The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminum nucleus ($\mu$–$e$ conversion, $\mu^{-}N \rightarrow e^{-}N$); a lepton flavor-violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\times10^{-15}$, or 90% upper limit of a branching ratio of $7\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the $\mu$–$e$ conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described.

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Fedorite is a rare phyllosilicate, having a crystal structure characterized by SiO4-tetrahedral double layers located between continuous layers formed by edge-sharing (Ca,Na)-octahedra, and containing interlayer K, Na atoms and H2O molecules. A mineralogical-petrographic and detailed crystal-chemical study of fedorite specimens from three districts of the Murun alkaline complex was performed. The sequence of the crystallization of minerals in association with fedorite was established. The studied fedorite samples differ in the content of interlayer potassium and water molecules. A comparative analysis based on polyhedral characteristics and deformation parameters was carried out. For the first time, EPR, optical absorption and emission spectra were obtained for fedorite. The raspberry-red coloration of the mineral specimens could be attributed to the presence of Mn4+ ions.

The work is necessitated by search for new materials to detect ionizing radiation.The rare-earth ions doped with ternary alkali earth-halide systems are promising scintillators showing high efficiency and energy resolution. Some aspects of crystal growth and data on the structural and luminescence properties of BaBrI and BaClI doped with low concentrations of Eu 2+ ions are reported. The crystals are grown by the vertical Bridgman method in sealed quartz ampoule. New crystallography data for BaClI single crystal obtained by single crystal X-ray diffraction method are presented in this paper. Emission, excitation and optical absorption spectra as well as luminescence decay kinetics are studied under excitation by X-ray, vacuum ultraviolet and ultraviolet radiation. The energies of the first 4f-5d transition in Eu 2+ and band gap of the crystals have been obtained. We have calculated the electronic band structure of the crystals using density functional theory as implemented in the Ab Initio. Calculated band gap energies are in accord with the experimental estimates. The energy of gaps between the occupied Eu 2+ 4f level and the valence band top are predicted. In addition, positions of lanthanide energy levels in relation to valence band have been constructed using the chemical shift model.Recently the research focus is shifted to the study of mixed halide compounds due to their superior light yield . 6 In a number of barium dihalides BaFI-BaClI-BaBrI-BaBrCl, the scintillation properties have been studied for Eu-doped BaFI, BaBrCl and BaBrI. 7-11 Despite their excellent properties, experimental data on optical absorption and excitation spectra in spectral region of 4f-5d and band to band transitions are scarce because single-crystals doped with high concentrations of Eu 2+ ions (more than 5 mol. %) were used. When measuring high concentration doped samples, the inner filter effects can be observed. These include reabsorption and non uniform excitation throughout the sample. These effects dramatically change the shape of excitation spectrum. Therefore, estimation of the lowest energy of 4f-5d transitions in Eu-doped BaBrI given in 8,10 is not correct. Furthermore, the experimental determination of band gap in these crystals is not possible due to high absorption related to allowed 4f 6 5d 1 → 4f 7 transitions in Eu 2+ ions. At this moment, the energy of band gap of the mixed halide compounds is based on theoretical estimates.We investigate luminescence, electrical and structural properties of undoped BaBrI, BaBrI-0.05 mol.% Eu 2+ and BaClI-0.1 mol.% Eu 2+ crystals. Absorption, excitation and emission spectra, photoluminescence decay time constants, dielectric properties and pulsed height spectra are presented. The vacuum referred binding (VRBE) energy diagram is constructed in conformity with density functional study. It displays the electron binding energy in the ground and excited state levels of all divalent and trivalent lanthanides ions in BaBrI and BaClI crystals. Methodology Growth and Structural Characteriza...

Sulfhydrylbystrite, Na5K2Ca(Al6Si6O24)(S5)(SH), cell parameters a = 12.9567(6) Å, c = 10.7711(5) Å, space group P31c, is a new mineral belonging to the cancrinite group. It was found at Malaya Bystraya lazurite deposit, Lake Baikal area, Eastern Siberian Region, Russia, associated with lazurite, calcite, diopside, phlogopite and pyrite. The mineral develops at the margins of masses of lazurite, replacing it in some areas with the formation of nonequilibrium lazurite-diopside-sulfhydrylbystrite association. It is translucent, yellow to orange, with vitreous lustre, yellow streak and Mohs hardness of 4.5–5. The empirical formula, based on 12 (Si + Al), is Na5.17K1.87Ca0.99[Al6.01Si5.99O24](S5)0.862–(SH0.86)Cl0.07, Z = 2. The crystal structure of sulfhydrylbystrite may be described as an ABAC stacking of six-membered rings of SiO4 and AlO4 tetrahedra and extra-framework cations and anions located within structural cages. There are two type of cages, cancrinite and losod, stacked into chains at (0, 0, z) and (⅔, ⅓, z), respectively. The cancrinite cage hosts Ca2+ and (SH)– ions, whereas the (S5)2– polyanion is in the losod cage associated with Na+ and K+ cations. In addition, (SH)– and (S5)2– anions are detected in the structure of a mineral for the first time.For comparison, a structural and compositional study of a bystrite sample from the same deposit was carried out. Bystrite is confirmed to contain pentasulfide anions in the losod cages, similar to those of sulfhydrylbystrite, in contrast to previous studies. However, bystrite has chloride in cancrinite cages, whereas sulfhydrylbystrite has hydrosulfide in that position. The unit-cell parameters are distinctly different: bystrite has a = 12.8527(6) Å, c = 10.6907(5) Å in the same P31c space group.

The results of a combined electron probe microanalysis, single-crystal X‑ray diffraction, and Fourier transform infrared study of a crystal of armstrongite from Khan Bogdo deposit (Gobi, Mongolia) are reported. Major element analysis provided (wt%): CaO 9.2(1), ZrO2 20.9(2), and SiO2 62.5(2). Significant concentrations of REE (0.45 wt%) were also detected. From single-crystal structural refinement, armstrongite resulted monoclinic [space group C2/m, a = 14.0178(7), b = 14.1289(6), c = 7.8366(3) Å, b = 109.436(3)°, V = 1463.6(1) Å3, Z = 4] and twinned with two individuals rotated around a twin twofold axis parallel to [100]. The analyzed crystal was refined up to R = 3.3% (Rw = 2.9%). The structural refinement showed that the investigated armstrongite has only two water groups per formula unit consistent with the infrared analysis. Indeed, the occurrence in the infrared spectrum of the armstrongite (here reported for the first time) of two bending vibration bands at about 1640 and 1610 cm–1 testifies to the presence of two water groups environments. The results of this integrated approach converged to the following empirical formula (based on Si = 6 atoms per formula unit): (Ca0.96Ce0.01Yb0.01)Zr0.99Si6O14.97·2.02H2O. Finally, the studied mineral shows a framework density (FD = 21.86) lying in the range of zeolites and microporous heterosilicates with tetrahedral-octahedral frameworks. The determined crystal chemical features are relevant for the possible employment of this mineral or of its synthetic analogs for technological applications

The structures of tokkoite, K2Ca4[Si7O18OH](OH,F) and tinaksite, K2Ca2NaTi[Si7O18OH]O from the Murun massif (Russia) were refined from single-crystal X-ray diffraction data in the triclinic space group P 1: Average crystallographic data are a≈10.423, b≈12.477, c≈7.112 Å, α≈89.92°, β≈99.68°, γ≈92.97°, V≈910.5 Å3 for tokkoite; a≈10.373, b≈12.176, c≈7.057 Å, α≈90.82°, β≈99.22°, γ≈ 92.80°, V≈878.5 Å3 for tinaksite. The substantial similarities between the geometrical parameters of the tokkoite and tinaksite structures led us to conclude that the two minerals are isostructural. However, major differences of tokkoite with respect to tinaksite are larger lattice constants, especially concerning the b parameter, longer distances, especially ; larger values of the M1–M3 and O20–O2 bond lengths, and a stronger distortion of the M1 polyhedron. Mössbauer analysis showed that significant trivalent iron is present, VIFe3+ 40.0(7)% in tokkoite and 12.8(3)% in tinaksite. It is confirmed that 2Ca2þ (M1þM2) +(F, OH)(O20) ↔ Ti4þ (M1) +Naþ(M2) +O(O20) is the exchange reaction that describes the relation between tokkoite and tinaksite. In addition, this exchange reaction causes local stress involving mainly the M1 site and its interaction with the M2 and M3 sites

A crystal chemical study of narsarsukite from the Murun alkaline massif, Russia has been carried out combining single crystal X-ray diffraction, electron microprobe analyses, micro-Fourier Transform infrared spectroscopy and X-ray photoelectron spectroscopy. The narsarsukite single crystals are tetragonal (space group I4/m) with unit cell parameters: 10.7140(1)  a  10.7183(2) Å and 7.9478(1)  c  7.9511(1) Å. The XPS analysis showed that Fe occurs in the mineral as Fe3+, whereas the FTIR spectrum evidenced that the studied sample is anhydrous. The Murun narsarsukite has average crystal chemical formula: \ud Na2.04K0.01(V5+0.01Ti0.74Zr0.01Al0.01Fe3+0.22Mg0.01)1.00Si4.00(O10.74F0.23OH0.03) 11.00. Structural disorder at octahedral and interstitial sites was modeled and discussed also in consideration of the main substitutional mechanism Ti4+ + O2- ⟷ Fe3+ + (F-, OH-) active in the structure of the mineral