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[en] The use of energy spectral information in radiologic measurements was investigated. The energy spectral characteristics of bremsstrahlung radiations filtered by the K-edge absorption of an element were studied by developing suitable models of the filtered spectra. Using the models, the measurement errors caused by the polyenergetic nonlinearity, when such radiations were used as pseudomonoenergetic sources, were investigated. The measurement errors were found to be minimal and simple correction methods were available. A performance criterion was established to determine the optimal energies for measurements. The measurement errors caused by noise from electronic systems and also from limited data accuracies were studied. The noise effects from different types of noise were compared, the effects were shown to be similar and energy values could be chosen so that they were optimal to all types of noise discussed. The optimal energies were also found to be obtainable from a wide variety of filter materials. After the efficacy of the filtered radiations and the determination of the optimal energies were investigated, the rest of this dissertation dealt with the implementation of the measurements. Since radiographic films are the normal recording device in the clinic, their use as detectors and recorders in our measurements was studied
[en] The internal bremsstrahlung spectra from the β decay of 185W and 32P were measured using a NaI(Tl) scintillation spectrometer with a standard geometrical arrangement. After making all the necessary corrections the experimental results are compared with the allowed theory of the Knipp, Uhlenbeck, and Bloch (KUB theory) and also with the Coulomb corrected theories of Lewis, Ford, and Nilsson. In the case of 185W it is found that from 78 to 200 keV the experimental distribution is in good agreement with the KUB theory whereas beyond 200 keV and below 78 keV the experimental points are far above even the highest Coulomb corrected theoretical distribution of Nilsson. The internal bremsstrahlung from this isotope has not been previously investigated. In the case of 32P the experimental relative intensity spectrum is compared with the KUB theory and also with the Coulomb corrected theory of Lewis and Ford. Fairly good agreement is obtained from 30 to 200 keV with the KUB theory but in the energy region from 200 to 900 keV, the experimental results deviate positively from both the KUB and Lewis and Ford theories. The experimental excess over the Lewis and Ford theory is 15% on the average
[en] LENA (Low Energy Neutrino Astronomy) is a next-generation liquid-scintillator neutrino detector with 50kt target mass. The broad spectrum of physics goals ranging from the sub-MeV to the GeV regime sets high demands on the photosensors. Currently, photomultipliers (PMTs) are the sensor of choice. However, besides detecting photons, they also emit light through bremsstrahlung or fluorescence induced by the electron avalanche in the dynode chain, which can produce further pulses in the same PMT or adjacent sensors. In order to study these effects and their connection to afterpulses occurring in the PMT, measurements of light emission and fast afterpulses have been carried through in collaboration with the CTA project. Both bremsstrahlung and fluorescence have been observed, with the first also being the origin of a type of fast afterpulses.
[en] The internal bremsstrahlung spectrum accompanying the non-unique second-forbidden β-decay of 36Cl is measured using the magnetic deflection technique. The true IB spectrum is obtained with the help of the inverse of the detector response matrix. The experimental data in the energy interval 80 to 700 keV are compared with the theoretical spectra of Knipp and Uhlenbeck, and Bloch, Lewis and Ford, and Chang and Falkoff. The agreement between the measurement and theory is not good throughout the energy region of the present investigation, though the experimental points are close to the second-forbidden scalar theory of Chang and Falkoff. (Auth.)
[en] Usually the triennial control of radiation protection devices such as survey meters are made by using radioactive sources for instance a Cs"1"3"7 source set at various distances to get a range of dose rates. A new method that does not use radioactive source has been developed, this method uses the Bremsstrahlung radiation emitted by an electron beam passing through a solid target. The photons that form the Bremsstrahlung radiation are emitted with a broad continuous spectrum of energy that can cover all the application domain of a survey meter. The proportional relationship between the dose rate of the photon beam and the intensity of the primary electron beam allows the measurement of the survey meter's response to the whole dose range by only acting on the parameters of the electron accelerator, no more need to move the survey meter or the radioactive source. (A.C.)
[en] The spectral intensity of bremsstrahlung from a pair plasma is calculated with fluctuation theory and particle orbit theory. The predictions given by the two theories agree with each other in the low frequency region. However, the fluctuation theory gives invalid results in the high frequency region because of the failure of the assumption made in the theory. Particle orbit theory shows that in the high frequency region the spectral intensity of bremsstrahlung from a pair plasma depends on the radiation frequency ω through the exponential factor exp(-ℎω/2T), where T is the plasma temperature.
[en] The energy-loss rates of degenerate neutron-star matter due to thermal bremsstrahlung of pseudoscalar particles and axions via neutron-proton collisions together with the mean-free path and the energy spectrum from neutron-neutron, neutron-proton, and neutron-neutron processes are calculated. Analytic expressions for these quantities are obtained in the general case where the pseudoscalar particle couples to the proton and neutron with different strengths and the protons and the neutrons have different Fermi momenta. These rates are compared with those of other authors