The effect of energy resolution on the extraction of information content from gamma-ray spectra

Nelson, K.; Gosnell, T.B.; Knapp, David A.

doi:10.1016/j.nima.2011.06.057

Cited by 14 publications

(12 citation statements)

References 6 publications

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“…The energy resolution that is achievable using classical scintillators such as NaI and CsI is, however, limited and does not meet the requirements for radioactive isotope identification. 3 An analysis of counting statistics demonstrates that resolution improves with an increase in luminosity, which usually results from a higher conversion efficiency, i.e. relatively more photons are generated per incident energy.…”

Section: Introductionmentioning

confidence: 99%

Quasiparticle spectra, absorption spectra, and excitonic properties of NaI andSrI2from many-body perturbation theory

et al. 2014

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We investigate the basic quantum mechanical processes behind non-proportional response of scintillators to incident radiation responsible for reduced resolution. For this purpose, we conduct a comparative first principles study of quasiparticle spectra on the basis of the G0W0 approximation as well as absorption spectra and excitonic properties by solving the Bethe-Salpeter equation for two important systems, NaI and SrI2. The former is a standard scintillator material with well-documented non-proportionality while the latter has recently been found to exhibit a very proportional response. We predict band gaps for NaI and SrI2 of 5.5 and 5.2 eV, respectively, in good agreement with experiment. Furthermore, we obtain binding energies for the groundstate excitons of 216 meV for NaI and 195 ± 25 meV for SrI2. We analyze the degree of exciton anisotropy and spatial extent by means of a coarse-grained electron-hole pair-correlation function. Thereby, it is shown that the excitons in NaI differ strongly from those in SrI2 in terms of structure and symmetry, even if their binding energies are similar. Furthermore, we show that quite unexpectedly the spatial extents of the highly anisotropic low-energy excitons in SrI2 in fact exceed those in NaI by a factor of two to three in terms of the full width at half maxima of the electron-hole pair-correlation function. PACS numbers: 71.35.-y 71.20.-b 71.15.Qe 78.70.Ps

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Section: Introductionmentioning

confidence: 99%

Quasiparticle spectra, absorption spectra, and excitonic properties of NaI andSrI2from many-body perturbation theory

et al. 2014

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“…[1][2][3] The energy resolved detection of radiation is of particular interest as it enables, for example, the identification of fissile materials. 4 According to counting statistics, the resolution increases with luminosity, which usually results from a higher conversion efficiency, i.e., relatively more photons are generated per incident energy. In practice, the resolution is further limited by the non-linear response of the scintillator to the energy of the incident radiation.…”

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confidence: 99%

Origin of resolution enhancement by co-doping of scintillators: Insight from electronic structure calculations

Åberg

Sadigh

Schleife

et al. 2014

Applied Physics Letters

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Citation for the published paper: Aberg, D. ; Sadigh, B. ; Schleife, A. (2014) "Origin of resolution enhancement by co-doping of scintillators: Insight from electronic structure calculations". Applied Physics Letters, vol. 104(21), http://dx.It was recently shown that the energy resolution of Ce-doped LaBr 3 scintillator radiation detectors can be crucially improved by co-doping with Sr, Ca, or Ba. Here, we outline a mechanism for this enhancement on the basis of electronic structure calculations. We show that (i) Br vacancies are the primary electron traps during the initial stage of thermalization of hot carriers, prior to hole capture by Ce dopants; (ii) isolated Br vacancies are associated with deep levels; (iii) Sr doping increases the Br vacancy concentration by several orders of magnitude; (iv) Sr La binds to V Br resulting in a stable neutral complex; and (v) association with Sr causes the deep vacancy level to move toward the conduction band edge. The latter is essential for reducing the effective carrier density available for Auger quenching during thermalization of hot carriers. Subsequent de-trapping of electrons from Sr La -V Br complexes can activate Ce dopants that have previously captured a hole leading to luminescence. This mechanism implies an overall reduction of Auger quenching of free carriers, which is expected to improve the linearity of the photon light yield with respect to the energy of incident electron or photon. V C 2014 AIP Publishing LLC.

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“…While the general potential of scintillators has been demonstrated, one of the current goals is to develop materials with improved energy resolution sufficient to detect fissile materials with a low probability of errors at ports, borders, and airports. 3 The current state-of-the-art material is Cedoped LaBr 3 , 4 which has been extensively characterized both experimentally [5][6][7][8] and theoretically. [8][9][10][11][12][13] Yet fundamental features of its electronic structure are still incompletely described and quantified.…”

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confidence: 99%

“…Previous electronic structure calculations of LaBr 3 have been based on the Hartree-Fock (HF) method, 9 , the LDA+U approach, 10 or hybrid exchange-correlation (XC) functionals. 9 As is well-known, the HF method grossly overestimates the band gap in extended systems and the two latter methods both rely on additional fitting parameters.…”

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confidence: 99%

Electronic structure of LaBr3from quasiparticle self-consistentGWcalculations

2012

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Rare-earth based scintillators in general and lanthanum bromide (LaBr3) in particular represent a challenging class of materials due to pronounced spin-orbit coupling and subtle interactions between d and f states that cannot be reproduced by standard density functional theory (DFT). Here a detailed investigation of the electronic band structure of LaBr3 using the quasi-particle self-consistent GW (QPscGW) method is presented. This parameter-free approach is shown to yield an excellent description of the electronic structure of LaBr3. Specifically it is able to reproduce the band gap, the correct level ordering and spacing of the 4f and 5d states, as well as the spin-orbit splitting of La-derived states. The QPscGW results are subsequently used to benchmark several computationally less demanding techniques including DFT+U , hybrid exchange-correlation functionals, and the G0W0 method. Spin-orbit coupling is included self-consistently at each QPscGW iteration and maximally localized Wannier functions are used to interpolate quasi-particle energies. The QPscGW results provide an excellent starting point for investigating the electronic structure of excited states, charge self-trapping, and activator ions in LaBr3 and related materials.

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The effect of energy resolution on the extraction of information content from gamma-ray spectra

Cited by 14 publications

References 6 publications

Quasiparticle spectra, absorption spectra, and excitonic properties of NaI andSrI2from many-body perturbation theory

Quasiparticle spectra, absorption spectra, and excitonic properties of NaI andSrI2from many-body perturbation theory

Origin of resolution enhancement by co-doping of scintillators: Insight from electronic structure calculations

Electronic structure of LaBr3from quasiparticle self-consistentGWcalculations

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