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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Conundrum wrote ...
(waitasec, doesen't carbon also add artefacts?)
Yes it does. But remember Mosely's discovery that when the square root of the frequency of the characteristic x-rays of an element is plotted against the atomic number, it will produce a straight line on your graph.
Carbon has six protons so its atomic number is 6.
Entering this figure into the handy calculator called Moseley's Modeling of X-ray Frequencies here:
and we find that the quantum energy of carbon's K-alpha emission is 0.255106875keV and its wavelength is 4.860080701470706nm.
Outside a well-equipped laboratory, it would be difficult to detect such feeble rays - both the source and the detector would have to be contained in a vacuum, because even the shortest journey through atmospheric air would stop them.
I have some proportional counter tubes with Be windows that will go down to 4keV on a good day, and some PIN photodiodes (BPX65) that can manage about 2keV if you take the lens out, but the carbon characteristic rays are so feeble that I can discount them altogether in my school of rough and ready science.
By contrast here are the characteristic X-ray spectra for Ni and Ag
And you can see from the Ag spectrum why silver is often used as a target in X-ray tubes - because of the powerful emission around 22keV, where it is penetrating enough to be useful, and sufficiently salient for it to be considered almost monochromatic if you have just 23 or 24kV on the anode.
Registered Member #2413
Joined: Sat Oct 03 2009, 08:27PM
Location: Essex, UK
Posts: 22
As far as I know they don't make higher voltage supercaps because the only way to make them go to 5V is by stacking 4 or 5 in series; any more than about a volt and a bit and the electrolyte breaks down right? So to make them high voltage, you'd need to stick a truckload in series, with lots of wasted space...
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059
the other way is to build multiple supercaps with inverse polarities (same sort of idea as a peltier module) in the same casing. so 4 1000F (doable) in series would give you 125F at 10V
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Home made super capacitors.
