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At least 469 records · Page 26

First Results from BREAD: Broadband Reflector Experiment for Axion Detection

We report R&D progress, as well as first dark photon search results with BREAD - a novel dish antenna for broadband ~$\mu$eV-eV wave-dark matter detection, which allows to utilize state-of-the-art high-field solenoidal magnets. Axions are converted non-resonantly to photons on a cylindrical metallic wall parallel to an external magnetic field. These photons are then focused using a novel reflector geometry onto a state-of-the-art high-sensitive photon detector. We recently demonstrated [PRL 128 (2022) 131801] that this concept using a $\sim 10\,{\rm m}^2$ conversion area in a $\sim 10\,{\rm T}$ solenoidal magnet has the potential to discover QCD axions spanning multiple decades in mass range. In this talk we discuss progress of our first stage pilot experiments - GigaBREAD and InfraBREAD - covering different mass ranges. We show first results of a room-temperature GigaBREAD prototype and discuss upscaling to larger, cryogenic and magnetized versions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Cryogen Safety Live #8876

Cryogenics (from the Greek word κρυος, meaning frost or icy cold) is the study of the effects and behavior of materials at very low temperature. This course is designed to provide trainees with an introduction to cryogen use, hazards associated with cryogen systems, cryogen safety components, and the requirements that govern the design and use of cryogen systems at Los Alamos National Laboratory (LANL). The knowledge you gain is intended to help you keep your workplace safe for you and your coworkers.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗

A Dendrite-Resistant Sodium/Porous-Carbon Anode for Solid-State Batteries – Strategies and Challenges for Low-Pressure Operation

Sodium solid-state batteries (Na-SSB) have gained interest recently due to the abundance of Na over Li, but they still tend to fail due to dendrites under practical current densities and cycling capacities. To overcome this, Na-SSBs are frequently tested with impractically high applied pressure. In this work, a porous carbon interfacial layer is utilized in conjunction with Na-ß”-Al2O3 solid electrolytes to enable Na-cycling at milder cell pressures. This sodium/porous carbon layer enables improved solid-state Na cycling in symmetric cells, up to a current density of 10 mA cm-2 at 25 °C. Cycling up to 1 mAh cm-2 is challenging with low pressure, but 1 mAh cm-2 capacity can be reliably cycled at 1 mA cm-2 at an elevated temperature of 60 °C in symmetric cells. Finally, the evolution of the interface and sodium/carbon anode is evaluated with cryogenic ion-milling and cross-sectional imaging revealing that, depending on testing temperature, pressure, current density, and capacity, void formation, Na-extraction from porous carbon, delamination of the porous carbon matrix, or a combination of these occurs at the interface between Na-metal and BASE. Despite this, excellent dendrite resistance is achieved, and a full-cell design utilizing a Na-transition metal oxide cathode is still able to achieve an areal capacity of ~ 2.7 mAh cm-2 at 0.125 mA cm-2. This work demonstrates an alternative pathway toward a Na-metal anode for Na-SSBs without the requirement of excessive stack pressure.

low-cost↗

A turnkey gaseous helium-cooled superconducting CORC ® dc power cable with integrated current leads

Abstract High-temperature superconducting (HTS) direct current (dc) power cable systems, capable of delivering power exceeding 10 MW while being cooled with cryogenic helium gas, have been developed for applications on naval electric ships, electric aircraft and in data centers. Current injection from room temperature into the superconducting power cable causes by far the greatest heat load to the cryogenic system. Efficient current leads with integrated helium gas heat exchangers were developed to inject a current exceeding 1 kA from room temperature into a superconducting Conductor on Round Core (CORC ® ) power cable, without the need for liquid nitrogen pre-cooling. A 2 m long single-pole CORC ® power cable system that included current leads was cooled using a Stirling cryocooler with a closed-loop helium gas circulation system. The turnkey power cable system allowed cool down from room temperature to its operating temperature of 60 K–70 K within 5 h, after which continuous operation at 1.2 kA was demonstrated. The successful development and demonstration of a CORC ® power cable with current leads containing integrated helium gas heat exchangers enables widespread implementation of HTS MW-class, high current density superconducting dc power cables in many applications with constrained space that require a power dense solution.

Physics↗

Spatially and temporally resolved plasma parameter estimations of laser heated MagLIF relevant gas pipes at NIF

The ability to control laser pre-heat is an integral part of the inertial confinement fusion concept known as Magnetized Liner Inertial Fusion. This process is studied at the National Ignition Facility (NIF) where 4 of the 192 laser beams are propagated through a 1-cm long gas cell where they deposit >20 kJ of energy into the gaseous fuel via inverse bremsstrahlung absorption. This process ionizes the gas, producing a plasma that follows behind the laser front and expands over the radius of the cell. Emission from this plasma, as viewed by a gated x-ray detector, can be used to build spatially and temporally resolved estimations of the pre-heat plasma's density and temperature profiles. This can then be used to estimate the plasma pressure, internal energy, and radiation losses. Estimations show the evolution of the plasma in magnetized and unmagnetized gas cells filled with ambient temperature neopentane (C5H12) +1% Ar, as well as unmagnetized cryogenically cooled (32 K) deuterium +1% Ne filled targets. This analysis shows the effects of initial gas-fill density, composition, and axial magnetization on the time-dependent plasma parameters. Previously, these parameters at the NIF had not been experimentally characterized, and these estimations provided a potential new means of testing radiation magneto-hydrodynamic predictive capability models. Results in unmagnetized targets have strong agreement with simulations. However, in targets with a 19 T applied axial magnetic field, this method yields electron temperatures up to 100% hotter than those predicted by HYDRA codes.

Bremsstrahlung↗

Design of the DUNE APATF cryogenic system

Fermi National Accelerator Laboratory (FNAL) is developing the international Long- Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) to advance neutrino science. The flagship of the DUNE project consists of a large particle detector constructed one-mile (1.6 km) beneath the surface at the Sanford Underground Research Facility (SURF) in Lead, SD. The SURF detector is the largest of its type ever built and is comprised of four cryostats totaling 70,000 tons of liquid argon (LAr) to record neutrino interactions with unprecedented precision. Each cryostat houses a detector, the first includes 150 Anode Panel Assemblies (APA) submersed within 17,500 tons of LAr. Before installing 150 APA within the SURF detector they will be cryogenically cooled to nominally 90 K at the APA Test Facility (APATF) utilizing nitrogen flows. The APATF cryogenic system is entirely located one-mile underground at the SURF facility and includes nominally 13 kW of refrigeration at 80 K, cryogenic transfer lines, APA test cryostats, a cryogenic control system, and various control and pressure safety elements to ensure performance and safety requirements are achieved. The APATF preliminary design is in progress and major considerations include an efficient, costeffective mechanism to deliver the required refrigeration to the APATF underground, support of rigid testing intervals to support the DUNE operating schedule, temperature stability of the APA and electronics within cryostats, efficient cryogenic system operation to minimize heat leak and/or liquid nitrogen consumption, thermo-mechanical stability and flexibility of components, and pressure safety of the APATF cryogenic system. Installation and integration of the APATF cryogenic system within the footprint and to adjacent sub-systems is also discussed.

43 PARTICLE ACCELERATORS↗

Freeze-induced crystallization: An overlooked pathway for mineral genesis in natural waters

Natural ice plays salient roles in making the Earth habitable and sustainable. Previously overlooked, its role in chemical processes is now of emerging interest, particularly due to the freeze concentration effect, which can substantially promote chemical reactions during ice formation. We demonstrate here that ice formation can serve as a dynamic and unique pathway for mineral genesis. Freezing solutions containing dissolved manganese and carbonates produced rhodochrosite (Mn II CO 3 ) even under slightly undersaturated conditions. At room temperature, by contrast, this occurred when the solution saturation level was increased by ca. 30,000 times. The cryogenic rhodochrosite formed spherical aggregates of nano-polycrystallites, distinctly different from the cubic monocrystalline particles observed at room temperature. The distinct feature likely resulted from the combined effects of the intensified supersaturation induced by the freeze concentration effect and the low temperatures within liquid-like layers, conditions that make liquid-like layers an exceptional environment for mineral genesis, unlike typical natural water systems. The cryogenic rhodochrosite formation was successfully demonstrated using in situ, real-time X-ray absorption spectroscopy (XAS), enabling direct observation of freeze-induced solid formation. In conclusion, our findings reveal that freeze-induced crystallization may be an active mineralization pathway, potentially influencing elemental cycles within the cryosphere and contributing to minerals with distinguishing properties and reactivities in the environment.

Earth, Atmospheric, and Planetary Sciences↗

Modelling of the laser amplification process with allowance for the effect of the temperature distribution in an Yb : YAG gain element on the thermophysical and lasing characteristics of the medium

A time-dependent three-dimensional model for the laser amplification process has been constructed with allowance for the effect of the temperature distribution on the thermophysical and lasing characteristics of gain media. We have performed numerical modelling of the laser amplification process in the gain elements of a two-stage subjoule-level cryogenic laser amplifier operating at a pulse repetition rate of up to 1 kHz. It has been shown that taking into account the temperature distribution is of critical importance in calculation of cryogenically cooled laser amplifiers pumped with high-power diodes. We have found optimal diode pump parameters at which the maximum achievable pulse energy at the amplifier output can reach 300 and 570 mJ at pulse repetition rates of 1000 and 500 Hz, respectively. (extreme light fields and their interaction with matter)

42 ENGINEERING↗

A case study of using x-ray Thomson scattering to diagnose the in-flight plasma conditions of DT cryogenic implosions

The design of inertial confinement fusion ignition targets requires radiation-hydrodynamics simulations with accurate models of the fundamental material properties (i.e., equation of state, opacity, and conductivity). Validation of these models is required via experimentation. A feasibility study of using spatially integrated, spectrally resolved, x-ray Thomson scattering measurements to diagnose the temperature, density, and ionization of the compressed DT shell of a cryogenic DT implosion at two-thirds convergence was conducted. Synthetic scattering spectra were generated using 1D implosion simulations from the LILAC code that were post processed with the x-ray scattering model, which is incorporated within SPECT3D. Analysis of two extreme adiabat capsule conditions showed that the plasma conditions for both compressed DT shells could be resolved.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Cryogenic Design and Thermal Analysis of EIC Central Detector (ePIC) Solenoid Magnet (MARCO)

The Electron Ion Collider (EIC) physics program utilizes a 2.0 T superconducting magnet at the heart of its ePIC detector system. This approximately 3.5 m long and 2.84 m diameter warm bore magnet has a 20 tons cold mass which is conduction-cooled using liquid helium at 4.5 K. A closed loop active thermosiphon system is chosen to facilitate the cooling and to maintain a minimum of 2 K temperature margin on the peak operating temperature (4.7 K) of the superconductor. Here, this paper presents the cryogenic design of the cooling system and the thermal analysis of the solenoid. A Computational fluid dynamics (CFD) model was developed to quantify the performance of the two–phase closed thermosiphon system and predict the temperature gradient on the cold mass.

Gopinath, Sandesh [Thomas Jefferson National Accel↗

Magnetic and Magnetocaloric Properties of the A 2 LnSbO 6 Lanthanide Oxides on the Frustrated fcc Lattice

Frustrated lanthanide oxides are promising candidates for cryogen-free magnetic refrigeration due to their suppressed ordering temperatures and high magnetic moments. While much attention has been paid to the garnet and pyrochlore lattices, the magnetocaloric effect in frustrated face-centered cubic (fcc) lattices remains relatively unexplored. We previously showed that the frustrated fcc double perovskite Ba 2 GdSbO 6 is a top-performing magnetocaloric material (per mol Gd) because of its small nearest-neighbor interaction between spins. Here we investigate different tuning parameters to maximize the magnetocaloric effect in the family of fcc lanthanide oxides, A 2 LnSbO 6 (A = {Ba 2+ , Sr 2+ } and Ln = {Nd 3+ , Tb 3+ , Gd 3+ , Ho 3+ , Dy 3+ , Er 3+ }), including chemical pressure via the A site cation and the magnetic ground state via the lanthanide ion. Bulk magnetic measurements indicate a possible trend between magnetic short-range fluctuations and the field-temperature phase space of the magnetocaloric effect, determined by whether an ion is a Kramers or a non-Kramers ion. We report for the first time on the synthesis and magnetic characterization of the Ca 2 LnSbO 6 series with tunable site disorder that can be used to control the deviations from Curie–Weiss behavior. Taken together, these results suggest fcc lanthanide oxides as tunable systems for magnetocaloric design.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Spectroscopic study of the coupling effect between the two gaps of magnesium diboride on its RF properties

This program studied the two-gap nature of magnesium diboride and its possible effects on the superconducting rf properties of this material. Magnesium diboride (MgB 2 ) is a BCS superconductor with a superconducting critical temperature of 39 K, high critical current density and no weak link behavior across the grain boundary. These properties make this material ideal for both power applications and electronic devices. In particular, the high superconducting critical temperature and high thermodynamic field suggests that MgB 2 could be an ideal material also for superconducting radio frequency (SRF) cavities operating at a much higher temperature than Nb cavities and, therefore, reducing noticeably the cryogenics costs. However, MgB 2 is a two gap superconductor and it has been suggested that the RF properties are dominated by the smaller gap, which would make this material not competitive with Nb and especially Nb 3 Sn. The main problem does not seem to be the double-gap nature of this material but rather the weak-coupling of the two gaps that in the presence of an RF field suppresses superconductivity all together at fields much lower than the thermodynamic field. The main goal of this proposal is to address the fundamental question of the coupling between the two gaps in MgB 2 and understand if it is possible to control it and ultimately improve the RF performance of MgB 2 . The project studied these questions by measuring the density of states in the presence of an in-plane current and focused on the effect of controlled disorder. Disorder, indeed, provides an important knob to tune the properties of MgB2 and provides the possibility of changing the coupling between the two bands, making this material a competitive material for SRF applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Building Initial Dynamic System Models for Digital Twins of the Cryogenic Moderator System at the ORNL Spallation Neutron Source

This work describes the initial development of dynamic system models of the cryogenic moderator system (CMS) of the Spallation Neutron Source (SNS) at ORNL as a part of the ORNL LDRD funded project Building TRANSFORM to Accelerate Digital Twin Applications for Nuclear Systems, LOIS 10563. The goal of the work is to start the dynamic system modeling effort with the end goal of using them for real-time applications as digital twins. The CMS is a cryogenic liquid hydrogen flow loop that provides moderation of the neutrons that are generated by the SNS. For optimal neutron production, the CMS needs to maintain a steady and controlled density of cryogenic hydrogen in the moderator section thus requiring precise temperature and pressure control. Due to the varied time scales and system characteristics, control of the system is complex, and diagnostics are also difficult. Difficulty in accessing the flow loop during operations, limited instrumentation and unknown design details of the equipment combine to make the case for having sophisticated digital twin models of the system. Operationally the CMS also provides a strong use case for digital twins due to the constant need of optimization and for troubleshooting/diagnostics. The large amount of data collected which are freely available for using in building the model and verifying and validating the model also makes it a great candidate for a proof-of-concept for digital twins. The project extends ORNL's capacity of development and implementation of the open-source dynamic system modeling tool TRANSFORM for engineering design and digital twin/real-time applications. Specific system configuration data for the CMS have been gathered and an initial dynamic model was created in the TRANSFORM library using Dymola as the solution platform. Models of increasing complexity are created to demonstrate the need for a multi-layered approach in digital twin modeling depending on the scale and phenomena being focused on. The dynamic modeling is shown to bring the dynamic operational aspects to the design process for systems as well as serve as a digital twin to the hardware and allow for models to be tuned and compared against real time operational data. These aims should help to push forward strategic goals of application of digital twins and increase the impact of ORNL systems modeling capabilities with TRANSFORM/Modelica for various advanced energy systems.

42 ENGINEERING↗

Deployment of POLARBEAR-2b

POLARBEAR-2b (PB-2b) is the second receiver in the Simons Array, a cosmic microwave background (CMB) polarization experiment. The Simons Array uses dichroic polarization sensitive lenslet-coupled sinuous antennas and transition-edge sensor (TES) bolometers made of superconducting films. These bolometers are read out with frequency multiplexing electronics. PB-2b contains ~7500 detectors in two bands at 90 and 150 GHz with arcminute resolution. The polarization of these detectors is modulated by a cryogenic continuously rotating half-wave plate. PB-2b was installed on its telescope in 2022 in the Atacama Desert at an altitude of 5.2 km. This paper will detail initial readout commissioning, test of a new loopgain monitoring method, and focusing the optics. Work is ongoing to commission the remaining ambient temperature readout electronics, measure detector time constants, and observe with the cryogenic half-wave plate spinning.

47 OTHER INSTRUMENTATION↗

A cryogenic muon tagging system based on kinetic inductance detectors for superconducting quantum processors

Ionizing radiation has emerged as a potential limiting factor for superconducting quantum processors, inducing quasiparticle bursts and correlated errors that challenge fault-tolerant operation. Atmospheric muons are particularly problematic due to their high energy and penetration power, making passive shielding ineffective. Therefore, monitoring the real-time muon flux is crucial to guide the development of alternative error-correction or mitigation strategies. We present the design, simulation, and first operation of a cryogenic muon-tagging system based on kinetic inductance detectors (KIDs), developed as a stand-alone cryogenic particle-tagging module for superconducting quantum processors. The system consists of two KIDs arranged in a vertical stack and operated at ∼20 mK. Monte Carlo simulations based on Geant4 guided the prototype design and provided reference expectations for muon-tagging efficiency and accidental coincidences due to ambient γ-rays. We observed a muon-induced coincidence rate among the top and bottom detectors of (192 ± 9) $\times\,10^{-3}$ events s$^{−1}$, in excellent agreement with the Monte Carlo prediction. The prototype achieves a muon-tagging efficiency of about 90% with negligible dead time. These results demonstrate the feasibility of operating a muon-tagging system at millikelvin temperatures and represent a key step toward the integration of cryogenic veto systems with multi-qubit chips to mitigate muon-induced errors.

Mariani, Ambra [INFN, Rome] (ORCID:000000028184857↗

Competing conduction mechanisms in high performance carbon nanotube fibers

The performance of carbon nanotube (CNT) cables, a contender for copper-wire replacement, is tied to its metallic and semi-conducting-like conductivity responses with temperature; the origin of the semi-conducting-like response however is an underappreciated incongruity in literature. With controlled aspect-ratio and doping-degree, over 61 unique cryogenic experiments including anisotropy and Hall measurements, CNT cable performance is explored at extreme temperatures (65 mK) and magnetic-fields (60 T). A semi-conducting-like conductivity response with temperature becomes temperature-independent approaching absolute-zero, uniquely demonstrating for the first time the necessity of heterogeneous fluctuation induced tunneling; complete de-doping leads to localized hopping, contrasting graphite's pure metallic-like response. High-field magneto-resistance (including novel +22 % longitudinal magneto-resistance near room-temperature) is analyzed with hopping and classical two-band models, both yielding a similar parameter useful for conductor development. Varying field-orientation angle uncovers significant two- and four-fold symmetries that are shown to be from Aharonov-Bohm-like corrections to the curvature-induced bandgap, a first for macroscale CNT fibers. Tight-binding calculations using Green's Function formalism model the largest, coherent transport to-date in commensurate CNT bundles in magnetic-field, revealing non-uniform transmission across bundle cross-sections with doping restoring uniformity; independent of doping, transport in bundle-junction-bundle systems are predominantly from CNTs adjacent to the other bundle—demonstrating that smaller bundles are more efficient for electronic transport. The final impact is predicting the ultimate conductivity of heterogeneous CNT cables using temperature and field-dependent transport, surpassing conductivity of traditional metals.

36 MATERIALS SCIENCE↗

Ultracold cryogenic TEM with liquid helium and high stability

Cryogenic transmission electron microscopy has revolutionized structural biology and materials science. To image below liquid nitrogen temperatures, various liquid helium stages have been constructed but have proven to be complex and unstable, making high-resolution imaging challenging. This problem is even more pronounced in side-entry specimen holders common on modern transmission electron microscopes. Here, we introduce an ultracold liquid helium transmission electron microscope side-entry specimen holder, featuring continuous cryogen flow and vibration decoupling. This instrument is compatible with modern aberration-corrected microscopes and achieves sub-25 K base temperature, ±2 mK thermal stability over many hours, and atomic resolution—setting the stage for a new era of cryogenic electron microscopy.

42 ENGINEERING↗