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RISS 인기검색어
- 검색키워드
- 저자 : Indra Raj Pandey (검색결과 8 건)
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Pandey, Indra Raj,Karki, Sujita,Kim, H.J.,Lee, M.H.,Kim, Y.D. Elsevier 2019 Journal of crystal growth Vol.512 No.-
<P><B>Abstract</B></P> <P>The inorganic material Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> was synthesized by solid-state reaction, and a single crystal of the compound was grown using the Czochralski technique. The crystal structure of the compound was confirmed by X-ray diffraction (XRD) analysis. The luminescence light yield and fluorescence decay time of the crystal were studied in a temperature range from room temperature to 10 K using a 280 nm light emitting diode (LED) source. The Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> crystal has no luminescence at room temperature, however, the luminescence intensity is enhanced at low temperatures. Transmittance spectrum measurement was performed to study the optical quality of the crystal. The luminescence light yield of the Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> was compared with that of a Li<SUB>2</SUB>MoO<SUB>4</SUB> crystal at different low temperatures. Because of the possibility of growing a single crystal of Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB>, which has a significant luminescence light yield at 10 K and no heavy elements, this crystal can be a good candidate for a rare event search experiment searching for neutrinoless double beta (0νββ) decay at cryogenic temperatures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single crystals of Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> is grown for first time. </LI> <LI> Powder XRD result of Na<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB> and Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> compound shows that, both compound has almost the same phase. </LI> <LI> Luminescence properties of new Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> crystal is reported. </LI> <LI> The luminescence result of Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> at 10 K is compared with Li<SUB>2</SUB>MoO<SUB>4</SUB> crystal. </LI> <LI> At 10 K, luminescence light yield of Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> is almost double than Li<SUB>2</SUB>MoO<SUB>4</SUB> crystal. </LI> </UL> </P>
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Indra Raj Pandey,Jae Young Choe,D. Joseph Daniel,H. J. Kim,Moo Hyun Lee,Sunghwan Kim 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.8
A single crystal of Na2W2O7 was grown by using the conventional Czochralski technique. The crystal structure of the grown sample was verified by using a powder X-ray diffraction (XRD) analysis. The luminescence, as well as scintillation, properties of the crystals were evaluated at room temperature. The emission spectra of the crystal were obtained by irradiating the sample with X-ray and proton sources. The trap level of the grown crystal was studied from 325 K to 500 K, and different kinematic parameters were calculated. The scintillation properties such as; energy resolution, light yield, uorescence decay time and ff/fi ratio of the crystal, were studied by using - (662 keV from 137Cs) and ff- (5.4 MeV from 241Am) sources. The luminescence and the scintillation results revealed that the Na2W2O7 crystal would be a good material for the dark matter search and for high-energy physics experiment.
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Pandey, Indra Raj,Kim, H.J.,Kim, Y.D. Elsevier 2017 Journal of crystal growth Vol.480 No.-
<P><B>Abstract</B></P> <P>Disodium dimolybdate (Na<SUB>2</SUB>Mo<SUB>2</SUB>O<SUB>7</SUB>) crystals were grown using the Czochralski technique. The thermal characteristics of the compound were analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements. The crystal structure of the grown sample was confirmed using X-ray diffraction (XRD). Luminescence properties were measured at room and low temperatures, using a light emitting diode (LED) source. Very weak luminescence was observed at room temperature; however, the luminescence intensity was enhanced at low temperatures. The crystal’s transmittance spectrum was measured for estimating its optical quality and energy band gap. The grown crystal exhibited a luminescence light yield of 55% compared with CaMoO<SUB>4</SUB> crystals at 10 K, when excited by a 280-nm-wavelength LED source, but does not have the drawbacks of radioactive Ca isotopes. These results suggest that at cryogenic temperatures, Na<SUB>2</SUB>Mo<SUB>2</SUB>O<SUB>7</SUB> crystal scintillators are promising for the detection of dark matter and neutrinoless double beta decay of <SUP>100</SUP>Mo.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single crystals of Na<SUB>2</SUB>Mo<SUB>2</SUB>O<SUB>7</SUB> was grown by Czochralski technique at first time. </LI> <LI> Scintillation properties of new Na<SUB>2</SUB>Mo<SUB>2</SUB>O<SUB>7</SUB> crystal scintillator was reported. </LI> <LI> The grown material was less hygroscopic than Li<SUB>2</SUB>MoO<SUB>4</SUB> single crystal. </LI> <LI> At 10 K, light yield of reported crystal was 55% as compared to reference CaMoO<SUB>4</SUB> crystal. </LI> <LI> This crystal was found promising candidate for 0ν2β decay and dark matter search at low temperature. </LI> </UL> </P>
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천종규,Kim Seonghwan,PANDEY INDRA RAJ,김홍주 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.8
In this study, we developed a cryogenic thermoluminescence (TL) measurement system and evaluated its performance. A graphical user interface-based data acquisition software is programmed to control the whole system, which includes the thermostat, photomultiplier tube, and counter. To test the measurement system, we use Na2W2O7 (NWO) crystal. The NWO crystal was grown with a conventional Czochralski system. At room temperature (300 K), a broadband emission spectra of the crystal was obtained in the range of 340–790 nm under the excitation of a 280 nm light emitting diode (LED) source. The glow curves of NWO crystals were measured from 9 to 300 K with the cryogenic TL measurement system developed in this study. Six glow peaks at 23, 35, 110, 143, 178, and 231 K were observed from 9 to 300 K. The measured glow curves were analyzed by computerized glow curve deconvolution technique. The activation energy, order of kinetics, frequency factor, and fgure of merit (FOM) for each peak were obtained. The calculated FOMs for all glow peaks were found to be less than 4%, which confrmed that the developed cryogenic TL measurement system works well.
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Sujita Karki,Pabitra Aryal,하대훈,김홍주,박향규,Indra Raj Pandey 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.7
Nano powders of CaMoO$_4$ were synthesized by using the precipitation method, and the obtained powders were dried inside a vacuum oven at 120 $^\circ$C. The phases of powders were analyzed by using X-ray diffraction (XRD), which revealed that CaMoO$_4$ was free from any extra phases. The surface morphologies of the powders were studied by using transmission electron microscopy (TEM), and the average particle sizes were quite small, being in the range of 7 nm. The optical properties were characterized by using ultraviolet-visible (UV-vis) absorption spectroscopy and the optical energy band gap was found to be 5.51 eV. The fluorescence decay time and the luminescence spectrum of the sample were measured under the excitation by Laser (266 nm), X-ray and proton sources. The obtained results were compared with the CaMoO$_4$ bulk crystal and sintered powder obtained from the solid state reaction.
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Khan, Arshad,Daniel, D. Joseph,Kim, Hongjoo,Pandey, Indra Raj,Shlegel, Vladimir,Lee, Moo Hyun,Kim, Yeongduk Elsevier 2019 Radiation measurements Vol.123 No.-
<P><B>Abstract</B></P> <P>A PbMoO<SUB>4</SUB> single crystal with optically good quality and crack free, bulk crystal is grown by the low thermal gradient Czochralski method. The luminescence and scintillation properties of the grown crystal are measured under the excitations by 4.4 eV UV, 662 keV γ, 5.5 MeV α, and β in the temperature range of 10–300 K. The light yield under UV and β excitations are found to enhance down to 10 K, however quenched below 50 K under γ and α excitations. The major luminescence and scintillation decay time constants are found to be 20 μs, 18 μs, and 28 μs, respectively, with 4.4 eV, 662 keV γ, and 5.5 MeV α excitations at 10 K. The thermally stimulated luminescence (TSL) glow curve measured after X-ray irradiation at 10 K, shows three overlapping peaks in the temperature range of 10–70 K. The TSL kinetic parameters such as trap depth (E) and frequency factor (s) are determined by using general order kinetics and found to be, 41.5 K (peak-1), 35 meV, 3.95 × 10<SUP>2</SUP> s<SUP>−1</SUP>, 51.1 K (peak-2), 121 meV, 4.31 × 10<SUP>10</SUP> s<SUP>−1</SUP>, and 56.8 K (peak-3), 123 meV, 3.32 × 10<SUP>9</SUP> s<SUP>−1</SUP>. The quenching of scintillation light yield under α and γ excitations at lower temperature is due to the self-trapping of electrons at (MoO<SUB>4</SUB>)<SUP>2-</SUP> molecular complex.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Luminescence, scintillation and TSL properties are studied in 10–300 K range. </LI> <LI> Scintillation light under α- and γ-rays excitation quenches below 50 K. </LI> <LI> Light yield enhances under UV and β-rays excitation down to 10 K. </LI> <LI> The major decay time becomes slower with decreasing the temperature. </LI> <LI> TSL kinetics parameters are calculated with general order kinetics. </LI> </UL> </P>
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