[Rockhounds] DIY XRD?
Jim Murowchick
murowchickj at umkc.edu
Thu Oct 23 14:35:10 PDT 2008
Another thought--the low energy Xrays are absorbed by air, so the work has
been done in a vacuum. But we can use helium instead of air to reduce
absorption of the low energy X rays in X-ray fluorescence. Perhaps filling
the chamber with helium at 1 atmosphere pressure might reduce absorption.
Jim
On 10/23/08 4:26 PM, "Jim Murowchick" <murowchickj at umkc.edu> wrote:
> 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
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>>>>>
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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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