Martin Nikl

Bio: Martin Nikl is an academic researcher from Academy of Sciences of the Czech Republic. The author has contributed to research in topics: Luminescence & Scintillation. The author has an hindex of 61, co-authored 845 publications receiving 19590 citations. Previous affiliations of Martin Nikl include University of Milan & Claude Bernard University Lyon 1.

Scintillation detectors for x-rays

Abstract: Recent research in the field of phosphor and scintillator materials and related detectors is reviewed. After a historical introduction the fundamental issues are explained regarding the interaction of x-ray radiation with a solid state. Crucial parameters and characteristics important for the performance of these materials in applications, including the employed measurement methods, are described. Extended description of the materials currently in use or under intense study is given. Scintillation detector configurations are further briefly overviewed and selected applications are mentioned in more detail to provide an illustration.

Recent R&D Trends in Inorganic Single-Crystal Scintillator Materials for Radiation Detection

Abstract: In this review, the major achievements and research and development (R&D) trends from the last decade in the field of single crystal scintillator materials are described. Two material families are included, namely, those of halide and oxide compounds. In most cases, the host crystals are doped with Ce3+, Pr3+ or Eu2+ rare earth ions. Their spin- and parity-allowed 5d–4f transitions enable a rapid scintillation response, on the order of tens to hundreds of nanoseconds. Technological recipes, extended characterization by means of optical and magnetic spectroscopies, and theoretical studies are described. The latter provide further support to experimental results and provide a better understanding of the host electronic band structure, energy levels of specific defects, and the emission centers themselves. Applications in medical imaging and dosimetry, security measures, high-energy physics and the high-tech industry, in which X(γ)-rays or particle beams are used and monitored, are recognized as the main driving factor for R&D activities in this field.

Composition Engineering in Cerium-Doped (Lu,Gd)3(Ga,Al)5O12 Single-Crystal Scintillators

Abstract: The Ce-doped (LuyGd1–x)3(Gay,Al1–y)5O12 single crystals were grown by the micropulling down method. Their structure and chemical composition were checked by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) techniques. Optical, luminescent, and scintillation characteristics were measured by the methods of time-resolved luminescence spectroscopy, including the light yield and scintillation decay. Balanced Gd and Ga admixture into the Lu3Al5O12 structure provided an excellent scintillator where the effect of shallow traps was suppressed, the spectrally corrected light yield value exceeded 40 000 photons/MeV, and scintillation decay was dominated by a 53 ns decay time value which is close to that of Ce3+ photoluminescence decay. This study provides an excellent example of a combinatorial approach where targeted single-crystal compositions are obtained by a flexible, time saving, and cost-effective crystal growth technique.

Wide Band Gap Scintillation Materials: Progress in the Technology and Material Understanding

Abstract: Luminescence and scintillation characteristics of four selected material systems, namely CsI:Tl(Na), CeF 3 , PbWO 4 and Ce-doped aluminium perovskites XAIO 3 :Ce (X=Y, Lu, Y-Lu) are reviewed. The progress in their physical understanding and related optimisation of their characteristics and technology are demonstrated. The important role of various defect states in the scintillator performance of these materials is stressed, which has led to the need for a deeper study of the processes of energy transfer and storage to achieve their intrinsic limits and full exploitation in scintillation detectors.

Band-gap engineering for removing shallow traps in rare-earth Lu 3 Al 5 O 12 garnet scintillators using Ga 3 + doping

Abstract: We employ a combination of first-principles calculations and optical characterization experiments to explain the mechanism by which Ga${}^{3+}$ doping prevents the trapping of free carriers due to shallow traps in RE${}_{3}$Al${}_{5}$O${}_{12}$ garnet scintillators (where RE represents a $3+$ rare-earth cation). Specifically, we confirm that Ga${}^{3+}$ doping does not reduce the defect concentration (defect engineering), but rather leads to shifts in the valence and conduction bands such that the energy level of shallow defects is no longer in the forbidden gap where electrons can be trapped (band-gap engineering).

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Nanocrystals of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, and I): Novel Optoelectronic Materials Showing Bright Emission with Wide Color Gamut

Abstract: Metal halides perovskites, such as hybrid organic–inorganic CH3NH3PbI3, are newcomer optoelectronic materials that have attracted enormous attention as solution-deposited absorbing layers in solar cells with power conversion efficiencies reaching 20%. Herein we demonstrate a new avenue for halide perovskites by designing highly luminescent perovskite-based colloidal quantum dot materials. We have synthesized monodisperse colloidal nanocubes (4–15 nm edge lengths) of fully inorganic cesium lead halide perovskites (CsPbX3, X = Cl, Br, and I or mixed halide systems Cl/Br and Br/I) using inexpensive commercial precursors. Through compositional modulations and quantum size-effects, the bandgap energies and emission spectra are readily tunable over the entire visible spectral region of 410–700 nm. The photoluminescence of CsPbX3 nanocrystals is characterized by narrow emission line-widths of 12–42 nm, wide color gamut covering up to 140% of the NTSC color standard, high quantum yields of up to 90%, and radiativ...

The CMS experiment at the CERN LHC

Abstract: The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 10(34)cm(-2)s(-1) (10(27)cm(-2)s(-1)). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4 pi solid angle. Forward sampling calorimeters extend the pseudo-rapidity coverage to high values (vertical bar eta vertical bar <= 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.

Fast Anion-Exchange in Highly Luminescent Nanocrystals of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, I)

Abstract: Postsynthetic chemical transformations of colloidal nanocrystals, such as ion-exchange reactions, provide an avenue to compositional fine-tuning or to otherwise inaccessible materials and morphologies. While cation-exchange is facile and commonplace, anion-exchange reactions have not received substantial deployment. Here we report fast, low-temperature, deliberately partial, or complete anion-exchange in highly luminescent semiconductor nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, I). By adjusting the halide ratios in the colloidal nanocrystal solution, the bright photoluminescence can be tuned over the entire visible spectral region (410–700 nm) while maintaining high quantum yields of 20–80% and narrow emission line widths of 10–40 nm (from blue to red). Furthermore, fast internanocrystal anion-exchange is demonstrated, leading to uniform CsPb(Cl/Br)3 or CsPb(Br/I)3 compositions simply by mixing CsPbCl3, CsPbBr3, and CsPbI3 nanocrystals in appropriate ratios.