Prepared by: Jared Schmidt Dept. of Electrical and Computer Engineering Utah State University

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: X-ray Fluorescence (XRF) Spectrometer Prepared by: Jared Schmidt Dept. of Electrical and Computer Engineering Utah State University E: magicarrow2@live.com; F: (435)797-3054 (ECE Dept.) 3/9/2012

2. Outline • Reference list • To probe further • Major applications • Basic working principle illustrated • A typical sample configuration in application (application notes) • Major specifications • Limitations ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Reference list • “X-ray spectroscopy”; Wikipedia.org; en.wikipedia.org/wiki/X-ray_spectroscopy • “Energy-dispersive X-ray spectroscopy”; Wikipedia.org; en.wikipedia.org/wiki/Energy-dispersive_X-ray_spectroscopy • “Wavelength-dispersive X-ray spectroscopy”; Wikipedia.org; en.wikipedia.org/wiki/Wavelength_dispersive_X-ray_spectroscopy • “WDS spectrometers”; Omni Instruments; www.omniinstruments.com/wds.html • “Spectrometer”; Ashlyn Chemunnoor Instruments PVT. LTD.; ashlynchemunnoor.tradeindia.com/Exporters_Suppliers/Exporter23343.1024C.105750P/Spectrometer.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. To explore further (survival pointers of web references etc) • “Geochemical Instrumentation and Analysis”; Science Education Resource Center; Montana State University; serc.carleton.edu/research_education/geochemsheets/techniques/XRF.html • Ron Jenkins; “X-ray Techniques: Overview”; Encyclopedia of Analytical Chemistry; R.A. Meyers (Ed.); Riley & Sons Ltd, Chichester, 2000; pg. 13269-13288; • “X-ray fluorescence”; Wikipedia.org; en.wikipedia.org/wiki/X-ray_fluorescence ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. Major Applications • X-ray spectroscopy is used in composition analysis • Identify type of elements in a substance • Identify the relative quantity of an element in a substance ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. Major Applications • Industrial Uses: • Quality control • Heavy metal detection • Waste product analysis • Soil analysis • Environmental studies • Cement production • Material validation ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Major Applications • Other uses • Bomb detection • Electron microscope imagery • Cosmic imagery and analysis • Forensics • Archaeology ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. Major Applications • Two methods of X-ray spectroscopy are common: • Energy-dispersive X-ray spectroscopy (EDS) • Wavelength-dispersive X-ray spectroscopy (WDS) • WDS separates the wavelengths of X-rays emitted by an excited sample and measures each wavelength individually. • EDS measures the wavelengths and intensity of X-rays emitted by an excited sample all at once. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. Energy-Dispersive Spectroscopy • Fast • Cheaper than WDS • Available in portable units • Used widely in industry • Less sensitive to sample positioning than WDS • Not as accurate as WDS • Lower spectral resolution than WDS Handheld X-ray spectrometer from Ashlyn Chemunnoor Instruments PVT. LTD. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. Wavelength-Dispersive Spectroscopy • Superior spectral resolution • Superior sensitivity • Slower than EDS • More sensitive to sample positioning error than EDS • Less portable than EDS Wavelength Dispersive X-ray Fluorescence Spectrometer from Ashlyn Chemunnoor Instruments PVT. LTD. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. Basic Working Principle • Light is emitted or absorbed through the change of electron energy states in an atom. • Absorption of light moves electrons to a higher energy state • Electrons moving to a lower energy state emits light • The wavelength of the light emitted is determined by the difference of the energy states the electron moves between. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. Basic Working Principle • X-ray photons are high energy photons which are emitted when an electron from an inner shell of an atom is lost (through some form of excitation) and is replaced by an electron from the outer shell. • Excitation is accomplished by bombarding the sample with one of four types of beams: • Electrons (as in an electron microscope) • Protons • X-rays • Gamma rays ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. Basic Working Principle • Every element has different electron arrangements and therefore emits different wavelengths of X-rays when excited. • These collective wavelengths are known as an element’s emission spectrum. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. Basic Working Principle • The emission spectra of a sample can be analyzed by analyzing the wavelengths of light and the intensity of each wavelength. • The spectrum (wavelengths) of emitted light is used to determine what elements are present in the sample • The intensity of each emitted spectrum can be used to determine the relative quantity of each element. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. Basic Working Principle • In an element’s emission spectrum, two or three characteristic wavelengths are dominant. • The strongest wavelength is the Ka wavelength • The next strongest is the Kb wavelength Typical X-ray fluorescence scan Courtesy of wikipedia.org ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. Sample Configuration Wavelength Dispersive X-ray Spectrometer • To the right is an example of a WDS setup. • X-rays from the X-ray tube excite the atoms in the sample. • The sample fluoresces. • To fluoresce means to receive light at a high frequency and re-emit it at a lower frequency or frequencies. Courtesy of Charles Miller and wikipedia.org ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Sample Configuration Wavelength Dispersive X-ray Spectrometer • The emitted light hits the analyzing crystal. • The crystal acts like a prism and reflects the light towards the goniometer. • A goniometer is a device that measures angles Courtesy of Charles Miller and wikipedia.org ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. Sample Configuration Wavelength Dispersive X-ray Spectrometer • The wavelength of the reflected light determines the direction of reflection off of the crystal. • The X-ray detector scans along the goniometer to determine the angle and intensity of the reflected light. • Intensity is used to determine element quantity Courtesy of Charles Miller and wikipedia.org ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. Major Specifications • Working principle (EDS, WDS, or other) • Measureable elements from periodic table • Type of detector • Excitation source (Electron, X-ray, etc.) • Power consumption • Weight and size • Safety features • Measurement time • Forms of samples (Liquid, powder, etc.) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

20. Limitations • X-ray spectroscopy can not be used to detect the presence of H, He, or Li. • Overexposure to X-rays is detrimental to health of humans. • Only works for surface of a material • Accuracy can be reduced in non-homogeneous and rough samples • Many elements’ spectra have multiple wavelengths in common. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators