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At least 271 records · Page 15

Decoupling of Arctic variability from the North Pacific in a warmer climate

The sea level pressure variability in the North Pacific modulates the climate of the Arctic and surrounding continents, substantially impacting ecosystems and indigenous communities. Our analysis based on data from the CESM2 Large Ensemble and different Model Intercomparison Project datasets reveals that the interannual variability of Arctic surface air temperature (SAT) gradually decouples from the contemporaneous atmospheric conditions over the North Pacific as external forcing increases in intensity in the future. Future projections show that the North Pacific-Arctic relationship during the fall season consistently weakens in magnitude until the end of this century, and in the 22nd and 23rd centuries, the relationship is negligible throughout the year. We show that under increased greenhouse gas emissions, the regional heat fluxes extensively control the Arctic temperature variability, and the strength of the projected North Pacific-Arctic relationship is strongly dependent on the Arctic sea ice extent. Our results suggest that under future warming, a strong coupling of Arctic SAT with the underlying ocean and a weakening of the meridional pressure gradient driven by an enhanced rate of sea ice retreat will weaken the interannual footprint of North Pacific variability on Arctic SAT. Therefore, we propose that the alarming rate of sea-ice decline over recent decades and projected in the near future could accelerate the rate of decoupling. Further, we suggest that mitigation strategies for the Arctic should focus on regional mechanisms operating on interannual and seasonal timescales.

54 ENVIRONMENTAL SCIENCES↗

Neutrino Induced Pion Production at SciBooNE

We report measurements of neutrino induced pion production processes on carbon target with an average energy of {approx}0.8 GeV by SciBooNE experiment at Fermilab. These measurements are important inputs for current and future accelerator-based neutrino oscillation experiments in the interpretation of neutrino oscillation signals.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

CERN and 60 years of science for peace

This paper presents CERN as it celebrates its 60{sup th} Anniversary since its founding. The presentation first discusses the mission of CERN and its role as an inter-governmental Organization. The paper also reviews aspects of the particle physics research programme, looking at both current and future accelerator-based facilities at the high-energy and intensity frontiers. Finally, the paper considers issues beyond fundamental research, such as capacity-building and the interface between Art and Science.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Towards high-efficiency particle detection using superconducting microwire arrays

Here, we present a detailed study of an 8-channel 1×1 mm 2 WSi superconducting microwire single photon detector (SMSPD) array exposed to 120 GeV hadron beam and 120 GeV muon beam at the CERN Super Proton Synchrotron H6 beamline. Following up on our first detailed characterization of the efficiency and response of an SMSPD fabricated on a 3 nm WSi film, we report measurements of enhanced particle detection efficiency using a sensor fabricated from a thicker 4.7 nm-thick WSi film. We also report the first SMSPD detection efficiency measurement made for muons. Measurements are enabled by a silicon tracking telescope providing 10 μm in-situ spatial resolution. The results show a fill factor-normalized detection efficiency of 75% and a time resolution of about 130 ps across pixels. These findings represent a significant advancement toward developing high-efficiency SMSPD charged particle tracking systems with simultaneous precision timing, with potential applications in future accelerator-based experiments such as the FCC-ee and Muon Collider.

Cryogenic detectors↗

Measurement of single- and double-differential cross sections for mesonless charged-current muon neutrino interactions on argon with final-state protons using the MicroBooNE detector

Charged-current neutrino interactions with final states containing zero mesons and at least one proton are of high interest for current and future accelerator-based neutrino oscillation experiments. Using the Booster Neutrino Beam and the MicroBooNE detector at Fermi National Accelerator Laboratory, we have obtained the first double-differential cross-section measurements of this channel for muon neutrino scattering on an argon target with a leading proton momentum threshold of 0.25 GeV/𝑐. We also report a flux-averaged total cross section of 𝜎 = (11.8±1.2) × 10 −38 cm 2 /Ar and several single-differential measurements which extend and improve upon previous results. Statistical and systematic uncertainties are quantified with a full treatment of correlations across 359 kinematic bins, including correlations between distributions describing different observables. The resulting dataset provides the most detailed information obtained to date for testing models of mesonless neutrino-argon scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Nonconservation of Lepton Numbers in the Neutrino Sector Could Change the Prospects for Core Collapse Supernova Explosions

We show that interactions violating the conservation of lepton numbers in the neutrino sector could significantly alter the standard low entropy picture for the presupernova collapsing core of a massive star. A rapid neutrino-antineutrino equilibration leads to entropy generation and enhanced electron capture and, hence, a lower electron fraction than in the standard model. This would affect the downstream core evolution, the prospects for a supernova explosion, and the emergent neutrino signal. If realized by lepton-number-violating neutrino self-interactions (LNV 𝜈⁢SI), the relevant mediator mass and coupling ranges can be probed by future accelerator-based experiments.

79 ASTRONOMY AND ASTROPHYSICS↗

Entanglement rearrangement in self-consistent nuclear structure calculations

Background: Entanglement plays a central role in a diverse array of increasingly important research areas, including quantum computation, simulation, measurement, sensing, and communication. Extensive suites of investigations have been performed to better understand entanglement in atomic and molecular quantum many-body systems, while the exploration of entanglement in the structure of nuclei and their reactions is presently in its infancy. Purpose: The goal of this work is to begin investigating the entanglement properties of nuclei from first-principles nuclear many-body calculations. We attempt to identify common features and emergent structures of entanglement that could ultimately lead to new and natural many-body schemes. With an eye toward quantum accelerators in future hybrid-supercomputers, criteria for partitioning nuclear many-body calculations into quantum and classical components may provide advantages in future large-scale computations. Along the way we look for explanations of the relative success of phenomenological models such as the nuclear shell model, and for better ways to match to low-energy nuclear effective field theories and lattice QCD calculations to nuclear many-body techniques that are based upon entanglement. Method: We explore the entanglement between single-particle states in 4 He and 6 He. The patterns of entanglement emerging from different single-particle bases are compared, and possible links with the convergence of observables are explored, in particular, ground-state energies. The nuclear wave functions are obtained by performing active-space no-core configuration-interaction calculations using a two-body nucleon-nucleon interaction derived from chiral effective field theory. Entanglement measures within single-particle bases exhibiting different degrees of complexity are determined, in particular, harmonic oscillator (HO), Hartree-Fock (HF), natural (NAT) and variational natural (VNAT) bases. Specifically, single-orbital entanglement entropy, two-orbital mutual information, and negativity are studied. Results: The entanglement structures in 4 He and 6 He are found to be more localized within NAT and VNAT bases than within a HO basis for the optimal HO parameters we have worked with. In particular a core-valence structure clearly emerges from the full no-core calculation of 6 He. Here, the two-nucleon mutual information shows that the VNAT basis, which typically exhibits good convergence properties, effectively decouples the active and inactive spaces. Conclusions: Measures of one- and two-nucleon entanglement are found to be useful in analyzing the structure of nuclear wave functions, in particular the efficacy of basis states, and may provide useful metrics toward developing more efficient schemes for ab initio computations of the structure and reactions of nuclei, and quantum many-body systems more generally.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Measurement of the differential cross section for neutral pion production in charged-current muon neutrino interactions on argon with the MicroBooNE detector

We present a measurement of neutral pion production in charged-current interactions using data recorded with the MicroBooNE detector exposed to Fermilab’s booster neutrino beam. The signal comprises one muon, one neutral pion, any number of nucleons, and no charged pions. Studying neutral pion production in the MicroBooNE detector provides an opportunity to better understand neutrino-argon interactions, and is crucial for future accelerator-based neutrino oscillation experiments. Using a dataset corresponding to 6.86 ×10 20 protons on target, we present single-differential cross sections in muon and neutral pion momenta, scattering angles with respect to the beam for the outgoing muon and neutral pion, as well as the opening angle between the muon and neutral pion. Data extracted cross sections are compared to generator predictions. We report good agreement between the data and the models for scattering angles, except for an over-prediction by generators at muon forward angles. Similarly, the agreement between data and the models as a function of momentum is good, except for an underprediction by generators in the medium momentum ranges, 200–400 MeV for muons and 100–200 MeV for pions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Conceptual Design of a 20 T Hybrid Cos-Theta Dipole Superconducting Magnet for Future High-Energy Particle Accelerators

High energy physics research will need more and more powerful circular accelerators in the next decades. It is therefore desirable to have dipole magnets able to produce the largest possible magnetic field, in order to keep the machine diameter within a reasonable size. A 20 T dipole is considered a desired achievement since it would allow the construction of an 80 km machine, able to circulate 100 TeV proton beams. In order to reach 20 T, a hybrid Low-Temperature Superconductor (LTS) - High-Temperature Superconductor (HTS) magnet is needed, since LTS technology is presently limited to ~16 T for accelerator magnet applications. In this paper, we present the design of a 6 layers 20 T hybrid dipole magnet using Nb 3 Sn (LTS) and Bi2212 (HTS). Here we show that it is possible to achieve this magnetic field with accelerator field quality, with sufficient margin on a realistic conductor, keeping the stresses within safe limit, avoiding conductor degradation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Towards a unified model of neutrino-nucleus interactions

The achievement of the goals of the ongoing and future accelerator-based neutrino experiments – notably the determination of CP violating phase in the lepton sector – will require the development of advanced models of neutrino-nucleus interactions. In this review, we summarise the present status of experimental studies of neutrino-nucleus scattering, and discuss the developments and perspectives of the theoretical approach based on factorisation of the nuclear cross section, which has recently emerged as a promising framework for the description of the variety of processes contributing to the detected signals.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Finite Element Modeling of Electrochemical Polishing of Niobium in Hydrofluoric-Sulfuric Acid Electrolyte

Niobium (Nb) used in superconducting radio-frequency cavities requires smooth surface to achieve optimal performance. In this work, a finite element model that coupled electrochemistry, heat transfer, and fluid dynamics was developed to investigate the electrochemical polishing mechanisms of Nb, using experimentally measured polarization results of coupon samples as validations. The current and potential distribution, oxide growth kinetics of Nb in a complex cavity geometry was investigated as a function of temperature and coolant flow. A low temperature coolant with intermediate flow rate was found to reduce surface current and ensure oxide uniformity. These results could shed light on the design of future particle accelerators.

SRF accelerator cavity↗

Beam-Dynamics Analysis of Long-Range Wakefield Effects on the SCRF Cavities at the Fast Facility

Long-range wakefields in superconducting RF (SCRF) cavities create complicated effects on beam dynamics in SCRF-based FEL beamlines. The driving bunch excites effectively an infinite number of structure modes (including HOMs) which oscillate within the SCRF cavity. Couplers with loads are used to damp the HOMs. However, these HOMs can persist for long periods of time in superconducting structures, which leads to long-range wakefields. Clear understanding of the long-range wakefield effects is a critical element for risk mitigation of future SCRF accelerators such as XFEL at DESY, LCLS-II XFEL, and MaRIE XFEL. We are currently developing numerical tools for simulating long-range wakefields in SCRF accelerators and plan to experimentally verify the tools by measuring these wakefields at the Fermilab Accelerator Science and Technology (FAST) facility. This paper previews the experimental conditions at the FAST 50 MeV beamline based on the simulation results.

43 PARTICLE ACCELERATORS↗

RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A 1.3 GHz RF test cell capable of operating both at high pressure and in vacuum with replaceable electrodes was designed, built, and power tested in preparation for testing the frequency and geometry effects of RF breakdown at Argonne National Lab. At the time of this report this cavity is still waiting for the 1.3 GHz klystron to be available at the Wakefield Test Facility. (3) Under a contract with Los Alamos National Lab, an 805 MHz RF test cavity, known as the All-Seasons Cavity (ASC), was designed and built by Muons, Inc. to operate either at high pressure or under vacuum. The LANL project to use the (ASC) was cancelled and the testing of the cavity has been continued under the grant reported on here using the Fermilab Mucool Test Area (MTA). The ASC is a true pillbox cavity that has performed under vacuum in high external magnetic field better than any other and has demonstrated that the high required accelerating gradients for many muon cooling beam line designs are possible. (4) Under ongoing support from the Muon Acceleration Program, microscopic surface analysis and computer simulations have been used to develop models of RF breakdown that apply to both pressurized and vacuum cavities. The understanding of RF breakdown will lead to better designs of RF cavities for many applications. An increase in the operating accelerating gradient, improved reliability and shorter conditioning times can generate very significant cost savings in many accelerator projects.

43 PARTICLE ACCELERATORS↗

Solid-State Ultra-High Power Amplifier Modules Based on 100 V RF GaN Technology for LINACS Operating at 325 and 650 MHz

Purpose / objectives. This research project explores the groundwork for developing a new high efficiency, high reliability and cost effective radio frequency technology to be used in power sources for future linear accelerators. The frequencies of operation are 650 and 325 MHz, in use at Fermi National Laboratory. The technology can be extended to other frequencies. Brief Description. In this research work ultra-high power solid-state radio frequency sources are proposed operating at the stated frequencies of interest. The approach employs high voltage Gallium Nitride radio frequency transistors, operating at 100 V or higher, to achieve 5-kilowatts continuous-wave and 10 kilowatts pulse power level in a small form factor. The 5 kilowatts building block reduces the required number of combiners and related losses to achieve megawatts power levels. The design employs harmonic tuning techniques as used in class E, F and inverse F power amplifiers to achieve >70% efficiency and assembly techniques that overcome heat dissipation in such high power density systems. Solid-state technology achieves million hour operating lifetime compared to 10 – 100 thousand hours for incumbent technology based on vacuum tubes. Additionally, the modular approach afforded by a solid-state solution avoids complete system shutdown when one module fails. Overall, the approach reduces capital and operating cost. Research Results. During Phase I radio frequency Gallium Nitride building block transistors with 50 mm gate periphery were designed and built which achieve ~600 W continuous-wave when operating at 100 V bias and 1-kW pulsed when operating at 150V. This level of performance has been demonstrated with operation at 325 and 650 MHz, and in both cases measured efficiency exceeded 70%. Potential Applications. The technology identified as suitable for high efficiency power sources in particle accelerators can also be applied in megawatt class radars and several industrial, scientific and medical applications such as microwave sintering, radio frequency and microwave ablation, oil percolation, MRI scanners and Nuclear Magnetic Resonance spectrometers, etc… The high efficiency of these devices also translates into reduced electrical power consumption and lower cost of operation.

100 VDC↗

Search for heavy Majorana neutrinos in pp collisions at √s = 8 TeV with the CMS detector & photodetector and calorimeter R&D for particle colliders

This thesis contains both physics analysis and hardware studies. It consists of two primary sections: the results of a search for heavy Majorana mass neutrinos, using the event signature of same (like) sign charged electron pairs ($e^{\pm} e^{\pm}$ ) and two jets, and the results of studies to upgrade the Hadronic Forward (HF) and Hadronic Endcap (HE) subdetectors in the Compact Muon Solenoid (CMS) detector in response to the high intensity proton-proton collisions generated at the Large Hadron Collider (LHC) at European Organization for Nuclear Research (CERN, Conseil Europ\'{e}en pour la Recherche Nucl\'{e}aire). In this search for Majorana mass neutrinos, same sign dielectron ($e^{\pm} e^{\pm}$) + dijet events in the final state have been considered as a signature for neutrino particles. The analyzed data corresponds to an integrated luminosity of 19.7 fb\textsuperscript{-1} of proton-proton collisions at a center of mass energy of $\sqrt{s} = 8 \text{TeV}$, collected using the CMS detector during the 2012 operation at the LHC. Monte Carlo simulations accounting for the theoretical expectations of the Standard Model (SM) and the detector limitations are used to prototype the experiment and to test proposed analysis steps. No excess of events is observed in the data beyond the expected SM background. Upper limits are set on the mixing element squared, $|{V}_{eN}|^{2}$, of the heavy Majorana neutrino with standard model neutrinos, as a function of Majorana neutrino mass for masses in the range of 40-500 $GeV/c^2$. The detector upgrade search comprises three sections of this thesis. The first section describes the test results of 1785 multianode Hamamatsu R7600U-200-M4 photomultiplier tubes (PMT) in numerous parameters such as gain, dark current, and timing characteristics, which provide insights on the expected performance of the upgraded CMS-HF detector. These PMTs replaced the previous single anode R7525 PMTs because the glass windows of previous PMTs are the source of Cherenkov radiation, which causes a background noise in the experiment. The second section reports characterization results of two types of PMTs in a novel operation mode for Secondary Emission (SE) Ionization Calorimetry, which is a novel technique to measure electromagnetic shower particles in extreme radiation environments. The third section presents the test results of novel scintillating materials for CMS experiment in specific and future particle accelerators in general. These materials are Polyethylene Naphthalate (PEN), Polyethylene Terephthalate (PET), high efficiency mirror (HEM) and quartz plates with various organic and inorganic coating materials such as p-Terphenyl (pTp), Anthracene and Gallium-doped Zinc Oxide (ZnO:Ga). We have investigated them for radiation hardness, light yield, timing characteristics, and scintillation and transmission properties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Technology Strategy Assessment: Findings from Storage Innovations 2030 Lithium-ion Batteries

This report on accelerating the future of lithium-ion batteries is released as part of the Storage Innovations (SI) 2030 strategic initiative. The objective of SI 2030 is to develop specific and quantifiable research, development, and deployment (RD&D) pathways toward achieving the targets identified in the Long-Duration Storage Energy Earthshot, which seeks to achieve 90% cost reductions for technologies that can provide 10 hours or longer of energy storage within the coming decade. Through SI 2030, the U.S. Department of Energy (DOE) is aiming to understand, analyze, and enable the innovations required to unlock the potential for long-duration applications in the following technologies.

25 ENERGY STORAGE↗

Neutrino-Nucleus Interactions in the Precision Era

Current and future accelerator-based neutrino facilities, leveraging intense neutrino beams and advanced detectors, aim to precisely determine neutrino properties and probe signals of weakly interacting beyond the Standard Model physics. Achieving discovery-level precision and fully exploring the physics potential of these experiments critically depends on the accuracy of our understanding of fundamental underlying neutrino-nucleus interaction processes. This talk will focus on neutrino interactions spanning energies from tens of MeV to a few GeV—a complex, multi-scale and multi-process domain spanning from low-energy nuclear physics to perturbative QCD, with no unified underlying framework currently known. In this seminar, I will provide an overview of the field, discuss recent advancements, and share examples of ongoing cross-community efforts addressing these challenges.

Pandey, Vishvas [Fermilab]↗

Impact of a track trigger at a multi-TeV muon collider

In the panorama of future particle accelerators, the Muon Collider seems to be the best choice for several reasons that will be explored in section 1.2. The main challenge is represented by the instability of the muons. At the desired instantaneous luminosities, an intense flow of secondary and tertiary particles from the interactions of the beam decay products with the machine elements reaches the detector, compromising its performance. Several studies are currently underway to mitigate the background and to have an efficient trigger. My work represents a first step towards understanding the basic characteristics of a trigger selection, which will subsequently guide the design of the trigger system. With this aim I produced and analyzed Higgs and di-Higgs signals with MadGraph and CERN-ROOT. In first section there is an introduction to Muon Collider, a brief history, a discussion of its benefits, a description of the detector and of the effects of the Beam Induced Background. Several operating center-of-mass energies are possible for this machine, in this report a center-of-mass of 3 TeV is assumed. Then I describe the event generation process. Finally I describe the entire analysis, in particular I analyzed the efficiency and the number of events for each process.

43 PARTICLE ACCELERATORS↗