Degradation of 81 keV 133Xe gamma-rays into the 31 keV X-ray peak in CsI scintillators

Keillor, Martin E.; Cooper, Matthew W.; Hayes, James C.; McIntyre, Justin I.

doi:10.1007/s10967-009-0244-y

Cited by 7 publications

(6 citation statements)

References 2 publications

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“…From Figure 8 , it is observed that the calculated band width of the CsI(Na) is 2.7 eV, which is consistent with the calculated results in Zhao Qiang’s work [ 6 ], and the band width of the CsI(Na) (010) surface is 2.99 eV, which decreased to 2.118 eV after the CsI(Na) (010) surface adsorbed H 2 O molecules. In other words, H 2 O molecular adsorption influences the band width and the electron density of state distribution, and that in turn affects the electron excitation process.…”

Section: Discussionsupporting

confidence: 86%

“…In order to investigate the CsI(Na) crystal scintillation degradation caused by the crystal surface adsorbing H 2 O molecules, we exposed CsI(Na) crystal to 25% relative humidity air at 15 °C temperature and 85% relative humidity air with different exposure time. Figure 3 and Figure 4 show the CsI(Na) crystal samples that were exposed for different times; we can see that the CsI(Na) crystal surface becomes more blurred with a longer exposure period; these blurred layers on the crystal surface, called “dead ” or “inactive” layers [ 6 , 13 ] on the surface of deteriorated detectors, were indirectly illustrated by the decrease in the scintillation performance. We measured the γ ray-excited emission spectra of crystals using the experimental setup in Figure 2 to study the effect caused by the “dead” layer under 137 Cs-662 keV γ ray excitation.…”

Section: Discussionmentioning

confidence: 99%

“…Our results also indicate that the CsI(Na) crystal surface absorbing H 2 O molecules changed the state and structure of the crystal surface and affected the scintillation characteristics, especially those of the film crystal. Studies [ 5 , 6 ] on Na-activated CsI detectors indicated that the detection efficiency of these crystals degraded rapidly under high humidity. The influence of air exposure on the structure, resistivity, and infrared transmittance of the CsI film were investigated by scanning electron microscopy and X-ray diffraction (XRD) [ 7 ]; the XRD results indicated the formation of a (110/220) texture when exposed to ambient air and the relaxation of tensile stress during recrystallization.…”

Section: Introductionmentioning

confidence: 99%

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Effect of H2O Molecule Adsorption on the Electronic Structure and Optical Properties of the CsI(Na) Crystal

et al. 2021

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We investigated H2O molecule adsorption that had an effect on the luminescence properties of the CsI(Na) crystal using experiments and first-principle calculations. We measured the emission spectra of the CsI(Na) crystal at different exposure times under gamma ray excitation. The experimental results showed that the energy resolution of the CsI(Na) crystal was worse when the crystal surface adsorbed more H2O molecules, and the crystal surface deliquescence decreased the luminescence efficiency of the CsI(Na) crystal. We studied the band structure, density of states, and optical properties changes caused by H2O molecule adsorption on the CsI(Na) (010) surface. The generalized gradient approximation (GGA) was used to describe the exchange and correlation potential between the electrons. Our calculation results showed that the band gap width of the CsI(Na) (010) surface decreased after adsorbing H2O molecules, while three new peaks appeared in the valence band, and the absorption coefficient decreased from 90,000 cm−1 to 65,000 cm−1, and the reflection coefficient decreased from 0.195 to 0.105. Further, the absorption coefficient was reduced by at least 25% because of H2O molecule adsorption, which led to the luminescence degradation of the CsI(Na) crystal.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of H2O Molecule Adsorption on the Electronic Structure and Optical Properties of the CsI(Na) Crystal

et al. 2021

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“…The energy deposition processes in the CsI(Na) detector, including a "dead" layer, have been experimentally demonstrated by direct observation of an additional X-ray decay peak isolated from the main photopeak that is supported by Monte Carlo simulation. [9] Readers who are interested in simulation results should refer to the original paper and references therein. These studies emphasize on the radioluminescence responses, but do not elucidate what is the "dead" layer, how the "dead" layer is developed, to what extend the "dead" layer can grow into the bulk crystal, and why the "dead" layer affects scintillation performance.…”

Section: Introductionmentioning

confidence: 99%

Effect of Humidity on Scintillation Performance in Na and Tl Activated CsI Crystals

Yang

Harmon

Doty

et al. 2014

IEEE Trans. Nucl. Sci.

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Time dependent photoluminescence and radioluminescence for sodium (Na) and thallium (Tl) activated cesium iodide (CsI) single crystals exposed to 50% and 75% relative humidity (RH) has been investigated. These results indicate that Tl activated crystals are more robust than the Na activated crystals against humidity induced scintillation degradation. The development of "etching pits" and "inactive" domains are the characteristics of deteriorated Na activated CsI crystals. These "inactive" domains, bearing a resemblance to a polycrystalline appearance beneath the crystal surface, can be readily detected by a 250 nm light emitting diode. These features are commonly observed at the corners and deep scratched areas where moisture condensation is more likely to occur. Mechanisms contributing to the scintillation degradation in Na activated CsI crystals were investigated by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). ToF-SIMS depth profiles indicate that Na has been preferentially diffused out of CsI crystal, leaving the Na concentration in these "inactive" domains below its scintillation threshold.

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“…Furthermore, the nanoparticles of NaI are more hygroscopic in the air than other alkali halides. An anti-moisture process after the deposition process of CsI:Na film is necessary because the hygroscopic nanoparticles remarkably decrease the luminescence scintillation and generate cracks in the cylindrical structure [9,12,[22][23][24][25]. In previous studies, the protective SiO 2 , Al, and parylene-N layers subsequently deposited on the CsI or CsI:Na film in the same vacuum chamber was investigated, respectively [14][15][16][17]19].…”

Section: Introductionmentioning

confidence: 99%

Luminescence of CsI and CsI:Na Films under LED and X-ray Excitation

Hsu

2019

Coatings

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In this study, we investigated the luminous properties of undoped cesium iodide (CsI) and Na-doped CsI (CsI:Na) films deposited by thermal vacuum evaporation and treated with different substrate temperatures, post-annealing temperatures, and deposition rates. The quality of the deposited films was evaluated by their XRD pattern, SEM cross-section/surface morphologies and UV/X-ray luminescence, the spectra of which were used to derive the luminescence mechanism of the deposited films. The 310 nm luminescence demonstrates that the exciting light arises from the electron–hole recombination through the self-trapped exciton (STE) process, which is characteristic of the host polycrystalline CsI. The broad-band luminescence from ~400 to 450 nm demonstrates the other electron–hole recombination between the new energy states created by doping Na in the forbidden gap of CsI. When we deposited higher quality films at a substrate temperature of 200 °C, the undoped CsI films showed preferred crystal orientation at (200), and the CsI:Na films co-evaporated by 1 wt.% NaI at (310) and had the highest UV/X-ray luminescence.

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Degradation of 81 keV 133Xe gamma-rays into the 31 keV X-ray peak in CsI scintillators

Cited by 7 publications

References 2 publications

Effect of H2O Molecule Adsorption on the Electronic Structure and Optical Properties of the CsI(Na) Crystal

Effect of H2O Molecule Adsorption on the Electronic Structure and Optical Properties of the CsI(Na) Crystal

Effect of Humidity on Scintillation Performance in Na and Tl Activated CsI Crystals

Luminescence of CsI and CsI:Na Films under LED and X-ray Excitation

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