[Rockhounds] DIY XRD?
Jim Murowchick
murowchickj at umkc.edu
Thu Oct 23 14:26:16 PDT 2008
Aside form some of the obvious practical problems of setting up a
diffractometer using tape X rays as a source, I have a feeling that it still
wouldn't be very useful for mineral ID. The Xrays produced are probably
very low energy/long wavelength, and might not be suitable for diffraction
by mineral structures. For most XRD, we use Cu K alpha radiation (1.5405Å),
and tubes using Cr, Co, Fe, or Mo are also used, with Mo having the shortest
wavelength (0.709Å) and Cr the longest (2.2897Å). These are effective in
diffraction because they have wavelengths comparable to the spacing between
planes in the crystal structures of minerals. If the tape X rays are
generated by electron transitions in carbon atoms, or something similar, the
wavelengths are much longer (45Å for C, 23.6Å for oxygen). The result on a
typical powder diffractogram would be that the peaks would appear at very
high 2-theta angles, if at all, and much of the pattern would not be
recordable by a typical goniometer.
Jim
Dr. James B. Murowchick
Associate Professor, Geology
Department of Geosciences, 420 Flarsheim Hall
5110 Rockhill Rd., Kansas City, MO 64110
816 235-2979 Fax: 816 235-5535
murowchickj at umkc.edu
On 10/23/08 11:30 AM, "Hans Durstling" <siniconb at gmail.com> wrote:
> Kitchen-table affordable Xrays should be no problem at all. Back in
> the days when people still tinkered and I could buy nitric acid at the
> corner drug store I remember reading in one of the scientific hobby
> publications that certain early radio tubes were a generous source of
> incidental Xrays and could be modified to make them much more so. Or
> given even rudimentary glass blowing ability and access to a good
> vacuum pump you should be able to make your own tube. Then all you'd
> need is a high voltage DC power supply which likely could be scavenged
> from a television, a computer or some other domestic device, thus
> leaving the bulk of the budget for lead and concrete; you wouldn't
> want to skimp on that.
>
> Cheers,
> Hans Durstling
> Moncton, Canada
> typing two handed again, broken arm mending
>
>
>
>
>
> On 10/23/08, J Bryan Kramer <codeburner at gmail.com> wrote:
>> It has been known for a year or two that lightning not only produces X-Rays
>> it produces Gamma.
>>
>> <http://cat.inist.fr/?aModele=afficheN&cpsidt=15675313>
>>
>> <http://news.ufl.edu/2003/01/30/lightxray/>
>>
>> <http://news.nationalgeographic.com/news/2007/10/071011-lightning-rays.html>
>>
>>
>> BK
>>
>>
>> On Thu, Oct 23, 2008 at 09:55, <Pmodreski at aol.com> wrote:
>>
>>> Ah, yes, now, let's not throw too much cold water on Kreigh's cool idea.
>>> Who knows, "in theory" it might work, but in practice... yeah, the amount
>>> of
>>> X-rays produced are probably very miniscule, and although in theory one
>>> might
>>> filter out just one wavelength of X-rays, in practice what one is starting
>>> with is probably too spread over a range of X-ray wavelengths, to be
>>> useful.
>>> And the X-rays are probably emitted in all directions, not focused
>>> geometrically at all, so by the time one collimated just the ones traveling
>>> in a
>>> particular direction toward the sample, one would again lose 99% of the
>>> tiny amount
>>> that had been produced... There was also the caveat in the story, that
>>> the
>>> X-rays were only detectable when the experiment was done in a vacuum
>>> chamber.
>>>
>>> I wonder, if a miniscule amount of X-rays are produced in any electrical
>>> discharge, where high-voltage electrons are hitting something; as in a
>>> lightning
>>> bolt, or even, in a static electricity discharge when you shuffle across
>>> the
>>> rug and touch your finger to something metal? Seems like that and the
>>> Scotch
>>> Tape, are just different versions of the same thing. That would be even
>>> the simpler way to generate the X-rays for Kreigh's homemade
>>> mini-diffractometer!
>>>
>>> Cheers, and keep at it, Kreigh,
>>> Pete
>>>
>>>
>>> In a message dated 10/22/2008 7:49:23 P.M. Mountain Daylight Time,
>>> Kreigh at tomaszewski.net writes:
>>>
>>> Bryan,
>>>
>>> The Bragg Equation requires the wavelength. Coherent x-rays from an
>>> incoherent source are fairly easy to produce using a small aperture
>>> monochromator. That problem was solved about a hundred years ago.
>>>
>>> I agree that the real problem is the energy. There has to be enough at
>>> some wavelength to produce a detectable beam out of the filtered
>>> source. I assume there is enough since they were able to x-ray a
>>> finger, but it might require a slower scan than a commercial unit; it
>>> is easy to make x-ray detection cumulative.
>>>
>>> How long will a roll of tape last? How many times can it be reused? I
>>> would be really happy to be able to get an analysis for the cost of a
>>> roll of tape.
>>>
>>> Kreigh
>>>
>>>
>>>
>>>
>>> On Wednesday, Oct 22, 2008, at 20:58 America/Detroit, J Bryan Kramer
>>> wrote:
>>>
>>>> Doesn't x-ray energy/wavelength make a difference for x-ray
>>>> diffraction? I
>>>> read that scotch tape article and it didn't sound like you could
>>>> control
>>>> much beyond being able to produce some sort of x-rays in bursts.
>>>>
>>>> BK
>>>>
>>>> On Wed, Oct 22, 2008 at 20:44, Kreigh Tomaszewski
>>>> <Kreigh at tomaszewski.net>wrote:
>>>>
>>>>> I've often wished I could move a lab into my basement and do x-ray
>>>>> analysis
>>>>> of minerals, but cost makes it just a dream.
>>>>>
>>>>> Now it has been discovered that unrolling scotch take in a vacuum
>>>>> produces
>>>>> x-rays.
>>>>>
>>>>> http://news.yahoo.com/s/ap/20081022/ap_on_sc/sci_scotch_tape_surprise
>>>>>
>>>>> Using a roll of tape, a small motor to unwind it, and a vacuum pump,
>>>>> to
>>>>> produce a source of x-rays turns the dream into a possible do it
>>>>> yourself
>>>>> project.
>>>>>
>>>>> The database for comparison against known minerals is available at
>>>>> places
>>>>> such as http://rruff.geo.arizona.edu/AMS/amcsd.php. The rest of the
>>>>> details are relatively trivial once you have a source of x-rays.
>>>>>
>>>>> http://productsearch.machinedesign.com/mdproducts/x_ray_diffraction
>>>>>
>>>>> Anybody interested in a science project?
>>>>>
>>>>> Kreigh
>>>>>
>>>>>
>>>>> --
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>>>>
>>>>
>>>>
>>>> --
>>>>
>>>>
>>>> "The thunderbolt falls on an inch of ground; but the light of it fills
>>>> the
>>>> horizon."
>>>>
>>>> Ralph Waldo Emerson
>>>>
>>>> J Bryan Krämer
>>>> North Florida, USA
>>>> photos at:
>>>> http://pbase.com/photoburner
>>>>
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>>
>>
>>
>> --
>>
>>
>> "The thunderbolt falls on an inch of ground; but the light of it fills the
>> horizon."
>>
>> Ralph Waldo Emerson
>>
>> J Bryan Krämer
>> North Florida, USA
>> photos at:
>> http://pbase.com/photoburner
>>
>>
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