Accession Number : ADA218003


Title :   Determinations of Photon Spectra


Descriptive Note : Master's thesis,


Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH


Personal Author(s) : Wannigman, David L.


Report Date : 1989


Pagination or Media Count : 77


Abstract : A method is developed to unfold photon spectra from measurements obtained with a sodium iodide counting system. A response matrix is computed by combining photon cross sections with probability distributions of path lengths for incident and internally generated photons in the energy range 0-2.8 MeV. This matrix is inverted and multiplied by a measured pulse height spectrum to obtain the photon energy distribution incident upon the detector. This deconvolution procedure provides improved information about the energy continuum of incident photons and can enhanced the identification of discrete gamma energies. Experiments were performed to verify the unfolding methodology and to evaluate the feasibility and accuracy of this technique. Measured spectra were acquired from indoor and outdoor environments and unfolded. The results show that measured spectra overestimate the number of photons below 240 keV by up to 30 %. When the total exposure was calculated directly from the measured spectra, the low energy contribution was overestimated by a factor of two. This may have implications on the interpretation and calibration of energy dependent dosimeters used for occupational and environmental monitoring. (JHD)


Descriptors :   *IODIDES , *PHOTONS , *SPECTRA , *COUNTING METHODS , SODIUM , PULSES , LOW ENERGY , LENGTH , GAMMA RAYS , CALIBRATION , HEIGHT , DOSIMETERS , ACCURACY , PATHS , PHOTON CROSS SECTIONS , PROBABILITY DISTRIBUTION FUNCTIONS , ENERGY


Subject Categories : ATOMIC AND MOLECULAR PHYSICS AND SPECTROSCOPY


Distribution Statement : APPROVED FOR PUBLIC RELEASE