On-line Power Monitoring Research Articles

Integrated photodetectors embedded within fiber laser based on hybrid rGO:ZnO nanostructures

Online power monitoring is helpful in fiber-optic communication applications. This report introduced an innovative all-fiber photodetector based on the polished side of an arc-shaped fiber for the optical signals’ in situ measurements. For this purpose, a metal-semiconductor–metal photodetector was designed with multiple interdigitated metal fingers of gold electrodes. A waveguide structure containing polymethyl methacrylate (PMMA), graphene layers, and zinc oxide nanostructures was developed and covered over the arc-shaped fiber. Due to the PMMA’s refractive index (n = 1.4905), the evanescent field of propagating mode was drawn out of the core, thus increasing the light interaction with semiconductor nanostructures. To study the influence of graphene flakes on the optoelectrical behavior of zinc oxide nanostructures, a suspension of graphene oxide (GO) and ZnO nanorods was synthesized and transferred onto the PMMA thin film, which was deposited on the polished side of the arc-shaped fiber. The morphological analysis indicates the formation of ZnO nanorods with different orientations, and these nanorods have the potential to enhance incident photon trapping greatly. Upon photon exposure, the guiding photons in the fiber evanescently coupled with the deposited nanostructures, and the photoexcited electron–hole pairs were generated in the semiconductor material. Using applied voltage across the interdigitated electrodes, the generated excitons were separated and increased the photocurrent, which was monitored precisely by source-measure equipment. The optoelectrical properties of fabricated devices showed that incorporating graphene layers can improve the photon detection performance of the fabricated all-fiber photodetectors based on ZnO nanostructures.

High speed and broadband fiber-integrated WS2/Bi2O2Se avalanche photodetector

Photodetectors based on two-dimensional(2D) materials have attracted tremendous attention in recent years because of their potential for development in compact and integrated devices. Owing to the high carrier mobility and air stability, the newly discovered 2D bismuth oxyselenide (Bi2O2Se) exhibits outstanding optoelectronic properties. However, the high dark current inevitably restricts the performance of the Bi2O2Se-based photodetectors. Here, we propose and demonstrate a fiber-integrated photodetector with a low dark current of ∼10 −10 A by assembling a WS2/Bi2O2Se Van der Waals heterostructure onto the end-face of a standard optical fiber. Benefiting from the narrow bandgap of the 2D materials, the fiber-integrated photodetector exhibits a broadband detection range from 650 to 1630 nm along with a responsivity of 1.13 AW−1. The fast rise time is measured as ∼410μs, while the fall time is ∼600μs. Taking advantage of the built-in potential in the WS2/Bi2O2Se heterostructure, the photodetector can work on self-powered mode. Applied a certainly high reverse voltage, the WS2/Bi2O2Se fiber-integrated photodetector can operate at avalanche breakdown region with an external quantum efficiency of 141% and an avalanche gain of 44 under the input power of 56.7μW. Finally, the fiber-integrated photodetector is applied to measure the wrist bending owing to its high photoresponsivity. These findings indicate that our proposed device has intriguing capabilities in terms of photodetection and on-line power monitoring, which enable our proposed device to have superb application potential in a fiber-integrated multi-function system.

Gold Enhanced Graphene-Based Photodetector on Optical Fiber with Ultrasensitivity over Near-Infrared Bands

Graphene has been widely used in photodetectors; however its photoresponsivity is limited due to the intrinsic low absorption of graphene. To enhance the graphene absorption, a waveguide structure with an extended interaction length and plasmonic resonance with light field enhancement are often employed. However, the operation bandwidth is narrowed when this happens. Here, a novel graphene-based all-fiber photodetector (AFPD) was demonstrated with ultrahigh responsivity over a full near-infrared band. The AFPD benefits from the gold-enhanced absorption when an interdigitated Au electrode is fabricated onto a Graphene-PMMA film covered over a side-polished fiber (SFP). Interestingly, the AFPD shows a photoresponsivity of >1 × 104 A/W and an external quantum efficiency of >4.6 × 106% over a broadband region of 980–1620 nm. The proposed device provides a simple, low-cost, efficient, and robust way to detect optical fiber signals with intriguing capabilities in terms of distributed photodetection and on-line power monitoring, which is highly desirable for a fiber-optic communication system.

Numerical and experimental study of control rods effects on neutronic power in TRR

Power of nuclear reactors are measured through different methods. Neutron Detectors are usually used for online power monitoring of nuclear reactors. The measured power by neutronic detectors is affected by the positions of control rods (CRs) in the core. The main contribution of this research is to investigate the effect of the CRs position on power monitoring in Tehran Research Reactor (TRR) from experimental and simulation aspects. The MTR_PC package is used to evaluate the effect of partial insertion of the CRs on the power calibration at the operating core of the TRR. The maximum impact of CRs position on the NDs response is about 25% during a cycle. Results of the thermal power calibration experiment are used to investigate the CRs effect on power calibration. In the first experiment, the results of two thermal power calibrations, with the same monitoring power 2 MW at the different configurations of CRs, are compared. Experimental investigation illustrates 9.5% changes in the real thermal power of TRR, while simulation predicts about 11%. In the second experiment, the power of TRR is increased to 5 MW and the thermal power calibration has been repeated in the new position of CRs and its result is compared with 5 MW. Both of the experiment and modeling results predict a similar effect of CRs on power calibration.

PowerTap: All-digital power meter modeling for run-time power monitoring

The power consumption is a key metric to design computing platforms. In particular, the variety and complexity of current applications fueled an increasing number of run-time power-aware optimization solutions to dynamically trade the computational power for the power consumption. In this scenario, the online power monitoring methodologies are the core of any power-aware optimization, since the incorrect assessment of the run-time power consumption prevents any effective actuation. This work proposes PowerTap, an all-digital power modeling methodology for designing online power monitoring solutions. In contrast with state-of-the-art solutions, PowerTap adds domain-specific constraints to the data-driven power modeling problem. PowerTap identifies the power model iteratively to balance the accuracy error of the power estimates and the complexity of the final monitoring infrastructure. As a representative use-case, we employed a complex hardware multi-threaded SIMD processor, also considering different operating clock frequencies. The RTL implementation of the identified power model targeting an Xilinx Artix 7 XC7A200T FPGAhighlights an accuracy error within 1.79% with an area overhead of 9.95% (LUT) and 3.87% (flip flops) and an average power overhead of 12.17 mW regardless of the operating conditions, i.e., number of software threads and operating frequency.

An Innovative Method for Online Power Monitoring in Nuclear Reactors

The monitoring of the power level during nuclear reactors operation is done by instruments, which measure the neutron flux. The calibration of this power is carried out by thermal means. Its accurate knowledge is critical to the fuel burnup calculations, and mainly to electrical power. Nuclear fuel burning is proportional to the thermal power released by the reactor and is extremely relevant for the calculation of uranium-235 mass burned, profile knowledge of fission products, the value of the radioactive decay heat, the activity and radiotoxicity. The objective of this paper is to present two methods for real time monitoring of nuclear reactor power using thermal processes. These methods have been developed and experimentally validated in the TRIGA nuclear research reactor at Nuclear Technology Development Center – CDTN (Belo Horizonte, Brazil), and are the focus of the paper described here. One uses the temperature difference between an instrumented fuel element and the pool water cooling below the reactor core. This method is innovative and the most reliable way of on-line power monitoring of the CDTN TRIGA reactor. For this methodology, a patent was deposited at the Brazilian Institute of Industrial Property (INPI) in 2012. The other method consists in real-time monitoring of the steady-state energy balance of the primary and secondary reactor cooling loops. This process is now the standard methodology for power calibration used in the CDTN TRIGA reactor. It also presents the uncertainty analysis for these thermal power measure procedures. Keywords: Instrumentation, nuclear reactor, power measurement, reactor TRIGA, temperature, thermal power.

Validation of neutron flux redistribution factors in JSI TRIGA reactor due to control rod movements

For efficient utilization of research reactors, such as TRIGA Mark II reactor in Ljubljana, it is important to know neutron flux distribution in the reactor as accurately as possible. The focus of this study is on the neutron flux redistributions due to control rod movements. For analyzing neutron flux redistributions, Monte Carlo calculations of fission rate distributions with the JSI TRIGA reactor model at different control rod configurations have been performed. Sensitivity of the detector response due to control rod movement have been studied. Optimal radial and axial positions of the detector have been determined. Measurements of the axial neutron flux distribution using the CEA manufactured fission chambers have been performed. The experiments at different control rod positions were conducted and compared with the MCNP calculations for a fixed detector axial position. In the future, simultaneous on-line measurements with multiple fission chambers will be performed inside the reactor core for a more accurate on-line power monitoring system.

Comparison of the On-Line Power Detection and Prediction System

The article presents a power detection and prediction system (PDPS) using fusion algorithms to be applied in the on-line power monitoring of the target device. The system contains multiple power detection units, a data integration unit, a target device, a power source and a main controller. Each power detection unit measures the assigned power source on real-time, and uses four current sensors to measure the current variety. We use fusion algorithms to be applied in current and voltage detection. We can calculate the real-time power values according to the estimated values of current and voltage measurement values. The main controller predicts the power loading for each power detection unit using auto-regression algorithm, and calculates the error value between the prediction value and the measurement value for each detection value, and compares the relation value on various condition.

Thermal methods for on-line power monitoring of the IPR-R1 TRIGA Reactor

The IPR-R1 Research Reactor is a TRIGA Mark I type reactor. It is a pool reactor, and the fuel elements are cooled by water natural convection. The heat removal capacity of this process is great enough for safety reasons at the current maximum 250 kW reactor power level. However, a heat removal system is provided for removing heat from the reactor pool water. Power monitoring of nuclear reactors is always done by means of neutronic instruments. In the IPR-R1 the power is measured by four nuclear channels. This work presents the results and methodology for monitoring the power of this reactor by three thermal processes. One method uses the temperature difference between an instrumented fuel element and the pool water below the reactor core. The other two methods consist in the steady-state energy balance of the primary and secondary reactor cooling loops.