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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

LANSCE CCL Performance Limits

This report summarizes the performance limits of the LANSCE Coupled-Cavity Linac (CCL). These results are captured or summarized directly from the references cited. This report was written in support of the LANSCE Modernization Project (LAMP). Many factors contribute to the performance limits of the CCL accelerator system. One performance limit is set by the CCL mechanical structure and available cooling. Heating of the structure is ultimately linked to the operating RF duty factor of the CCL. Another performance limit is set by the maximum RF and beam duty factors that can be supported by the 805-MHz klystrons and associated HVDC power supplies. The RF and HVDC systems also set limits for the maximum peak beam current that can be accelerated in the CCL. And finally, a maximum beam current limit is set by the beam dynamics determined by the details of the CCL physics design (number of cells per CCL tank, accelerating gradients, magnetic focusing lattice, beam losses, etc.). This limit can be informed by both simulation results and beam measurement data, if available. A detailed explanation of each performance limit is given in the sections below. The results are summarized in the table below. In all cases, it is assumed that the CCL and the RF system are operating in their nominal beam production configuration – nominal magnet set points and nominal cavity fields, unless otherwise specified.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

EM and beam dynamics modeling of CCL with CST Studio

The 800-MeV proton linac at LANSCE consists of a drift-tube linac, which brings the beam to 100 MeV, followed by a coupled-cavity linac (CCL). Each of 44 CCL modules contain multiple tanks, and it is fed by a single 805-MHz klystron. CCL tanks are multi-cell blocks of identical re-entrant sidecoupled cavities, which are followed by drifts with magnetic quadrupole doublets. Bridge couplers – special cavities displaced from the beam axis – electromagnetically couple CCL tanks over such drifts. We have developed 3D CST models of CCL tanks of the LANSCE linac. Their electromagnetic analysis is performed using MicroWave Studio. Beam dynamics is modeled with Particle Studio for bunch trains with realistic beam distributions using the CST calculated RF fields and quadrupole magnetic fields to determine the output beam parameters.

42 ENGINEERING↗
DOE OSTI2020

Materials Data on Sn(CCl)2 by Materials Project

Sn(CCl)2 crystallizes in the orthorhombic Imma space group. The structure is one-dimensional and consists of two Sn(CCl)2 ribbons oriented in the (0, 1, 0) direction. Sn2+ is bonded in a tetrahedral geometry to two equivalent C and two equivalent Cl1- atoms. Both Sn–C bond lengths are 2.08 Å. Both Sn–Cl bond lengths are 2.34 Å. C is bonded in a linear geometry to one Sn2+ and one C atom. The C–C bond length is 1.23 Å. Cl1- is bonded in a single-bond geometry to one Sn2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sb2H12Pd(CCl)4 by Materials Project

PdSb2H12(CCl)4 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of two PdSb2H12(CCl)4 clusters. Pd2+ is bonded in a distorted L-shaped geometry to one Sb3+ and two Cl1- atoms. The Pd–Sb bond length is 2.55 Å. Both Pd–Cl bond lengths are 2.40 Å. There are four inequivalent C4- sites. In the first C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sb3+ and three H1+ atoms. The C–Sb bond length is 2.15 Å. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. In the second C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sb3+ and three H1+ atoms. The C–Sb bond length is 2.15 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the third C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sb3+ and three H1+ atoms. The C–Sb bond length is 2.15 Å. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. In the fourth C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sb3+ and three H1+ atoms. The C–Sb bond length is 2.14 Å. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. There are two inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded in a 5-coordinate geometry to one Pd2+, two C4-, and two Cl1- atoms. There are one shorter (2.43 Å) and one longer (3.01 Å) Sb–Cl bond lengths. In the second Sb3+ site, Sb3+ is bonded in a 5-coordinate geometry to two C4- and two Cl1- atoms. There are one shorter (2.42 Å) and one longer (3.08 Å) Sb–Cl bond lengths. There are twelve inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Sb3+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Sb3+ atom. In the third Cl1- site, Cl1- is bonded in a distorted water-like geometry to one Pd2+ and one Sb3+ atom. In the fourth Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Pd2+ and one Sb3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sn(CCl)2 by Materials Project

(C)2SnCl2 crystallizes in the orthorhombic Imma space group. The structure is one-dimensional and consists of four 7772-99-8 molecules and two C ribbons oriented in the (1, 0, 0) direction. In each C ribbon, C is bonded in a linear geometry to two equivalent C atoms. Both C–C bond lengths are 1.32 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CCl by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2022

Predicted Impacts of Pt and Ionomer Distributions on Low-Pt-Loaded PEMFC Performance

Low-cost, high performance proton exchange membrane fuel cells (PEMFCs) have been difficult to develop due to limited understanding of coupled processes in the cathode catalyst layer (CCL). Low-Pt-loaded PEMFCs suffer losses beyond those predicted solely due to reduced catalyst area. Although consensus links these losses to thin ionomer films in the CCL, a precise mechanistic explanation remains elusive. In this publication, we present a physically based PEMFC model with novel structure-property relationships for thin-film Nafion, validated against PEMFC data with low Pt loading. Results suggest that flooding exacerbates kinetic limitations in low-loaded PEMFCs, shifting the Faradaic current distribution. As current density increases, protons travel further into the CCL, resulting in higher Ohmic overpotentials. We also present a parametric study of CCL design parameters. We find that graded Pt and ionomer loadings reduce Ohmic losses and flooding, but individually do not provide significant improvements. However, a dual-graded CCL (i.e., graded Pt and ionomer) is predicted to significantly improve the maximum power density and limiting current compared to uniformly loaded CCLs. This work highlights the importance of accurate transport parameters for thin-film Nafion and provides a pathway to low-cost PEMFCs via precise control of CCL microstructures.

08 HYDROGEN↗
DOE OSTI2025

LAMP Emittance Budget, Rev. 1

This report summarizes the performance limits of the LANSCE Coupled-Cavity Linac (CCL). These results are captured or summarized directly from the references cited. This report was written in support of the LANSCE Modernization Project (LAMP). This brief report summarizes the emittance budget for the LANSCE Modernization Project (LAMP). While the project Key Performance Parameters (KPPs) specify threshold and objective requirements for charge delivered to each experimental area, no upper limits on beam emittances are specified. To maintain low losses in the high-energy section of the LANSCE linac and hands-on maintenance, some upper limits on beam emittance need to be specified for the new LAMP front-end performance. The scope of the LAMP project replaces the injector section and drift-tube linac (DTL) up to 100 MeV of the existing LANSCE linac. This new design replacement will be integrated with the remaining coupled cavity linac (CCL) which makes up most of the accelerator at LANSCE and accelerates the beam to a final energy of 800 MeV. The initial approach that has been used to define an emittance budget for the new LAMP front end is based on recent and historical measured beam emittances at 100 MeV for the three beam types accelerated at LANSCE: H+ (protons for isotope production), LBEG (H- beam for delivery to proton radiography and to the Lujan neutron spallation target, and MPEG (H- beam for delivery to the Weapons Neutron Research facility). The emittance budget (upper limit) for each beam type has been selected to maintain the losses in the CCL to a level approximately equivalent to those observed in present operations to first order. However, the goal of the LAMP project is to improve the quality of the beams injected into the CCL, if possible, thus allowing for higher average current operation while also lowering beam losses and activation at high beam energies. The table below summarizes the beam measurements evaluated and used to establish a conservative emittance budget for LAMP based on known historical beam losses and activation. However, based on estimates of the CCL admittance and the Isotope Production Facility (IPF) beamline acceptance, a more relaxed transverse emittance upper limit of 0.095 π-cm-mrad, rms, normalized may be acceptable at 100 MeV while still meeting the LAMP performance requirements for charge delivery to each LANSCE experimental area and maintaining hands-on maintenance. This upper limit is supported by a recent analysis of operational data. Additionally, the present conceptual LAMP front-end design meets this requirement.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

0D and 2D: The Cases of Phenylethylammonium Tin Bromide Hybrids

Tin halide perovskites and perovskite-related materials have emerged as promising lead-free hybrid materials for various optoelectronic applications. While remarkable progress has been achieved in the development of organic tin halide hybrids with diverse structures and controlled dimensionalities at the molecular level, some controversial results that have been reported recently need to be addressed. For instance, different photophysical properties have been reported for two-dimensional (2D) (PEA) 2 SnBr 4 (PEA = phenylethylammonium) by several groups with distinct emission peaks at around 468 and 550 nm. Here we report our efforts in the synthesis of phenylethylammonium tin bromide hybrids with zero-dimensional (0D) and 2D structures, and characterizations of their structural and photophysical properties. 0D [(PEA) 4 SnBr 6 ][(PEA)Br] 2 [CCl 2 H 2 ] 2 was found to exhibit strong yellow emission peak at 566 nm with a photoluminescence quantum efficiency (PLQE) of ~90%, while 2D (PEA) 2 SnBr 4 had weak emission peak at 470 nm with a PLQE of <0.1%. Interestingly, 0D [(PEA) 4 SnBr 6 ][(PEA)Br] 2 [CCl 2 H 2 ] 2 can be converted into 2D (PEA) 2 SnBr 4 upon drying, which would return to 0D [(PEA) 4 SnBr 6 ][(PEA)Br] 2 [CCl 2 H 2 ] 2 upon addition of dichloromethane. Powder X-ray diffraction results confirmed the reversible transformation between 0D and 2D structures. Density functional theory calculations showed that excitons in 0D [(PEA) 4 SnBr 6 ][(PEA)Br] 2 [CCl 2 H 2 ] 2 are highly localized, resulting in a strongly Stokes shifted broadband emission, while delocalized electronic states in 2D (PEA) 2 SnBr 4 result in weaker exciton binding, a higher exciton mobility, and a higher nonradiative decay.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Editors’ Choice—Ionomer Side Chain Length and Equivalent Weight Impact on High Current Density Transport Resistances in PEMFC Cathodes

Cell voltage at high current densities (HCD) of an operating proton-exchange membrane fuel cell (PEMFC) suffers from losses due to the local-O 2 and bulk-H + transport resistances in the cathode catalyst layer (CCL). Particularly, the interaction of perfluorosulfonic acid (PFSA) ionomer with the carbon supported platinum catalyst plays a critical role in controlling reactant transport to the active site. In this study, we perform a systematic analysis of the side chain length and equivalent weight (EW) of PFSA ionomers on the CCL transport resistances. Ex situ measurements were carried out to quantify the ionomer characteristics such as the molecular weight, proton conductivity and water uptake. Nanomorphology of ionomers cast as 60–120 nm thin-films is characterized using grazing-incidence X-ray scattering. In situ fuel cell electrochemical diagnostic measurements were carried out to quantify the reactant (H + /O 2 ) transport properties of the CCL. Ionomer EW was found to play a major role with decreasing EW yielding higher proton conductivity and water uptake that led to lower bulk-H + and local-O 2 transport resistances in the CCL. Finally, a 1D-semi-empirical performance model has been developed to quantify the impact of ionomer EW on cell voltage loss factors.

08 HYDROGEN↗
DOE OSTI2020

Elucidating the Role of Ionomer in the Performance of Platinum Group Metal-free Catalyst Layer via in situ Electrochemical Diagnostics

The ionomer content in platinum group metal (PGM)-free polymer electrolyte fuel cell (PEFC) cathode catalyst layer (CCL) plays an important role in the electrode gas transport properties, proton conductivity, and hence, membrane electrode assembly (MEA) performance. In this work, the ionomer content in the CCL is varied, influencing electrode microstructure by altering porosity, tortuosity, as well as ionomer distribution and coverage of the catalyst particles. A novel technique consisting of a H 2 pump, combined with a Pt black sensor layer, is used to measure the bulk mass transport resistance of a series of PGM-free CCL prepared with different ionomer contents. The values for bulk electrode mass transport resistance are contrasted with electrode proton transport resistance in the cathode catalyst layer, establishing a clearly defined trade-off between two key performance limiting phenomena and identifying a need for novel PGM-free electrode fabrication strategies.

25 ENERGY STORAGE↗
DOE OSTI2020

The Effect of Proton Conductivity of Fe–N–C–Based Cathode on PEM Fuel cell Performance

A model–based impedance spectroscopy is used to determine proton conductivity, oxygen transport parameter, double layer capacitance and oxygen reduction reaction (ORR) Tafel slope in the Fe–N–C cathode catalyst layer (CCL) of a PEM fuel cell. Experimental spectra of two cells differing by the membrane thickness only are processed using a physics–based model for PEMFC impedance. The spectra have been measured in the range of current densities from 25 to 800 mA cm -2 . The ORR Tafel slope of both the cells shows almost linear growth with the current density. In one of the cells, the CCL proton conductivity σp strongly decays at the current density of 100 mA cm -2 ; this decay is accompanied by the step growth of the double layer capacitance. Other minor variations of proton conductivity and double layer capacitance with the cell current occur also in a counterphase; presumed origin of this effect is discussed. The oxygen diffusion coefficient in the cathode exhibits explosive growth with the cell current. We attribute this effect to formation of temperature and pressure gradients in the CCL due to strongly non–uniform distribution of ORR rate in the electrode.

25 ENERGY STORAGE↗
DOE OSTI2020

Materials Data on AlB6H6(CCl3)2 by Materials Project

AlB2H6(CCl)2(BCl)4 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of sixteen chloroborane molecules and four AlB2H6(CCl)2 clusters. In each AlB2H6(CCl)2 cluster, Al3+ is bonded in a distorted trigonal pyramidal geometry to two C+3.50- and two Cl1- atoms. Both Al–C bond lengths are 1.95 Å. There are one shorter (2.47 Å) and one longer (2.52 Å) Al–Cl bond lengths. There are two inequivalent B1+ sites. In the first B1+ site, B1+ is bonded in a single-bond geometry to one Cl1- atom. The B–Cl bond length is 1.83 Å. In the second B1+ site, B1+ is bonded in a single-bond geometry to one Cl1- atom. The B–Cl bond length is 1.83 Å. There are two inequivalent C+3.50- sites. In the first C+3.50- site, C+3.50- is bonded to one Al3+ and three H+0.67+ atoms to form corner-sharing CAlH3 tetrahedra. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. In the second C+3.50- site, C+3.50- is bonded to one Al3+ and three H+0.67+ atoms to form corner-sharing CAlH3 tetrahedra. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. There are six inequivalent H+0.67+ sites. In the first H+0.67+ site, H+0.67+ is bonded in a single-bond geometry to one C+3.50- atom. In the second H+0.67+ site, H+0.67+ is bonded in a single-bond geometry to one C+3.50- atom. In the third H+0.67+ site, H+0.67+ is bonded in a single-bond geometry to one C+3.50- atom. In the fourth H+0.67+ site, H+0.67+ is bonded in a single-bond geometry to one C+3.50- atom. In the fifth H+0.67+ site, H+0.67+ is bonded in a single-bond geometry to one C+3.50- atom. In the sixth H+0.67+ site, H+0.67+ is bonded in a single-bond geometry to one C+3.50- atom. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a water-like geometry to one Al3+ and one B1+ atom. In the second Cl1- site, Cl1- is bonded in a water-like geometry to one Al3+ and one B1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Wogonoside attenuates liver fibrosis by triggering hepatic stellate cell ferroptosis through SOCS1 / P53 / SLC7A11 pathway

Abstract Wogonoside (WG) is a flavonoid chemical component extracted from Scutellaria baicalensis, which exerts therapeutic effects on liver diseases. Ferroptosis, a novel form of programmed cell death, regulates diverse physiological/pathological processes. In this study, we attempted to investigate a novel mechanism by which WG mitigates liver fibrosis by inducing ferroptosis in hepatic stellate cells (HSCs). A CCl 4 ‐induced mouse liver fibrosis model and a rat HSC line were employed for in vivo and in vitro experiments, both treated with WG. Firstly, the levels of the fibrotic markers α‐smooth muscle actin (α‐SMA) and α1(I)collagen (COL1α1) were effectively decreased by WG in CCl 4 ‐induced mice and HSC‐T6 cells. Additionally, mitochondrial condensation and mitochondrial ridge breakage were observed in WG‐treated HSC‐T6 cells. Furthermore, ferroptotic events including depletion of SLC7A11, GPX4 and GSH, and accumulation of iron, ROS and MDA were discovered in WG‐treated HSC‐T6 cells. Intriguingly, these ferroptotic events did not appear in hepatocytes or macrophages. WG‐elicited HSC ferroptosis and ECM reduction were dramatically abrogated by ferrostatin‐1 (Fer‐1), a ferroptosis inhibitor. Importantly, our results confirm that SOCS1/P53/SLC7A11 is a signaling pathway which promotes WG attenuation of liver fibrosis. On the contrary, WG mitigated liver fibrosis and inducted HSC‐T6 cell ferroptosis were hindered by SOCS1 siRNA and pifithrin‐α (PFT‐α). These findings demonstrate that SOCS1/P53/SLC7A11‐mediated HSC ferroptosis is associated with WG alleviating liver fibrosis, which provides a new clue for the treatment of liver fibrosis.

Liu, Guofang↗
DOE OSTI2022

Design of PGM-free cathodic catalyst layers for advanced PEM fuel cells

Here, the design of cathodic catalysts layer (CCL) consisted of Platinum Group Metal-free (PGM-free) electrocatalysts was done by catalyst coated membrane approach. Three different Fe-Mn-N-C compounds were synthesized with Fe:Mn ratio of 1:1, 2:1 and 2:1 with modified heat treatment profile. The catalysts were characterized by X-ray photoelectron spectroscopy, X-ray powder diffraction, pore and particle size distribution, zeta potential and transmission electron microscopy. Electrocatalysts were integrated into membrane electrode assembly and evaluated by electrochemical methods. Electrochemical impedance spectroscopy in combination with modeling were used for estimation of proton conductivity of CCL and its oxygen diffusivity. It was found that all CCLs possess extremely high proton conductivity, which was demonstrated for the first time for these types of PGM-free catalysts. The observed ORR mechanism was predominantly 4e- due to peroxide/radicals scavenging effect of Mn.

impedance↗