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Grenadier's big thread of RÃ¶ntgen related shenanigans

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LAN_403

Arcstarter

Wed Nov 03 2010, 01:49AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

I have been thinking about buying a lead ingot and casting a few sheets for X-ray shielding. But, it costs 16 dollars for one ingot, so i will have to use some steel as shielding as well. But ill need like 4 times as much of that

Adam Munich

Wed Nov 03 2010, 02:06AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Two words; Wheel weights. I got about 100lbs of free lead just by asking the auto shops around here. It's 4% antimony so it's quite hard, but still pourable.

Just plop them all in a big pot and put it on a propane burner set to medium. Since most of the weights will be covered in plastic, it will smoke something mean. Cover the pot. After about two hours everything will be melted and the smoke will die down, then you can pour it into muffin tins. I have a box of 120 lead mini-muffins next to my TV, and it's likely going to stay there (heavy!)

Proud Mary

Wed Nov 03 2010, 10:44AM

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

I've found the Medi-Ray products catalogue inspirational when giving old lead shielding a makeover to get the bright new look of today.

MarShield do a range of custom designs for their lead aprons, so no one need worry about being caught on the hop by shielding colours clashing with a new outfit:

1288782906 543 FT0 Marshield Lead Apron Covers

Adam Munich

Thu Nov 04 2010, 03:44AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Alright another update. Things are taking a little longer then expected because I only have enough clay to make one side at a time. I also got distracted with carbon arc lamps.

I've decided to take pictures of every step and make a stop motion build video at the end. Kind of like this. (I'd give anything for that helmet)

All hardened.

Came out pretty easily.

Good thing I used clay.

Uh oh, too wet.

This should fix that.

And it did.

More template cutting.

Perfect!

More clay rolling.

Cut cut.

Decided to not waste so much plaster this time.

All dry.

Came out very easily.

Too wet...

Not too big of a problem.

I should start casting lead by Saturday. I also looked at that medi-ray stuff, and I had no idea lead could be machined so nicely. Too bad I don't have a CNC or a lathe.

Proud Mary

Thu Nov 04 2010, 11:29AM

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

Grenadier wrote ...

I also looked at that medi-ray stuff, and I had no idea lead could be machined so nicely. Too bad I don't have a CNC or a lathe.

If you can find two cheap stainless steel kitchen food containers/canisters, one of which nests inside the other, you can use them to cast very good cylinders - as one needs with transmission target tubes, both for shielding and as an oil cooling jacket. Securing the smaller container inside the larger with steel standoffs, or bolts, you can pour in the molten lead and leave it to solidify without having to extract it from a mold. The outer stainless steel canister makes an excellent surface for dayglo orange epoxy enamel, and seals the lead securely from contact and interaction with the environment.

If the design is well thought through, the original screws or bolts used to hold the canisters apart can also be used to mount the cylinder. These also help to stop the lead rattling loose, as there is a small shrinkage as the Pb changes phase.

As a note of caution, some stainless steel food canisters also contain plastics, and these are useless for our purpose.

Lead shot and casting resins can also be used to mold bespoke shielding parts with an excellent finish and professional appearance.

I am presently working up the design of my first X-ray spectrometer, and will start a projects thread about it in the next few weeks, so interested parties will be able to see my shielding methods for themselves.

Adam Munich

Thu Nov 04 2010, 07:51PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

That sounds pretty easy to do, but it would be a cylinder, and cylinders make poor use of space inside a square box. I picked a prism because there will be a lot of extra space, and extra space means more oil. More oil means more thermal mass and thus more heat capacity. I might put a thermometer in there too, since I would have no idea how hot things are getting inside.

Since I plan on sealing the lead box I may just use the PCB oil that came with the head. It has a high thermal capacity, a relatively high boiling point compared to vegetable oil smoke points, and it is non-flammable. Not only that, it won't degrade like vegetable oils will. Plus it's light. Wow, I can see why the manufactures loved this stuff.

As for your x-ray spectrometer, how are you going to differentiate between the energies?

Proud Mary

Thu Nov 04 2010, 09:10PM

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

Grenadier wrote ...

As for your x-ray spectrometer, how are you going to differentiate between the energies?

I've had for some time a range of new sealed proportional counter tubes covering ~1.5keV to 50keV - and the transmission target tubes to match - but my attempts to find a multichannel pulse amplitude analyser at an affordable price had so far met without success.

I was browsing through October's abstracts a few weeks ago, when I chanced upon the following:

Nakaye, Y. Kawai, J. Recording X-ray spectra with an audio digitizer X-Ray Spectrometry, Volume 39, Issue 5, 318â€“320, September/October 2010

X-ray spectra were recorded with a notebook computer and analyzed by software on the computer, without a pulse height analyzer (PHA) or a digital signal processor (DSP). An audio (microphone or line) input on a personal computer has a built-in analogue-to-digital converter (ADC) for digital audio recording. The output signal of the X-ray detector is recorded through the audio input of the computer and then analyzed by software on the computer. On the basis of this method, X-rays from a radium source were measured with a cadmium telluride detector. K X-rays of bismuth were detected. Full width at half maximum (FWHM) was 5.6 keV at KÎ± of bismuth (77.1 keV), enough to separate KÎ² (87.3 keV) from KÎ± of bismuth. The present method achieved almost equal energy resolution as that of the regular method (5.3 keV FWHM at 77.1 keV).

I'd been worrying away at a similar solution to the problem for the last year - I'd imagined a V-F converter plugged into the audio card and a waterfall spectrum display - so the Japanese paper confirmed what I already knew: that I had all the parts, tools, and know-how to build an X-ray spectrometer, and that it wouldn't be a dead end project, but would naturally lead on to more experiments and a greater understanding of soft X-rays, where all the exciting research is happening nowadays - in my view at least.

Adam Munich

Thu Nov 04 2010, 10:41PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Proud Mary wrote ...

but my attempts to find a multichannel pulse amplitude analyser at an affordable price had so far met without success.

Hmm... What about using an arduino for data logging? At 16 something megahertz the clock is fast enough, and you can use some analog to digital converters to harvest the data. Maxim has a 1wire chip that can harvest four 16 bit analog channels, and if you use ten inputs on an arduino that's 40 channels.

Proud Mary

Thu Nov 04 2010, 11:16PM

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

Grenadier wrote ...

Proud Mary wrote ...

but my attempts to find a multichannel pulse amplitude analyser at an affordable price had so far met without success.

Designing and making the spectrometer hardware to a good standard places me already right at the very edge of my modest abilities, so I'll just stick with Nakaye's peer-reviewed paper for the pulse amplitude spectrum analysis for the time being, though I may condition the pulses as a second step once I have some signals to analyse. Anyway, I'll be starting a project thread about it when I can find the time to build and photograph each stage in a way that others might find interesting or helpful.

Adam Munich

Fri Nov 12 2010, 06:15AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Moar progress;

Third mold's done.

Sanding things nice and smooth.
Is it level?
[link]
Mmm... Muffins.
Nothing like some coffee warm things up.
Level things off with some pennies.
Mercury switches make great levels.
Plumbum falls.
Crap I, there is some bubbling and a hairline crack.
I'll have some more lead in my cheese plz.
Bake at 350, maybe this will drive out the water.
Crap II, something broke.
That's nothing a little tape can't fix.
When the lead oxidizes it's ready to pour.
Attempt 5. Yes 5. Turns out the large piece of plaster is really hydroscopic. After 5 pours all the water has been driven out and things work great. This really makes a quick task a long one though.
After that the mold has seen some better days, and has also changed color.
Repeat that 2x.
Visitor.
Casting the 14x11
Casting the 14x20
All the pieces. Due to my poor measurement, they're all around 9mm thick. Oh well, extra protection.
They all line up quite nicely. A few need to be bent a little bit, but soldering shouldn't be very hard to do.
25 lbs.. Not too bad actually.

So next up is soldering. Not sure how I'm going to do that, may have to borrow a 100w solder gun from someone. I'm going to hate to drill an aperature hole in this box, but it'd be useless without one. I also wonder how I'm going to drill a 1.5" hole in hard lead. Maybe I'll have my school's tech dept CNC one.

Since this sheild is really hefty, it should be good all the way up to 120kVp. I have no reason to go that high though.

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