Lead Fluoride Research Articles

Developing an alternative calorimeter solution for the future Muon Collider: The Crilin design

The Crilin calorimeter represents a novel approach in the development of electromagnetic calorimeters for future colliders, especially for a Muon Collider. This paper details the design and performance of the innovative semi-homogeneous Crilin calorimeter, highlighting its capabilities in mitigating beam-induced backgrounds (BIB) while maintaining excellent time resolution (less than 50 ps), longitudinal segmentation, and fine granularity. These performances are achieved throughout a series of stackable and interchangeable lead fluoride (PbF2) crystal matrices readout by surface-mount UV-extended Silicon Photo-multipliers. Simulated and experimental results demonstrate the Crilin design’s potential to work as an efficient and cost-effective alternative to traditional electromagnetic calorimeters. Crilin radiation tolerance is discussed, as measured in several irradiation campaigns, as well as timing performances during a beam test at CERN-H2 with 120 GeV electrons for the latest prototype, Proto-1. Additionally, a description of the results from a recent beam test conducted at the LNF Beam Test Facility with 450 MeV electrons is provided, aiming to measure light yield losses due to irradiation.

The CRILIN calorimeter: gamma radiation resistance of crystals and SiPMs

The Crilin calorimeter is a semi-homogeneous calorimetric system based on Lead Fluoride (PbF2) crystals with UV-extended Silicon Photomultipliers (SiPMs) proposed for the Muon Collider. This study investigates the radiation resistance of crystals and SiPMs, subjected to 10 kGy gamma irradiation, equivalent to a 10-year service life in the Muon Collider. Our findings indicate that while PbF2 crystals exhibit a decrease in transmittance post-irradiation with partial recovery over time, the alternative PbWO4-Ultra Fast (PWO-UF) demonstrates exceptional radiation hardness, maintaining stable transmittance. SiPMs showed an increase in dark current and breakdown voltage post-irradiation, with less degradation observed in the SiPM biased during the exposure to radiation compared to the unbiased component. These results underscore the viability of PbF2 for radiation-tolerant calorimeters, though improvements in production homogeneity are needed. The superior performance of PWO-UF crystals suggests they are a promising alternative for high-radiation applications, but their higher cost must be carefully considered.

Lead fluoride as a multifunctional modifier in bismuth gadolinium borate glasses: Optical, structural, and radiation attenuation characterization

This study systematically evaluates the role of PbF2 in altering the optical and radiation shielding properties of bismuth gadolinium borate glasses with compositions 30Bi2O3–Gd2O3-xPbF2-(70-x)B2O3, for x ranging from 0 to 40 mol. %. The introduction of PbF2 significantly modified the absorbance profile, exhibiting distinct absorption peaks at 3.45, 4.15, and 4.69 eV, shifting from a flat curve in the undoped sample to well-defined peaks with increasing PbF2 content. Crucially, a reduction in both the direct and indirect optical band gaps was observed as the PbF2 content increased, indicating changes in the electronic structure of the glasses. Photon and neutron shielding capabilities were analyzed, revealing that the linear attenuation coefficient (μ), half-value layer (T0.5), and effective atomic number (Zeff) were enhanced with PbF2 additions. Notably, the BGPB5 sample contained 40 mol. % PbF2 outperformed other compositions, offering the highest attenuation efficiency, which surpassed some conventional glasses and concretes. Simultaneously, an inversely proportional relationship was found between PbF2 concentration and the effective removal cross-section for fast neutrons (ΣR), demonstrating the BGPB1 sample's superiority as a neutron shield. The incorporation of PbF2 in the glass matrix not only improved gamma radiation shielding but also tuned the optical properties, marking these glasses as potential candidates for multifunctional radiation shielding applications.

A Water-in-Salt Electrolyte for Room-Temperature Fluoride-Ion Batteries Based on a Hydrophobic-Hydrophilic Salt.

Realizing room-temperature, efficient, and reversible fluoride-ion redox is critical to commercializing the fluoride-ion battery, a promising post-lithium-ion battery technology. However, this is challenging due to the absence of usable electrolytes, which usually suffer from insufficient ionic conductivity and poor (electro)chemical stability. Herein we report a water-in-salt (WIS) electrolyte based on the tetramethylammonium fluoride salt, an organic salt consisting of hydrophobic cations and hydrophilic anions. The new WIS electrolyte exhibits an electrochemical stability window of 2.47 V (2.08-4.55 V vs Li+/Li) with a room-temperature ionic conductivity of 30.6 mS/cm and a fluoride-ion transference number of 0.479, enabling reversible (de)fluoridation redox of lead and copper fluoride electrodes. The relationship between the salt property, the solvation structure, and the ionic transport behavior is jointly revealed by computational simulations and spectroscopic analysis.

A comprehensive DFT study on the structural, electronic, elastic, and optical behaviour of CsPbF3 under the effect of stress

Fluoro-perovskite compounds are important and auspicious materials according to their properties in photovoltaic anti-reflective coating and optoelectronics. In this study, the structural, mechanical, and optoelectronic properties of Cesium Lead Fluoride CsPbF3 were investigated using first principle calculations with generalized gradient approximations. The effect of stress on the crystal structure of CsPbF3 was examined at 0, 20, 40, and 59 GPa. It was found that the lattice constant is decreased with increasing stress, and the elastic, electronic, and optical properties of the material were significantly affected. The density of states and band gap of CsPbF3 were also calculated, and the band gap was found to be zero at 59 GPa. The cubical structure of CsPbF3 is distorted at 58 GPa. The various mechanical characteristics such as the bulk modulus, shear modulus, Young’s modulus, and Poisson ratio were derived and discussed. The results indicate that CsPbF3 exhibits ductile behaviour and anisotropic nature under stress, and the increase in refractive index, absorption, reflectivity, and conductivity at high stress make it a promising material for optoelectronic devices.

Study of electrical conductivity of fluorine-conducting solid electrolytes based on lead fluoride

Samples of solid electrolytes based on β-Pb F2 doped with ScF3 were synthesized. The dependence lg σT has been studied from 1/Т the samples received. Significant changes in electrical conductivity and enthalpy are observed at an impurity concentration of 0,05±0,02. It has been established that as the content of SсF3 molecules in a solid solution increases, the number of defective regions increases and at a certain impurity concentration their spatial overlap occurs. The formation of a closed three-dimensional network of the defect phase corresponds to percolation and is accompanied by a change (often sharp) in the conductivity and other properties of solid solutions.

Er3+: B2O3-TeO2-ZnO-PbF2−M2O/MF (M = Li, Na, and K) glasses: An inspection of structural, thermal, optical, chromatic, and near-infrared luminescence traits for displays and potential C-band amplification

Six 1.0 mol% Er2O3-doped lead fluoride zinc borotellurite glasses comprising different alkali metal oxides and fluorides (K2O, Na2O, Li2O, KF, NaF, and LiF) have been synthesized via melting and quick-quench approach and structural, thermal, optical, chromatic, upconversion, and NIR (near-infrared) emission features and fluorescence decay times were explored. Main structural units BO3 and BO4, as well as TeO4 and TeO3, are affirmed in all glasses networks by Fourier transform infrared and Raman spectroscopy. For transition 4I13/2 →4I15/2, σemi (emission cross-section) has been assessed by applying Füchtbauer–Ladenburg and McCumber's theories. For Li2O and NaF constituting glasses, acquired peak absorption cross-section (4I15/2→4I13/2) values are 0.999 × 10−20 cm2 and 1.093 × 10−20 cm2, while σemiM (4I13/2→4I15/2) values are 1.064 × 10−20 cm2 and 1.174 × 10−20 cm2 individually. At various P (population inversion) values, calculated gain spectra revealed the C- band amplification from P = 40%.

Isotropic pressure induced structural, electronic, photocatalytic, elastic and mechanical properties of RbPbF3: GGA-PBE and HSE03 based computational estimation

The main objective of this study is to present a comprehensive computational analysis, with Generalized Gradient Approximations (GGA) and Heyd–Scuseria–Ernzerhof (HSE03) correlation functionals, of the structural, optoelectronic, photocatalytic and elastic properties of Rubidium Lead Fluoride (RbPbF3) under the systematic isotropic pressure range of 0–55 GPa. Under stress a systematic decrease in lattice parameters and band gap (4.869 eV − 1.105 eV) is observed upto 55 GPa. For comprehensive evaluation of band gap, PDOS and EPDOS have also been determined. Photocatalytic properties of RbPbF3 under stress demonstrate the best photocatalytic water-splitting potential, aligning with the band gap estimation. The significant variation in optical parameters is found with a varying stress array from 0–55 GPa. Optically this compound can be utilized as a UV detector because absorption bands are seen in the UV spectrum. The material exhibits mechanical stability, and ductile behavior, with ionic and covalent bonding. The anisotropic nature is observed in our estimated results.

Thermal, structural and optical properties of tungsten-fluorophosphate glasses and glass-ceramics with high lead fluoride contents

Eu3+-doped lead fluorophosphate glass samples were prepared in the ternary system (40-x)NaPO3-xWO3-60PbF2 by the melt-quenching method. The influence of the NaPO3/WO3 ratio on the thermal and structural properties as well as on the ability of these compositions to crystallize as glass-ceramics containing lead fluoride phase β-PbF2 was investigated. Thermal properties and characteristic temperatures were determined by DSC and used to define suitable heat-treatment temperatures for selective crystallization. The corresponding crystalline phases and average crystallite sizes were determined by X-ray diffraction. Structural changes versus composition were also studied by Raman spectroscopy. UV-visible absorption spectra were used to determine the bandgap energies versus composition. Specific compositions exhibiting β-PbF2 crystallization were selected and Eu3+ emission spectra were used to check the Eu3+ environment and crystallization state as a function of heat-treatment conditions and glass composition. The results suggest that progressive β-PbF2 crystallization promotes a higher symmetry and lower phonon energy environment of Eu3+ resulting in longer excited state lifetimes only for WO3 richer compositions.

Interfacial Topochemical Fluoridation of MAPbI3 by Fluoropolymers

Herein it is demonstrated that, under conditions relevant to perovskite synthesis (>140 °C in air), fluoride can topochemically react across the interface between a halide perovskite and a fluoropolymer when in close contact, thereby creating a small quantity of strongly bonded lead fluoride species. The quantity increases with temperature and processing duration. Photoinduced charge carrier lifetime provides a metric for the resulting changes in electronic structure of the perovskite. Under short-duration and/or moderate temperature processing, fluoride transfer to the perovskite yields increased carrier lifetimes, up to 3-fold longer than control samples, which is attributed to passivation of surface defects. Under more forcing conditions, the trend reverses: excessive fluoridation leads to shortened carrier lifetimes, which is ascribed to substantial interfacial formation of PbF2. It is demonstrated that an interface with bulk crystalline PbF2 quenches perovskite photoluminescence, likely due to PbF2 serving as an electron acceptor for the conduction band of MAPbI3.

Effect of Lead Fluoride on the Spectroscopic Properties of Dy3+-Doped Borate-Based Glasses

Effect of Lead Fluoride on the Spectroscopic Properties of Dy3+-Doped Borate-Based Glasses

Accelerator based epithermal neutron source for clinical boron neutron capture therapy

The world’s first accelerator based epithermal neutron source for clinical boron neutron capture therapy (BNCT) was designed, developed, and commissioned between 2008 and 2010 by Sumitomo Heavy Industries in collaboration with Kyoto University at the Kyoto University Institute for Integrated Radiation and Nuclear Science. The accelerator system is cyclotron-based and accelerates a proton up to an energy of approximately 30 MeV. The proton strikes a beryllium target, which produces fast neutrons that traverse a beam shaping assembly composed of a combination of lead, iron, aluminum, and calcium fluoride to reduce the neutron energy down to the epithermal range (∼10 keV) suitable for BNCT. The system is designed to produce an epithermal neutron flux of up to 1.4 × 10 9 n · cm − 2 · s − 1 (exiting from the moderator of a 12 cm diameter collimator) with a proton current of 1 mA. In 2017, the same type of accelerator was installed at the Kansai BNCT Medical Center and in March 2020 the system received medical device approval in Japan (Sumitomo Heavy Industries, NeuCure® BNCT system). Soon after, BNCT for unresectable, locally advanced, and recurrent carcinoma of the head and neck region was approved by the Japanese government for reimbursement covered by the national health insurance system.

Response of Lead Fluoride (PbF2) Crystal under X-ray and Gamma Ray Radiation

Background: In this research, the response of a 10 × 10 × 10 mm3 commercially available PbF2 crystal was experimentally assessed under X-ray and gamma ray radiation to verify the possible application of this material in X-ray medical imaging. Methods: The measurements were performed under X-ray from 50 to 130 kVp and gamma ray excitation (Tc-99m 140 keV and I-131 365 keV). The PbF2 response was experimentally assessed by the determination of the absolute luminescence efficiency (AE), X-ray luminescence efficiency (XLE), and the stopping power of this scintillating crystal in terms of the energy absorption efficiency (EAE). The results were compared with bismuth germanate (BGO) crystal, which is commonly used in medical imaging modalities. Results: The AE of PbF2 gradually decreased from 50 kVp up to 130 kVp. The maximum value was 0.61 efficiency units (EU) at 140 keV, and the minimum value was 0.03 EU at 71 keV (130 kVp). Similarly, low values appeared for the XLE, where the maximum value was 16.9 × 10−5 at 140 keV. Conclusions: These findings show that the PbF2 scintillator has unacceptably low luminescence efficiency. Although PbF2 can effectively absorb radiation, the scintillation light, at room temperatures, is negligible, and, thus, it could not be used in medical imaging applications in the examined energy range.

R&D status for an innovative crystal calorimeter for the future Muon Collider

The measurement of physics processes at new energy frontier experiments requires excellent spatial, time, and energy resolutions to resolve the structure of collimated high-energy jets. Calorimeters, as other detectors, must face this increasing performance demand. In a future TeV-scale Muon Collider, the beam-induced background (BIB) represents the main challenge in the design of the detectors and of the event reconstruction algorithms and can pose serious limitations to the physics performance. However, it is possible to reduce the BIB impact on the Muon Collider calorimeter by exploiting some of its characteristics and by ensuring high granularity, excellent timing, longitudinal segmentation and good energy resolution. The proposed R&D is an innovative semi-homogeneous electromagnetic calorimeter based on stackable modules of lead fluoride crystals (PbF2) readout by surface-mount UV-extended Silicon Photomultipliers (SiPMs): the Crilin calorimeter (CRystal calorImeter with Longitudinal INformation). The calorimeter should operate in a very harsh radiation environment, withstanding yearly a neutron flux of 1014 n1MeV /cm2 and a dose of 100 krad. In this paper, the radiation tolerance measured in several irradiation campaigns and the timing performances evaluated during a test beam at CERN-H2 with 120-GeV electron are discussed. A description of the latest prototype Proto-1, that will be shortly tested, is also provided.

CONDUCTIVITY OF SOLID FLUORIDE-CONDUC­TING PHASES BaxPb0.86-xSn1.14F4

This work presents the results of research of complex solid fluoride ion conducting phases based on lead and tin fluorides. Structure and conductive properties of solid solutions based on PbSnF4 were investigated. Series of samples were synthesized with replacement of lead cations with barium cations in structure of Pb0.86Sn1.14F4 in the concentration range of 0 ≤x ≤0.86. The barium cation has a larger radius and does not have a stereoactive lone pair of electrons, which can have a significant contribution to the conductivity of the synthesized phases and the characteristics of fluoride ion transportation in them.
 It was established that with partial or complete replacement of lead cations with barium cations in the fluoride ion conducting phases in Pb0.86Sn1.14F4 solid solutions of BaxPb0.86‑xSn1.14F4 , where x takes the values 0 ≤x ≤0.86 are formed. The symmetry of the crystal lattice of the synthesized phases in the concentration range of 0 ≤x ≤0.43 corresponds to the structural type of β-PbSnF4 (space group P4/ nmm). Farther increase in the content of barium fluoride cause their crystal lattice to rearrange and approach the structural type of BaSnF4 with preservation of the space group symmetry. The conductive properties of the synthesized phases were investigated.
 We register increase in conductivity of samples bound to increase of barium cation content in the range of 0 ≤x ≤0.43. After reaching peak in conductivity of samples it gradually lowers with increase of barium cation content in the range of 0.43 ≤x ≤0.86.
 The fluoride ion conducting phase Pb0.43Ba0.43Sn1.14F4, isostructural to β-PbSnF4, in comparison with the currently known fluoride-conducting phases has have the highest electrical conductivity in a wide temperature range. Its conductivity is almost two orders of magnitude higher than that of β-PbSnF4 and is 0.12 S/cm at 373 K. With 19FNMR method, it was determined that electrical conductivity is mainly provided by internodal fluorine anions, which are localized between layers of barium and stanium cations. The transfer numbers for fluorine anions in the synthesized phases correspond to the theoretical ones.

Crilin: CRystal calorImeter with Longitudinal InformatioN for a future Muon Collider

In modern experiment, a high granularity is required in order to distinguish signal particles from background and to solve the substructures necessary for jet identification. Time of arrival measurements in the calorimeter could play an important role in HL-LHC, since a high number of pile-up collisions is expected, and the timing could be used to assign clusters to the corresponding interaction vertex. In a Muon Collider, the timing could be used to remove signals produced by beam-induced background, asynchronous with respect to the bunch crossing. The calorimeter energy resolution is also fundamental to measure the kinematic properties of jets: a finely segmented calorimeter design should be favored in order to solve the jet substructure. However, this contrasts with the requirement for high timing resolution even for signal events involving low energy deposits, such as in the case of high impulse muons. Our proposed design, the Crilin calorimeter, is a semi-homogeneous calorimeter based on Lead Fluoride (PbF2) Crystals readout by surface-mount UV-extended Silicon Photomultipliers (SiPMs). In this paper, the development of a small prototype consisting of 2 layers of 3 × 3 crystals each is reported along with the relative results.

Mechanical Design of an Electromagnetic Calorimeter Prototype for a Future Muon Collider

Measurement of physics processes at new energy frontier experiments requires excellent spatial, time, and energy resolutions to resolve the structure of collimated high-energy jets. In a future Muon Collider, beam-induced backgrounds (BIB) represent the main challenge in the design of the detectors and of the event reconstruction algorithms. The technology and the design of the calorimeters should be chosen to reduce the effect of the BIB, while keeping good physics performance. Several requirements can be inferred: (i) high granularity to reduce the overlap of BIB particles in the same calorimeter cell; (ii) excellent timing (of the order of 100 ps) to reduce the out-of-time component of the BIB; (iii) longitudinal segmentation to distinguish the signal showers from the fake showers produced by the BIB. Moreover, the calorimeter should operate in a very harsh radiation environment, withstanding yearly a neutron flux of 1014 n1MeV/cm2 and a dose of 100 krad. Our proposal consists of a semi-homogeneous electromagnetic calorimeter based on Lead Fluoride Crystals (PbF2) readout by surface-mount UV-extended Silicon Photomultipliers (SiPMs): the Crilin calorimeter. In this paper, we report the mechanical design for the development of a small-scale prototype, consisting of 2 layers of 3 × 3 crystals.

Crilin: A Semi-Homogeneous Calorimeter for a Future Muon Collider

Calorimeters, as other detectors, have to face the increasing performance demands of the new energy frontier experiments. For a future Muon Collider the main challenge is given by the Beam Induced Background that may pose limitations to the physics performance. However, it is possible to reduce the BIB impact by exploiting some of its characteristics by ensuring high granularity, excellent timing, longitudinal segmentation and good energy resolution. The proposed design, the Crilin calorimeter, is an alternative semi-homogeneous ECAL barrel for the Muon Collider based on Lead Fluoride Crystals (PbF2) with a surface-mount UV-extended Silicon Photomultipliers (SiPMs) readout with an optimized design for a future Muon Collider.

Crilin: A CRystal calorImeter with Longitudinal InformatioN for a future Muon Collider

The measurement of physics processes at new energy frontier experiments requires excellent spatial, time, and energy resolutions to resolve the structure of collimated high-energy jets. In a future Muon Collider, the beam-induced backgrounds (BIB) represent the main challenge in the design of the detectors and of the event reconstruction algorithms. The technology and the design of the calorimeters should be chosen to reduce the effect of the BIB, while keeping good physics performance. Several requirements can be inferred: i) high granularity to reduce the overlap of BIB particles in the same calorimeter cell; ii) excellent timing (of the order of 100 ps) to reduce the out-of-time component of the BIB; iii) longitudinal segmentation to distinguish the signal showers from the fake showers produced by the BIB; iv) good energy resolution (less than 10%/√E) to obtain good physics performance, as has been already demonstrated for conceptual particle flow calorimeters. Our proposal consists of a semi-homogeneous electromagnetic calorimeter based on lead fluoride crystals (PbF2) read out by surface-mount UV-extended Silicon Photomultipliers (SiPMs): the Crilin calorimeter. In this paper, the performance of the Crilin calorimeter in the Muon Collider framework for hadron jets reconstruction has been analyzed. We report the characterisation of individual components together with the development of a small-scale prototype, consisting of 2 layers of 3 × 3 crystals each.

AC conductivity and modulus studies on (1-x)β-PbF2:xCeO2 composite solid electrolytes

Cubic Lead fluoride [β-PbF2] composite solid electrolyte systems are prepared by dispersing nano CeO2 (< 100nm) in different mol% (5, 10, 15, 20, 25) through the mechanical milling method. XRD and FTIR (ATR method) studies confirm that these are formed in two-phase systems. Scanning Electron Microscope (SEM) images of dispersed systems showed a change in surface morphology with respect to the host. Complex impedance spectroscopy is employed in the frequency range 0.5 to 10 MHz by varying temperatures from 30 to 350°C to study the electric and dielectric properties. Analysis of impedance and modulus spectra revealed the non-Debye nature of these composites. Conductivity measurements on these composites suggest that the frequency exponent (n) in Jonscher’s power law is found to be temperature dependent. The overlapping large polaron tunneling (OLPT) model could be suggested as a suitable hopping mechanism. The variation of the ‘β’ value obtained from the Kohlrausch-Williams-Watts (KWW) function shows a similar variation of ‘n’ in the Jonscher’s power law with temperature.