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Laser absorption spectroscopy studies to characterize Cs oven performances for the negative ion source SPIDER
摘要： The SPIDER H?/D? ion source is currently in operation in the Neutral Beam Test facility (NBTF) at Consorzio RFX (Padova, Italy) to prove the possibility of generating up to 40 A of negative ions, with a maximum extracted current density of 350 A/m2 (H)/285 A/m2 (D) and a fraction of co-extracted electrons not greater than 0.5 (H)/1 (D). These performances are required for the realization of the ITER Neutral Beam Injector (NBI), which should deliver 16.7 MW to the plasma by means of negative ions accelerated up to 1 MeV and neutralized before being injected into the ITER tokamak. In order to obtain such high extracted current densities and low co-extracted electron fractions it is necessary to lower the work function of the surface of the acceleration system grid facing the source; this will be accomplished by coating the surfaces with Cs, routinely evaporated by three ovens. The functionality of the ovens has been tested at the CAesium oven Test Stand (CATS), hosted at NBTF. The test stand is equipped with several diagnostics, among which a Laser Absorption Spectroscopy (LAS) diagnostic. Using a tunable laser diode, the LAS diagnostic gets the high resolution absorption spectrum of the Cs 852 nm D2 line along a line of sight to measure Cs density at ground state. The paper describes the test stand and the LAS diagnostic, together with the characterization of the ovens to be installed in SPIDER. The paper will also study the systematic density underestimation e?ect caused by Cs ground state depopulation, as a function of laser intensity and of Cs density, in the perspective of correcting the density evaluation.
关键词： Plasma diagnostics - interferometry, spectroscopy and imaging,Ion sources (positive ions, negative ions, electron cyclotron resonance (ECR), electron beam (EBIS))
更新于2025-09-16 10:30:52
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Enhanced emission from thermally stable Eu3+ doped CaB2Si2O8 red phosphors via alkali metal modification for W-LEDs application
摘要： M+/Eu3+ (M = Li, Na, K) co-doped CaB2Si2O8 phosphors have been synthesized by a solid-state reaction approach. XRD measurements confirm that the phase purity of the CaB2Si2O8 host is maintained after the introduction of alkali metal ions and Eu3+ ions. The emission intensity of Eu3+ ions is enhanced by a factor of 1.75 and 1.55 with the incorporation of Li+ and Na+ ions, respectively, originating from the charge compensation and improved asymmetry in the crystal field, while the addition of K+ ions to the composition results in a decreased luminescence intensity due to the structural-defect-related quenching. Temperature dependent measurement reveals that the prepared phosphor exhibits excellent thermal stability with 81% at 423 K of the integrated emission intensity at 298 K. A white light-emitting diode (W-LED) device is fabricated based on the synthesized Eu3+ doped CaB2Si2O8 red phosphor modified by Li ions. All these results indicate that the synthesized phosphor is a promising red-emitting material for W-LEDs application.
关键词： Red phosphor,Eu3+ ions,W-LEDs,Alkali metal ions
更新于2025-09-16 10:30:52
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Photodissociation of Arylbenzopyrroloimidazolones under Laser Desorption/Ionization Conditions
摘要： The photodissociation of aryl-substituted tetrahydropyrroloimidazolones under laser desorption/ionization conditions was shown to be a general process. The compounds tend to form complex dimeric ions and rearrangement products. The fragmentation of this kind was explained by the π–π stacking interactions between the benzene rings of substituents and intermolecular hydrogen bonds in crystals, which are partially preserved on transfer from solid to gas phase.
关键词： dimeric ions,laser desorption and ionization,arylbenzopyrroloimidazolones,fragmentation
更新于2025-09-16 10:30:52
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Optical Electronics (An Introduction) || 3. Bulk solid-state lasers
摘要： Solid-state lasers use solid-state laser medium as the working substance. Usually, solid work materials are incorporated in the matrix with a small amount of activated ions. Laser transition occurs between different energy levels during ion activation. Matrix materials are mainly crystal, glass, and ceramics, and activated ions can be categorized as trivalent rare earth metal ions, divalent rare earth metal ions, transition metal ions, and actinide metal ions.
关键词： crystal,activated ions,laser medium,heat capacity laser,ceramics,LD-pumped,glass,solid-state lasers
更新于2025-09-16 10:30:52
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Photons and charges from colloidal doped semiconductor quantum dots
摘要： The utility of colloidal semiconductor quantum dots as a source of photons and charge carriers for photonic and photovoltaic applications has created a large field of research focused on tailoring and broadening their functionality beyond what an exciton can provide. One approach towards expanding the range of characteristics of photons and charge carriers from quantum dots is through doping impurity ions (e.g. Mn2+, Cu+, and Yb3+) in the host quantum dots. In addition to the progress in synthesis enabling fine control of the structure of the doped quantum dots, a mechanistic understanding of the underlying processes correlated with the structure has been crucial in revealing the full potential of the doped quantum dots as the source of photons and charge carriers. In this review, we discuss the recent progress made in gaining microscopic understanding of the photophysical pathways that give rise to unique dopant-related luminescence and the generation of energetic hot electrons via exciton-to-hot electron upconversion.
关键词： doping impurity ions,charge carriers,photons,hot electrons,colloidal semiconductor quantum dots,photophysical pathways
更新于2025-09-16 10:30:52
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Enhancing electron diffusion length in narrow-bandgap perovskites for efficient monolithic perovskite tandem solar cells
摘要： Developing multijunction perovskite solar cells (PSCs) is an attractive route to boost PSC efficiencies to above the single-junction Shockley-Queisser limit. However, commonly used tin-based narrow-bandgap perovskites have shorter carrier diffusion lengths and lower absorption coefficient than lead-based perovskites, limiting the efficiency of perovskite-perovskite tandem solar cells. In this work, we discover that the charge collection efficiency in tin-based PSCs is limited by a short diffusion length of electrons. Adding 0.03 molar percent of cadmium ions into tin-perovskite precursors reduce the background free hole concentration and electron trap density, yielding a long electron diffusion length of 2.72 ± 0.15 μm. It increases the optimized thickness of narrow-bandgap perovskite films to 1000 nm, yielding exceptional stabilized efficiencies of 20.2 and 22.7% for single junction narrow-bandgap PSCs and monolithic perovskite-perovskite tandem cells, respectively. This work provides a promising method to enhance the optoelectronic properties of narrow-bandgap perovskites and unleash the potential of perovskite-perovskite tandem solar cells.
关键词： narrow-bandgap perovskites,perovskite solar cells,tandem solar cells,electron diffusion length,cadmium ions
更新于2025-09-16 10:30:52
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Full-color persistent luminescence tuning: A marriage of perovskite quantum dots and lanthanide ions
摘要： In modern society, luminescent materials capable of emitting various colored lights are critically important for lighting and display systems. As a typical kind of luminescent materials, the persistent luminescence phosphors have been widely investigated as night-light vision materials due to their many significant applications such as emergency route signage and security signals, bio-labels, photocatalysts, anti-counterfeiting, optical sensors, and optical data storage. However, realizing multicolored persistent luminescence phosphors has been a long-standing challenge, thus posing a serious problem in their practical applications. In a recent publication in Angewandte Chemie International Edition, Prof. Xueyuan Chen and co-workers demonstrated a simple but effective approach to fine-tuning the persistent luminescence colors, based upon the composites of lanthanide ions doped CaAl2O4:Eu2+,Nd3+ (CAO) blue persistent phosphors with all-inorganic CsPbX3 (X = Cl, Br, and I) perovskite quantum dots (PeQDs). With the help of the radiative energy transfer from CAO blue persistent phosphors to CsPbX3 PeQDs, the persistent luminescence colors can be precisely controlled through tailoring of the PeQDs bandgap. The approach allowed access to full-spectrum persistent luminescence with wavelengths covering the entire visible spectral range by single-wavelength excitation, thus offering new opportunities for persistent luminescence materials in many important emerging applications.
关键词： persistent luminescence,lanthanide ions,full-color tuning,perovskite quantum dots
更新于2025-09-16 10:30:52
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Versitile X-ray diagnostics of laser-produced high-temperature plasmas using an ultra-high luminosity spectrometer
摘要： Versitile diagnostics of high-temperature magnesium laser-produced plasmas is performed using an ultra-high luminosity X-ray focusing crystal spectrometer. The plasmas are produced by focusing nanosecond laser pulses (0.53 mm, 1 J, 2 ns) on a massive magnesium target. The absolute intensities and X-ray yields are measured for the resonance lines of H- and He-like ions (spectral range: D?l = 8 –10 ?), the electron temperature of plasmas is determined (range: Te = 200 – 550 eV), and the behaviour of these parameters is established in a broad range of laser pulse energy EL (10 mJ – 1 J). This approach permits the parameters of laser-plasma radiation sources to be monitored in real time in a wide intensity range (difference in intensity: over 104) and in a broad range of plasma parameters.
关键词： laser-produced plasmas,X-ray spectrometers,high-temperature plasma diagnostics,X-ray spectroscopy and metrology,multiply charged ions
更新于2025-09-16 10:30:52
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[IEEE 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - Sao Paulo, Brazil (2019.8.26-2019.8.30)] 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - Influence of Silver nanoparticles on Tb <sup>3+</sup> doped TeO <sub/>2</sub> -ZnO glasses covered Silicon solar cell
摘要： This work shows the increase of silicon solar cell efficiency due to Tb3+ doped tellurite (TeO2-ZnO-Na2O-PbO) glass with silver nanoparticles used as cover layer. Due to Tb3+ down-conversion process optimized by the plasmon resonance of the metallic nanoparticles, enhancement of ~4.93% was observed when compared to the efficiency of the uncovered solar cell. The samples are prepared using the melting quenching techinique and the electrical characterization is performed using a solar simulator in order to obtain the current-voltage and power-voltage curve. As there is a mismatch between the solar spectrum and the one of the silicon solar cell, the procedure presented in this work represents an alternative to increase the number of photons that are converted from the ultraviolet region to the visible one and opens the posibility for application with new photovoltaic devices based on organic or inorganic materials.
关键词： tellurite,Silicon solar cells,Tb3+ ions,efficiency,silver nanoparticles
更新于2025-09-16 10:30:52
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AIP Conference Proceedings [AIP Publishing ADVANCES IN BASIC SCIENCE (ICABS 2019) - Bahal, India (7–9 February 2019)] ADVANCES IN BASIC SCIENCE (ICABS 2019) - Upconversion emission of Ag nanoparticles with Er3+/Yb3+ ions in tellurite glasses under 980nm laser excitation
摘要： The light upconversion in Er3+ - Yb3+ doped TeO2 -WO3- Li2O (TWLEY) doped glass containing silver nanoparticles (NPs) has been reported. Tellurite based glasses have been prepared by melt quenching technique with small amount Ag nanoparticles(NPs). The optical excitation is made at 980 nm in resonance with the 2F5/2→2F7/2 transition of Yb3+ ions in glass system. Intense emission bands centered at 525nm, 550nm, and 654 nm were observed corresponding to Er3+ ions transitions. Upconversion fluorescence Intensity of the glasses samples are also observed at 980nm femtosecond laser excitation using two photons microscope. For this green and red colour intensity measurement of the TWLEY with Ag NPs glass sample has been analyzed by intensity histograms. Results show that plasmon enhances upconversion of silver and rare-earth doped glasses may be utilized to explore its potential for multiphoton microscopy.
关键词： Tellurite glasses,Ag nanoparticles,Er3+/Yb3+ ions,980nm laser excitation,Upconversion emission
更新于2025-09-16 10:30:52