A nice tutorial link on the subject:
and another from Bruker, the XRF gun folks:
essentially saying the same things, the first probably written by a tech the second by a sales person.
From the first link this is what I needed to know, condensed down:
To see an element, you must send in at least 2 keV more of energy to see that element.
Source Filter: Allows you to focus on key elemental ranges to identify elements at detection limits
The green filter is composed of 150 ¦Ìm (6mil) Cu, 25 ¦Ìm (1mil) Ti, and 300 ¦Ìm (12mil) Al. The green filter sees the optimization in a higher energy range, from 13 - 17 keV (Th, Rb, U, Sr, Y, Zr, Nb, Mo). Use 40kVp @30uA
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The red filter uses 25 ¦Ìm(1mil) Cu, 25 ¦Ìm (1mil) Ti, and 300 ¦Ìm (12mil) Al - with the red filter we end up with a zone of about 9 - 12 keV were there is an ideal signal to background ratio for elements (Pb, Hg As, Br, Au). Use 40kVp @30uA
The black filter (250 ¦Ìm Cu/25 ¦Ìm Ti/300 ¦Ìm Al). You can see much higher peaks for the heaviest elements (Ba, La, ?Ce).?Use 40kVp @30uA or 45kVp @30ua for K¡¯s from La+Ce
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The above are the K-Edge type filters, utilizing the abrupt change in X-Ray absorption at the K (or L) edge of an element. Each element is different. These are effective and don/t require much in the area of exciter power. FYI what I'm doing with Cd and Al etc. metals is different and requires more power (or longer count times). The Cd for example is more of a secondary-target system with a built in attenuator. I like to think of it simply as a wavelength shifter.
Both obviously work, in different ways.
Geo
