is the X-ray fluorescence alloy analyser device expensive and high maintenance?
If so, could it get a lot cheaper if we restrict ourselves to the task proposed in the OP, i.e. just finding the traces of tungsten on a “yes-no” basis? Or is that not a real simplification given the mechanism of this measurement process on real life tungsten alloys?
Wouldn’t any method based on taking a sample need to core the coin? Otherwise you could take tungsten or a tungsten alloy and just coat it with pure gold.
Oh, and along the same line as the thermal conductivity, you could also use electrical conductivity.
does X-Ray fluorescence test involve a sample rather than just being able to stick the entire coin into the scanner?
Neutron activation analysis could easily determine every element in the alloys nondestructively.
from wikipedia:
if we could keep intensity of irradiation very low by trading off for low accuracy (we only want a yes-no answer, after all) that might not be a problem. But if there is a high threshold of irradiation for this to work on the most basic level, then we will end up with radioactive coins.
Another unpleasant thing about this is that the government might not allow people, or even companies, to have machines with radioactive emitters inside. The sort of people who try to prohibit laser pointers and even kitchen knives (in England) might not look kindly on this stuff.
It’s very likely that you have machines with radioactive emitters already inside your home:
Now, the type of radiation, and the strength of it, is another issue entirely… 
Not quite on topic, but in light of recent events, counterfeit Euro coinsmight be what need testing.
I think that you simply have to look at this as a positive thing. If all/many coins are radioactive, people will rush to spend them, which will increase the velocity of money. Win!
The one I linked to, which is the one I’m most familiar with and have used; you just place the nose piece against the item in question and pull the trigger. The results than appear on the screen.
Its REALLY easy to use, and it will give you quantitative answers to “how much” metal you have. They are routinely used to measure lead and other metal contaminations in paint, and toys. I think pretty much any metal is suitable for analysis.
For full disclosure, I have a remote professional interest in this device and could probably put you in touch with people who would be happy to answer your questions and even sell you one.
send me your contact info via PM here and I can put you in touch with the folks that make the device.
ok, so does this thing work as an “x ray” that examines the object as a whole, or is it just examining stuff on the surface? Could you cheat it by using a coin with gold on the outside and tungsten on the inside? Or is there some particular magic coin width that we would need to use to make sure that the coin gets scanned in entirety, either from one side or else with two separate scans, one for each side?
There is a certain “penetration depth” for the sample, but I don’t know what that is. I don’t think it will be an issue with coins though. I’m going to make an educated guess that the penetration depth is several mm’s but maybe not a full centimeter.
Again, I’m absolutely sure I can put you in touch with someone intimate with making and selling this particular device; and they can answer your questions much more rapidly and more accurately than I can…they might even be able to do a demonstration for you
Here are some youtube links to the XRF…
Sigene, I figure that people here at SD are more likely to be interested in answering inquisitive questions of a freelance programmer and inventor like myself than the salesmen of the company you mention. Getting answers out of busy professionals usually requires a fancier job title than what I have nowadays.
Incidentally, so why do you think these guys haven’t yet started advertising over at Glenn Beck’s show? Is this thingie (or a possible lower end derivative aimed just at tungsten detection) just too expensive for that potential market?
Is this a real question? These guys aren’t marketing it as fake tungsten coin detector because that’s not a problem that exists and there are several trivially easy ways to tell a tungsten coin from a gold one.
XRF makes sense, but can we be a bit destructive and use a LIBS? Plasmas and lasers are cooler, after all.
what are the several? So far we have identified only one hypothetical simple way involving listening to the coin jingle. Whether or not this will actually work correctly on tungsten alloys that can be used in fake coins is still an open question for empirical research.
Have I missed any other trivial methods here?
In terms of whether or not there is the fake coins problem in the first place, well, it wouldn’t be too hard to create such, right? If somebody wanted to do economic warfare against people who watch Glenn Beck, wouldn’t the somebody eventually try that? You don’t have to agree with people’s worldviews, but people do spend money based on them.
I’ve suspected the stories about the fake coins were coming from that crowd marketing the gold. The thread I linked to initially was an offshoot from some CT about gold-missing-from-ft.-knox.
Then again, the demographic we’re talking about fooling probably wouldn’t think to check the density, either. So why bother with tungsten? Lead’s a lot cheaper.
what stories? Have you already heard stories of fake tungsten coins? I started the OP based on the hypothetical threat of such, not based on actual rumors of this already happening.
What TriPolar referenced, I believe, is about claims of tungsten “gold” ingots owned by the government or banks or something like that. I.e. it is an issue completely unrelated to people’s holding of gold. Just another one of “hee hee, the government is soo broke” info tidbits. Well, plus minus a ton of gold will not make this government any more or less broke, if you ask me.
so you think that density checking is too hard using off the shelf equipment? Then maybe you should start selling an “compute the density and check for tungsten traces in 10 easy steps” kit?
It’s not too hard; it’s just that most people wouldn’t have the critical thinking facilities for it to even occur to them.