Physics 736 Experimental Methods in Nuclear-, Particle-, and Astrophysics - Basic nuclear processes and radiation sources - Karsten Heeger heeger@wisc.edu
Course Organization Instructor Prof. Karsten Heeger Email: heeger@wisc.edu Office: Chamberlin Hall, room 4114! Lectures & Office Hours Lectures:!! Mon, Wed, 2.30-3.45pm, room 2223 course will meet twice a week Office Hours:! email me to fix a time, or see me after the lectures Course Webpages! Course info, schedule, homework, lectures, etc http://neutrino.physics.wisc.edu/teaching/phys736! Library Course Reserve Page with protected information https://www.library.wisc.edu/course-pages/viewer/show/5081 Grader Paul Hinrichs Email: phinrichs@wisc.edu
Class Schedule will be rescheduled
Karsten Heeger, Univ. of Wisconsin NUSS, July 13, 2009
Karsten Heeger, Univ. of Wisconsin NUSS, July 13, 2009
Why do we go to such remote places for science?
Particles & Radiation What are we interested in measuring?
Particles & Radiation What are we interested in measuring? Charged particle radiation fast electrons heavy charged particles Uncharged particles and radiation electromagnetic radiation neutrons neutrinos WIMPS?
Radioactivity
Radioactivity
Alpha Decay proton number (Z) neutron number (N)
Alpha Decay Text Gamow 1928 alpha energy spectrum Trbh 1.2. Characteristics of some alpha cmitters lsotope Half-life Encrgies lmcvl Branching alpha source ala- 2lho z2cm 433 yrs. I 38 days 163 days 5.4E6 5.ut 5.305 6.t t3 6.070 t5% r2.e% td)7c 74h 26q.
Beta-decay Ul f J. List of pure p- crnitters h,cc Half-lifc E* [McVl t rc + i ts t ccr q6 TA trc EPD Dfl 12.26yr 5730 yr l4.2td u.4d t7.9 d!.$ x ld yr l5j d Dyt tl.7 yt/6h 2.l2xrd y 2.62yt 3.tt yr 0.0186 0.156 t.710 0.24t o.16l 0.714 0.2s2 0.()67 0.54/2.27 0.292 o.xu o.76
Electron Capture or Auger electron
Annihilation Radiation intensity height thick Na-22 source
Internal Conversion nuclear excitation transferred to atomic electron ejection of electron looks like 2-step process classically -> single quantum process, amplitude can be calculated with pertubation theory
Beta-Spectrum and Internal Conversion Lines Internal Conversion Process: - information from the internal conversion electrons about the binding energies of the electrons in the daughter atom - relative intensities of these internal conversion electron peaks can give information about the electric multipole character of the nucleus. internal conversion can be useful source of monoenergetic e -
Beta-Spectrum and Internal Conversion - 203 Hg, which decays to 203 Tl by beta emission, leaving the 203 Tl in an electromagnetically excited state. - can proceed to the ground state by emitting a 279.190 kev gamma ray, or by internal conversion. In this case the internal conversion is more probable. - internal conversion process can interact with any of the orbital electrons, the result is a spectrum of internal conversion electrons which will be seen as superimposed upon the electron energy spectrum of the beta emission. - Energy yield of this electromagnetic transition: 279.190 kev => ejected electrons will have that energy minus their binding energy in the 203 Tl daughter atom. Electron emissions from the Hg-203 to Tl-203 decay, measured by A. H. Wapstra, et al., Physica 20, 169 (1954)
Auger Electrons
Neutron Sources spontaneous fission nuclear reactions
Nuclear Processes and Radiation Sources basic nuclear processes alpha decay beta decay electron capture annihilation radiation internal conversion γ emission of nucleus, X-rays Auger electrons neutron sources fission nuclear reactions radiation sources source encapsulation (thick vs thin) energy of source radiation (continuous, monoenergetic, degradation) backgrounds from radiation sources (e.g. gamma)
Radioactivity natural fossil cosmogenic artificial/man-made nuclear laboratories/accelerators in reactors (fusion, fission)
Nuclei with 10 8 yr < T1/2 < 10 12 yr isotopic abundance is terrestrial mix
40 K
Natural Radioactivity Chains 3 chains of natural radioactivity τ1>> τi 1
Chains of Natural Radioactivity
Flux of Cosmic Radiation peaked at ~ 300 MeV falling like E -3 outside Earthʼs atmosphere
Cosmic-Ray Induced Showers Fluxes as a function of depth
Production of Artificial Radioactivity nuclei emerging from target can be mass selected
Poisson Distribution
Poisson Distribution
Radioactive Decay Chains
Karsten Heeger, Univ. of Wisconsin NUSS, July 13, 2009