The Compton Effect Research Presentation

1. The Compton EffectResearch Presentation PHYS-3313, Fall 2013 Nov. 27, 2013 Brian Ferguson, Garrett Brown, Greg Collier, and Ravi Subramaniam Presented by Greg Collier

2. Hamlet’s ParticleOne Boson’s answer to the question‘To be (A particle) or not to be (A particle)?’

3. A Brief History of Light • In the late 17th and early 18th Century, scientists were divided as to the nature of Light as either corpuscular (particle-like) or wave-like. • In the 1700’s Isaac Newton was an avid proponent of the “corpuscular” (particle) theory of Light. He believed Light traveled in straight “rays”. • In 1678, Christian Huygens presented his wave theory. He believed that Light propagates as a wave of concentric circles from the point of origin. • In 1802, Thomas Young and Augustin Fresnel demonstrated that Light clearly behaves like a wave with their double-slit interference pattern experiments. • In 1850, Jean Foucault established that Light travels more slowly in water than in air. This was considered one of the final blows to the corpuscular (particle) theory of Light.

4. Trouble on the Horizon • J. J. Thomson’s classical theory of the scattering of X-rays, though supported by earlier experiments, failed to explain the results of more recent late 19th century and early 20th century experiments. • Thomson’s classical theory, based on electrodynamics and Maxwell’s equations, lead to the result that the energy scattered by an electron that is hit by an X-ray was the same regardless of the wavelength of the incident rays. • Thomson’s theory of scattering requires that scattering electrons give rise to radiation of the same frequency as that of the radiation falling on them. • However, spectroscopic examination of scattered X-rays from graphite and other materials, has yielded wavelengths different from the incident rays! • What is going on here? Is classical electrodynamics sufficient to explain X-ray scattering phenomena?

5. Enter Quantum Mechanics • In 1900, Max Planck presented what is now known as the “Planck Postulate”, the idea that Electromagnetic energy could only be emitted in quantized form with energy being a multiple of E = hc/λ. • This postulate replaced classical electromagnetism • Knowing that the wavelength and frequency of light are inversely proportional, Compton extended Planck’s conception of the quantized light and predicted that a change in wavelength corresponded to a change in energy. • A change in energy after a collision with another particle would imply that light carried momentum as well as energy. • Could Photons have mass?

6. Enter the Compton Effect • X-rays scattered from a target are expected to have an increase in wavelength and a deviation in angle of their flight path with respect to the equation shown. • Electrons are predicted to recoil with relativistic velocities depending on photon energy and scattering angle.

7. Animation of the Process PennState Animations for Physics and Astronomy

8. Experimental Setup • In order to test this theory, a Molybdenum X-ray tube emits high energy photons towards carbon target placed at different angles. • The scattered X-rays are diffracted through a slowly rotating calcite crystal so that the intensities of specific X-ray wavelengths can be measured. • An ionization chamber measures the intensity of X-rays at specific wavelengths.

9. As we can see, the Experimental Results are in agreement with the Theoretical Results. Experimental Results

10. Plot of Scattered Photon Behavior More energy transferred to election at steeper angles Intensity vs. Scattering Angle of Photons. Classical Theory vs. Compton’s Theory

11. Implications • This shows that the photon behaves like a particle, showing that Einstein was correct on the Photon Particle Concept. • Light does have momentum. • Light is quantized. • Thus, photons exhibit a particle wave duality.

12. Applications of the Compton Effect • As it is the case for many concepts as fundamental as The Compton Effect, it has a wide range of uses in analytical processes…

13. Radiobiology The Compton Effect is used in Radiation therapy that treats both cancer and thyrotoxicosis

14. Compton Scattering Imaging The CE also had revolutionary effects on medical biology. The 3-D Positron Emission Tomography scanner makes a 3-D model of the human brain. Medicalphysicsweb.org The Compton Camera utilizes gamma imaging for spectroscopy bhcancercenter.com

15. Nuclear Compton Scattering • In Nuclear physics, many researchers take advantage of The Compton Effect by bombarding their substrate with Gamma rays and detecting them as they scatter. Compton Scattering and 3He Three-body Photodisintegration "A High-pressure Polarized 3He Gas Target for the High Intensity Gamma Source (HIγS) Facility at Duke Free Electron Laser Laboratory", K. Kramer, X. Zong, R. Lu, D. Dutta, H. Gao, X. Qian, Q. Ye, X. Zhu, T. Averett, S. Fuchs, Nuclear Inst. and Methods in Physics Research, A, 582, 318-325, 2007

16. Inverse Compton Scattering • Inverse Compton Scattering is widely used in astrophysics. • X-Ray telescopes are fundamentally based on the Compton Effect. http://venables.asu.edu/quant/proj/compton.html

18. CGRO Compton Gamma Ray Observatory The Compton Gamma Ray Observatory uses the principles of the Compton Effect as analytical equipment onboard the space shuttle Atlantis. I could cover the Electromagnetic spectrum from 30 keV to 30 GeV. It utilizes: Burst And Transient Source Experiment Oriented Scintillation Spectrometer Experiment Imaging Compton Telescope Energetic Gamma Ray Experiment Telescope

19. Attack of the Acronyms COM GMA LCS GLECS Comtal UVvis FTIR NMR NDT LXeGRIT LXeTPC SPECT (is) Micro-TPC

20. Compton Scattering can even explain why the sky is blue. The Oxygen molecules as dioxide and trioxide scatter the UV rays causing them to lose momentum and shift to the visible spectrum and appear blue.