Energy dispersive X-ray fluorescence (EDXRF) - Experimental Physics

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different mines in the region as well as the tracing of mercantile and trade routes. 3 Proposed experimental work on coin archeometry using EDXRF The objective of the proposed experiment is to analyze and study the historical coins of the sub-continent that were minted in the region from approximately 200 BC to 1947 AD. For this purpose, a collaboration with the Lahore museum would be beneficial since these museums possess a treasure of coins which were minted and used during different historical periods. The X-ray spectroscopy of the coins can provide a good opportunity to understand the technology, political and economic history of different reigns and empires of the sub-continent. The hardware components used for self-assembled EDXRF spectrometer include an X-ray source, a Si X-ray detector and a radiation shielding box, all three mounted on a transportable unit. The data will be analyzed using a digital pulse processor and personal computer. The complete setup is shown in Figure 1. The X-rays possess an energy of 25 keV and are produced from a Ag anode. (a) 1 (b) 4 3 2 Figure 2: (a) The EDXRF hardware components including the X-ray generator and detector mounted on the base plate. 1: X-ray tube, 2: Si-detector, 3: sample holder and 4: radiation shielding. (b) Sample coin mounted on the sample holder. 3.1 Softwares for quantitative analysis 3.1.1 ADMCA 2.0: element identification software ADMCA 2.0 is a Windows-based software package that acquires and displays the spectral data and performs the necessary signal processing. Spectral analysis features include setting regions of interest (ROI) for the peaks obtained and element distinction on the basis of characteristic energies of the centroid for the respective 4
peak. A typical output from ADMCA is shown in Table 2 which contains a list of regions of interest, the corresponding centroid for each peak in terms of energy and the corresponding element. 3.1.2 XRS-FP concentration analysis software The ADMCA 2.0 has an active link to the XRS-FP software, which correlates the intensities of the characteristic X-ray lines to the elemental concentration. The concentrations are computed by the following processes. 1. A spectrum of a reference standard sample is acquired whose elemental concentrations are already known to us (for e.g., Steel 316, whose concentrations in weight percentage are given for Cr, Fe, Ni, Cu, Mn, Mo). Shown below in Table 1 is a list of the three available reference samples along with their compositions. Sample Samplecode Elemental composition Stainless steel SS-316 Cr, Fe, Ni, Cu, Mn, Mo Chromium Copper IARM-158B Cr, Ag, Al, Fe, Mn, Ni, Pb, Si, Sn, Zn, Cu, As, C, Co, Sb Silicon Brass 31XWSB7 Si, Zn, Cu, Al, Pb, Fe, Mn, Ni, P, Sb, Sn, As, Bi, Cd, Co, Cr Table 1: Reference samples used for calibration. The samples are acquired from Amptek [7] (SS-316) and Brammer [8] (IARM-158B, 31XWSB7). 2. The spectrum from the reference sample is loaded into the XRS-FP and all the elements present in the steel sample are defined and their respective known concentrations provided against them. 3. The spectrum is processed according to the steps presented in Figure 3 and then deconvoluted. The theoretical calibration coefficients (taking into the account the setup geometry and matrix effects) are then calculated by the software. 4. The calibration coefficients not only depend on the specific geometric parameters but also on how the intensity is related to concentration for each element in the reference sample. 5. The calibration coefficients thus obtained for the particular elements help determining the concentrations of the respective elements in any unknown sample. Table 2 and 3 present the data from the ADMCA and XRS-FP softwares for a standard steel-316. The spectrum is shown in Figure 4. 5
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Energy dispersive X-ray fluorescence (EDXRF) - Experimental Physics

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