Positron Annihilation Spectroscopy of KCl (Zn) crystals

Biganeh, A.; Kakuee, O.; Rafi‐Kheiri, H.

doi:10.1016/j.apradiso.2020.109330

Cited by 8 publications

(3 citation statements)

References 41 publications

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“…Research shows that due to the presence of chlorine in PVC polymer, like other halogens, it can act as a strong inhibitor in the formation of Ps. 3,4 The purpose of this research is to try to understand the performance of PVC polymer material and PVC-EVA polymer mixture at the atomic level and how to form polar and non-polar bonds. To achieve this, the coincidence Doppler broadening spectrometer (CDBS) is used to measure and understand the chemical environment of materials at the place of positron annihilation (structural defects) by measuring the momentum distribution of the valence or core electrons that participated in the annihilation process.…”

Section: Introductionmentioning

confidence: 99%

“…The electron affinity difference between the two atoms C¬ (2.55) and O (3.44) in the carbonyl group (C=O) in the EVA acetate part is about 0.89, which indicates a strong polar group in the polymer structure. Research shows that due to the presence of chlorine in PVC polymer, like other halogens, it can act as a strong inhibitor in the formation of Ps 3,4 …”

Section: Introductionmentioning

confidence: 99%

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Characterization of polar groups in polyvinyl chloride–ethyl vinyl acetate blends using coincidence Doppler broadening spectroscopy

Ghasemifard,

Ghamari

2023

J of Applied Polymer Sci

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Coincidence Doppler broadening spectroscopy (CDBS), known for its exceptional precision, is extensively employed in examining the electronic states of polymers. In this study, polyvinyl chloride (PVC)–ethyl vinyl acetate (EVA) polymers blends were prepared using conventional techniques, following specific ratios (75:25, 50:50, and 25:75, respectively). Spectroscopic analysis reveals that the longitudinal component of linear momentum surpasses the momentum unit (i.e., 10−3 m0c) when considering the ratio curve associated with the participation of oxygen core electrons. When compared to non‐polymer samples, the PVA polymer and PVA–EVA polymer blend exhibit greater free volume voids in contrast to non‐polymer structural defects. Furthermore, the annihilation of ortho‐positronium with core electrons, likely EVA oxygen core electrons, contributes to the measured free volume voids. An increased annihilation of positrons or positroniums by oxygen in the CDBS spectrum leads to higher calculated W parameter values. Conversely, as the PVC content increases, the W parameter decreases, suggesting reduced ortho‐positronium annihilation and consequently, enhanced formation of para‐positronium in the overall annihilation process. In summary, this investigation demonstrates the utility of CDBS in elucidating the electronic states and free volume voids in PVC and EVA polymers.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterization of polar groups in polyvinyl chloride–ethyl vinyl acetate blends using coincidence Doppler broadening spectroscopy

Ghasemifard,

Ghamari

2023

J of Applied Polymer Sci

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“…Coincidence Doppler Broadening Spectroscopy (CDBS) is an effective technique for the research of material defects and the chemical environment of positron annihilation sites [1][2][3][4][5][6][7]. The positrons, which can be produced by positron source 22 Na, annihilate with electrons in the material sample to be studied.…”

Section: Introductionmentioning

confidence: 99%

A fully digital coincidence Doppler broadening spectrometer based on FPGA

et al. 2023

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In this article, we implemented a fully digital Coincidence Doppler Broadening (CDB) spectrometer consisting of two HPGe detectors, a fully digital processing and acquisition board, and a dedicated software system. The Field Programmable Gate Array (FPGA) on the board extracts energy and time stamp of digitized pulses from HPGe detectors, and communicates with the dedicated software by which the single channel spectrums and 2D coincidence spectrum were produced. We designed an instruction set dedicated to the CDB Spectrometer and the controller module in FPGA so that the FPGA subsystem is fully controllable and configurable. The trapezoidal pulse shaping algorithm was implemented in FPGA whose arguments are all configurable through the dedicated software by the instruction set. We examined the long-term stability of the spectrometer by 511 keV peak position of both channels. The 2D Gaussian fitting is performed on coincidence spectrum by the software to correct the peak drift of both channels. The results show that this method effectively improves the Doppler-broadened spectrum, by which the peak-to-background ratio increases from 7.0 × 105 to 1.9 × 106.

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