MRI:Development of Gas Electron Multiplier Based Fluorescence X ray Detector for Dilute Elements

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Technical abstract:Gas Electron Multiplier (GEM) based fluorescence X-ray gas detector is an indispensable tool for characterizing dilute elements of 10 parts per million (ppm) and below using X-ray Fluorescence Spectroscopy (XFS). When atoms of a dilute element in a sample are excited by a tuned energy synchrotron radiation beamline, they emit weak X ray fluorescence signal. The fluorescence X-ray signal has low penetrating power, is severely attenuated by air, and ionizes few electrons in an ionization chamber. Detecting the small primary electronic charge signal is very difficult using conventional fluorescence detectors with low signal to noise (S/N) ratio. To improve the S/N ratio, we propose to use a single and multiple gas electron multiplier (GEM) to amplify the ionized primary electronic charge without noise in an ionization chamber. The amplified charge will enhance the S/N ratio, improve the detection, analysis, and facilitate to characterize dilute samples. Conventional fluorescence detectors are affected by micro phonic vibrations, temperature, light, have small S/N ratio, and occasional gain drift with time. The GEM based detector is rigid, gas leak proof, allows cascaded multiple GEMs for gain control, avoids spark discharge from high fields due to a single GEM, has noise free electron amplification, and allows measuring fast signal with high rate capability. The detector has flexible window size for x-ray entrance, flexible solid angle of acceptance, variable GEM dimension, uses multiple gas mixtures, operates at atmospheric pressure, and at room temperature. This project is performed in collaboration with Morgan State University, Brookhaven National Laboratory (BNL), and Southern University Baton Rouge to enhance, educate and train minority students in building new detectors that will be used at the National Synchrotron Light Source (NSLS) and at other national and international laboratories.Non-technical abstract:Detecting dilute elements of ten parts per million and below, in natural or manufactured samples requires a high signal to noise (S/N) ratio detector. When a dilute element under test is excited by a tuned energy synchrotron beamline, it releases a characteristic fluoresce X-ray that is used to ionize a noble gas producing a charge signal. This primary charge signal is too small to be detected because of the large noise interference introduced by electronic amplifiers. The proposed detector uses a gas electron multiplier (GEM) that multiplies or amplifies the small primary charge created by the dilute element fluorescence X-ray. The GEM amplified charge signal amplitude far exceeds the level of the noise produced by the electronic amplifiers providing a high S/N ratio. This will allow better detection and characterization of dilute elements in various samples. This project is performed in collaboration with Morgan State University, Brookhaven National Laboratory (BNL), and Southern University Baton Rouge to enhance, educate, and train minority students in building new detectors that can be used at the National Synchrotron Light Source (NSLS) and at other national and international laboratories.