THIN-FILM XRF SAMPLE CUP WINDOWS

A thin-film window is defined as a substance that is used to retain powdered, liquid, slurry or other types of samples in sample cups for x-ray spectrochemical analysis. To qualify for suitability, the substance must possess specific characteristics: reasonable degrees of chemical attack resistance; sample retention strength; uniformity of thickness; relative freedom of influential trace element impurities; multi-axial to minimize preferred orientation; and relatively high analyte-line transmission values, especially for the less energetic (KeV) or longer wavelengths (Å). The combination of density, gauge and mass attenuation coefficients are the principle factors controlling analyte-line transmission in accordance with Lambert's Law:

I/Io = exp [-(µ/d)(dt)]: Where, I/Io = percent incident and transmitted radiation

Few substances are characterized with all of these properties and explain why there is such a diversity of thin-film windows. All window materials tend to have varying degrees of static electricity. It presents the most troublesome in handling for attachment to sample cups and any clippings from trimming the excess material tend to annoyingly adhere to any nearby objects. The exception is a thin-film integrated in SpectroMembrane Carrier Frames. The most suitable thin-film windows for x-ray applications are: Polyester, Prolene®, Polypropylene, Polyimide (Kapton®), Mylar® and Etnom™ Thin-Films.

Typical Properties of Thin-Film Windows

THIN-FILM TYPE	TYPICAL UNIFORMITY	TRACE IMPURITY LEVEL, PPM	DENSITY, GM/CC	STRUCTURAL FORMULA
Mylar®, Hostaphan®, Polyester	1 - 2% per package; less than 5% between different lots	Ca, P, Sb, Fe, Zn	1.38	C₁₀H₈O₄
Prolene®, Polypropylene		Ca, P, Fe, Cu, Zr, Ti, Al	0.91	C₃H₆
Etnom^TM		Si, Ca, P, Zn, Sb	1.36	C₁₄H₁₀O₄
Polyimide (Kapton®)		None reported of significant value	1.42	C₂₀H₁₀O₅N₂

CONTINUOUS ROLLS

Thin-film Windows in rolls are the most economical. Each roll is 3" x 300' (7.6 cm x 91.4 m) and contained in a serrated edged box. The necessary length is pulled out and cut against the serrated cutting edge. Trimming is generally required after sample cup attachment. Each roll serves approximately 1200 sample preparations depending upon sample cup dimensions and practice.

PRE-CUT CIRCLES

Moderately priced pre-cut Windows are 2.5" (6.4 cm) in diameter and packaged 500 and 1000 circles per box. Each circle is supported on individual carrier papers for ease of handling and to minimize contamination. Depending upon sample cup size and practice, minimizes or eliminates trimming excess material with a scissors.

PRE-MOUNTED SPECTROMEMBRANE® WINDOW FRAMES

This is the ultimate in Thin-Film Window attachment convenience. Perforated Windows are pre-mounted on carrier frames that completely eliminate direct handling, contamination and static electricity annoyances. During attachment, they automatically detach from the frames. No experience necessary. The windows are available in 3" (76.2 mm) or 2.5" (63.5 mm) diameters for close accommodation by both small and large diameter sample cups.