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NERS/BIOE 481
Lecture 03
X-ray Sources

Syllabus

III. Sources of Radiation

  1. Radiation Units
    1. Units (ICRU)
      1. Flux - # / sec
      2. Fluence - # / m^2 (# / sr)
      3. Fluence rate - # / m^2 / sec ( # / sr / sec)
      4. Energy fluence rate - keV / m^2 / sec
    2. Solid Angle
      1. Differential
      2. Total
      3. Conversion from /sr to /m^2
    3. Xray emission
      1. Production per electrons, #/mA-s
      2. Differential energy production, #/ keV
    4. Radiation Exposure
      1. Air ionization measure
      2. SI unit, coulombs/kilogram ( C/kg )
      3. Classic unit, Roentgen (R or mR) = 2.58 x 10^-4 C/kg
  2. Electron impact x-ray tubes
    1. X-ray generator systems
      1. X-ray tube
      2. Tube housing
      3. High voltage generator
      4. Control system
    2. electron beam
      1. cathodes
      2. focus
      3. current vs filament current
      4. space charge
      5. anode power limits
    3. target/housing heat
      1. static power density
      2. line focus
      3. rotation
      4. tube cooling
      5. power ratings
      6. high power devices
  3. X-ray Energy Spectrum
    1. Bremsstralung (continuous)
      1. Classical model
        1. Kramers-theory
        2. Kulenkampf-exp.
        3. total production efficiency
      2. integral formulations
        1. diff. cross section
        2. stopping power
        3. simplified integral solutions
        4. self absorbtion
        5. intrinsic filtration
        6. prior integral models
        7. The Storm model
    2. Characteristic
      1. characteristic energy
        1. relaxation rules
        2. energy, Mosely law
      2. fluorescent fraction
        1. radiative emissions vs auger electron
        2. Total radiative fraction
        3. K-n transition probabilities
      3. Intensity
        1. direct production
        2. indirect production
        3. Green and Cosslett theory 1961
          • Direct/Indirect versus Z
          • Total intensity versus E (overvoltage)
      4. Empiracle relations
        1. Webster and Clark 1917
        2. Storm 1972
        3. Green and Cosslett 1968
    3. Experimental spectral data
      1. US FDA
      2. Boone's polynomial fits to FDA data
      3. Mercier
    4. Examples
      1. General radiography (tungsten target)
      2. Mammography(molybdenum target)
  4. Other X-ray Sources
    1. Novel cathodes
    2. Megavoltage sources (Linac)
    3. Synchrotron sources