Leukemia, Lymphoma. or Thyroid Cancer.

When you increase the KV the efficiency of x-ray production increases, so if you double the KV you get much more than 2 times the amount of x-rays. At 70KV something like .5-1% of the electron energy is converted into x-rays, at 10MEV 90% of the electron energy is converted into x-rays. Another big factor at this low energy level is "inherent filtration" In other words at low energy a lot of soft x-rays may be generated, but they do not make it through the glass tube envelope, turn up the KV a little and they do.

There is no direct formula to calculate the quantity of x-rays generated vs the KV increase amount, just to many variables.

In the lower medical imaging KV range, a 10KV increase will give you about 2 times the X-ray output, this applies to the 55-75KV range. From 80KV to 120KV its the 10% rule, so a 10% increase in KV gives you roughly 2 times the amount of x-rays, from a biological dose perspective. Remember when you go up in KV the X-rays become more penetrating, and much more of them can reach your bone marrow where most of the serious shit happens a few years later.

For fluoroscopy please use some form of remote viewing, in other words have a light sensitive CCD camera viewing the green fluorecent screen, instead of your eyeball. Pixel artifacts are much better than cataracs in your eyes :) Better yet buy an X-ray image intensification tube on ebay, if that's not in the budget then make the poor mans version:

A good way to do this is to use your X-ray sensitive fluorescent screen, with a 90 deg. mirror by the screen, so that your camera is not in the direct X-ray radiation cone path. Now the light from the fluorescent screen gets reflected 90 deg to the camera lens, but the x-rays do not reflect. Then as an added measure a sheet of leaded glass can be inserted between the mirror, and the camera. I recommend against shielding the camera on the sides, this way if you have a radiation leak, or a lot of scatter you may know, from the speckles on the still frame shots! It helps to have a fast lens on your camera, or a special low light camera like the cheap B&W low light security ones on ebay. Do not try a web cam, or some other dinky lens camera which resembles a "pinhole camera", you need to collect some light here. Your regular digital camera is great on the high ASA, and low light setting for stills. A front surface mirror coated with Al helps also, they are about 92% reflective vs the 70% range for normal mirrors, thats 20% more light for the camera, and 20% less X-rays needed.

Remember photon collection efficiency is much easyer, than more X-ray output. Plus the whole thing can be put in a light tight box, so that you do not need to darken the room, and dark adapt your eyes to see the image. An added plus is that a well lit room reduces the chance of accidently getting to close to a HV connection, or object. Many years ago I once got close enough to a live 70KV 5-10ma circuit to where I noticed the corona on my hand!!! while viewing a dim screen. I sleep much better now knowing that I am well past the 10-15 year maximum radiation induced cancer latency period from that time. I did have a lead apron though, even then.

If you just cannot get yourself to buy a good radiation detector, then call all the local hospitals and see if you can get an old lead apron, and thyroid neck shield. At 60-80KV they stop about 92-98% of the X-rays. They usualy have some because when they get crappy looking they are often replaced. To end I would say please do not do fluoro, it is just asking for trouble, but if you must then at least use a remote viewing method like a camera facing your screen, and wear a lead apron. Take Care....Lutz

PS: If you get Lymphoma from your fun time, then you will get to see a great really cool machine!!! They will use a 10 million volt linear accelerator, to make 10MV X-rays to blast your lymph system at 400 rads a minute. If you close your eyes during the treatment you will sometimes see a blue light, (No its not God waiting for you, or the light of angels) its the direct stimulation of your retina by all of the scatter radiation, this is best enjoyed when they are zapping the upper lymph system by your neck, so be sure to dark adapt your eyes, and ask them to dim the lights. Enjoy and savor this moment, because soon the missery of radiation sickness will kick in, most folks stop at starbucks on the way home, and smoke a little dope for the nausea. Dont worry if you did not catch the blue light durring this treatment, you will get to do it all again several more times, as soon as you get some energy back so that you can get out of bed again. Best of all they accept VISA, and American Express, if you live in a civilized country like Europe then the entire show is free.

No Seriously, be careful we like having you around, you can play and be safe, its not that hard.

EEYORE

Wed Dec 23 2009, 01:27AM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

Hello,
So I am a bit confused about what anode voltage I should be shooting for. Should I keep it at 30kV or should I make a multiplier to take it up to 60kV or so? From what I understand, more current is a bad thing. How about I keep it at 50uA?

Now for safety viewing...I am not actually using bare screen, but a fluoroscope made here by one of our members:

How does my lead-lined viewing chamber sound as far as safetly goes? Shouldnt be too hard to wrap some PVC pipe in lead sheet, place the object inside, place the xray output in one way and have the fluoroscope in the other. I would make sure everything was tight fitting with lead overlapping joints.
As to my chicken wing comments, I am not being serious. Just some humor. I am taking this thing much more seriously than that.

Matt

LutzH

Wed Dec 23 2009, 03:02AM

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

Hello:

Thanks for the clarification, you should be just fine with this fluoro set up, it should be perfectly safe given propper precations, unlike direct screen viewing which is a bad idea period. Sorry for the humor from before I was under the impression this was a direct viewing setup.

As far as KV goes it depends what you are looking at. 30KV is to low period, the surfaces of the intensifier tube, and others alone will attenuate up to 50% of the beam. I would start at 50-60KV minimum. Below this the cathode efficiency is very low because your tube is designed for about 70-90KV.

60KV is about right for in-animate objects. If radiation exposure is a concern for the object, then I would go up to about 80KV.

With the fluoro unit in question you will not even begin to stress the cathode at 60KV+. Check the tube to see if it has more than 1 focal spot. If it has a small focal spot then use this one for high detail, or magnification work. In other words you can get away with directly enlarging the image by having the receptor a ways away from the object, if you have a small focal spot tube.

For shielding 1/16 inch of lead is fine, at 80KV you need a little more like 2mm - 1/8". If the tube has sat for a while, run it at low KV like 30KV for a while, it will re-absorb liberated gasses just like an ion pump. Then it will handle the full rated KV. In medical fluoroscopy 60-70KV is used for bone work on hands and feet. For thicker parts like hips, and backs, around 80KV is used.

Also your tube has a glass output window so it will not need a lot of filtration. The purpose of filtration is to remove the soft X-rays which do not contribute to your image anyway. I would use about .5mm of Aluminum as a filter. I know that you are not doing people, but removing the soft X-rays will still help reduce the amount of scatter radiation. Aluminum flashing for roof work is close to .5mm, and can be cut with scissors.

One Tip: A housing with oil insulation is best. You do have to make room for the expansion of the oil from heat if you do this. A rubber diaphram at one end works great, and does a SS bellows. Clear PVC pipe also makes a great housing material, you can wrap it in lead, and leave a hole by the anode. The advantage is that you can view the filament with the Al filter removed, (With no HV applied) This can be very handy.

You can wire the X-ray tube two ways:

First is with the cathode at ground: Here you can only use 45KV max with this tube, because the 90KV rating is for 45KV+ and 45KV- which form the 90KV between them. With good insulation like oil you can push it to maybe 50-55KV safely this way.

Second and best is to apply both seperate anode and cathode HV, with an isolation transformer or a battery at the 30KV- cathode potential to run the filament. This way at 60KV you are only at 30KV above ground at any point, this makes the HV connections, and insulation much more simple, which is why they do it in the first place for almost any tube above 40KV. Dual VM's with one HF center tapped tranny, or an HF tranny with dual secondary coils are commonly used today.

Modern isolation filament tranny's look like a flyback with heavy wire, the same core is used, just with thicker wire on the bobbin.

Another insulation method is Teflon powder tapped, or vibrated in, so that voids are filled. For 60KV with 30KV+ and 30KV- this should work fine, at low average power like under .5ma where heat buildup is no big deal. Fireworks supply houses carry Teflon powder. Adding some large radius anticorona terminations at the ends of the tube help also. Modified small metal doorknobs are great for this.

I hope this helps, take care......Lutz :)

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