Search

Your search keyword '"Melcher, Charles"' showing total 391 results
Start Over Author "Melcher, Charles"
391 results on '"Melcher, Charles"'

3. Needs, trends, and advances in scintillators for radiographic imaging and tomography

Author

Wang, Zhehui, Dujardin, Christophe, Freeman, Matthew S., Gehring, Amanda E., Hunter, James F., Lecoq, Paul, Liu, Wei, Melcher, Charles L., Morris, C. L., Nikl, Martin, Pilania, Ghanshyam, Pokharel, Reeju, Robertson, Daniel G., Rutstrom, Daniel J., Sjue, Sky K., Tremsin, Anton S., Watson, S. A., Wiggins, Brenden W., Winch, Nicola M., and Zhuravleva, Mariya

Subjects
Physics - Instrumentation and Detectors
Abstract

Scintillators are important materials for radiographic imaging and tomography (RadIT), when ionizing radiations are used to reveal internal structures of materials. Since its invention by R\"ontgen, RadIT now come in many modalities such as absorption-based X-ray radiography, phase contrast X-ray imaging, coherent X-ray diffractive imaging, high-energy X- and $\gamma-$ray radiography at above 1 MeV, X-ray computed tomography (CT), proton imaging and tomography (IT), neutron IT, positron emission tomography (PET), high-energy electron radiography, muon tomography, etc. Spatial, temporal resolution, sensitivity, and radiation hardness, among others, are common metrics for RadIT performance, which are enabled by, in addition to scintillators, advances in high-luminosity accelerators and high-power lasers, photodetectors especially CMOS pixelated sensor arrays, and lately data science. Medical imaging, nondestructive testing, nuclear safety and safeguards are traditional RadIT applications. Examples of growing or emerging applications include space, additive manufacturing, machine vision, and virtual reality or `metaverse'. Scintillator metrics such as light yield and decay time are correlated to RadIT metrics. More than 160 kinds of scintillators and applications are presented during the SCINT22 conference. New trends include inorganic and organic scintillator heterostructures, liquid phase synthesis of perovskites and $\mu$m-thick films, use of multiphysics models and data science to guide scintillator development, structural innovations such as photonic crystals, nanoscintillators enhanced by the Purcell effect, novel scintillator fibers, and multilayer configurations. Opportunities exist through optimization of RadIT with reduced radiation dose, data-driven measurements, photon/particle counting and tracking methods supplementing time-integrated measurements, and multimodal RadIT., Comment: 45 pages, 43 Figures, SCINT22 conference overview

Published
2022
Full Text
View/download PDF

17. Scintillation Properties and Electronic Structure of Intrinsic and Extrinsic Mixed Elpasolites Cs2NaRBr3I3 (R = La, Y)

Author

Wei, Hua, Du, Mao-Hua, Stand, Luis, Zhao, Zhao, Shi, Honglin, Zhuravleva, Mariya, and Melcher, Charles L.

Subjects
Condensed Matter - Materials Science
Abstract

Scintillators attract wide research interest for their distinct applications in radiation detection. Elpasolite halides are among the most promising scintillators due to their high structural symmetry and good scintillation performance. Better understanding of their underlying scintillation mechanism opens up new possibilities in scintillator development. In this work, we employ a variety of experimental techniques to study the two mixed-anion elpasolites Cs2NaRBr3I3 (R = La, Y). The emission of intrinsic Cs2NaRBr3I3 with a light yield ranging from 20,000 to 40,000 ph/MeV is dominant by self-trapped exciton emission. Partial substitution of R with Ce introduces a competing emission, the Ce3+ 5d to 4f radiative transition. Ab initio calculations were performed to investigate the electronic structures as well as the binding energies of polarons in Cs2NaRBr6. The calculated large self-trapped exciton binding energies are consistent with the observed high light yield due to self-trapped exciton emission. The unique electronic structure of halide elpasolites as calculated enhances the STE stability and the STE emission. The highly tunable scintillation properties of mixed-anion elpasolites underscore the role of their complex scintillation mechanism. Our study provides guidance for the design of new elpasolites scintillators with exceptional energy resolution and light yield desirable for applications., Comment: 12 pages, 14 figures, 60% of the work was presented at 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference. The manuscript is pubilshed on Physical Review Applied

Published
2015
Full Text
View/download PDF

19. New ultrafast scintillators with core valence luminescence: Cs2MgCl4 and Cs3MgCl5.

Author

Rutstrom, Daniel, Stand, Luis, Windsor, Dylan, Xu, Haixuan, Kapusta, Maciej, Melcher, Charles L., and Zhuravleva, Mariya

Abstract

Future experiments in high energy physics and medical imaging require radiation detectors having properties which are not presently available. The main limitations arise from a lack of suitable scintillation crystals. This dilemma prompts the need for research leading to the discovery of new fast and bright scintillator materials that combine unique properties to fulfil modern experiment requirements without compromises. In this work, single crystals of Cs2MgCl4 and Cs3MgCl5 up to 12 mm in diameter are grown via the vertical Bridgman method. Scintillation properties are reported for the first time, and core valence luminescence is observed for both compounds. X-ray excited radioluminescence emission of Cs2MgCl4 is centered at 295 nm, with a scintillation decay time of 2.25 ± 0.05 ns and relatively high core-valence light yield of 2200 ± 110 ph per MeV. Cs3MgCl5 has two main emission peaks centered at 242 nm and 302 nm, a decay time of 1.46 ± 0.05 ns, and a light yield of 1340 ± 70 ph per MeV. The better coincidence time resolution (CTR) is obtained with Cs2MgCl4, which is measured to be 129 ± 4 ps FWHM. Density functional theory (DFT) calculations are also performed and provide supporting evidence that the observed scintillation originates from core valence luminescence. The combination of speed and brightness of these new scintillators could be useful for fast timing applications in which moderately dense materials are required. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

38. Needs, Trends, and Advances in Scintillators for Radiographic Imaging and Tomography

Author

Wang, Zhehui, primary, Dujardin, Christophe, additional, Freeman, Matthew S., additional, Gehring, Amanda E., additional, Hunter, James F., additional, Lecoq, Paul, additional, Liu, Wei, additional, Melcher, Charles L., additional, Morris, C. L., additional, Nikl, Martin, additional, Pilania, Ghanshyam, additional, Pokharel, Reeju, additional, Robertson, Daniel G., additional, Rutstrom, Daniel J., additional, Sjue, Sky K., additional, Tremsin, Anton S., additional, Watson, S. A., additional, Wiggins, Brenden W., additional, Winch, Nicola M., additional, and Zhuravleva, Mariya, additional

Published
2023
Full Text
View/download PDF

41. Crystal growth and phase formation of high‐entropy rare‐earth monoclinic aluminates.

Author

Pianassola, Matheus, Loveday, Madeline, Lalk, Rebecca, Pestovich, Kimberly, Melcher, Charles L., and Zhuravleva, Mariya

Subjects
CRYSTAL growth, PHASE transitions, RARE earth metals, ELECTRON probe microanalysis, ALUMINATES, X-ray powder diffraction
Abstract

For the first time, high‐entropy rare‐earth monoclinic aluminate crystals were grown via directional solidification using the micro‐pulling‐down method. Five high‐entropy compositions were formulated with a general formula RE4Al2O9, where RE is an equiatomic mixture of five rare‐earth elements. The rare‐earth elements included were Lu, Yb, Er, Y, Ho, Dy, Tb, Gd, Eu, Sm, Nd, and La. High‐temperature powder X‐ray diffraction and Rietveld structure refinement indicated that all crystals were a single monoclinic phase and that rare‐earth average ionic radius did not affect phase purity. At room temperature, the refined lattice parameters increased consistently with increasing average ionic radii of the five compositions. One of the crystals had a typical high‐temperature phase transition of single‐RE RE4Al2O9 in the range of 1100–1150°C, which consisted of a lattice contraction upon heating. Differential scanning calorimetry indicated a thermal event corresponding to that phase transition. Electron probe microanalysis revealed Al‐rich inclusions on the surface of the crystals. Crystals containing Tb had dark surface features that became lighter after annealing in a reducing atmosphere, which indicated that Tb4+ may be responsible for the dark features. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results