Dense Absorber Research Articles

Selenization of mixed metal oxides for dense and ZnSe-free Cu2ZnSnSe4 absorber films

Cu2ZnSnSe4 (CZTSe) films were prepared by direct selenization of Cu2O, SnO2 and Zn2SnO4 precursors. Oxides precursors were prepared by baking hydroxides precipitation. In order to obtain ZnSe-free CZTSe films, Zn2SnO4 was used to replace separated ZnO and SnO2 as one of the precursors. Through X-ray diffraction (XRD), scanning electron microscopy (SEM), it was found that CZTSe films, with micron-sized dense grains, were obtained in our work. From Raman spectra, it was also found that the ZnSe secondary phase was absent after the selenization. An energy bandgap about 0.86eV was obtained in our work, which confirmed the Stannite-CZTSe structure.

Absorption features in the quasar HS 1603 + 3820 II. Distance to the absorber obtained from photoionisation modelling

We present the photoionisation modelling of the intrinsic absorber in the bright quasar HS 1603+3820. We constructed the broad-band spectral energy distribution using the optical/UV/X-ray observations from different instruments as inputs for the photoionisation calculations. The spectra from the Keck telescope show extremely high Civ to Hi ratios, for the first absorber in system A, named A1. This value, together with high column density of Civ ion, place strong constraints on the photoionisation model. We used two photoionisation codes to derive the hydrogen number density at the cloud illuminated surface. By estimating bolometric luminosity of HS 1603+3820 using the typical formula for quasars, we calculated the distance to A1. We could find one photoionization solution, by assuming either a constant density cloud (which was modelled using cloudy), or a stratified cloud (which was modelled using titan), as well as the solar abundances. This model explained both the ionic column density of Civ and the high Civ to Hi ratio. The location of A1 is 0.1pc, and it is situated even closer to the nucleus than the possible location of the Broad Line Region in this object. The upper limit of the distance is sensitive to the adopted covering factor and the carbon abundance. Photoionisation modelling always prefers dense clouds with the number density n0=1010−1012cm−3, which explains intrinsic absorption in HS 1603+3820. This number density is of the same order as that in the disk atmosphere at the implied distance of A1. Therefore, our results show that the disk wind that escapes from the outermost accretion disk atmosphere can build up dense absorber in quasars.

Does transmission of a weak optical pulse in a dense absorption medium require quantization of the optical field?

We present an analysis of the transmission of a weak optical pulse, with energy 1ℏω0, through a dense absorbing medium with absorption frequency ω0. We analyze the system by treating the optical pulse classically and the absorbing medium quantum mechanically. We find that the probabilistic back reaction of the quantum absorber on the classical pulse impresses statistical behavior on the pulse that does not arise from quantization of the optical field. All properties of the optical transmission and atomic absorption are self-consistent without contradiction. Issues relating to conservation of energy are resolved by considering the impact of superposition states on conservation laws in individual interactions. As a result, we conclude that transmission of a weak optical pulse with energy 1ℏω0 through a dense atomic absorber does not require quantization of the field.

Amorphous Cu–In–S Nanoparticles as Precursors for CuInSe2 Thin‐Film Solar Cells with a High Efficiency

CuInSe2 (CISe) absorber layers for thin-film solar cells were fabricated through the selenization of amorphous Cu-In-S nanoparticles, which were prepared by using a low-temperature colloidal process within one minute without any external heating. Two strategies for obtaining highly dense CISe absorber films were used in this work; the first was the modification of nanoparticle surface through chelate complexation with ethanolamine, and the second strategy utilized the lattice expansion that occurred when S atoms in the precursor particles were replaced with Se during selenization. The synergy of these two strategies allowed formation of highly dense CISe thin films, and devices fabricated using the absorber layer demonstrated efficiencies of up to 7.94% under AM 1.5G illumination without an anti-reflection coating.

Facile Microwave-Assisted Synthesis of Multiphase CuInSe2 Nanoparticles and Role of Secondary CuSe Phase on Photovoltaic Device Performance

Multiphase CuInSe2 (CISe) nanoparticles including the secondary CuSe phase are synthesized by a polyol-based, microwave-assisted solvothermal method. It is demonstrated that the reaction chemistry involving formation of the CISe phase is adjusted depending on the heretofore unrecognized chemical nature of polyol solvent, allowing for formation of secondary CuSe phase-incorporated multiphase CISe nanoparticles. The critical role of CuSe phase in generating the pore-free, dense CISe absorber layer for a high-performance thin-film photovoltaic device is investigated through the comparative study on CISe absorber layers derived from both multiphase and single-phase CISe nanoparticles.

Motion Simulation of Desulfurized Fly Ash in Dense Flow Absorber Based on Computational Fluid Dynamics

The motion track of desulfurized fly ash in flue gas was simulated by means of Fluent software. The abrasion and deposition of desulfurized fly ash to inner surface and other internals inside of dense flow absorber were studied. The results show that, under the simulated condition, the flue gas streamline is uniform inside of dense flow absorber which is installed with the equipment of baffle plates and four-layer delta wing plates. The desulfurized fly ash could be distributed uniformly and the pressure loss is approximately 340Pa. The abrasion rate of desulfurized fly ash to No.1 baffle plate is higher and the distribution is relatively concentrated, however, the abrasion rate of desulfurized fly ash to other layers of baffle plate and delta wing plate is lower and the distribution is relatively uniform. Besides, the abrasion rate of the dense flow absorber top and the A-convex surface is higher as well. Most desulfurized fly ash deposits on the bottom of ash hopper and some deposits on parts of baffle plates and delta wing plates. The deposition rate of B-convex surface is higher than that of A-convex surface. In reality, the highly corrosive parts inside of dense flow absorber should adopt wear-resistant materials. Meanwhile, water content of desulfurized fly ash should be controlled to avoid hardening of desulfurized fly ash which is deposited.

A New View of Microcrystalline Silicon: The Role of Plasma Processing in Achieving a Dense and Stable Absorber Material for Photovoltaic Applications

AbstractTo further lower production costs and increase conversion efficiency of thin‐film silicon solar modules, challenges are the deposition of high‐quality microcrystalline silicon (μc‐Si:H) at an increased rate and on textured substrates that guarantee efficient light trapping. A qualitative model that explains how plasma processes act on the properties of μc‐Si:H and on the related solar cell performance is presented, evidencing the growth of two different material phases. The first phase, which gives signature for bulk defect density, can be obtained at high quality over a wide range of plasma process parameters and dominates cell performance on flat substrates. The second phase, which consists of nanoporous 2D regions, typically appears when the material is grown on substrates with inappropriate roughness, and alters or even dominates the electrical performance of the device. The formation of this second material phase is shown to be highly sensitive to deposition conditions and substrate geometry, especially at high deposition rates. This porous material phase is more prone to the incorporation of contaminants present in the plasma during film deposition and is reported to lead to solar cells with instabilities with respect to humidity exposure and post‐deposition oxidation. It is demonstrated how defective zones influence can be mitigated by the choice of suitable plasma processes and silicon sub‐oxide doped layers, for reaching high efficiency stable thin film silicon solar cells.

Dynamic transition from complete population transfer to self-induced transparency

We explore the connection between adiabatic rapid passage, a technique that allows for robust complete population transfer (CPT) in a resonant absorber, and self-induced transparency solitons. We employ the auxiliary differential equation finite-difference time-domain method to fully resolve the dynamics of femtosecond light pulses propagating through an absorbing two-level medium. Using the example of linearly chirped Gaussian pulses we find that the pulses achieving robust CPT for a single two-level system are also pulses that will transform into solitary waves when incident on a resonantly absorbing medium. At the entrance into the absorber strongly chirped, adiabatic pulses completely transfer the electronic population from the ground to the upper state. As the pulses suffer absorption they undergo a dynamic transition and quickly split into an off-resonant radiation part and one or several unchirped solitary pulses that may carry away some of the initially achieved population inversion. This spectral and temporal transformation process limits the spatial depths of the region of CPT in a dense absorber regardless of the initial pulse amplitude. We also show that the frequency-domain pulse area, defined as the spectral amplitude at the resonance frequency, allows for a better distinction between the regimes of $2\ensuremath{\pi}$-pulse and $0\ensuremath{\pi}$-pulse formation than time-domain measurements.

A hybrid ink of binary copper sulfide nanoparticles and indium precursor solution for a dense CuInSe2 absorber thin film and its photovoltaic performance

A newly developed hybrid ink of binary CuS nanoparticles and In precursor solution was prepared to form a CuInSe2 (CIS) thin film. Previously, we have shown a CIS thin film solar cell with 4.19% conversion efficiency using the hybrid ink of Cu2−xSe nanoparticles and In precursor. Deposition using hybrid ink offers advantages including the provision of stress-relief and crack-deflection centers by pure material based nanoparticles and effective binding with the nanoparticles by precursor solutions without other organic binders. Here, we demonstrate volume expansion of a thin film for forming a well-grown absorber layer using CuS nanoparticles instead of Cu2−xSe. Binary nanoparticles were synthesized by a low temperature colloidal process and a precursor solution was prepared by using a non-toxic chelating agent to disperse the In component stably. The band gap of the CIS thin film was 1.08 eV, as determined by external quantum efficiency (EQE) measurements, and the reproducible conversion efficiency of the fabricated device was 6.23%.

Detector Systems at CLIC

Abstract The Compact Linear Collider CLIC is designed to deliver e + e – collisions at a center of mass energy of up to 3 TeV. The detector systems at this collider have to provide highly efficient tracking and excellent jet energy resolution and hermeticity for multi-TeV final states with multiple jets and leptons. In addition, the detector systems have to be capable of distinguishing physics events from large beam-induced background at a crossing frequency of 2 GHz. Like for the detector concepts at the ILC, CLIC detectors are based on event reconstruction using particle flow algorithms. The two detector concepts for the ILC, ILD and SID, were adapted for CLIC using calorimeters with dense absorbers limiting leakage through increased compactness, as well as modified forward and vertex detector geometries and precise time stamping to cope with increased background levels. The overall detector concepts for CLIC are presented, with particular emphasis on the main detector and engineering challenges, such as: the ultra-thin vertex detector with high resolution and fast time-stamping, hadronic calorimetry using tungsten absorbers, and event reconstruction techniques related to particle flow algorithms and beam background suppression.

Radiation burst from a singleγ-photon field

The radiation burst from a single $\ensuremath{\gamma}$-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto et al. [Phys. Rev. Lett. 66, 2037 (1991)] and it was named the ``gamma echo.'' The echo is generated by a 180${}^{\ensuremath{\circ}}$ phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto et al. as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.

Commissioning and calibration of the Zero Degree Calorimeters for the ALICE experiment

The ALICE experiment at the CERN LHC will study the properties of matter at the extreme temperature and energy density conditions produced in heavy ion collisions. The impact parameter of the collision will be estimated by means of the Zero Degree Calorimeters (ZDC), that measure the energy carried away by the non-interacting (spectator) nucleons. All the spectator nucleons have the same energy, therefore the calorimeter response is proportional to their number, providing a direct information on the centrality of the collision. Two identical sets of hadronic calorimeters are located at opposite sides with respect to the interaction point, 116 m away from it, where the two LHC beams circulate in two different pipes. Each set of detectors consists of a neutron (ZN) calorimeter, placed between the two beam pipes and a proton (ZP) calorimeter, positioned externally to the outgoing beam pipe. The ZDC are spaghetti calorimeters, which detect the Cherenkov light produced by the charged particles of the shower in the quartz fibers, acting as the active material embedded in a dense absorber matrix. In summer 2007 the ZN and ZP calorimeters have been placed on a movable platform and then installed in the LHC tunnel. The results of the commissioning studies are shown. The monitoring systems adopted to control the stability of the PMT responses, i.e. light injection with a laser diode and cosmic rays, are described in detail. The foreseen calibration with e.m. dissociation events in Pb-Pb collisions will also be discussed. Finally the first measurements carried out during the commissioning in the LHC tunnel will be presented.

Comissioning and calibration of the Zero Degree Calorimeters for the ALICE experiment

The Zero Degree Calorimeters (ZDCs) for the ALICE experiment will measure the energy of the spectator nucleons in heavy ion collisions at the CERN LHC. Since all the spectator nucleons have the same energy, the calorimeter reponse is proportional to their umber providing a direct information on the centrality of the collision. Two sets of ZDCs are located at opposite sides with respect to the interaction point (I), 116 m away from it Each set consists of a neutron (ZN) calorimeter, placed between the two beam pipes, an a proton (ZP) calorimeter, posioned externally to the outgoing beam pipe. The ZDCs spaghetti calorimeters, which detect the Cherenkov light produced by the shower particle in silica optical fibers embedded in a dense absorber. In summer 2007 the ZN and ZP calorimeters have been placed on a movable platform and then installed in the LHC tunnel. The results of the commissioning studies and in particular the solutions adopted to control the stability of the PMTs response will be shown: light injection with a larser diode and cosmic rays. The foreseen calibration with e.m. dissociation event in Pb-Pb collisions will also be disussed. Finally the it meaurements carried out during the commissining in the LHC tunnel will be presentend.

Zero degree Cherenkov calorimeters for the ALICE experiment

The collision centrality in the ALICE experiment will be determined by the Zero Degree Calorimeters (ZDCs) that will measure the spectator nucleons energy in heavy ion collisions. The ZDCs detect the Cherenkov light produced by the fast particles in the shower that cross the quartz fibers, acting as the active material embedded in a dense absorber matrix. Test beam results of the calorimeters are presented.

The Symbiotic System SS73 17 Seen with Suzaku

Abstract We observed with Suzaku the symbiotic star SS73 17, motivated by the discovery by the INTEGRAL satellite and the Swift BAT survey that it emits hard X-rays. Our observations showed a highly-absorbed X-ray spectrum with $N_{\rm H} \gt 10^{23}$cm$^{-2}$, equivalent to $A_{V} \gt 26$, although the source has B magnitude 11.3 and is also bright in UV. The source also shows strong, narrow iron lines including fluorescent FeK as well as FeXXV and FeXXVI. The X-ray spectrum can be fit with a thermal model including an absorption component that partially covers the source. Most of the equivalent width of the iron fluorescent line in this model can be explained as a combination of reprocessing in a dense absorber plus reflection off a white dwarf surface, but it is likely that the continuum is partially seen in reflection as well. Unlike other symbiotic systems that show hard X-ray emission (CH Cyg, RT Cru, T CrB, GX1$+$4), SS73 17 is not known to have shown nova-like optical variability, X-ray flashes, or pulsations, and has always shown faint soft X-ray emission. As a result, although it is likely a white dwarf, the nature of the compact object in SS73 17 is still uncertain. SS73 17 is probably an extreme example of the recently discovered and relatively small class of hard X-ray emitting symbiotic systems.

The zero degree calorimeters for the ALICE experiment

The Zero Degree Calorimeters (ZDC) for the ALICE experiment will measure the energy of the spectator nucleons in heavy ion collisions at the CERN LHC, providing a direct measure of the centrality of the collisions. ZDC are spaghetti calorimeters, which detect the Cherenkov light produced by the shower particles in silica optical fibers embedded in a dense absorber. The main characteristics of the ZP and ZN detectors are described in this article. The calorimeters were tested at the CERN SPS using pion and electron beams with momenta ranging from 50 to 200 GeV / c . Test beam results such as the calorimeter response, the energy resolution, the signal uniformity and the localizing capability are presented.

Effects of Se Atmosphere on the Densification of Absorber Layer Using Cu(In,Ga)Se<sub>2</sub> Nanoparticles for Solar Cells

To make a dense CIGS absorber layer, spray deposited CIGS films were annealed in the two-zone RTP furnace in Se atmosphere. More Se supply by increasing Se evaporation temperature or by increasing the flow rate of carrier gas resulted in the larger CIGS grains. However, a thick MoSe2 layer was formed between CIGS and Mo, as the Se supply increased, results in partial detachment of CIGS/MoSe2/Mo layers from the glass substrate. From the result, it was found that the short heat- treatment with high Se vapor pressure is better than the long heat-treatment with low Se vapor pressure. The large CIGS grains without peeling off, can be obtained from the following conditions; Se evaporation temperature of 450oC, substrate temperature of 550oC, annealing time of 5 min, and flow rate of carrier gas of 30 sccm.

Nanoparticle derived Cu(In, Ga)Se2 absorber layer for thin film solar cells

A non-vacuum process for fabrication of Cu(In, Ga)Se2 (CIGS) absorber layer from the corresponding nanoparticle precursors was described. CIGS nanoparticle precursors was prepared by a low temperature colloidal route by reacting the starting materials (CuI, InI3, GaI3 and Na2Se) in organic solvents, by which fine CIGS nanoparticles of about 20nm in diameter with chemical composition of Cu0.9In0.64Ga0.23Se2.00 were obtained. The nanoparticle precursors were mixed with organic binder material for the rheology of the mixture to be adjusted for the doctor blade method. After depositing the mixture of CIGS with binder on Mo/glass substrate, the samples were preheated on the hot plate in air to evaporate remaining solvents and to burn the organic binder material. Subsequently, the resultant (porous) CIGS/Mo/glass sample was selenized in a two-zone Rapid Thermal Process (RTP) furnace in order to get a solar cell applicable dense CIGS absorber layer. The selenization at 550°C for 15min with Se gas evaporated at 400°C resulted in the growth of CIGS particles up to a few hundred nanometers in grain size in the upper parts of the layer with remaining unreacted small particles in the lower parts.

Performance of the Zero Degree Calorimeters for the ALICE Experiment

The zero degree calorimeters (ZDCs) for the ALICE experiment will measure the energy of the spectator nucleons in heavy ion collisions at the CERN LHC. The dipole magnets of the LHC beam optics will separate the ion beams from the spectator protons; the spectator protons and neutrons will be respectively detected by the proton (ZP) and the neutron (ZN) calorimeters. Since all the spectator nucleons have the same energy, the calorimeter response is proportional to their number, providing a direct information on the centrality of the collision. ZDCs are spaghetti calorimeters, which detect the Cherenkov light produced by the shower particles in silica optical fibers embedded in a dense absorber. The technical characteristics of ZP and ZN detectors are described. The calorimeters have been tested at the CERN SPS using pion and electron beams with momenta ranging from 50 to 200 GeV/c; the ZN detector behaviour has also been studied with an indium beam of 158 GeV/c per nucleon. The beam test results are presented: the calorimeters response, the energy resolution and the localizing capability. Also the signal uniformity and a comparison between the transverse profile of the hadronic and electromagnetic shower are discussed. Moreover the differences between the ZP detector responses to protons and pions of the same energy have been investigated, exploiting the proton contamination in the positive pion beams.

A SimultaneousRXTEandXMM‐NewtonObservation of the Broad‐Line Radio Galaxy 3C 111

We present the results of simultaneous XMM-Newton and RXTE observations of the broad-line radio galaxy 3C 111. We find that the Compton reflection bump is extremely weak; however, broad residuals are clearly present in the spectrum near the Fe Kα emission line region. When fitted with a Gaussian emission line, the feature has an equivalent width of 40-100 eV and FWHM of greater than 20,000 km s-1; however, the exact properties of this weak line are highly dependent on the chosen continuum model. The width of the line suggests an origin in the inner accretion disk, which is, however, inconsistent with the lack of Compton reflection. We find that much of the broad residual emission can be attributed to continuum curvature. The data are consistent with a model in which the primary power-law continuum is reprocessed by an accretion disk that is truncated at small radii. Alternatively, the primary source could be partially covered by a dense absorber. The latter model is less attractive than the former because of the small inclination angle of the jet of 3C 111 to the line of sight. We consider it likely that the curved continuum of the partial covering model is fortuitously similar to the continuum shape of the reprocessing model. In both models, the fit is greatly improved by the addition of an unresolved Fe Kα emission line, which could arise in either a Compton-thin obscuring torus or dense clouds lying along the line of sight. We also find that there are unacceptable residuals at low energies in the MOS data in particular, which were modeled as a Gaussian with an energy of ~1.5 keV; we attribute these residuals to calibration uncertainties of the MOS detectors.