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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Modeling of RMS Current in CSI Filter Capacitor and Minimum Conduction Loss Operation of CSI-Fed PMSM Drives for Traction Applications

This paper presents a new minimum conduction loss (MCL) torque control algorithm for current source inverter- (CSI-) fed permanent-magnet synchronous machine drives that improves the overall machine drive efficiency by minimizing the combined conduction losses in the inverter and machine at each operating point. First, analytical models of conduction losses in CSI-fed motor drives are presented, and a closed-form expression for optimal d-axis stator current to achieve MCL operation is derived. An expression for the rms current in both wye- and delta-connected CSI output capacitors is derived. A detailed simulation model that emulates the operation of a 100 kW SiC CSI-fed integrated machine drive (IMD) has been developed based on experimental results and finite element analysis. This simulation model is used to evaluate the proposed MCL control algorithm applied to a CSI-fed IMD system for a battery-electric vehicle traction drive, and the predicted total drive system loss with MCL control is compared to predicted losses with maximum-torque-per-ampere (MTPA) and minimum dc-link current (MDCC) control. Results show that MCL control can achieve loss reductions compared to the other two control algorithms over a wide range of operating conditions, with significant loss reductions >20% in the medium-speed regime.

42 ENGINEERING↗
DOE OSTI2021

Comprehensive Efficiency Analysis of Current Source Inverter Based on CSI-Type Double Pulse Test and Genetic Algorithm

A current-source inverter (CSI) has a natural output voltage boost feature that can be advantageous for traction applications. Switching frequency is one of the easily-controlled variables that can be adjusted to improve the CSI efficiency at different operating points when the boost function is used. This paper investigates a CSI-based double-pulse test (DPT) measurement that mimics normal operation of the CSI. A loss model of the CSI is developed based on the CSI-type DPT experimental results. The impacts of the switching frequency and voltage boost ratio on the CSI efficiency and output voltage ripple are investigated. Based on the loss model, a genetic algorithm has been introduced that makes it possible to optimize the CSI's switching frequency and modulation index to maximize its efficiency under any desired operating condition.

current-source inverter, genetic algorithm, SPM ma↗
DOE OSTI2020

Performance of CsI:Tl Cyrstal with a Spectrum Matching Photomultiplier Tube

This report documents an effort to improve the energy resolution for a thallium doped cesium iodide (CsI:T1) scintillator paired with a spectrum matching photomultiplier tube (PMT). A comparison of the differences in the pulse height spectra from thallium doped (CsI:T1) and sodium doped (CsI:Na) single crystals with PMTs of different spectrum responses was performed. Results show that energy resolution of the detector only improves 0.5% at room temperature when these scintillators are coupled with a spectrum matching PMT. Based on a spectrum matching PMT, the best results for energy resolution are 7.39% and 7.88% for CsI:T1 and CsI:Na scintillators, respectively. The improvement is primarily attributed to the increase of photon statistics from the increase of photons (N) being detected in the spectrum matching PMT. Other factors, such as optical quantum yield and non-proportionality of the CsI:T1 and CsI:Na crystals, that can affect the energy resolution were also studied and reported. The results indicate that although the use of a spectrum matching PMT enhances the photon statistics, it also exacerbates the nonproportionality response. Consequently, a promised improvement on energy resolution due solely to photon statistics was not fully realized.

36 MATERIALS SCIENCE↗
DOE OSTI2020

CsI(Tl) pulse shape discrimination with the Belle II electromagnetic calorimeter as a novel method to improve particle identification at electron–positron colliders

Here we describe the implementation and performance of CsI(Tl) pulse shape discrimination for the Belle II electromagnetic calorimeter, representing the first application of CsI(Tl) pulse shape discrimination for particle identification at an electron–positron collider. The pulse shape characterization algorithms applied by the Belle II calorimeter are described. Control samples of $γ, μ^+, π^±, K^±$ and $ρ/ \bar{ρ}$ are used to demonstrate the significant insight into the secondary particle composition of calorimeter clusters that is provided by CsI(Tl) pulse shape discrimination. Comparisons with simulation are presented and provide further validation for newly developed CsI(Tl) scintillation response simulation techniques, which when incorporated with GEANT4 simulations allow the particle dependent scintillation response of CsI(Tl) to be modelled. Comparisons between data and simulation also demonstrate that pulse shape discrimination can be a new tool to identify sources of improvement in the simulation of hadronic interactions in materials. The $K^0_L$ efficiency and photon-as-hadron fake-rate of a multivariate classifier that is trained to use pulse shape discrimination is presented and comparisons are made to a shower-shape based approach. CsI(Tl) pulse shape discrimination is shown to reduce the photon-as-hadron fake-rate by over a factor of 3 at photon energies of 0.2 GeV and over a factor 10 at photon energies of 1 GeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Topological Equivalence of VSI and CSI Commutation Cells and Its Application to Switching Resonance Analysis and Damper Design

This paper proposes the concept of the topological equivalence between the commutation cells of a voltage source inverter (VSI) and a current source inverter (CSI) using duality and equivalent circuit transformation techniques. A switching resonance of CSI is analyzed and an effective three-phase RC damper is derived from the dc-link RC damper of VSIs based on the topological equivalence of the VSI and CSI commutation cells. Furthermore, a new three-phase RC damper design framework utilizing the topological equivalence is proposed. Here, experimental results verify that the proposed three-phase RC damper design for CSI significantly reduces the switching resonance and improves the CSI’s output waveform total harmonics distortions (THDs).

42 ENGINEERING↗
DOE OSTI2024

Comprehensive Comparative Analysis: VSI-based vs. CSI-based Motor Drive Systems with Sinusoidal Output Voltage

The emergence of wide-bandgap (WBG) power devices opens opportunities for current source inverters (CSIs) to provide a promising alternative drive configuration for motor drive applications. The sinusoidal output voltage of CSI offers significant advantages for numerous motor drive applications, including reducing the risks associated with motor terminal overvoltages and bearing discharge currents. This paper compares the performance of CSIs and voltage source inverters (VSIs) with the same performance capabilities. More specifically, sine filters are added to the VSI output terminals to match the CSI performance, and a front-end boost converter is added to the VSI to match the CSI’s voltage-boost capability. The results show that the CSI active components require 48% less volume than the VSI, combined with other performance advantages that make it an appealing candidate for some future motor drive applications.

current source inverter, motor drive system, passi↗
DOE OSTI2023

Alternative Vector PWM for CSI Common-Mode Voltage Reduction During Voltage-Boost Operation with Low Modulation Index

This paper proposes a new pulse-width modulation (PWM) scheme named alternative vector PWM (AVM) algorithm that reduces the common-mode voltage (vCM) generated by a 3-phase current source inverter (CSI) during operation within a portion of its voltage-boost regime when the CSI’s modulation index is below 1/3–√(=0.5774). Three different active current vector pairs (one conventional pair with adjacent active current vectors and two proposed pairs with non-adjacent active current vectors) are used to reduce vCM based on the CSI’s output voltage conditions. Experimental results confirm significant reductions in major vCM spectral components by up to approx. 85% between the 3rd harmonic of the fundamental frequency and the CSI’s PWM frequency, validating the advantages of the proposed AVM algorithm over the conventional PWM.

42 ENGINEERING↗
DOE OSTI2020

Materials Data on CsI by Materials Project

CsI is alpha Niobium phosphide-like structured and crystallizes in the orthorhombic Pnma space group. The structure is two-dimensional and consists of four CsI sheets oriented in the (0, 0, 1) direction. Cs1+ is bonded in a square co-planar geometry to four equivalent I1- atoms. There are two shorter (3.81 Å) and two longer (3.82 Å) Cs–I bond lengths. I1- is bonded in a square co-planar geometry to four equivalent Cs1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reaction losses of charged particles in CsI(Tl) crystals

To efficiently detect energetic light charged particles, it is common to use arrays of energy-loss telescopes involving two or more layers of detection media. As the energy of the particles increases, thicker layers are usually needed. However, carrying out measurements with thick-telescopes may require corrections for the losses due to nuclear reactions induced by the incident particles on nuclei within the detector and for the scattering of incident particles out of the detector, without depositing their full energy in the active material. In this paper, we develop a method for measuring such corrections and determine the reaction and out-scattering losses for data measured with the silicon-CsI(Tl) telescopes of the newly developed HiRA10 array. Here, the extracted efficiencies are in good agreement with model predictions using the GEANT4 reaction loss algorithm for Z = 1 and Z = 2 isotopes. After correcting for the HiRA10 geometry, we obtain a general function that describes the loss of efficiency due to reaction losses in CsI(Tl) crystals as a function of range.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Monte Carlo simulation of the passage of $\gamma$-rays and $\alpha$-particles in CsI

In this work, theoretical and computational methods for simulating the creation of ionization tracks by fast ions in solids were applied to the passage of a-particles in CsI, an inorganic scintillator commonly used for radiation detection. The methods were implemented in a Monte Carlo program to simulate the interaction of $\alpha$-particles, with incident energies of up to 1 MeV, with CsI. The simulations followed the fate of individual electron-hole pairs and thus allowed for a detailed description of the microscopic structure of ionization tracks created by incident radiation. Simulations were also performed with $\gamma$-rays of the same energy to compare and contrast the ionization tracks obtained with both types of particle. Intrinsic properties such as the mean energy per electron-hole pair, Fano factor, maximum theoretical light yield, and spatial distributions of electron-hole pairs were computed for both $\alpha$-particles and $\gamma$-rays. $\alpha$-particles created cylindrical tracks that were initially aligned with the incident direction and with initial radii of a few nanometers, whereas $\gamma$-rays showed significant scattering, resulting in probability distributions with lower intensities and much greater radial extents.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

CsI calorimeter for the J-PARC KOTO experiment

An electromagnetic calorimeter made of undoped CsI crystals is used in the J-PARC KOTO experiment to search for new physics beyond the standard model with the KL → π 0 νν¯ decay. The calorimeter is designed to operate in vacuum of 0.1 Pa and in a high-rate environment where the counting rate due to KL decays is O(100) kHz. A special method to calibrate the calorimeter during the data taking without using a tracking system for charged particles is reported. The energy, position, and timing resolutions of the calorimeter were evaluated in several beam tests, and the resolutions satisfy the required performance. Finally, the energy resolution with the total energy E is 0.66 ⊕ 1.81/ √ E[GeV]% in the inner region of the calorimeter.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Materials Data on CsI by Materials Project

CsI is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Cs1+ is bonded to six equivalent I1- atoms to form a mixture of edge and corner-sharing CsI6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Cs–I bond lengths are 3.93 Å. I1- is bonded to six equivalent Cs1+ atoms to form a mixture of edge and corner-sharing ICs6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsY by Materials Project

CsY is alpha Samarium-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Cs is bonded to six equivalent Cs and six equivalent Y atoms to form CsCs6Y6 cuboctahedra that share corners with eighteen equivalent CsCs6Y6 cuboctahedra, edges with six equivalent CsCs6Y6 cuboctahedra, edges with twelve equivalent YCs6Y6 cuboctahedra, faces with eight equivalent CsCs6Y6 cuboctahedra, and faces with twelve equivalent YCs6Y6 cuboctahedra. All Cs–Cs bond lengths are 3.84 Å. All Cs–Y bond lengths are 4.36 Å. Y is bonded to six equivalent Cs and six equivalent Y atoms to form YCs6Y6 cuboctahedra that share corners with eighteen equivalent YCs6Y6 cuboctahedra, edges with six equivalent YCs6Y6 cuboctahedra, edges with twelve equivalent CsCs6Y6 cuboctahedra, faces with eight equivalent YCs6Y6 cuboctahedra, and faces with twelve equivalent CsCs6Y6 cuboctahedra. All Y–Y bond lengths are 3.84 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsY(PO3)4 by Materials Project

CsY(PO3)4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Cs1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Cs–O bond distances ranging from 3.12–3.39 Å. Y3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Y–O bond distances ranging from 2.31–2.45 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.50–1.63 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. There is two shorter (1.50 Å) and two longer (1.63 Å) P–O bond length. In the third P5+ site, P5+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.50–1.63 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.50–1.63 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cs1+ and two P5+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cs1+ and two P5+ atoms. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one Cs1+, one Y3+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to one Cs1+, one Y3+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one Cs1+, one Y3+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to one Cs1+, one Y3+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to one Cs1+, one Y3+, and one P5+ atom. In the ninth O2- site, O2- is bonded in a distorted single-bond geometry to one Cs1+, one Y3+, and one P5+ atom. In the tenth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the eleventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Y3+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a distorted single-bond geometry to one Cs1+, one Y3+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsY(MoO4)2 by Materials Project

CsY(MoO4)2 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. Cs1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Cs–O bond distances ranging from 3.22–3.58 Å. Y3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Y–O bond distances ranging from 2.29–2.54 Å. Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.76–1.86 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Cs1+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cs1+, one Y3+, and one Mo6+ atom. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cs1+, one Y3+, and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Y3+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsY(MoO4)2 by Materials Project

CsY(MoO4)2 crystallizes in the orthorhombic Pccm space group. The structure is three-dimensional. Cs1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (3.17 Å) and four longer (3.38 Å) Cs–O bond lengths. Y3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.31 Å) and four longer (2.50 Å) Y–O bond lengths. Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.75–1.87 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cs1+, one Y3+, and one Mo6+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Y3+ and one Mo6+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Cs1+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsY(MoO4)2 by Materials Project

CsY(MoO4)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Cs1+ is bonded to twelve O2- atoms to form CsO12 cuboctahedra that share edges with six equivalent CsO12 cuboctahedra, edges with six equivalent MoO4 tetrahedra, and faces with two equivalent YO6 octahedra. There are six shorter (3.36 Å) and six longer (3.57 Å) Cs–O bond lengths. Y3+ is bonded to six equivalent O2- atoms to form YO6 octahedra that share corners with six equivalent MoO4 tetrahedra and faces with two equivalent CsO12 cuboctahedra. All Y–O bond lengths are 2.26 Å. Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three equivalent YO6 octahedra and edges with three equivalent CsO12 cuboctahedra. The corner-sharing octahedral tilt angles are 19°. There is one shorter (1.75 Å) and three longer (1.81 Å) Mo–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+, one Y3+, and one Mo6+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to three equivalent Cs1+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗