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Response of Waveguide-Integrated Germanium-on-Silicon p-i-n Photodiodes to Neutron Displacement Damage
摘要： The effects of 14-MeV neutron displacement damage (DD) on waveguide-integrated germanium-on-silicon p-i-n photodiodes (PDs) for silicon photonics have been investigated up to fluences of 7.5×1012 n/cm2 (14 MeV), or 1.4×1013 n1-MeVeq /cm2(Si). The study includes measurements of dark current-voltage characteristics across temperature from 150-375 K, measurements of PD junction capacitance, spectral response measurements from 1260 nm to 1360 nm, and frequency response measurements. The devices are found to be susceptible to DD-induced carrier removal effects; however, they also continue to operate without meaningful impact to performance for the DD dose levels examined. Since the PD test chips include silicon photonic integrated grating couplers and waveguides which carry the optical signal to the PD, some assessment of the impact of DD on these passive devices can also be inferred. This work does not examine the short-term annealing or transient behavior of the DD, and instead has only considered the lasting damage that remains after any initial period of room temperature annealing.
关键词： displacement damage,photonics,Radiation effects,neutron radiation,photodiodes,optoelectronic devices
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Light and Slow-Neutron Diffraction Properties of Holographic Nanodiamond Composite Gratings
摘要： Photopolymerizable nanoparticle-polymer composite (NPC) is a photonic nanocomposite material consisting of photopolymer uniformly dispersed with nanoparticles (e.g., SiO2 and ZrO2). The distribution of dispersed nanoparticles can be manipulated holographically by light. This technique, the so-called holographic assembly of nanoparticles in polymer, enables us to perform the single step formation of large area photonic lattice structures for photonic applications such as holographic data storage, holographic diffractive elements and nonlinear optics. Furthermore, we showed that holographic NPC gratings could control slow-neutron (cold and very cold neutron) beams for neutron interferometer. Here we demonstrate for the first time the use of nanodiamonds (NDs), an intriguing allotrope of carbon, in NPCs to construct holographic NPC gratings with very large refractive index modulation amplitudes (Δn) and thus to efficiently control light and slow-neutron beams. This is possible because NDs have very high bulk refractive index at optical wavelengths and very large coherent and very small incoherent scattering cross sections with low absorption at slow-neutron wavelengths.
关键词： holographic grating,photopolymer,diffraction,slow-neutron,nanodiamond
更新于2025-09-12 10:27:22
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Stress distribution in laser metal deposited multi-layer thick-walled parts of Ti-6Al-4V
摘要： The laser metal deposition is an additive manufacturing technology enabling the production of large scale complex parts without additional treatment like welding or machining. The study of the origin of the stress field during laser metal deposition is essential for solving a number of problems, including: the assessment of cold and hot cracking; prediction of the fatigue resistance, and the stress corrosion cracking. The quantitative study of transient and residual stresses in build parts is necessary for optimising the parameters of processing and post-production stress relieving heat treatment. Residual stress field in laser metal deposited 50-layer (4-pass per layer) wall of Ti-6Al-4V was analysed experimentally using neutron diffraction and numerically using finite element simulation. Long dwell time between passes and a rigid substrate was used in order to simulate conditions of large scale parts fabrication. An analysis of the calculated and experimentally measured residual stress field showed that near the edges of the buildup there is a region where all three components of stress field are tensile, and normal stress exceeds the yield stress by more than 25%. Moreover, normal plastic strain in this area are also tensile and reaches 2.5-3%. The longitudinal tensile stress closes to yield stress on almost the entire length of the several last layers near the top of the buildup. Residual stress field calculated using neutron diffraction data according to interplanar lattice distance obtained assuming plane stress approach has a satisfactory agreement with FE simulated results.
关键词： Neutron diffraction,Laser metal deposition,Simulation,Residual stress,Titanium alloy
更新于2025-09-12 10:27:22
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Structural evolution of fused silica below the glass-transition temperature revealed by in-situ neutron total scattering
摘要： The common belief that glass structure is completely frozen-in at room temperature is challenged at both macroscopic and atomic scales. Here, we demonstrate an analytical method to elucidate the fine details of a continuous structural change of fused silica (FS) at temperatures below the glass-transition temperature using in-situ neutron total scattering. We find that the SiO4 tetrahedron expands through the entire temperature range with a local coefficient of thermal expansion of 9.1 × 10?6 K?1, while the average medium-range distance, derived from the first sharp diffraction peak of the structure factor, expands at a rate of 21 × 10?6 K?1. Such an expansion difference reflects glass-structure changes within the "rigid-unit mode" model, where each tetrahedron behaves as a rigid unit and the flexible rotations between rigid units lead to more than two times higher medium-range thermal expansion. We further demonstrate that such rotations change the shape of individual rings, leading to a measurable change in the first sharp diffraction peak (FSDP). This study paves the way to measure the structural changes of other silicate glasses, especially through the glass transition.
关键词： Structural change of fused silica,Short- and medium-range structure,In-situ neutron total scattering,First sharp diffraction peak,Rigid-unit mode
更新于2025-09-12 10:27:22
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Solid-State Phase Transformations in Thermally Treated Ti–6Al–4V Alloy Fabricated via Laser Powder Bed Fusion
摘要： Laser Powder Bed Fusion (LPBF) technology was used to produce samples based on the Ti–6Al–4V alloy for biomedical applications. Solid-state phase transformations induced by thermal treatments were studied by neutron di?raction (ND), X-ray di?raction (XRD), scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). Although, ND analysis is rather uncommon in such studies, this technique allowed evidencing the presence of retained β in α’ martensite of the as-produced (#AP) sample. The retained β was not detectable by XRD analysis, nor by STEM observations. Martensite contains a high number of defects, mainly dislocations, that anneal during the thermal treatment. Element di?usion and partitioning are the main mechanisms in the α ? β transformation that causes lattice expansion during heating and determines the ?nal shape and size of phases. The retained β phase plays a key role in the α’ → β transformation kinetics.
关键词： X-ray di?raction,neutron di?raction,Ti alloys,phase transformations,thermal treatments,additive manufacturing,scanning transmission electron microscopy,energy-dispersive spectroscopy
更新于2025-09-12 10:27:22
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Impact of Donor–Acceptor Interaction and Solvent Additive on the Vertical Composition Distribution of Bulk-Heterojunction Polymer Solar Cells
摘要： The vertical composition distribution of bulk-heterojunction (BHJ) photoactive layer is known to have dramatic effects on photovoltaic performance in polymer solar cells. However, the vertical composition distribution evolution rules of BHJ films are still elusive. In this contribution, three BHJ film systems, composed of polymer donor PBDB-T and three different classes of acceptor –fullerene acceptor PCBM, small molecule acceptor ITIC, and polymer acceptor N2200 –are systematically investigated using neutron reflectometry to examine how donor–acceptor interaction and solvent additive impact the vertical composition distribution. Our results show that those three BHJ films possess homogeneous vertical composition distributions across the bulk of the film. While very different composition accumulations near the top and bottom surface were observed which could be attributed to different repulsion, miscibility, and phase separation between the donor and acceptor components as approved by the measurement of donor–acceptor Flory–Huggins interaction parameter χ. Moreover, the solvent additive 1,8-diiodooctane (DIO) can induce more distinct vertical composition distribution especially in non-fullerene acceptor based BHJ films. Thus, higher power conversion efficiencies were achieved in inverted solar cells because of facilitated charge transport in active layer, improved carrier collection at electrodes, suppressed charge recombination in BHJ solar cells.
关键词： Flory–Huggins Interaction Parameter χ,Bulk-Heterojunction,Neutron Reflectometry,Polymer Solar Cells,Vertical Composition Distribution
更新于2025-09-12 10:27:22
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Data Acquisition System for ITER Neutron Diagnostic Divertor Neutron Flux Monitor
摘要： The ITER nuclear diagnostics Divertor Neutron Flux Monitor (DNFM) is designed to determine the ITER fusion power. DNFM diagnostic provides a neutron yield and fusion power measurements for both deuterium-deuterium and deuterium-tritium plasmas with the required time resolution and uncertainty. The data acquisition system (DAQ) is a part of the DNFM diagnostic. This system is designed for signal processing of the three neutron detectors modules, each including six fission chambers (FC). The DAQ system performs the following functions: FCs bias generation and signals detection; transformation of the measurement data into neutron flux values at the location of the detector module; detectors module FCs and measurement channels calibration with external neutron source; data transfer to the upper systems – CODAC; diagnostics of measurement channels and their components, including a detector modules and a communication lines.
关键词： Divertor Neutron Flux Monitor,Neutron Diagnostic,Fission Chambers,ITER,Data Acquisition System
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [AIP Publishing LLC EXOTIC NUCLEI AND NUCLEAR/PARTICLE ASTROPHYSICS (V). FROM NUCLEI TO STARS: Carpathian Summer School of Physics 2014 - Sinaia, Romania (13–26 July 2014)] - Perspectives for neutron and gamma spectroscopy in high power laser driven experiments at ELI-NP
摘要： The measurement of energy spectra of neutrons and gamma rays emitted by nuclei, together with charge particles spectroscopy, are the main tools for understanding nuclear phenomena occurring also in high power laser driven experiments. However, the large number of particles emitted in a very short time, in particular the strong X-rays flash produced in laser-target interaction, impose adaptation of technique currently used in nuclear physics experiment at accelerator based facilities. These aspects are discussed (Section 1) in the context of proposed studies at high power laser system of ELI-NP. Preliminary results from two experiments performed at Titan (LLNL) and ELFIE (LULI) facilities using plastic scintillators for neutron detection (Section 2) and LaBr3(Ce) scintillators for gamma detection (Section 3) are presented demonstrating the capabilities and the limitations of the employed methods. Possible improvements of these spectroscopic methods and their proposed implementation at ELI-NP will be discussed as well in the last section.
关键词： gamma spectroscopy,neutron spectroscopy,nuclear physics,ELI-NP,high power laser
更新于2025-09-11 14:15:04
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Gold nanoparticles as a potent radiosensitizer in neutron therapy
摘要： The purpose of this study was to investigate the potential of gold nanoparticles as radiosensitizer for use in neutron therapy against hepatocellular carcinoma. The hepatocellular carcinoma cells lines Huh7 and HepG2 were irradiated with γ and neutron radiation in the presence or absence of gold nanoparticles. Effects were evaluated by transmission electron microscopy, cell survival, cell cycle, DNA damage, migration, and invasiveness. Gold nanoparticles significantly enhanced the radiosensitivity of Huh7 and HepG2 cells to γ-rays by 1.41- and 1.16-fold, respectively, and by 1.80- and 1.35-fold to neutron radiation, which has high linear energy transfer. Accordingly, exposure to neutron radiation in the presence of gold nanoparticles induced cell cycle arrest, DNA damage, and cell death to a significantly higher extent, and suppressed cell migration and invasiveness more robustly. These effects are presumably due to the ability of gold nanoparticles to amplify the effective dose from neutron radiation more efficiently. The data suggest that gold nanoparticles may be clinically useful in combination therapy against hepatocellular carcinoma by enhancing the toxicity of radiation with high linear energy transfer.
关键词： neutron therapy,cancer,radiosensitizer,γ-ray,gold nanoparticles
更新于2025-09-11 14:15:04
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Spectroscopic and thermal analysis of lead-free multipurpose radiation shielding glasses
摘要： The genetic algorithm was used to identify glasses, of the composition 50Bi2O3-(50-x) B2O3-xBaO with wt.%, that have a similar half-value layer (HVL) and neutron removal cross-section. The structure of these glasses was further explored using a combination of spectroscopic and thermal analysis in order to ascertain whether they possess advantageous physical properties comparable to traditional materials used in nuclear reactor design. Differential scanning calorimetry (DSC) analysis was used to examine the thermal profile of the glass system and to identify glass transition temperature Tg and softening temperature Ts. Glass of the composition 50Bi2O3-30B2O3-20BaO had exhibited the highest thermal stability. Analysis of the Raman spectra of the samples confirmed the presence of BiO6 octahedrons and B-O-B bonds in poly borate chains. A deconvolution of the IR spectra was carried out to determine the relative proportions of BO3 triangles to BO4 tetrahedral units in the glass network that would affect the density and bulk modulus. Optical absorption spectrum of the samples exhibited absorption peaks in the blue region along with a broad band of absorption at longer red wavelengths associated with excitation of bismuth ions. When compared to traditional heavy concretes used in radiation shielding, the bismuth-barium borate glasses exhibited superior performance over conventional barite concrete as a gamma-radiation shield and was comparable to limonite concrete as a neutron radiation shield. The bulk modulus of the glass series was also found to be comparable to that of regular concrete at approximately to 30 GPa.
关键词： Half-value layer,Heavy metal oxide,Neutron removal cross-section,Genetic algorithm
更新于2025-09-10 09:29:36