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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Multipole approximation of special nonlinear magnets for the IOTA ring

All existing focusing optics for accelerators are built to be "linear", i.e. the transverse focusing force is proportional to the particle displacement from the closed orbit. Such approach is used in order to make trajectories stable in the entire area of phase space, because the potential describing linear focusing is integrable and does not produce chaotic motion. Technically, the needed field is achieved with the help of dipole and quadrupole magnets. But the linear motion is unstable to perturbations in the focusing fields and excludes any betatron tune spread over particle's energy, which is beneficial for the beam stability. Moreover, the focusing strength depends on the particle's energy deviation from the designed one. These undesired effects are usually suppressed by the addition of non- linear elements, such as sextupoles and octupoles. Unfortunately, these additions make focusing potential nonintegrabe, leading to the limitation of stable phase space area. Recent research showed, that there exist non-linear potentials that, nevertheless, are fully integrable [1, 2]. Thus, there is an opportunity to create stable non-linear focusing optics that provides high betatron tune spread and mitigate magnetic field errors. This approach is to be implemented in electron storage ring called Integrable Optics Test Accelerator (IOTA) at Fermilab [3]. The main goal is to show the possibility to implement the nonlinear integrable system in a realistic accelerator design. Development of a magnet, which creates exact non-linear potential, is a technically complicated task, that takes much time and efforts. However, it is possible to expand the non- linear potential into superposition of multipoles of even orders (i.e quadrupole, octupole, etc.). Though this series is not convergent in the entire space, a few low order terms can be used to model the true potential in some limited area. In turn, each of the multipole potentials can be generated by speci ed electrical current in PCB coiled on the surface of storage ring's vacuum tube. Such approach is much cheaper than the creation of a magnet of solid iron with high current coil and faster than the development of \exact" non-linear magnet, but it can help identify some features of non-linear integrable optics application. The goal of this research work is to find analytically the angular distribution of electrical current on the surface of the vacuum tube, which creates inside it multipole potential with given parameters. Hereafter, there is the task to develop a model of flexible printed circuit board (PCB), which could be coiled around the vacuum tube in order to provide the desired current distribution.

Vorobev, Viktor↗
DOE OSTI2011

P and T Violating Form Factors of the Deuteron

We calculate the electric-dipole and magnetic-quadrupole form factors of the deuteron that arise as a low-energy manifestation of parity and time-reversal violation in quark-gluon interactions. We consider the QCD vacuum angle and the dimension-six operators that originate from physics beyond the standard model: the quark electric and chromoelectric dipole moments and the gluon chromoelectric dipole moment. Within the framework of two-flavor chiral perturbation theory, we show that in combination with the nucleon electric dipole moment, the deuteron moments would allow an identification of the dominant source(s) of symmetry violation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Nonlinear dynamics experiments

The goal of nonlinear dynamics experiments is to improve the understanding of single particle effects that increase the particle amplitude and lead to loss. Particle motion in storage rings is nearly conservative and for transverse dynamics the Hamiltonian in action angle variables (I{sub x},I{sub y},{phi}{sub x},{phi}{sub y}) near an isolated resonance k{nu}{sub x} + l{nu}{sub y} {approx} p is H = I{sub x}{nu}{sub x0} + I{sub y}{nu}{sub y0} + g(I{sub x}, I{sub y}) + h(I{sub x}, I{sub y})cos(k{phi}{sub x} + l{phi}{sub y} - p{theta}), (1) where k, l, p are integers, {theta} = 2{pi}s/L is the azimuth, and s and L are the path length and circumference respectively. The amplitude dependent tunes are given by {nu}{sub x,y}(I{sub x},I{sub y}) = {nu}{sub x0,y0} + {partial_derivative}g(I{sub x},I{sub y})/{partial_derivative}I{sub x,y} (2) and h(I{sub x},I{sub y}) is the resonance driving term (RDT). If the motion is governed by multiple resonances, h(I{sub x},I{sub y}) has to be replace by a series of terms. The particle motion is completely determined by the terms g and h, which can be calculated from higher order multipoles (Sec. ??), or obtained from simulations. Deviations from pure Hamiltonian motion occur due to synchrotron radiation damping (Sec. ??) in lepton or very high energy hadron rings, parameter variations, and diffusion processes such as residual gas and intrabeam scattering. The time scale of the non-Hamiltonian process determines the applicability of the Hamiltonian analysis. Transverse nonlinearities are introduced through sextupoles or higher order multipoles and magnetic field errors in dipoles and quadrupoles. Sextupoles can already drive all resonances. The beam-beam interaction and space charge also introduce nonlinear fields. Intentionally introduced nonlinearities are used to extract beam on a resonance or through capture in stable islands. Localization and minimization of nonlinearities in a ring is a general strategy to decrease emittance growth and increase the beam lifetime. The minimization of nonlinear effects can be done locally or globally. Except for resonant extraction, amplitude increase and particle loss is the result of chaotic particle motion. Large chaotic regions allow particles to increase their amplitudes, and ensures their ultimate loss. However, chaotic particles can, on average, still survive the time period of interest, i.e. the storage time. Nonlinear dynamics experiments aim to determine either the detuning and driving terms g and h directly, or their effect on other quantities. Nonlinear phenomena observed in experiments include phase space deformations and resonant islands in Poincare surfaces of section, nonlinear phase advances, amplitude detuning g, decoherence (Sec. ??), resonance driving terms h, smear, halo formation, echoes (Sec. ??), the tune response matrix, dynamic aperture (Sec. ??), emittance growth, and particle loss. Nonlinear experiments can also be done in the longitudinal plane.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Testing high-current superconducting subscale dipole coils with superconducting transformer

Several sub-scale superconducting dipole coils are being developed at Fermilab in the framework of the U.S. Magnet Development Program. These coils are made of high-current LTS and HTS cables with maximum currents of up to 10 kA. A superconducting current transformer with a maximum DC current up to ~25 kA previously developed at Fermilab for Nb3Sn Rutherford cable testing was modified and adapted for small dipole coil testing. This paper describes its commissioning using a NbTi dipole magnet impregnated with TELENE. This magnet was wound out of 6/1 NbTi cable.

Barzi, Emanuela↗
DOE OSTI2018

A GRB Afterglow Model Consistent with Hypernova Observations

In this paper we describe the afterglows of the long gamma-ray-burst (GRB) 130427A within the context of a binary-driven hypernova. The afterglows originate from the interaction between a newly born neutron star ($ν$NS), created by an Ic supernova (SN), and a mildly relativistic ejecta of a hypernova (HN). Such an HN in turn results from the impact of the GRB on the original SN Ic. The mildly relativistic expansion velocity of the afterglow ($Γ ~ 3$) is determined, using our model-independent approach, from the thermal emission between 196 and 461 s. The power law in the optical and X-ray bands of the afterglow is shown to arise from the synchrotron emission of relativistic electrons in the expanding magnetized HN ejecta. Two components contribute to the injected energy: the kinetic energy of the mildly relativistic expanding HN and the rotational energy of the fast-rotating highly magnetized $ν$NS. We reproduce the afterglow in all wavelengths from the optical (10 14 Hz) to the X-ray band (10 19 Hz) over times from 604 s to 5.18 × 10 6 s relative to the Fermi-GBM trigger. Initially, the emission is dominated by the loss of kinetic energy of the HN component. After 10 5 s the emission is dominated by the loss of rotational energy of the $ν$NS, for which we adopt an initial rotation period of 2 ms and a dipole plus quadrupole magnetic field of $\lesssim$ 7 × 10 12 G or ~10 14 G. This scenario with a progenitor composed of a CO core and an NS companion differs from the traditional ultra-relativistic-jetted treatments of the afterglows originating from a single black hole.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Molecular Heterogeneous Multiferroics (DOE BES Final Technical Report)

This project aims to explore a new class of molecular heterogeneous multiferroics towards room temperature stimuli-responsive magnetoelectricity by untangling the complex interplay between molecular magnetism and molecular ferroelectricity, and their stimuli-responsiveness. The research hypothesis is to examine if the rational design and molecular engineering of hydrogen bonded molecular heterogeneous multiferroics will enable rapid proton-transfer between molecular ferroelectric and magnetic building blocks to control its magnetism and intramolecular spin and dipole interactions, a promising pathway toward a new mechanism of room temperature ME coupling effect in molecular materials. With arbitrary choice and precise organization of molecular building blocks underlying tunable spin and dipole interactions, driven by external stimuli (electrical, magnetic and optical), a variety of multifunctional molecular multiferroics will be created and characterized, which could provide the understanding for the design of next-generation stimuli-responsive molecular magnetoelectronics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Strain Distribution in REBCO-Coated Conductors Bent With the Constant-Perimeter Geometry

Here, cable and magnet applications require bending REBa 2 Cu 3 O 7-δ (REBCO, RE = rare earth) tapes around a former to carry high current or generate specific magnetic fields. With a high aspect ratio, REBCO tapes favor the bending along their broad surfaces (easy way) than their thin edges (hard way). The easy-way bending forms can be effectively determined by the constant-perimeter method that was developed in the 1970s to fabricate accelerator magnets with flat thin conductors. The method, however, does not consider the strain distribution in the REBCO layer that can result from bending. Therefore, the REBCO layer can be overstrained and damaged even if it is bent in an easy way as determined by the constant-perimeter method. To address this issue, we developed a numerical approach to determine the strain in the REBCO layer using the local curvatures of the tape neutral plane. Two orthogonal strain components are determined: the axial component along the tape length and the transverse component along the tape width. These two components can be used to determine the conductor critical current after bending. The approach is demonstrated with four examples relevant for applications: a helical form for cables, forms for canted cos θ dipole and quadrupole magnets, and a form for the coil end design. The approach allows us to optimize the design of REBCO cables and magnets based on the constant-perimeter geometry and to reduce the strain-induced critical current degradation.

(REBCO RE = rare earth) coated conductors↗
DOE OSTI2022

Electron Cloud Simulations for the Electron-Ion Collider in Brookhaven National Laboratory

For high-intensity circular accelerators and storage rings, if the secondary electron emission yield (SEY) of the vacuum chamber surfaces is high, an EC (Electron Cloud) could build up with the passage of the circulating beam. The presence of EC can strongly affect the beam quality, such as transverse instabilities, transverse emittance growth, and beam loss. Furthermore, the heat load from EC can exceed the available cryogenic capability. For the RHIC superconducting (SC) arc magnets, to be used for the hadron storage ring of the Electron-Ion Collider (EIC), the dynamic heat load budget is 0.5 W/m to the 4.5 K stainless steel beam pipe. This can limit the maximum beam bunches or intensity of the EIC, hence diminishing the luminosity provided by the EIC. The EC has affected the beam instability and significantly contributed to cryogenic heat load in the Large Hadron Collider (LHC). Positron storage rings for which ECs have been a critical factor in the design and performance include KEKB in Japan and EC buildup remains one of the concerns for future high-intensity accelerators design. EC considerations have driven the SuperKEKB collider design and the positron damping ring for the proposed International Linear Collider (ILC). The LHC luminosity upgrade is contingent on reducing the bunch spacing to 25 ns; at this bunch spacing, severe EC buildup has been observed. The success of the upgrade is likely contingent on limiting EC buildup. To study the EC heat load, we did some EC simulations with PyECLOUD code for the dipole, quadrupole, sextupole magnets, and the warm (drift) section of the EIC hadron storage ring. PyECLOUD is an EC simulation code developed by CERN. The code has been validated and used to study EC in the LHC, SPS, and PS. To eliminate EC buildup, the sources of electrons must be minimized. First, we will reduce the production of electrons due to residual gas ionization by specifying the maximum gas density, which requires a vacuum chamber with low electron-stimulated desorption (ESD) yields and a sufficient (preferably distributed) pumping speed. Second, we should reduce the secondary electrons with a lower secondary electron yield (SEY) material.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Spontaneous Demagnetization of a Dipolar Spinor Bose Gas in an Ultralow Magnetic Field

We study the spinor properties of S=3 {sup 52}Cr condensates, in which dipole-dipole interactions allow changes in magnetization. We observe a demagnetization of the Bose-Einstein condensate (BEC) when the magnetic field is quenched below a critical value corresponding to a phase transition between a ferromagnetic and a nonpolarized ground state, which occurs when spin-dependent contact interactions overwhelm the linear Zeeman effect. The critical field is increased when the density is raised by loading the BEC in a deep 2D optical lattice. The magnetization dynamics is set by dipole-dipole interactions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

THE QUASI-BIENNIAL PERIODICITY AS A WINDOW ON THE SOLAR MAGNETIC DYNAMO CONFIGURATION

Manifestations of the solar magnetic activity through periodicities of about 11 and 2 years are now clearly seen in all solar activity indices. In this paper, we add information about the mechanism driving the 2-year period by studying the time and latitudinal properties of acoustic modes that are sensitive probes of the subsurface layers. We use almost 17 years of high-quality resolved data provided by the Global Oscillation Network Group to investigate the solar cycle changes in p-mode frequencies for spherical degrees l from 0 to 120 and 1600 {mu}Hz {<=}{nu} {<=} 3500 {mu}Hz. For both periodic components of solar activity, we locate the origin of the frequency shift in the subsurface layers and find evidence that a sudden enhancement in amplitude occurs in just the last few hundred kilometers. We also show that, in both cases, the size of the shift increases toward equatorial latitudes and from minimum to maximum solar activity, but, in agreement with previous findings, the quasi-biennial periodicity (QBP) causes a weaker shift in mode frequencies and a slower enhancement than that caused by the 11-year cycle. We compare our observational findings with the features predicted by different models, that try to explain the origin of this QBP and conclude that the observed properties could result from the beating between a dipole and quadrupole magnetic configuration of the dynamo.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

Supersolid and charge-density-wave states from anisotropic interaction in an optical lattice

We show anisotropy of the dipole interaction between magnetic atoms or polar molecules can stabilize new quantum phases in an optical lattice. Using a well-controlled numerical method based on the tensor network algorithm, we calculate the phase diagram of the resultant effective Hamiltonian in a two-dimensional square lattice - an anisotropic Hubbard model of hard-core bosons with attractive interaction in one direction and repulsive interaction in the other direction. Besides the conventional superfluid and the Mott insulator states, we find the striped and the checkerboard charge-density-wave states and the supersolid phase that interconnect the superfluid and the striped solid states. The transition to the supersolid phase has a mechanism different from the case of the soft-core Bose-Hubbard model.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Spin correlations and new physics in τ -lepton decays at the LHC

We use spin correlations to constrain anomalous τ -lepton couplings at the LHC including its anomalous magnetic moment, electric dipole moment and weak dipole moments. Single spin correlations are ideal to probe interference terms between the SM and new dipole-type couplings as they are not suppressed by the τ -lepton mass. Double spin asymmetries give rise to T -odd correlations useful to probe CP violation purely within the new physics amplitudes, as their appearance from interference with the SM is suppressed by m τ . We compare our constraints to those obtained earlier on the basis of deviations from the Drell-Yan cross-section.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

FLArE up dark sectors with EM form factors at the LHC forward physics facility

Despite being mostly secluded, dark sector particles may feebly interact with photons via a small mass-dimension 4 millicharge, a mass-dimension 5 magnetic and electric dipole moment, or a mass-dimension 6 anapole moment and charge radius. If sufficiently light, the LHC may produce an intense and collimated beam of these particles in the far forward direction. We study the prospects of searching for such dark sector particles with electromagnetic form factors via their electron scattering signature in the Forward Liquid Argon Experiment (FLArE) at the Forward Physics Facility (FPF). We find that FLArE can provide new probes of sub-GeV dark particles with dipole moments and strong sensitivities for millicharged particles in the 100 MeV to 100 GeV region. This complements other search strategies using scintillation signatures or dark matter direct detection and allows for probing strongly interacting dark matter motivated by the EDGES anomaly. Along with the FORMOSA detector, this leads to a very versatile and leading experimental program in the search for millicharged particles in the FPF.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

PandaX-II constraints on spin-dependent WIMP-nucleon effective interactions

We present PandaX-II constraints on candidate WIMP-nucleon effective interactions involving the nucleon or WIMP spin, including, in addition to standard axial spin-dependent (SD) scattering, various couplings among vector and axial currents, magnetic and electric dipole moments, and tensor interactions. The data set corresponding to a total exposure of 54-ton-days is reanalyzed to determine constraints as a function of the WIMP mass and isospin coupling. We obtain WIMP-nucleon cross section bounds of 1.6 x 10 –41 cm 2 and 9.0 x 10 –42 cm 2 (90% c.l.) for neutron-only SD and tensor coupling, respectively, for a mass M WIMP ~ 40 GeV/c 2 . The SD limits are the best currently available for M WIMP > 40 GeV/c 2 . We show that PandaX-II has reached a sensitivity sufficient to probe a variety of other candidate spin-dependent interactions at the weak scale.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

SMEFT ATLAS: The landscape beyond the Standard Model

The Standard Model Effective Field Theory (SMEFT) based on the unbroken gauge group SU(3) 𝐶 ⊗SU(2) 𝐿 ⊗U(1) 𝑌 and containing only particles of the Standard Model (SM) has developed in the last decade to a mature field. It is the framework to be used in the energy gap from scales sufficiently higher than the electroweak scale up to the lowest energy scale at which new particles show up. We summarize the present status of this theory with a particular emphasize on its role in the indirect search for new physics (NP). While flavour physics of both quarks and leptons is the main topic of our review, we also discuss electric dipole moments, anomalous magnetic moments (𝑔−2) 𝜇,𝑒 , 𝑍-pole observables, Higgs observables and high-𝑝𝑇 scattering processes within the SMEFT. We group the observables into ten classes and list for each class the most relevant operators and the corresponding renormalization group equations (RGEs). We exhibit the correlations between different classes implied both by the operator mixing and the SU(2) 𝐿 gauge symmetry. Our main goal is to provide an insight into the complicated operator structure of this framework which hopefully will facilitate the identification of valid ultraviolet completions behind possible anomalies observed in future data. Numerous colourful charts, and 85 tables, while representing rather complicated RG evolution from the NP scale down to the electroweak scale, beautify the involved SMEFT landscape. Over 1000 references to the literature underline the importance and the popularity of this field. We discuss both top-down and bottom-up approaches as well as their interplay. This allows us eventually to present an atlas of different landscapes beyond the SM that includes heavy gauge bosons and scalars, vector-like quarks and leptons and leptoquarks.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Optical Stark and Zeeman Spectroscopy of Thorium Fluoride, ThF, and Thorium Chloride, ThCl

Experimentally and theoretically determined magnetic and electric dipole moments, bond distances and vibrational spacings are used for a comparative study of the bonding in ThF and ThCl. Numerous bands in the visible electronic spectra between 16400 cm -1 -18800 cm -1 of supersonically cooled molecular beam samples have been detected using medium resolution (Δν≈ 0.1cm -1 ), two dimensional (2D) spectroscopy. High resolution (Δν < 20 MHz) field-free, Stark, and Zeeman spectroscopy of the detected [18.6] Ω=3/2 – X 2 Δ 3/2 band of ThF near 538.4 nm and the [18.2] Ω=3/2 – X 2 Δ 3/2 band of ThCl near 551.0 nm have been recorded and analyzed. Stark shifts and splitting were analyzed to produce | r μ el | values of 1.453(7) D and 0.588(9) D, for the X 2 Δ 3/2 and [18.6]Ω=3/2 states of ThF, respectively, and 2.022(35) D and 3.020(55) D, for the X 2 Δ 3/2 and [18.2]Ω=3/2 states of ThCl. Zeeman splittings and shifts were analyzed to produce g e values of 1.038(4) and 1.079(4) for the X 2 Δ 3/2 and [18.6]Ω=3/2 states of ThF and 1.130(4) and 1.638(4) for the X 2 Δ 3/2 and [18.2]Ω=3/2 states of ThCl. Analysis of g e values demonstrate that the X 2 Δ 3/2 and [18.6]Ω=3/2 states of ThF and the X 2 Δ 3/2 state of ThCl are predominately 2 Δ 3/2 spin-orbit components, whereas the [18.2] Ω=3/2 state of ThCl is an admixture of 2 Δ 3/2 and 2 Π 3/2 spin-orbit components. A molecular orbital description of the ground states is used to rationalize the observed | r μ el | values for the ThX(X=F,Cl,O and S) series, and garner insight into the bonding mechanism. The dipole moments in the ground state of ThF and ThCl have been calculated using relativistic coupled-cluster methods. It is demonstrated that the systematic inclusion of electron-correlation contributions plays an essential role in obtaining accurate predictions for the dipole-moment values in ThF and ThCl.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗