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The intermediate band solar cell (IBSC) has drawn the attention of the scientific community as a means to achieve high-efficiency solar cells. Complete IBSC devices have been manufactured using quantum dots, highly mismatched alloys, or bulk materials with deep-level impurities. Characterization of these devices has led, among other experimental results, to the demonstration of the two operating principles...
The frequency upconversion emission from Er3+-Yb3+ codoped Y2O3 phosphor synthesized by low temperature, urea assisted combustion technique has been studied upon excitation at 980 nm diode laser. The effect of incorporation of Zn2+ ion on upconversion (UC) emission bands around 409 nm, 523 nm, 551 nm, 661 nm arises due to the transitions 2H9/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 →...
The limiting efficiency for photovoltaic energy conversion based on a semiconductor pn-junction is typically determined using the method of detailed balance put forth by Shockley and Queisser. Here we describe how this theory is altered in the presence of a photonic structure that is capable of modifying the absorption and emission of photons. By incorporating specifically designed photonic structures,...
9Be convertor has been successfully used in photoneutron and x-ray radiography system (PNXR) to achieve material identification by combining X-ray imaging and photoneutron imaging technologies together within one 7 MeV LINAC. The photoneutron convertor, a 2.6 kg 9Be cylinder of 16cm × 7 cm that converts photons to photoneutrons, has the advantages of high neutron yield (1010∼1011 n/s), robustness...
This work provides a preliminary analysis of the influence of additional filtration composition on Half Value Layer (HVL) determination and the significance on using Inverse Square Law (ISL) in conventional radiology and mammography considering realistic geometry. It compares Deterministic Calculation (DC), Monte Carlo Method (MC) and Experimental Results (ER) in order to make the purposed analysis...
One advantage of a combined PET/CT scanner is that a fast CT acquisition provides a high quality attenuation correction map for PET reconstruction. A diagnostic CT system typically operates in a voltage range from 80 kVp to 140 kVp. The choice of optimal spectrum depends on the specific application. In diagnostic imaging, contrast, noise and dose all play important roles. The designated CT scan for...
The development of photon counting detectors enables us to decompose materials in x-ray CT images. The photon counting detection can measure a linear attenuation coefficient of a given energy range, thereby contributing to the material decomposition or identification. In this detection, measured photon counts were affected by statistical noise, making it difficult to obtain accurate measurements of...
Eu2+-doped LiF/CaF2 eutectic scintillators with different Eu concentrations were fabricated by the simple solidification method. Eu concentrations were 0.005, 0.02, 0.05, 0.1, 0.3, 1, 3, and 5%, and they looked visibly semitransparent. In SEM analysis, fine lamellar structure was observed in Eu low concentration samples. Radioluminescence spectra were collected under X-ray exposure and Eu2+ 5d-4f...
The optimum geometric configuration of the detector system for non-destructive assay (NDA) of special nuclear material (SNM) by using nuclear resonance fluorescence (NRF) measurements has been studied. A Monte Carlo radiation transport code, GEANT4, has been developed to calculate NRF interaction, as well the simulation performed for detector array consist of seven LaBr3:Ce (1.5″ × 3″) detectors positioned...
Geant4 is a large-scale particle physics package that facilitates every aspect of particle transport simulation. This includes, but is not limited to, geometry description, material definition, tracking of particles passing through and interacting with matter, storage of event data, and visualization. As more detailed and complex simulations are required in different application domains, there is...
The development of the technology for the growth of inorganic scintillating fibers has initiated a significant progress in the production of compact inorganic scintillators during the last years. Triggered by the traditional applications of fibers based on plastic scintillators, there are strong arguments for replacing those fibers by inorganic crystals. One can rely on a significantly higher light...
In 2012, Wehe D.K. and coauthors proposed a method of light yield amplification in scintillation detectors. A trivalent activator ion RE3+ captures an electron produced by a particle in scintillator and becomes a divalent rare earth ion RE2+. The scintillator is illuminated by laser photons that excite RE2+ ions, which quickly de-excite and generate light photons. By cyclically excitation RE2+ ions,...
At present, Cs-137 is used as a standard in the calibration of radiation detectors or dosimeters because it is a monoenergetic source (662 keV) and has a long half-life of 30.07 years. When radiation detector is calibrated, it is desireable to calibrate for wide energies. For example 200 keV energy region is important because some detector response is too high and scatter photon energy tend to be...
The purpose of our research is to measure the amount of contrast agents used in x-ray CT accurately. The use of contrast agents such as gold nano-particles enables molecular imaging with the x-ray CT system. To realize an energy discriminating measurement, we have developed a photon counting detector with a CdTe semiconductor that is able to measure x-rays with the count rate of 107 cps/mm2 with four...
Dual- and multi-energy X-ray imaging opens a door of additional capability for X-ray imaging systems. Decoupling the interleaved information of material and energy is one of the key issues. This work is to propose a new method to decompose the energy-dependent information and material-dependent information. Our method introduce an system-based optimization idea in picking basis functions which, in...
An efficient all-fiber compact ∼ 50 cm long microstructured optical fiber-based 3–4.2 µm mid-IR light source with power conversion efficiency > 28% has been designed by exploiting FWM with Er3+-doped ZBLAN fiber as the pump.
Terahertz emitters and detectors made from AIIIBV semiconductors were investigated by means of a tunable wavelength laser system. THz excitation spectra of InAs and InSb has been investigated. It was shown that subsidiary valley position can be determined quite accurately. As terahertz detectors, the photoconductors manufactured from GaAs and InGaAs epitaxial layers grown by MBE at low substrate temperatures...
Carbon-based nanostructures have been the center of intense research and development for more than two decades now. Of these materials, graphene, a two-dimensional (2D) layered material system, has had a significant impact on science and technology in recent years after it was experimentally isolated in single layers in 2004. The recent emergence of other classes of two-dimensional (2D) layered systems...
The timely and accurate detection of threat contraband especially for ports-of-entry (e.g. harbors, bays, borders, airports) is an extremely critical problem of national security. The investigation of advanced techniques to reliably and accurately detect threats and reject non-threats is the major focus of this effort. The characterization of signal processing models based on xray transport physics...
The influence of compositional fluctuations of N in GaInNAs Quantum Well (QW) lasers has been studied using a rate equation model. These fluctuations can be treated as Quantum-Dot (QD)-like fluctuations at the Conduction Band Edge (CBE). The gain model includes the QW material gain derived using a Band Anti-Crossing (BAC) model and includes QD fluctuations in the conduction band. For low N, (N ∼ 1%),...
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