Desenvolvimento de um sistema portátil de macro XRF que utiliza aprendizado de máquina para reconhecimento de padrões de cores em pigmentos usados na área de Arqueometria

Abstract

Lately, research centers and universities have been developing portable XRF systems, motivated by simplicity in assembly and ease in obtaining the associated technology with this technique. There is a wide application variety for portable XRF systems, however, the Archeometry area is the most promising, because of its non-invasive portable systems available to conduct studies in museums. Usually, the displacement to a laboratory is somewhat complicated by several factors (space, security, etc.). The MA-XRF equipment type available on the commercial market, which is labeled as portable, is not suitable for researchers. They often need more information, beyond data collection, and the usual equipments can hardly be modified for general purposes. Thus, this work aims to develop and validate a low-cost, portable, automated, MA-XRF equipment that uses a learning color identification in a given cultural heritage that correlates colors and their positions. Researchers need to be able to measure specific spots in an automated way with XRF. In the XRF system, a low-power X-ray tube (Au anode, 40 kV, 200 μA) and an SDD type detector with a PX5 digital pulse processor are used, which are coupled to a Z focal adjustment stage concerning sample, a horizontal movement stage (X-axis), a vertical movement stage (Y-axis) and a control center managed by a Raspberry Pi microcomputer. The system characterization consists of repeatability and reproducibility tests, determinating spatial resolution and system alignment. In the applicability demonstration, measurements were taken in samples at Laboratório de Instrumentação Eletrônica e Técnicas Analíticas (LIETA) (a painting by an unknown artist, wooden crafts of Brazil's northeast, modern Portuguese tiles and a ceramic piece from the Chancay culture/ Peru) and at the Imperial Museum, Petrópolis-RJ, (painting parts from “Battle of Campo Grande” by Pedro Américo and Emperor D. Pedro II's imperial carriage parts). For the Imperial Museum measurements, it was necessary to change the X-ray tube, quickly and easily, to one with an Ag anode. From the generated spectra, the elementary distribution maps for each sample were obtained. The final system analysis showed that MA-XRF equipment is easy to handle and performs reliable measurements in addition to being portable.