PHY138Y Nuclear and Radiation

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1 PHY13Y Nuclear and Radiation Professor Tony Key MP01 Announcements Error in Worked Problems: 2.5(i) Photon Fluence Misuse of the word Power should be energy fluence rate. - $5 to Jere Problem Set #3,no. A Radioactive Tracer A 95 mci radioactive tracer is made in a nuclear reactor. When it is delivered to a hospital 1 hours later its activity is 75 mc What is the tracer's half-life? A. The lowest usable level of activity is 5 mci. B. For how long after delivery is the sample usable? The second part of the question should read: B. For how long after IT IS MADE is the sample usable? Thanks to Stuart! Definition of Intensity Means different things to different folks. Usually it is one of: photon fluence energy fluence photon fluence rate energy fluence rate Usually it is clear in context e.g PS#2, comparison of the intensity of X-rays traversing two different paths. Solving Problems Read the question three times Draw a diagram ALWAYS! Write down - what is given, - what is required Make a plan Use Common Sense!! Work parametrically (in symbols) Announcements MP problems set #3 due Friday at midnite MP problems set # due Sunday 23 rd March at midnite Memorize the definitions! Check out the Flash animations! Read the notes! Do check the Bulletin link

This Week Readings Supplementary Notes III : SNIII Radioactivity Discovery Alpha, ta, Gamma Decay BUT

of photons crossing one square metre Φ = N/S Photon Fluence Rate no.

fluence by the energy of each photon) Φ(x) = Φ(0) exp(-µx) µ-linear attenuation coefficient µ/ρ mass

2 This Week Readings Supplementary Notes III : SNIII Radioactivity Discovery Alpha, ta, Gamma Decay BUT first.. Quick review - X-ray pictures Essentials of Radiation so far... Photon Fluence no. of photons crossing one square metre Φ = N/S Photon Fluence Rate no. of photons crossing one square metre per second - φ Energy Fluence & Energy Fluence Rate (multiply fluence by the energy of each photon) Φ(x) = Φ(0) exp(-µx) µ-linear attenuation coefficient µ/ρ mass attenuation coefficient, µ m Chest X - Ray X Ray of the Spine and Pelvis X Ray of the Stomach and Colon Regular Chest X-ray Computer Axial Tomography

Computer Axial Tomography CAT scan Hounsfield

1979 Computer Axial Tomography (CAT scan)

pl (view the applets in the link to Einstein s

LIVER KIDNEYS SPINE PANCREAS SPLEEN cquerel

3 Computer Axial Tomography CAT scan Hounsfield Cormack Nobel Prize in Physiology or Medicine 1979 Computer Axial Tomography (CAT scan) Hounsfield & Cormack Nobel Prize 1979 CT SCAN WEB SITE Go to (view the applets in the link to Einstein s Legacy) Axial CT Scan of a human mid-section LIVER KIDNEYS SPINE PANCREAS SPLEEN cquerel Axial CT Scan of a student s brain Discovered Radioactivity in Uranium Salts Nobel Prize 1903

4 Marie and Pierre Curie Isolated Radium Marie Curie 2 nd Nobel Prize (Chemistry) 1911 Nobel Prize 1903 Artificial Radioactivity Marie Joliot-Curie Frederic Joliot Isotopes of N, P, Si, Al Nobel Prize (Chemistry) 1935 Who Is This Guy?? Hans Geiger e + Developed the Geiger-Müller Tube used by Rutherford

cylinder Parent Daughter 23 92 U Alpha Decay

5 Geiger-Müller Tube ~ 1 kv inert gas Radiation ALPHA DECAY Metal envelope Glass cylinder Parent Daughter U Alpha Decay of Uranium-23 To Thorium-23 α = He 2 K Th Th α K α

Energy (alpha) ~1/r ~30 MeV ALPHA DECAY ~5 MeV Energy (alpha) ALPHA DECAY P.E. Forbidden Region ~ 0 MeV Forbidden Region In Forbidden Region P.E. > Total Energy r = R E total The Amazing Quantum World The lifetime of alpha emitters increases with the energy of the alpha particle.

6 Energy (alpha) ~1/r ~30 MeV ALPHA DECAY ~5 MeV Energy (alpha) ALPHA DECAY P.E. Forbidden Region ~ 0 MeV Forbidden Region In Forbidden Region P.E. > Total Energy r = R E total The Amazing Quantum World The lifetime of alpha emitters increases with the energy of the alpha particle. A. TRUE B. FALSE E 2 ~30 MeV ALPHA DECAY is an unstable nucleus that decays to two alpha particles : ~ 50 microns E 1 + ~ 0 MeV Calculate the kinetic energy of each of the alpha particles from the decay.

7 Calculate the kinetic energy of one of the alpha particles from the decay. Nucleus + ATOMIC Mass (u) Q VALUE : Energy available for the decay Parent Daughter + Decay Products Q/c 2 = Mass(Parent) {Mass(daughter) + Mass(decay products)} (nuclear masses) Converted to Kinetic Energy of Daughter and decay products Radioactive Decay To calculate a Q value, we need NUCLEAR masses. But the tables list only ATOMIC masses SO we have to convert ATOMIC masses to NUCLEAR masses by subtracting the masses of the Z electrons (as usual, we neglect the binding energy of the electrons in the atom). Calculate the kinetic energy of one of the alpha particles from the decay. Nucleus + ATOMIC Mass (u) u = MeV/c 2

PHY138Y Nuclear and Radiation

PHY138Y Nuclear and Radiation Professor Tony Key MP401 key@physics.utoronto.ca Announcements Next and last Representative Assembly, Friday of next week (23 rd ) MP713 me 12:10 FRIDAY 23 rd FREE COOKIES