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DOE OSTI2018

Magnetorotational Mechanism of the Explosion of Core-Collapse Supernovae

The idea of the magnetorotational explosion mechanism is that the energy of rotation of the neutron star formed in the course of a collapse is transformed into the energy of an expanding shock wave by means of a magnetic field. In the two-dimensional case, the time of this transformation depends weakly on the initial strength of the poloidal magnetic field because of the development of a magnetorotational instability. Differential rotation leads to the twisting and growth of the toroidal magnetic-field component, which becomes much stronger than the poloidal component. As a result, the development of the instability and an exponential growth of all field components occur. The explosion topology depends on the structure of the magnetic field. In the case where the initial configuration of the magnetic field is close to a dipole configuration, the ejection of matter has a jet character, whereas, in the case of a quadrupole configuration, there arises an equatorial ejection. In either case, the energy release is sufficient for explaining the observed average energy of supernova explosion. Neutrinos are emitted as the collapse and the formation of a rapidly rotating neutron star proceeds. In addition, neutrino radiation arises in the process of magnetorotational explosion owing to additional rotational-energy losses. If the mass of a newborn neutron star exceeds the mass limit for a nonrotating neutron star, then subsequent gradual energy losses may later lead to the formation of a black hole. In that case, the energy carried away by a repeated flash of neutrino radiation increases substantially. In order to explain an interval of 4.5 hours between the two observed neutrino signals from SN 1987A, it is necessary to assume a weakening of the magnetorotional instability and a small initial magnetic field (10{sup 9}−10{sup 10} G) in the newly formed rotating neutron star. The existence of a black hole in the SN 1987A remnant could explain the absence of any visible pointlike source at the center of the explosion.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

Long-range interactions between chiral molecules

Results of molecular quantum electrodynamics calculations of discriminatory interactions between two chiral molecules undergoing resonance energy transfer, van der Waals dispersion, and optical binding are presented. A characteristic feature of the theory is that the radiation field is quantized with signals consequently propagating between centres at the speed of light. In order to correctly describe optically active chromophores, it is necessary to include magnetic as well as electric dipole coupling terms in the time-dependent perturbation theory computations. Recent work investigating the effect of an absorptive and dispersive chiral medium on the rate of migration of energy will also be discussed.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2017

Measurement of higher-order multipole amplitudes in ψ ( 3686 ) → γ χ c 1 , 2 with χ c 1 , 2 → γ J / ψ and search for the transition η c ( 2 S ) → γ J / ψ

Using 106 ×10 6 ψ (3686) events collected with the BESIII detector, we measure multipole amplitudes for the decay ψ (3686) → γχ c1,2 → γγ J/ψ beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole (M2) amplitude for ψ (3686) → γχ c1,2 → γγ J/ψ and the normalized electric-octupole amplitudes for ψ ( 3686 ) → γχ c2 , χ c2 → γJ/ψ are determined. The M2 amplitudes for ψ (3686) → γ χ c1 and χ c1,2 → γ J / ψ are found to differ significantly from zero and are consistent with theoretical predictions. We also obtain the ratios of M2 contributions of ψ ( 3686 ) and J /ψ decays to χ c1,2 , b$1\atop{2}$/ b$2\atop{2}$ = 1.35 ± 0.72 and a$1\atop{2}$/a$2\atop{2}$ = 0.617 ± 0.083 , which agree well with theoretical expectations. By considering the multipole contributions of χ c 1 , 2 , we measure the product branching fractions for the cascade decays ψ ( 3686 ) → γχ c0,1,2 → γγJ/ψ and search for the process η c (2S) → γJ/ψ through ψ ( 3686 ) → γη c (2S). The product branching fraction for ψ (3686) → γχ c0 → γγJ/ψ is 3σ larger than published measurements, while those of ψ (3686) → γχ c1,2 → γγJ/ψ are consistent. In conclusion, no significant signal for the decay ψ ( 3686 ) → γη c (2S) → γγJ/ψ is observed, and the upper limit of the product branching fraction at the 90% confidence level is determined.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

Compact, Achromatic Non-scaling FFAG Accelerator for HEP, Commercial and Medical Applications (CRADA FRA-2008-0005 Final Report)

Proton and light-ion accelerators have many research and medical applications, but the current state of technology in accelerators severely limits their widespread use: (1) synchrotrons have an intrinsic low duty cycle and become quite large for light ions; and (2) cyclotrons do not have energy variability and require complex superconducting magnets for high energy. A new concept in non-scaling Fixed-Field Alternating-Gradient (FFAGs) has been invented that incorporates both the energy variability of the synchrotron and the high duty cycle of the cyclotron. The concept uses normal-conducting, combined-function magnets that apply only constant (dipole) and linear-gradient (quadrupole) fields to stabilize the accelerator. This project will develop an optimized design for a new non-scaling and cost-effective innovation in FFAG accelerators. The accelerator design will have optics that can stably accelerate protons to 250 MeV (or higher) and carbon ions to =200 MeV, an energy considered ideal for radiation therapy. Phase I will optimize, fully simulate, and demonstrate the feasibility of this accelerator. Commercial Applications and other Benefits as described by the awardee: The fixed-field acceleration concept should eliminate some of the most pronounced technical difficulties, expense, maintenance, and required expertise faced in conventional proton and light-ion accelerators. In addition to the application for high energy physics, these accelerators should have application in cancer treatment, radiopharmaceuticals, and medical isotope production, and materials science.

43 PARTICLE ACCELERATORS↗

DOE OSTI2026

Modeling the Effect of the Heliospheric Magnetic Field on Cosmic Ray Muon Shadows

Shadows cast in the cosmic ray (CR) muon sky by the Sun were located using muon data from the MINOS far detector in Northern Minnesota. The shadows were observed independently across three time periods; near solar minimum, near solar maximum, and over the entire 13 year span of the data. A distribution of muon positions for each shadow was then sampled to simulate CR motions near the Sun using the Parker spiral model of the Heliospheric Magnetic Field (HMF) and a dipole model of the Geomagnetic Field (GMF). The resulting particle distributions were then compared to their position with respect to the Sun. Results show that the Parker spiral model is most consistent with the solar minimum shadow and least consistent with the solar maximum shadow, as expected. The simple Parker spiral is more consistent with the data for a harder CR spectrum than is actually present, indicating the need for a more detailed HMF model. Plausible modifications to the Parker spiral model which would affect the overall shift of the Sun's CR shadow are discussed.

Adamson, P. [Fermilab]↗

DOE OSTI2018

Conceptual Design of a Large Aperture Dipole for Testing of Cables and Insert Coils at High Field

© 2017 IEEE. Advances in the performance of low- and high-temperature superconductors enable the development of advanced magnets for a range of applications, including tokamaks for fusion energy, dipoles, and quadrupoles for hadron colliders, and solenoids for nuclear magnetic resonance studies. The capability of testing prototype cables and insert coils at high field is critical to these developments. We present here the conceptual design of a test facility dipole with features suitable to support the advanced magnet development efforts of both Fusion and HEP communities. In particular, a background field of 15 T is provided over a minimum homogeneous length of 1000 mm, and the magnet clear bore of approximately 144 × 94 mm can accommodate large fusion conductors as well as prototype coils for high field dipoles, along with flexible cryogenic and mechanical provisions for sample characterization. Two technical solutions are considered. The first uses a forced flow cable-in-conduit conductor and follows the design developed by EFDA for the EDIPO magnet. The second uses a bath cooled Rutherford cable and follows a block-coil design similar to the CERN FRESCA2 dipole, and the LBNL HD and LD1 dipoles. Following a comparison between the two approaches, we present two designs for the Rutherford cable approach including performance objectives, key parameters, and preliminary magnetic, mechanical and quench protection analysis.

Bruzzone, Pierluigi↗

DOE OSTI2014

Modeling the X-rays from the central compact object PSR J1852+0040 in Kesteven 79: Evidence for a strongly magnetized neutron star

I present modeling of the X-ray pulsations from the central compact object (CCO) PSR J1852+0040 in the Galactic supernova remnant Kesteven 79. In the context of thermal surface radiation from a rotating neutron star (NS), a conventional polar cap model can reproduce the broad, large-amplitude X-ray pulse only with a 'pencil plus fan' beam emission pattern, which is characteristic of ≳ 10{sup 12} G NS atmospheres, much greater than the ∼10{sup 10} G external dipole field inferred from the pulsar spin-down rate. This discrepancy can be explained by an axially displaced dipole. For other beaming patterns, it is necessary to invoke high-aspect-ratio emitting regions that are greatly longitudinally elongated, possibly due to an extremely offset dipole. For all assumed emission models, the existence of strong internal magnetic fields (≳ 10{sup 14} G) that preferentially channel internal heat to only a portion of the exterior is required to account for the implied high-temperature contrast across the stellar surface. This lends further observational evidence in support of the 'hidden' strong magnetic field scenario, in which CCOs possess submerged magnetic fields that are substantially stronger than the external dipole field, presumably due to burial by fallback of supernova ejecta. I also conduct phase-resolved X-ray spectroscopy and find no evidence for prominent spin-phase-dependent absorption features that could be produced by cyclotron absorption/scattering.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

North-south asymmetric solar cycle evolution: Signatures in the photosphere and consequences in the corona

The heliospheric current sheet is the continuum of the coronal magnetic equator that divides the heliospheric magnetic field into two sectors (polarities). Several recent studies have shown that the heliospheric current sheet is southward shifted during approximately 3 years in the solar declining phase (the so-called bashful ballerina phenomenon). In this article we study the hemispherical asymmetry in the photospheric and coronal magnetic fields using Wilcox Solar Observatory measurements of the photospheric magnetic field since 1976 as well as the potential field source surface model. Multipole analysis of the photospheric magnetic field shows that during the late declining phase of solar cycles since the 1970s, the 'bashful ballerina phenomenon' is a consequence of the g{sub 2}{sup 0} quadrupole term, signed oppositely to the dipole moment. Surges of new flux transport magnetic field from low latitudes to the poles, thus leading to a systematically varying contribution to the g{sub 2}{sup 0}-term from different latitudes. In the case of a north-south asymmetric flux production, this is seen as a quadrupole contribution traveling toward higher latitudes. When the quadrupole term is largest, the main contribution comes from the polar latitudes. At least during the four recent solar cycles, the g{sub 2}{sup 0}-term arises because the magnitude of the southern polar field is larger than the magnitude found in the north in the declining phase of the cycle. In the heliosphere this hemispheric asymmetry of the coronal fields is seen as a southward shift of the heliospheric current sheet by about 2°.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2010

Development and Test of Collaring Methods for Nb$_3$SN Quadrupole Magnets

Fermilab is developing Nb 3 Sn quadrupole magnets for the planned upgrade of interaction regions of the Large Hadron Collider (LHC). Two distinctly different approaches have been employed, one using quadrupole‐symmetric and one using dipole‐symmetric collar laminations. This paper describes the design features of both collar types, collaring techniques for brittle Nb 3 Sn coils, and compares the advantages and disadvantages of the two approaches. Results of mechanical analysis for quadrupoles based on dipole‐type and quadrupole‐type collars are presented. Magnet construction issues and test results are reported. Test results include coil and component strain measurements during construction. Plans for the completion and test of the first dipole‐symmetric assembly are described.

Bossert, R.↗

DOE OSTI2017

SIMULATION STUDY OF HEMISPHERIC PHASE-ASYMMETRY IN THE SOLAR CYCLE

Observations of the Sun suggest that solar activities systematically create north–south hemispheric asymmetries. For instance, the hemisphere in which sunspot activity is more active tends to switch after the early half of each solar cycle. Svalgaard and Kamide recently pointed out that the time gaps of polar field reversal between the northern and southern hemispheres are simply consequences of the asymmetry of sunspot activity. However, the mechanism underlying the asymmetric feature in solar cycle activity is not yet well understood. In this paper, in order to explain the cause of the asymmetry from the theoretical point of view, we investigate the relationship between the dipole- and quadrupole-type components of the magnetic field in the solar cycle using the mean-field theory based on the flux transport dynamo model. As a result, we found that there are two different attractors of the solar cycle, in which either the north or the south polar field is first reversed, and that the flux transport dynamo model explains well the phase-asymmetry of sunspot activity and the polar field reversal without any ad hoc source of asymmetry.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Fast magnetic response in gigahertz-band for columnar-structured Fe nanoparticle assembly

High density Fe-based ferromagnetic nanoparticle (NP) assembly is expected to have unique magnetic properties, such as superferromagnetism and super-spin-glass, different from magnetically isolated NP systems due to strong dipole interactions among the NPs. A high dipole interaction field, H{sub dip}, of ∼3.5 kOe can result in a high effective internal field to the magnetic moment of the NP, expecting for ultra-fast magnetic response, that is, a high magnetic resonance frequency, f{sub r}, of ∼10 GHz. However, for a simply molded Fe NP assembly, a low f{sub r} was observed due to inhomogeneous distribution of the internal field, implying the necessity of a unidirectional state of H{sub dip} for higher f{sub r}. In this study, we fabricated a columnar Fe NP assembly for realizing the unidirectional state of H{sub dip} by applying our uniquely developed external field-induced agglomeration method for monodispersed Fe NPs (13 nm in average size) as a function of the field (0–30 kOe) and volume fraction of the Fe NPs (0.5%–51%) in a polymer matrix with dimensions of 4 mm × 4 mm × 0.7 mm{sup t}. A columnar-structured Fe NP assembly was successfully achieved along an in-plane direction (defined as the x-axis) under optimized conditions. From static magnetization curves, induced uniaxial magnetic anisotropy was observed according to the shape of the columnar structure of the Fe NP assembly, where easy and hard axes of magnetization were realized along the parallel (x-axis) and normal directions (in-plane y-axis and z-axis in the thickness direction) to the external field during the process, respectively. Interestingly, this fabricated columnar-structured Fe NP assembly exhibited very high f{sub r} in the range from 3 to 11 GHz judging from the complex susceptibility spectra obtained. The f{sub r} values were well-scaled by a modified Snoek's-limit-law using demagnetization factors quantitatively estimated from the static magnetization curves. Thus, shape-induced anisotropy originating from the unidirectional state of H{sub dip} in the columnar structure of the Fe NP assembly plays an important role for high frequency magnetic response in the GHz-band.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Advanced Design for the WIQ Magnet With Steering Corrector Function

The Facility for Rare Isotopes Beams (FRIB) delivers heavy-ion primary beams at energies of up to 300 MeV/u at 10 kW of beam power to generate rare isotope beams for experiments and will eventually operate at beam power of 400 kW. The preseprator of the Advanced Rare Isotope Separator (ARIS) is equipped with six warm-iron quadrupole (WIQ) singlets and two dipoles integrated right after the production target. They have a compact structure and operate in a high radiation vacuum environment within a hot cell having remote handling capabilities for installation and maintenance. Due to asymmetry with respect to the quadrupole poles, nested sextupole excitations in WIQs induce vertical dipoles that offset the centroid trajectory; Magnet misalignments also result in trajectory offsets. Such offsets degrade separator performance but can be minimized by changing the current distribution on sextupole and octupole coils. In this work, we show how modifications to the WIQ coil design can allow superimposed dipole fields to be included to the octupole and sextupole windings, as well as addition of dipole components by splitting coil currents over groups with separator power supplies. Adjusting the group currents can cancel the sextupole-induced vertical dipole component which can be as high as 0.012 Tm. Octupole coil changes may superimpose a horizontal dipole integrated strength as high as 0.0332 Tm. Unwanted higher harmonics induced as a side effect of the new design are kept to a minimum such that separator performance is preserved as much as possible.

Accelerator magnets↗

DOE OSTI2012

HANLE EFFECT FOR STELLAR DIPOLES AND QUADRUPOLES

We derive exact expressions for the degree of lineal polarization over a resolved or integrated stellar disc due to resonance scattering and the Hanle effect from a dipolar or quadrupolar distribution of magnetic fields. We apply the theory of scattering polarization within the formalism of the spherical tensors representation for the density matrix and radiation field. The distribution of linear polarization over the stellar disk for different configurations of the magnetic field is studied and its topology discussed. For an unresolved dipole, the resulting polarization can be expressed in terms of just three functions (of the inclination angle and effective dipole strength) that are calculated numerically and their behavior discussed. Dipolar and (aligned) quadrupoles are considered in some detail, but the techniques here-in particular, the extensive use of the spherical tensor formalism for polarization-can easily be applied to more general field configurations.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

Magnetic and Structural Design of a 15 T $Nb_3Sn$ Accelerator Depole Model

Hadron Colliders (HC) are the most powerful discovery tools in modern high energy physics. A 100 TeV scale HC with a nominal operation field of at least 15 T is being considered for the post-LHC era. The choice of a 15 T nominal field requires using the Nb3Sn technology. Practical demonstration of this field level in an accelerator-quality magnet and substantial reduction of the magnet costs are the key conditions for realization of such a machine. FNAL has started the development of a 15 T $Nb_{3}Sn$ dipole demonstrator for a 100 TeV scale HC. The magnet design is based on 4-layer shell type coils, graded between the inner and outer layers to maximize the performance. The experience gained during the 11-T dipole R&D campaign is applied to different aspects of the magnet design. This paper describes the magnetic and structural designs and parameters of the 15 T $Nb_3Sn$ dipole and the steps towards the demonstration model.

43 PARTICLE ACCELERATORS↗

DOE OSTI2018

Reasonable Beam Deviation Envelope for Ray-tracing

At NSLS-II the unused dipole radiation is intercepted by the photon absorbers installed inside the vacuum chamber. The water-cooled absorbers are designed to take away the heat therefore the temperature is kept within the safety limit. However, if the beam orbit is severely perturbed, the radiation fan could pass through the geometry and strikes on the vacuum chamber components. This ray-leakage is a possible reason of the accelerator component temperature rise observed during the high-current operations. The goal of this work is to find the maximum beam deviation at the dipole hence ray-tracing can be re-examined under the operational constraints. The beam is confined to the orbit by the bending and focusing magnets. At NSLS-II the orbit is further controlled by a real time orbit feedback loop. Beam could be lost in any unpredictable direction if the magnet malfunctions. Consequently reasonable assumptions must be made to define the deviation envelope. It was determined that the dipole radiation is not powerful enough to cause damage within 10 ms, for example, if the rf power is shut off and the beam deviates from the orbit. Therefore we consider the radiation produced by the stored beam only; temporarily processes, such as unstable oscillating beam, should not be a concern. The orbit of the stored beam can be altered during magnet failures. The dipole current is interlocked to a small range of ±2% from the nominal value. If the dipole current changes slowly the beam energy automatically adjusts and the orbit remains the same. If the dipole current changes rapidly the beam will not be stable. Therefore dipole variation need not to be considered. For the other magnets we consider one magnet failure at a time because it is unlikely that two fail at the same time. It was found that the beam lifetime drops dramatically if one quadrupole power supply is turned off; therefore this scenario does not meet the stable beam condition. The current of one quadrupole could drop but will not result in orbit change with the feedback on. Beam could survive if one sextupole power supply is turned off, but the orbit will not be changed. Magnet could partially fail, for example, one or part of the coil shorts due to break-down. This is a low probability event and will not be considered. During daily operations the orbit is changed by the correctors and the rf frequency. In this work the correctors and the rf frequency are varied to explore the deviation envelope.

36 MATERIALS SCIENCE↗

DOE OSTI2016

SOLAR CYCLE 25: ANOTHER MODERATE CYCLE?

Surface flux transport simulations for the descending phase of Cycle 24 using random sources (emerging bipolar magnetic regions) with empirically determined scatter of their properties provide a prediction of the axial dipole moment during the upcoming activity minimum together with a realistic uncertainty range. The expectation value for the dipole moment around 2020 (2.5 ± 1.1 G) is comparable to that observed at the end of Cycle 23 (about 2 G). The empirical correlation between the dipole moment during solar minimum and the strength of the subsequent cycle thus suggests that Cycle 25 will be of moderate amplitude, not much higher than that of the current cycle. However, the intrinsic uncertainty of such predictions resulting from the random scatter of the source properties is considerable and fundamentally limits the reliability with which such predictions can be made before activity minimum is reached.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

Scanning systems for particle cancer therapy

A particle beam to treat malignant tissue is delivered to a patient by a gantry. The gantry includes a plurality of small magnets sequentially arranged along a beam tube to transfer the particle beam with strong focusing and a small dispersion function, whereby a beam size is very small, allowing for the small magnet size. Magnets arranged along the beam tube uses combined function magnets where the magnetic field is a combination of a bending dipole field with a focusing or defocusing quadrupole field. A triplet set of combined function magnets defines the beam size at the patient. A scanning system of magnets arranged along the beam tube after the bending system delivers the particle beam in a direction normal to the patient, to minimize healthy skin and tissue exposure to the particle beam.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2014

Alkali-vapor magnetic resonance driven by fictitious radiofrequency fields

We demonstrate an all-optical {sup 133}Cs scalar magnetometer, operating in nonzero magnetic field, in which the magnetic resonance is driven by an effective oscillating magnetic field provided by the AC Stark shift of an intensity-modulated laser beam. We achieve a projected shot-noise-limited sensitivity of 1.7fT/√(Hz) and measure a technical noise floor of 40fT/√(Hz). These results are essentially identical to a coil-driven scalar magnetometer using the same setup. This all-optical scheme offers advantages over traditional coil-driven magnetometers for use in arrays and in magnetically sensitive fundamental physics experiments, e.g., searches for a permanent electric dipole moment of the neutron.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗