Agreeing with David Starley and David Killick,
New machines are now on the market and all three major companies,
NITON, InnoveX
and Oxford Instruments have x-ray tube versions. It is true that they tend to
come with an Ag target, making Ag difficult to identity in small quantities,
but the target can be changed to a Rh one. The cautions that David Killick
mentioned are still appropriate. They can truly only measure elements above
Ti, but they are quite accurate. I have tested all three against EPMA
data and
been very pleased with the results (this includes high purity silver
and various
copper alloys). There is talk of a vacuum attachment that can allow for
detection of lighter elements (company called KeyMaster sells one now)
but I am
unclear how they will get around variable pressure issues.
Aaron Shugar
Quoting David Starley <[log in to unmask]>:
> Just to add to david's note. The technology has moved on somewhat and
> several firms now market truely hand-held XRF instruments using an
> X-ray tube and running off rechargable batteries. I've tested a
> couple of these and was impressed - For example, getting a visible
> the mercury "shoulder" on the Au peak for traces of firegilding on
> armour - something that our old Kevex instrument struggled with. Of
> course the usual cautions about air gaps and unprepared surfaces
> apply and the area of excitation is large at c 1cm dia (this can be
> reduced with colimators but with major reduction in counts and a
> difficulty in targetting small areas of interest). Another possible
> problem is that I believe they use an Ag target and I don't know how
> reliably this silver in the material under investigation can be
> quantified.
>
> Dave
>
>
> David Starley PhD
> Science Officer
>
> Royal Armouries Museum
> Conservation Department
> Armouries Drive
> Leeds LS10 1LT
> United Kingdom
>
> Tel. 0044 (0)113 220 1919
> Fax 0044 (0)113 220 1917
>
>
> -----Original Message-----
> From: Arch-Metals Group [mailto:[log in to unmask]]On Behalf Of
> david killick
> Sent: 17 September 2005 18:35
> To: [log in to unmask]
> Subject: Re: Handheld XRF
>
>
> 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
>>
>
>
> The statements and opinions expressed here do not necessarily
> represent those of Royal Armouries museum. This message is sent in
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>
--
Dr. Aaron Shugar
Archaeometallurgy Laboratory
Lehigh University
5 East Packer Ave
Bethlehem, PA
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