Use of lead-glass capillaries for micro-focusing of highly-energetic (0–60 keV) synchrotron radiation† K. Janssensa, L. Vinczea, B. Vekemansa, F. Adamsa, M. Hallerb and A. Kno ¨chelb aDepartment of Chemistry, University of Antwerp (UIA), B-2610 Antwerp, Belgium bInstitut fu ¨r Anorganische und Analytische Chemie, Universita ¨t Hamburg, D-20146, Germany The performance of ellipsoidally shaped lead-glass capillaries Labor, DORIS storage ring, Hamburg, Germany),10 is shown in Fig. 1. The DORIS ring is a second generation synchrotron for focusing the polychromatic synchrotron beam produced by a bending magnet of the DORIS positron storage ring and the radiation used at Beamline L is produced by a bending magnet, yielding the primary energy distribution shown in (Hasylab, Hamburg, Germany) is discussed. The size, intensity and energy distribution of the focused beam produced Fig. 2. Compared with the situation at NSLS (National Synchrotron Light Source, Brookhaven National Laboratories, by such capillaries are compared with those of beams generated by means of straight borosilicate capillaries, NY, USA), where a similar m-XRF instrument is installed at Beamline X26A,9 the much more energetic nature of the white indicating that beam sizes of ca. 4 mm at the sample surface can be obtained with a total flux density that is ca. ten times spectrum available at the Hasylab beamline is evident from Fig. 2, making it possible to use the K lines of heavy elements higher than when a collimated beam is employed. Synchrotron radiation with energies up to 60 keV is focused, leaving the in trace level XRF analysis (see, e.g., ref. 11). In Fig. 1, the use of a straight glass capillary tube for beam collimation is original energy distribution of the white synchrotron beam virtually unchanged. The analytical characteristics of the indicated. The devices represent a simple and inexpensive way of generating an X-ray microbeam down to 10–20 mm in m-XRF set-up at Beamline L of Hasylab, when equipped with a lead-glass capillary, were investigated by means of NIST diameter; however, they do not focus the beam in the sense that they cause the flux density to increase. The operating SRMs and indicate that interference-free absolute/relative detection limits in the 1–10 fg/0.8–2 ppm range are achievable principle of X-ray capillary tubes is explained in detail else- where.12,13 Usually, borosilicate glass is employed for capillary from 100 mm silicate-type samples for the elements from Mn (Z=25) to Gd (Z=64) using their Ka lines within 1000 s manufacture.13–18 As a result of multiple total reflections of the X-ray photons on the inner walls of the capillary tube [see counting time. Elemental yields are situated in the 10–100 counts s-1 per 100 mA per (mg cm-2 ) range. As illustrations of the type of investigations these highly energetic, micrometre- sized beams make possible, the two-dimensional mapping of the distribution of REEs (rare earth elements) and other heavy elements in geological igneous rock samples and the three- dimensional non-destructive analysis of heavy metals (such as V, Fe, Ni and Mo) in individual fly-ash particles by means of fluorescence microtomography are briefly described. Keywords: X-ray fluorescence analysis; microscopic X-ray fluorescence analysis; synchrotron radiation; X-ray capillaries; micro-analysis; fluorescence tomography; three-dimensional analysis; rare earth elements; fly-ash; heavy metals Fig. 1 Schematic diagram of the m-XRF spectrometer installed at Beamline L of Hasylab (Hamburg, Germany). Instead of using a broad cone of radiation which conventionally is produced in an X-ray tube, microscopic XRF makes use of collimated or focused microbeams of energetic photons to induce the emission of characteristic radiation in a microscopic spot on (or immediately below) the surface of a material under investigation. Refs. 1–3 present reviews of the technique. Microscopic XRF analysis can be performed using both ( high- end) laboratory sources4 and synchrotron radiation (SR) sources.5 With respect to the SR-based instrumentation, in general, a distinction can be made between on the one hand set-ups that employ monochromatic microbeams, usually incorporating elaborate X-ray optics in order to focus the primary beam, 6–8 and on the other hand instruments that make use of a polychromatic beam to excite the sample.9,10 The latter instruments usually are of simpler design as the high intensity of the SR and the fact that the entire energy spectrum of the original beam is used for sample excitation allow simple collimation of the primary beam down to ca. Fig. 2 Primary energy distribution [in photons s-1 0.1% energy 10 mm diameter.9 A schematic diagram of such a set-up, band width (BW)-1 ] of the white synchrotron beam produced by installed at Beamline L of Hasylab (Hamburger Synchrotron bending magnets of the NSLS (National Synchrotron Light Source, Brookhaven National Laboratories, NY, USA) and DORIS-III ( Hasylab, Hamburg, Germany) storage rings as seen through a † Presented at the XXX Colloquium Spectroscopicum Internationale (CSI), Melbourne, Australia, September 21–26, 1997. 10×10 mm2 pinhole at a distance d from the ring. Journal of Analytical Atomic Spectrometry, May 1998, Vol. 13 (339–350) 339