Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 1 Spectrum if all energy is captured in detector. Allows identification of gamma energy. Large Detector (in depth?!). Photo Peak or Full Energy Peak…? Doppler. Cost. Crystal growth. (with atoms, why??) Photoelectric Absorption Photoelectric Absorption. Principles of Spectrometry Auger

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 2 Spectroscopy, energy deposition. Consider what might escape. Size and material of detector. Shield lining. Considerations for shields and detectors? Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 3 HPGe HW 15 Principles of Spectrometry

“Probability” for photoelectric absorption: Strong Z dependence. shields and detectors Considerations for shields and detectors. Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 4 Practical Theoretical Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 5 Efficiency considerations. Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 6 NaI or BGO HPGe Efficiency vs. Resolution Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 7 shields and detectors? Considerations for shields and detectors? Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 8 In the figure: Photoelectric suppressed. Single Compton (effect of crystal dimensions). Below MeV. Compton Scattering Compton Scattering. Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 9 Reproduce the graph. Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 10 Compton scattering is predominant for energies typical of radioisotope sources. “Probability” per atom increases linearly with Z (Why). Electron density. Effect of binding energy. Effect of polarized photons. Compton fraction. Klein-Nishina formula Let the recoil electron be emitted at an angle , calculate cot(  ) as a function of tan(  /2). HW 16 Principles of Spectrometry 

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 11 Note tendency for forward scattering at high energies. shields and detectors? Sources vs. accelerators??? Considerations for shields and detectors? Sources vs. accelerators??? HW 17 What is Thomson scattering. Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 12 If you need to measure gamma ray yield from nuclear reactions (using particle accelerators), the photon energies could be as high as 10 MeV. What is the typical Ge detector to be used? Prepared with Monte Carlo simulations. Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 13 Single peak if electron and positron “kinetic” energies are captured by the detector. But annihilation! Rest mass of electron and positron. Gamma must have MeV minimum energy for PP to occur. Two annihilation photons are then created when positron recombines with an electron. These photons may or may not be captured, causing single and double escape peaks in the spectrum (effect of crystal dimensions). Pair Production Pair Production. Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 14 Low-energy gamma. High-energy gamma. Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 15 Probability of pair production. Dependence on Z? Recoil nucleus,Why? Effect of screening? HW 18 Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 16 Principles of Spectrometry Importance in Linacs?

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 17 Very large detector. All secondary radiation, including Compton scattered gamma rays, Bremsstrahlung, x-rays and annihilation photons, are captured in detector volume Large photofraction (fraction of full energy events) is desired in any detector Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 18 Very small detectors. All secondary radiation, including Compton scattered gamma rays and annihilation photons, are not captured in detector volume (escaping). Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 19 A typical detector. Principles of Spectrometry

Radiation Detection and Measurement, JU, First Semester, (Saed Dababneh). 20 Effect of surrounding material. Detectors are normally shielded to minimize as much as possible the counting of ambient background radiation. X-rays and lining. Principles of Spectrometry