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ENU4612
| Term | Definition |
|---|---|
| Fast electrons | Beta particles (β⁺ or β⁻), energetic electrons from any process |
| Heavy charged particles | All energetic ions with mass ≥ 1 amu |
| Charged Particulate Radiation | Fast electrons or Heavy charged particles (e.g. Alpha particles, protons, fission products, nuclear reaction products) |
| Electromagnetic radiation | X-rays from electron shell rearrangement, gamma rays from nuclear transitions |
| Neutrons | Generated in nuclear processes |
| Uncharged Radiation | Electromagnetic radiation, Neutrons, and Further divided into slow neutron and fast neutron subcategories |
| hardness | Radiations differ in their "___________" or ability to penetrate thicknesses of material. |
| Soft Radiations (e.g.) | Alpha particles and Low-energy X-rays, |
| Soft Radiations (Source Thickness) | micrometers |
| Soft Radiations (Problem) | Self-absorption affects number and energy spectrum |
| Medium Penetration (e.g.) | Beta particles which are more penetrating than alphas |
| Medium Penetration (Source Thickness) | Few tenths of millimeter |
| Medium Penetration (Tolerance) | Can usually be tolerated |
| Hard Radiations (e.g.) | Gamma rays and Neutrons |
| Hard Radiations (Source Thickness) | Millimeters to centimeters |
| Hard Radiations (Advantage) | Minimal self-absorption effects |
| Self-Absorption Effect | Only atoms near the surface contribute photons that escape from thicker sources. This affects both the intensity and energy spectrum of emerging radiation. |
| Fundamental Law of Radioactive Decay | dN/dt|decay = -λN; Where: N = number of radioactive nuclei, λ = decay constant |
| milli (m) | 0.001 or 10^-3 |
| micro (μ) | 0.000001 or 10^-6 |
| nano (n) | 0.000000001 or 10^-9 |
| kilo (k) | 1000 or 10^3 |
| mega (M) | 1000000 or 10^6 |
| giga (G) | 1000000000 or 10^9 |
| Curie (Ci) | Exactly 3.7 × 10¹⁰ disintegrations/second, Based on activity of 1 gram of pure ²²⁶Ra, More suitable for laboratory sources, historical unit |
| Becquerel (Bq) | One disintegration per second, Adopted in 1975, Conversion: 1 Bq = 2.703 × 10⁻¹¹ Ci |
| Activity | _________ measures source disintegration rate, which is NOT synonymous with radiation emission rate |
| Specific Activity | _____________________ = Activity/Mass = λN/(NM/Av) = λAv/M; M = molecular weight of sample, Av = Avogadro's number (6.02 × 10²³ nuclei/mole), λ = radioisotope decay constant (= ln 2/half-life) |
| Pure samples | Unmixed with other nuclear species |
| Diluted samples | Mixed with stable nuclei of same element |
| Chemical compounds | Additional stable nuclei from other elements |
| large | Higher specific activity are obtained using radionuclides with _____ λ |
| Short half-life = | = high specific activity |
| Electron Volt (eV) | Traditional unit, Kinetic energy gained by electron accelerated through 1 volt potential difference, Convenient for particulate radiation |
| Joule (J) | 1 eV = 1.602 × 10⁻¹⁹ J; SI unit though eV is not likely to be phased out due to physical basis and universal use in literature |
| Planck's constant | h = 6.626 × 10⁻³⁴ J·s or 4.135 × 10⁻¹⁵ eV·s |
| Energy-Frequency | E = hν |
| Wavelength-Energy | λ = 1.240 × 10⁻⁶/E; where λ is in meters and E is in eV |
| Beta Decay | Continuous energy spectrum from nuclear decay |
| Internal Conversion | Monoenergetic electrons from nuclear transitions |
| Auger Electrons | Low-energy electrons from atomic processes roughly the analogue of internal conversion electrons when the excitation energy originates in the atom rather than in the nucleus |
| Fast Electron Sources | The most common source of fast electrons in radiation measurements |
| Beta Decay equation | A ZX → AZ+1Y + β⁻ + ν- |
| Recoil nucleus | Very small recoil energy, below ionization threshold |
| Beta Decay Products | Final nucleus Y, beta particle, antineutrino |
| Neutrino | Extremely small interaction probability - undetectable |
| Beta Decay Detectable radiation | Only the fast electron (beta particle) |
| Beta Decay Source Availability | Most radionuclides from neutron bombardment are beta-active, Large assortment readily available from reactor production, Wide range of half-lives: days to thousands of years, Many decay to excited states → gamma rays also emitted |
| Q-Value and Energy Sharing in Beta Decay | Each specific beta decay transition is characterized by a fixed decay energy or Q-value. Since recoil nucleus energy is virtually zero, this energy is shared between the beta particle and the "invisible" neutrino |
| Beta Decay Energy Distribution | Range: Zero to "beta endpoint energy", Endpoint energy: Numerically equal to Q-value, Shape: Continuous spectrum (see Fig. 1.1), Multiple components: If several excited states populated |
| "Pure" Beta-Minus Sources | nuclides that decay directly to ground state (no gamma contamination); e.g. 3H, 14C, 32P |
| Internal Conversion Process | -Begins with excited nuclear state -Alternative to gamma-ray emission -Nuclear excitation energy transferred directly to orbital electron -Most often occurs for somewhat inhibited gamma emission |
| Internal Conversion Formula | Ee- = Eex - Eb Ee- = conversion electron energy Eex = nuclear excitation energy Eb = electron binding energy in original shell |
| Electron Shell Groups | K-shell conversion: Highest electron relative yield L-shell conversion: Lower electron relative yield M-shell conversion: Lowest electron relative yield |
| Auger Electron Energy Formula | EAuger = Eatomic excitation - Ebinding energy |
| Auger Electrons Process | - Initial state: Vacancy in normally complete electron shell - Cause: Preceding process (e.g., electron capture) - Competing process: Characteristic X-ray emission - Alternative: Energy transferred directly to outer electron |
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