High Absolute Efficiency Research Articles

Performance of Borated Centrifugally Tensioned Metastable Fluid Detector Detector Versus Ludlum 42-49B, Fuji NSN3 Detectors for Fission Energy Spectrum Neutron Detection With the Source Within Lead/Concrete Shielded Configurations

Abstract This paper presents the results of neutron detection efficiency and dosimetry between a borated centrifugally tensioned metastable fluid detector (B-CTMFD) configured to detect thermal to fast neutrons versus two widely used neutron detection devices of similar form factors: moderated He-3 based Ludlum-42-49B neutron detector, and, the Fuji Electric's NSN3TM (NNSN3) pressurized nitrogen-methane filled neutron detector. The one-on-one performance comparisons were conducted using soft (Cf-252 fission) neutron spectrum isotope neutron sources positioned behind various levels of lead and concrete shielding ranging in thickness from 0 cm (unshielded) to up to 30 cm. The comparisons were conducted with Monte Carlo N-Particle transport code (MCNP) code simulations to account for three-dimensional effects and to relate the absolute detection rate with the dose rate—to derive the sensitivity factor (cpm/μSv/h). While the Ludlum 42-49B and NSN3 detectors operate at a fixed sensitivity setting, the centrifugally tensioned metastable fluid detector (CTMFD) can be (and was) operated to detect and separate the contributions from epithermal (0.02 eV–0.2 MeV) and from fast (>0.2 MeV) neutrons at various sensitivity levels by varying the tensioned metastable negative pressure (Pneg) from 0.3 MPa to 0.7 MPa. The B-CTMFD (configured for detecting the full 0.02 eV to 12 MeV neutrons >0.1 MeV neutron detection at Pneg = 0.7 MPa) offered relative sensitivity enhancements of up to ∼22× greater than Ludlum and over 5× greater than NSN3, over the 0-15 cm range of Pb shielding, and the 0–30 cm concrete shield thickness. The contribution from detecting down scattered neutrons increases with increased thickness, especially for concrete shielding. The B-CTMFD design overcomes the detection penalty (up to 60% depending on shielding type and thickness) inherent in the nonborated centrifugally tensioned metastable fluid detector (NB-CTMFD), designed only to detect fast-energy neutrons—as described in the companion (Part-1) paper. However, unlike the NB-CTMFD, which used 100% decafluorapentane (DFP) (C5H2F10), the B-CTMFD requires the use of an azeotropic mixture of DFP, methanol, and tri-methyl borate (TMB—C3H9BO3, using natural boron) in 80:4:16 proportion. The B-CTMFD was about 6 times more sensitive than NB-CTMFD under the most heavily shielded condition and, taken together, also offered 2-energy bin neutron spectroscopic enablement, together with 22-5× higher absolute efficiency and relative sensitivity compared with the nonspectroscopic Ludlum (He-3) and NSN3 (methane-nitrogen) based detectors. From an intrinsic efficiency standpoint, the B-CTMFD operating at Pneg = 0.7 MPa state demonstrated ∼103× higher intrinsic efficiency over Ludlum 42-49B and NSN3 detectors, respectively.

Bifunctional Manipulation of Terahertz Waves with High‐Efficiency Transmissive Dielectric Metasurfaces

Multifunctional terahertz (THz) devices in transmission mode are highly desired in integration-optics applications, but conventional devices are bulky in size and inefficient. While ultra-thin multifunctional THz devices are recently demonstrated based on reflective metasurfaces, their transmissive counterparts suffer from severe limitations in efficiency and functionality. Here, based on high aspect-ratio silicon micropillars exhibiting wide transmission-phase tuning ranges with high transmission-amplitudes, a set of dielectric metasurfaces is designed and fabricated to achieve efficient spin-multiplexed wavefront controls on THz waves. As a benchmark test, the photonic-spin-Hall-effect is experimentally demonstrated with a record high absolute efficiency of 92% using a dielectric metasurface encoded with geometric phases only. Next, spin-multiplexed controls on circularly polarized THz beams (e.g., anomalous refraction and focusing) are experimentally demonstrated with experimental efficiency reaching 88%, based on a dielectric meta-device encoded with both spin-independent resonant phases and spin-dependent geometric phases. Finally, high-efficiency spin-multiplexed dual holographic images are experimentally realized with the third meta-device encoded with both resonant and geometric phases. Both near-field and far-field measurements are performed to characterize these devices, yielding results in agreement with full-wave simulations. The study paves the way to realize multifunctional, high-performance, and ultra-compact THz devices for applications in biology sensing, communications, and so on.

Enhanced Stability of Exposed PECVD Grown Thin n + Poly-Si/SiO x Passivating Contacts With Al2O3 Capping Layer During High Temperature Firing

Carrier selective poly-Si/SiOx contacts have become a very strong contender for next generation high-efficiency Si solar cells as well as Si-based tandem cells. A thin unmetallized poly-Si/SiOx passivated contact on the top surface of the bottom Si cell provides an excellent opportunity for higher efficiency two-terminal Si-based tandem cells. However, this article shows that when the manufacturable low-cost screen-printed contacts are applied on the rear side of the Si cell, the exposed poly-Si/SiOx contact on the front undergoes appreciable degradation in J0 during high temperature contact firing without a capping layer on the front poly-Si. In this article, unmetallized n-TOPCon structures with ~10-nm poly-Si showed significant degradation after a typical simulated firing process (~750 °C), resulting in decreased implied Voc from 728 to 708 mV and increased J0 from 5 to 15 fA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . We found that a ~7-nm Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> capping layer on poly-Si provides excellent protection with no degradation and can also be easily removed after firing for subsequent processing. For comparison, PECVD grown ~20 nm SiNx and SiOx layers were also investigated for firing stability. The SiNx capping layer was also found to be effective in preserving stability, but the SiOx failed due to lack of hydrogen supply. Large area n-type front junction Si solar cells were fabricated with a boron diffused screen-printed emitter on the front and Ag evaporated thin n-TOPCon on the rear to demonstrate ~0.3% higher absolute efficiency when the rear n-TOPCon was capped with Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> during the firing of the front screen-printed contacts.

Enabling High Efficiency Nanoplasmonics with Novel Nanoantenna Architectures.

Surface plasmon polaritons (SPPs) are propagating excitations that arise from coupling of light with collective electron oscillations. Characterized by high field intensity and nanometric dimensions, SPPs fashion rapid expansion of interest from fundamental and applicative perspectives. However, high metallic losses at optical frequencies still make nanoplasmonics impractical when high absolute efficiency is paramount, with major challenge is efficient plasmon generation in deep nanoscale. Here we introduce the Plantenna, the first reported nanodevice with the potential of addressing these limitations utilizing novel plasmonic architecture. The Plantenna has simple 2D structure, ultracompact dimensions and is fabricated on Silicon chip for future CMOS integration. We design the Plantenna to feed channel (20 nm × 20 nm) nanoplasmonic waveguides, achieving 52% coupling efficiency with Plantenna dimensions of λ3/17,000. We theoretically and experimentally show that the Plantenna enormously outperforms dipole couplers, achieving 28 dB higher efficiency with broad polarization diversity and huge local field enhancement. Our findings confirm the Plantenna as enabling device for high efficiency plasmonic technologies such as quantum nanoplasmonics, molecular strong coupling and plasmon nanolasers.

Light emission efficiency and imaging performance of Lu2O3:Eu nanophosphor under X-ray radiography conditions: Comparison with Gd2O2S:Eu

Nanocrystallic europium-activated lutetium oxide (Lu2O3:Eu) is a strong candidate for use in digital medical imaging applications, due to its spectroscopic and structural properties. The aim of the present study was to investigate the imaging and efficiency properties of a 33.3mg/cm2 Lu2O3:Eu scintillating screen coupled to a high resolution RadEye HR CMOS photodetector under radiographic imaging conditions. Since Lu2O3:Eu emits light in the red wavelength range, the light emission efficiency and the imaging performance were compared with results for a Gd2O2S:Eu phosphor screen. Parameters such as the Absolute Efficiency (AE), the X-ray Luminescence Efficiency (XLE), and the Detector Quantum Gain (DQG), were investigated. The imaging characteristics of Lu2O3:Eu nanophosphor screen were investigated in terms of the Modulation Transfer Function (MTF), the Normalized Noise Power Spectrum (NNPS) and the Detective Quantum Efficiency (DQE). It was found that Lu2O3:Eu nanophosphor has higher AE and XLE by a factor of 1.32 and 1.37 on average, respectively, in the whole radiographic energy range in comparison with the Gd2O2S:Eu screen. DQG was also found higher in the energy range from 50kVp to 100kVp and comparable thereafter. The imaging quality of Lu2O3:Eu nanophosphor coupled to the CMOS sensor was found to outmatch in any aspect in comparison with the Gd2O2S:Eu screen. These results indicate that Lu2O3:Eu nanophosphor could be considered for further research in order to be used in medical imaging applications.

Parallel adaptive computing on meta-systems including NOWs

Load analysis of meta-systems including NOWs or COWs has shown that only a few percentage of the available power is used during long periods of time. Therefore, in order to exploit the idle time when executing a parallel application work load must be sent to a machine as soon as the latter becomes available. Furthermore, in order to keep respected the ownership of workstations work has to be stopped and resumed later as soon as the machine executing it is requisitioned by its owner. As a consequence, users need an adaptive system allowing to return events related to the goings and comings of workstations. On the other hand, it is necessary to provide them a parallel adaptive programming methodology that plans the handling of these events. In this paper, we present the MARS (MARS: multi-user adaptive resource scheduler, developed at LIFL laboratory, Universit é de Lille I) system and its parallel adaptive programming methodology through the block-based Gauss–Jordan algorithm used in numerical analysis to invert large matrices. Moreover, we propose a work scheduling strategy and an application-oriented solution for the fault tolerance issue. Furthermore, we present some experimental results obtained on a DEC/ALPHA COW and a SUN/Sparc4 NOW. The results show that very high absolute efficiencies can be obtained if the size of the blocks is well chosen. We also present some experimentations related to the adaptability of the application in a meta-system including the DEC/ALPHA COW and the SUN/Sparc4 NOW. The results show that the management of the adaptability consumes just a short percentage of execution time.

Parallel processing on the multi‐PSI computer and its evaluation — a programming paradigm based on a small‐grain highly concurrent object model

AbstractMulti‐PSI is a distributed‐memory MIMD (multiple‐instruction, multiple‐data) computer that has 64 processors. Problems of knowledge processing, which are the object of the Multi‐PSI, must be divided into many partial problems in order to achieve a favorable load balance because a characteristic of the computation is the dynamic loss of uniformity. This, however, has the danger of increasing the communication overhead. Therefore, in order to constrain the communication overhead and achieve a favorable load balance, in this paper, we propose a programming method oriented to the above problem. In this methodology, the problem is formulated as multiple communicating objects and the degrees of freedom in the load allocation are maintained. On the other hand, when the load is allocated, the communication objects are estimated from the system performance and the objects' characteristics, and the processing granularity is adjusted so that it is within the tolerance. This program methodology was applied to the three program developments of the shortest path problem, the LSI routing problem, and logic simulation; each was implemented with high efficiency. For example, in the shortest path program, 260,000 small‐grained objects were distributed over 64 processors and reached about 75% efficiency. In addition, in the logic simulation composed of 12,000 objects (gates), a high absolute efficiency of 99 thousand events/second and a 48‐fold increase in speed with 64 processors were obtained. Along with confirming the effectiveness of this programming methodology, these results demonstrated. that high efficiency can be realized in parallel processing for some degree of granularity even in a distributed‐memory parallel computer.

The relationship of adenosine triphosphatase activity to tension and power output of insect flight muscle.

1. On a simple model of actomyosin interaction, the tension cost (ATP hydrolysed/unit tension) and the frequency of low amplitude oscillation optimum for work production are both determined by the rate of detachment from the actin filament of the myosin crossbridge. To test this model, the two parameters were measured under different conditions using glycerol-extracted Lethocerus cordofanus dorsal longitudinal flight muscle fibres. 2. The ATPase activity of the static muscle rose by an amount approximately proportional to the rise in tension as the muscle was stretched. 3. When the muscle fibres were sinusoidally oscillated at 5-10 Hz by 2% of their resting length they produced a large amount of mechanical power and hydrolysed approximately twice as much ATP per unit mean tension as they did when static. The ATPase activity was linearly related to the mean tension during oscillation. 4. The experiments were repeated at temperatures between 12 and 30 degrees C and the tension cost and the optimal frequency of oscillation of the fibres were found to rise with temperature. 5. Removal of phosphate from the incubating medium reduced both the tension cost and the optimal working frequency. Addition of pyrophosphate or sulphate reduced both parameters still further. 6. From these results the tension cost of static muscle was shown to be proportional to its optimal working frequency. 7. ATPase activity rose monotonically with power production at work-producing frequencies and at moderate degrees of stretch. A high absolute efficiency was found under a wide range of conditions. 8. The proportionality between tension cost and optimal frequency is evidence for the proposed model of actomyosin interaction.

Scintillation counting of 32P without added scintillator in aqueous solutions and organic solvents and on dry chromatographic media

Čerenkov radiation produced by 32P makes possible a convenient and efficient method for determination of 32P in virtually any sample utilizing conventional scintillation counters. Organic solvents provide high absolute efficiencies—the highest efficiency measured, approximately 80%, was obtained with toluene. Approximately 50% absolute efficiency is obtained in aqueous solutions with very little variation when strong acids, bases, or salts are present. Paper and silica gel give similar efficiencies with no liquid present because Čerenkov radiation occurs in polyethylene and in glass. Samples are completely unaltered by the counting. Counting conditions are constant for all samples. The efficiency varies with volume, solution composition, and vial material. Efficiencies relative to water for a wide variety of aqueous solutions and organic solvents have been determined using a rapid, highly accurate method.