Proton induced X-ray analysis of Nd:YAG

Abstract

Proton induced X-ray emission (PIXE) is famously effective for revealing trace elements in biological tissue in which the majority elements (H, C, N and O) have low Z. When the majority elements in a compound have high atomic numbers, the yield of K and L X-rays following proton bombardment often mask those of lighter trace elements, or dominate the counting rate to such an extent that the time required to detect a small signal with statistical significance becomes prohibitively long. We have confronted these difficulties with a PIXE analysis of YAG crystals and ceramics with neodymium doping up to nine atomic percent. The K X-rays of aluminum (1.74keV) and yttrium (15keV) dominate the PIXE spectrum. The L X-rays from neodymium group near 5keV provide determination of the neodymium content of Nd:YAG to 1:1000. Clear signals of traces of zinc, nickel and copper were recovered from the spectra of some of the samples by persistent experiments at low counting rates that avoided pile up of the signals from the majority elements. An appropriate polyethylene filter was used to prevent scattered protons from striking the detector and its supporting structure. Double proton beam collimation prevented spurious PIXE from the chamber walls, beam stop and the primary collimator. No material was near the sample except a polyethylene film strip that supported the sample.