Our conservation department here has one of these, and I've made some
use of it. There are two types - the genuinely portable ones with
radioactive sources for excitation, and the semiportable types that
have a miniature x-ray tube and need to be plugged in to the mains or a
portable power supply. The one I've used has the radioactive source,
and I doubt that I would bother to buy one if I had $25,000 lying
around, which I don't. All handheld XRFs have an air gap between sample
and detector that absorbs weak x-rays, and thus can't detect anything
of lower atomic number than sodium, but there are additional
limitations with radioactive sources. None of them cover the whole
range of elements that I would want in analyzing slags, so one would
have to change sources to get a full listing of elements in the sample.
(The americium source is the most common, and will only give you
elements with atomic numbers from titanium up; from titanium down the
iron sources is used. The sources only last a few years, and are very
expensive to replace. Being radioactive, they are also a real pain as
far as permits are concerned - perhaps not a concern if only used in
Britain, but taking one abroad would require all sorts of permits.
Our conservation department make a lot of use of this instrument in
collections management - for example, it's a quick way of finding out
if older biological specimens have been conserved with arsenic. But I
frankly would not spend such a large amount for an instrument to be
used in the field. You can put together a little collection of field
tools for archaeometallurgy - an acid bottle, a charcoal block and
blowpipe, a short length of platinum wire, a few chemicals, a miniature
propane torch, a scratch plate, a magnet, a hand lens, a small short-
and long-wave UV lamp, and a copy of an old text (pre-1960's) on
determinative mineralogy (to tell you how to make effective use of the
first four items listed) for about $250. These will identify the major
elements in most samples that you will encounter in the field at
minimal cost.
Dave Killick
On Sep 16, 2005, at 4:38 PM, Evelyne Godfrey wrote:
> Dear All,
>
> I seem to recall messages about portable handheld XRF meters on this
> List
> some time ago... could someone remind me of what the bottom line was,
> in
> terms of cost, usefulness, whether there was one type more recommended
> than
> another? We're analysing archaeological and museum artefacts, and
> historic
> architectural samples of different materials, although primarily metal.
>
> Cheers,
> Evelyne
>
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