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We propose a method for studying nonlinearity in the cathodoluminescence (CL) characteristics of wide-bandgap materials based on the measurements of the CL energy dependence on the total energy of a pulsed electron beam E b using its bremsstrahlung. It is shown that the x-ray radiant energy produced by a high-power (∼ 10 MW / cm 2) electron beam with particle energies of 50–300 keV is proportional to E b in the case of weak variations in the electron energy distribution of the beam. This direct proportionality between E b and the x-ray radiant energy is experimentally confirmed in the current experiment by measuring the dependence of the molecular nitrogen emission radiant energy at 337 nm excited by a direct electron impact (the 0-0 vibrational transition of the second positive system of the emission bands of N 2 molecule) on the total electron beam energy E b. Using this result, the dependencies of the CL radiant energy on E b are studied for undoped Bi 4 Ge 3 O 12 , PbWO 4 , CeF 3 , and BaF 2 crystals with bright intrinsic luminescence. An interpretation of these dependencies is given using a simple theoretical model and photoluminescence nonlinearity data published in the literature. We estimate the average concentration of the electronic excitations (EE) provided by the electron beam (10 18 – 10 19 e.– h. p. / cm 3) and obtain the approximate dependencies of the CL yield on the EE density for the studied materials. For the CeF 3 crystal, different CL yield dependencies on the EE density are found for the bands at 300 and 350 nm. [ABSTRACT FROM AUTHOR]

Pr3+ doped high density germanate glasses were prepared by the melt-quenching method. The physical and luminescent properties were investigated. The glass containing BaF 2 represented maximum phonon energy of 810 cm−1, and the glass density was greater than 6 g/cm3. The glass exhibited good radiation resistance under 2 h of X-ray irradiation. Intense blue, green emissions and weak red emissions were observed when the glass was excited by X-ray, and the blue fluorescence lifetimes were in the range of 9.15–12.59 μs The results show that Pr3+ doped germanate glass could be a potential scintillating material in the field of X-ray detection for fast events. [ABSTRACT FROM AUTHOR]

Fast and heavy inorganic scintillators with suitable radiation tolerance are required to face the challenges presented at future hadron colliders of high energy and intensity. Up to 5 GGy and 5 × 1018 neq/cm2 of one-MeV-equivalent neutron fluence is expected by the forward calorimeter at the Future Hadron Circular Collider. This paper reports the results of an investigation of proton- and neutron-induced radiation damage in various fast and heavy inorganic scintillators, such as LYSO:Ce crystals, LuAG:Ce ceramics, and BaF2 crystals. The experiments were carried out at the Blue Room with 800 MeV proton fluence up to 3.0 × 1015 p/cm2 and at the East Port with one MeV equivalent neutron fluence up to 9.2 × 1015 neq/cm2, respectively, at the Los Alamos Neutron Science Center. Experiments were also carried out at the CERN PS-IRRAD proton facility with 24 GeV proton fluence up to 8.2 × 1015 p/cm2. Research and development will continue to develop LuAG:Ce ceramics and BaF2:Y crystals with improved optical quality, F/T ratio, and radiation hardness. [ABSTRACT FROM AUTHOR]

Ce3+-doped dense glasses with high light yield (LY) are promising scintillators for use in high-energy particle physics research and radiation sensors for high-energy X- and γ- ray detection. In this work, Ce3+-doped (60-x)SiO 2 -xBaF 2 -20Al 2 O 3 -20Gd 2 O 3 oxyfluoride glasses have been prepared under a CO reducing atmosphere. Substitution of SiO 2 by BaF 2 has been made to increase the density, and the effects on luminescence and scintillation properties have been investigated. The amorphous nature of the prepared glass is confirmed by the XRD profile showing an absence of any diffraction peaks. The broad photoluminescence (PL) emission band of the Ce3+ 5d–4f transition in the 330–580 nm range is observed peaking around 385 nm and the PL decay is governed in the range of 46–53 ns decay time. The 10 mol% BaF 2 glass with density of 4.54 g/cm3 shows the highest LY value of 1590 photons/MeV and energy resolution of 16.5% in the pulse height spectrum of 662 keV γ rays, and the LY of 141 photons/MeV and energy resolution of 21.7% in the pulse height spectrum of 5.5 MeV α particles. • Ce3+-doped (60-x)SiO 2 -xBaF 2 -20Al 2 O 3 -20Gd 2 O 3 (x = 0–20) glasses were prepared under CO atmosphere. • XRD pattern confirms an amorphous nature of the prepared glass. • Gd3+ to Ce3+ energy transfer was observed in the prepared glasses. • Light yield of 1590 photons/MeV at 662 keV γ rays was obtained for 10 mol% BaF 2 containing glass. • Energy transport efficiency in scintillation process increases with increasing BaF 2 content. [ABSTRACT FROM AUTHOR]

The physical, electronic and optical properties of Barium halides have been investigated by both experimental and theoretical approaches. The First Principle electronic structure and optical properties were calculated by DFT formalism using Full Potential Linearized Augmented Plane Wave plus local orbitals (FP-LAPW + lo) implementing different appropriate exchange-correlation functionals in WIEN2k code at various applied volumetric pressure up to 50 GPa. All the properties of these halides were analyzed and compared using their cation-anion radii ratio and ionicity. Except BaF 2 , the other three halides show ionic to covalent transformation at 50 GPa applied pressure. Both experimental and theoretical results compare reasonably well. The scintillation efficiency of these three halides was found to be directly proportional to their ionicity or band gap. • Study of physical, electronic and optical properties of Barium halides by experimental and theoretical approaches. • All the properties of the halides were analyzed and compared using their cation-anion radii ratio and ionicity. • The direct type band gap of the three halides decrease with pressure at least till 50 GPa. • Observed ionic to covalent transformation at 50 GPa applied pressure. • Experimental and theoretical results match reasonably well. [ABSTRACT FROM AUTHOR]

The short-wavelength sub-nanosecond luminescence in BaF 2 material, discovered in the early 80s, gave a new direction to research into fast scintillators and phosphors. In contrast to 'typical' luminescence occurring within the forbidden band gap, the new type of emission was due to transitions between the upper core and valence bands. Thus it was named core-valence luminescence (CVL); the terms cross-luminescence and Auger-free luminescence have also been used. Given its unusual nature, this new luminescence process has attracted considerable interest in the field of condensed matter physics. During the sequent decades (till the end of the previous century) CVL has been experimentally observed in several dozen compounds and the conditions for detecting CVL have been established. Interest in this kind of luminescence increased in recent years due to the emergence of new methods of crystal synthesis, the development of high-speed solid-state photodetectors, and the construction of unique modern set-ups using synchrotron radiation. This paper analyzes the numerous studies of CVL, obtained mainly over the past decade. Experimental and theoretical data on this topic are considered in detail. Special attention is given to new results on scintillation characteristics of BaF 2 in the form of single crystals, ceramics, nanoparticles, and composites. The features of CVL in binary and ternary compounds are discussed. Some Cs- and Ba-based ternary halides show relatively high light yields and represent promising fast scintillators. The prospects of using materials with CVL as fast scintillators for time-of-flight positron emission tomography and other applications are deliberated. • Overview of recent theoretical and experimental findings on Core Valence luminescence. • Most attractive CVL crystals for ultrafast scintillator applications analyzed. • Prospects for future studies and underexplored CVL materials listed. [ABSTRACT FROM AUTHOR]

Due to their reported fast decay times, Cs 2 ZnCl 4 and Cs 3 ZnCl 5 are promising candidates for detection of gamma rays and X-rays in high count rate and fast timing applications. In this work, we show that single crystals with better optical quality than previously demonstrated – and larger in size – can be grown via the vertical Bridgman method. Highly transparent Ø7 mm crystals of undoped Cs 2 ZnCl 4 and Cs 3 ZnCl 5 are grown and measured to have light yields surpassing those previously reported, achieving 1980 ± 100 ph/MeV and 1460 ± 70 ph/MeV at 662 keV – a 55% and 232% improvement, respectively. We observe single-component scintillation decay times for both Cs 2 ZnCl 4 (1.66 ns) and Cs 3 ZnCl 5 (0.82 ns) and radioluminescence emission with maximum intensity at ∼290 nm. Scalability of these materials is also evaluated based on growth of Ø22 mm crystals. Minimal cracking is observed, and the fast decay times are maintained at this size. Coincidence time resolution of 3 × 3 × 5 mm3 and 7 × 7 × 10 mm3 pixels cut from Ø22 mm Cs 2 ZnCl 4 are measured to be 148 ± 1 ps FWHM and 175 ± 1 ps FWHM, respectively. The improved performance and ability to be fabricated in large sizes now place Cs 2 ZnCl 4 and Cs 3 ZnCl 5 on the map as potential contenders for radiation detection applications where BaF 2 – the most commonly used ultrafast inorganic scintillator – is typically considered. • Single crystals of Cs 2 ZnCl 4 and Cs 3 ZnCl 5 were grown by the vertical Bridgman method. • Cs 2 ZnCl 4 had a scintillation decay time of 1.66 ns and light yield of 1980 ph/MeV at 662 keV. • Cs 3 ZnCl 5 had a scintillation decay time of 0.82 ns and light yield of 1460 ph/MeV at 662 keV. • The coincidence time resolution of Cs 2 ZnCl 4 was measured to be as good as 136 ± 2 ps FWHM. [ABSTRACT FROM AUTHOR]