X‐Ray fluorescence analysis of five heavy elements (Pb, Pt, W, Sn, and Ag) was performed using the portable synchrotron MIRRORCLE‐20. The characteristic K X‐rays (K&agr; and K&bgr;) were clearly observed for all of the five samples. This verifies that MRRORCLE‐20 generates X‐rays of energy higher than that of the Pb K absorption edge (88.0 keV). In addition to these characteristic K X‐rays, several peaks with short lifetimes were also observed in all the samples. © 2004 American Institute of Physics