Secondary Magnetization Research Articles

Coexistence of Superconductivity and Magnetic Ordering in the In-Ag Alloy Under Nanoconfinement.

The impact of the interface phenomena on the properties of nanostructured materials is the focus of modern physics. We studied the magnetic properties of the nanostructured In-Ag alloy confined within a porous glass. The alloy composition was close to the eutectic point in the indium-rich range of the phase diagram. Temperature dependences of DC magnetization evidenced two superconducting transitions at 4.05 and 3.38 K. The magnetization isotherms demonstrated the superposition of two hysteresis loops with low and high critical fields below the second transition, a single hysteresis between the transitions and ferromagnetism with weak remanence in the normal state of the alloy. The shape of the loop seen below the second transition, which closes at a low magnetic field, corresponded to the intermediate state of the type-I superconductor. It was ascribed to strongly linked indium segregates. The loop observed below the first transition is referred to as type-II superconductivity. The secondary and tertiary magnetization branches measured at decreasing and increasing fields were shifted relative to each other, revealing the proximity of superconducting and ferromagnetic phases at the nanometer scale. This phenomenon was observed for the first time in the alloy, whose components were not magnetic in bulk. The sign of the shift shows the dominant role of the stray fields of ferromagnetic regions. Ferromagnetism was suggested to emerge at the interface between the In and AgIn2 segregates.

Remagnetization of Upper Triassic Limestone From the Central Lhasa Terrane (Tibet): Identification, Mechanisms, and Implications for Diagnosing Secondary Remanent Magnetization in Carbonate Rocks

Remagnetization of Upper Triassic Limestone From the Central Lhasa Terrane (Tibet): Identification, Mechanisms, and Implications for Diagnosing Secondary Remanent Magnetization in Carbonate Rocks

Inductance Modeling and Analysis of a Discontinuous Primary and Discontinuous Secondary Permanent Magnet Linear Synchronous Motor

Inductance Modeling and Analysis of a Discontinuous Primary and Discontinuous Secondary Permanent Magnet Linear Synchronous Motor

Paleomagnetic and Rock Magnetic Study of the Gulerghat Area Amravati, Maharashtra

Magnetic Polarity and Stratigraphicstudies of the Narnala section from Akot and Amravatidistricts area(Lat. 21000'-21015'N; Long. 770–77015'E) are carried out. Total thousandsof oriented samples from fresh basalts were collected at close intervals. Detailed palaeomagnetic investigation where carried on 250 samples collected from 20 lava flows belonging to 17 selected traverses were subjected to progressive thermal demagnetizer at 15 different steps of temperatures from 50˚C to 600˚C. Traverse attaining a total thickness of 800m in the study area. Some rocks may fail to retain the magnetic record due to the modification subsequence to their formations by a number of natural phenomena like geotectonic disturbance, metamorphism and alteration, which can produce various degrees of secondary magnetisation in the rock. The secondary magnetisation acquired by the rock is unstable as compared to naturally remain magnetism which can be removed by cleaning techniques like stepwise Alternating field demagnetisation (AFD) and Thermal demagnetisation (TD). The palaeomagnetic results indicate that the most of the flows showed irregular natural remnant directions while a few specimen even from other flows for which a meaningful NRM could be deciphered also showed inconsistent directions. Only 35% of the samples showing irregular directions initially improved on alternating field and stepwise thermal demagnetization. High degree of alteration of the flows appears to have affected the stability of the palaeomagnetic directions. The mean palaeomagnetic directions indicate the presence of lower transitional directions at the bottom part of the sequence and upper reversed polarity in remaining part of the sequence with a few samples showing scattered behavior. The polarity transition has take place in the study area. Ancient latitude calculated for the study area is 30o S and that of Nagpur is 31o S indicating that India has drifted by 51o due N which is more than 5000 Kms. since the formation of this lavas.

Characteristics Analysis and Optimization of Secondary Permanent Magnet Flux-Switching Linear Machines

Characteristics Analysis and Optimization of Secondary Permanent Magnet Flux-Switching Linear Machines

Magnetic polarity & stratigraphy of the Bundelkund area Amravati, Maharashtra

Magnetic Polarity and Stratigraphic studies of the Bundelkund area Amravati districts (Lat. 21000'-21015'N; Long. 770–77015'E) are carried out. Total thousands of oriented samples from fresh basalts were collected at close intervals. Detailed palaeomagnetic investigation where carried on 250 samples collected from 20 lava flows belonging to 03 selected traverses were subjected to progressive thermal demagnetizer at 15 different steps of temperatures from 50˚C to 600˚C. Traverse attaining a total thickness of 800m in the study area. Some rocks may fail to retain the magnetic record due to the modification subsequence to their formations by a number of natural phenomena like geotectonic disturbance, metamorphism and alteration, which can produce various degrees of secondary magnetisation in the rock. The secondary magnetisation acquired by the rock is unstable as compared to naturally remain magnetism which can be removed by cleaning techniques like stepwise Alternating field demagnetisation (AFD) and Thermal demagnetisation (TD). The palaeomagnetic results indicate that the most of the flows showed irregular natural remnant directions while a few specimen even from other flows for which a meaningful NRM could be deciphered also showed inconsistent directions. Only 35% of the samples showing irregular directions initially improved on alternating field and stepwise thermal demagnetization. High degree of alteration of the flows appears to have affected the stability of the palaeomagnetic directions. The mean palaeomagnetic directions indicate the presence of lower transitional directions at the bottom part of the sequence and upper reversed polarity in remaining part of the sequence with a few samples showing scattered behavior. The polarity transition has take place in the study area. Ancient latitude calculated for the study area is 30o S and that of Nagpur is 31o S indicating that India has drifted by 51o due N which is more than 5000 Kms. since the formation of this lavas.

Exothermic events in a fossil seismogenic fault acquiring thermoviscous remanent magnetization in an exhumed accretionary complex

Detecting exothermic events within fault rocks is key to understanding fault behavior. While paleo-temperature studies of fault rocks have been conducted via vitrinite reflectance or magnetic analysis, secondary remanent magnetization caused by exothermic events within fault rocks has not been examined directly. Direct detection of the secondary remanence has the advantage of revealing both paleo-temperature constraints and the paleomagnetic direction, which can help assess the relationship between secondary remanence and deformation. We conducted thermal and alternating-field demagnetization analyses and other rock–magnetic experiments on a fossil seismogenic fault zone and the surrounding host rocks in an exhumed accretionary complex. The fault zone comprises a few cataclastic zones, including thin-slip zones. The blocking temperature in the secondary magnetization site was detected at 300–360 °C only in cataclasite with magnetite or pyrrhotite as carriers. The paleomagnetic direction of the secondary magnetization is characteristic in the cataclasite, and the blocking temperature was higher than the paleo-maximum temperature of the host rocks. Therefore, the blocking temperature records a local exothermic event in the cataclasite. Thermoviscous remanent magnetization (TVRM) were suggested as candidate mechanisms for the blocking temperature.

Paleomagnetism and age of the Leucite Hills Volcanic complex, Wyoming: Implications for eruptive history, landscape evolution, and the geomagnetic instability timescale (GITS)

The Leucite Hills Volcanic Field, southwest Wyoming comprises two dozen volcanic features including necks, flows, dikes, and plugs. It has been the focus of many petrologic studies as its volcanic and shallow intrusive rocks are one of the only surficial manifestations of ultrapotassic lamproite. We build on paleomagnetic findings of Sheriff and Shive (1980) by providing further paleomagnetic data from the Boars Tusk dike and Black Rock flows. We also characterize the magnetic mineral assemblage of these lamproites. Principal component analysis of alternating field (AF) and thermal demagnetization data indicate that the dike and breccias of Boars Tusk record a reversed magnetic polarity and the Black Rock lava records a normal polarity, both consistent with previous findings. This recording is typically carried by minerals with coercivities >15 mT and susceptibility measurements indicate magnetite, maghemite, and titanomagnetite as likely magnetic carriers. AF and thermal demagnetization experiments evince secondary magnetizations held by lower coercivity grains, likely caused by lightning strikes. 40Ar/39Ar incremental heating experiments from Boars Tusk and Black Rock give plateau ages of ∼2500 ka and ∼900 ka, respectively. Recent advances in the chronology of geomagnetic field reversals and excursions during the Quaternary permit integration of the Boars Tusk dike into the lower Matuyama chron, whereas the Black Rock lavas most probably record the Kamikatsura excursion. Notably, Black Rock records high inclinations that suggest the short-lived excursion achieved a full geomagnetic reversal, something not observed at other localities recording the Kamikatsura excursion. The Leucite Hills offer further opportunities to refine the Quaternary geomagnetic instability time scale (GITS), and to improve understanding of the eruptive and geomorphic evolution of this unusual volcanism.

Evaluating the Compatibility of Hematite (U‐Th)/He Data and Hematite‐Carried Secondary Magnetizations: An Example From the Colorado Front Range

AbstractAncient magnetization(s), often recorded by hematite (Fe2O3), provide key paleomagnetic constraints on plate interactions through time. Primary remanent magnetizations may be modified or overprinted by secondary processes that complicate interpretations of paleomagnetic data. Hematite (U‐Th)/He (hematite He) dating has the potential to resolve when secondary magnetizations were acquired. Here, we compare hematite He data and paleomagnetic results in Paleoproterozoic crystalline rocks, meters below a major nonconformity in the Colorado Front Range, USA. Prior work and new rock magnetic data indicate that pervasive hematite alteration records a secondary chemical remanent magnetization (CRM) during the Permo‐Carboniferous Reverse Superchron, coincident with the Ancestral Rocky Mountain orogeny. We target minor hematite‐coated faults cutting basement for (U‐Th)/He analyses because they are of sufficient hematite purity to yield geologically meaningful dates. Two samples yield overlapping and scattered individual hematite He dates ranging from ∼138 to 27 Ma (n = 33), significantly younger than the age of the late Paleozoic CRM. Scanning electron microscopy, electron probe microanalysis, and Raman spectroscopy indicate that aliquots have variable grain size distributions and fluorocarbonate impurities. Thermal history models support hematite on fault surfaces mineralized coeval with CRM acquisition during the late Paleozoic, and hematite He data scatter reflects variable He loss during Mesozoic burial owing to differences in grain size distribution from fault slip comminution and in chemistry among aliquots. Our results underscore the differences in temperature sensitivity and sampling requirements between paleomagnetic and hematite He investigations and illustrate that hematite He dates will usually be younger than preserved remanent magnetizations.

No Late Cretaceous true polar wander oscillation and implications for stability of Earth relative to the rotation axis

Knowledge of Earth's stability with respect to the spin axis sets boundary conditions for understanding the deep mantle and interpreting records of past climate. Recently it has been argued that the solid Earth rotated by 12∘, and then rotated back, 86 to 78 million years ago. Herein we reanalyze the paleomagnetic data and report new rock magnetic analyses, from the Scaglia Rossa limestone of Italy on which this true polar wander (TPW) was based. We find that these data record an unrecognized secondary magnetization carried by authigenic hematite. This overprint has a differential angular effect on the normal and reversed polarity primary magnetizations, creating biased directions. This bias, together with probable tectonic and sedimentary slide rotations, creates false polar wander signals. The recognition of these artifacts serves as a cautionary tale and indicates that the null hypothesis of no large TPW since the Late Cretaceous cannot be rejected. This stability is fundamentally different from that of other planetary bodies which have undergone large polar wander, and provides the framework for Earth's climate history. Because of uncertainties in paleolongitude and geomagnetic field morphology, the unambiguous definition of terrestrial TPW deeper in time remains elusive.

Research on Air Gap Magnetic Field Characteristics of Trapezoidal Halbach Permanent Magnet Linear Synchronous Motor Based on Improved Equivalent Surface Current Method

Accurate analysis of the air gap magnetic field is the focus of research in the field of precision permanent magnet linear synchronous motors. In this paper, the two-dimensional air gap magnetic field of a secondary trapezoidal Halbach permanent magnet array coreless permanent magnet linear synchronous motor (PMLSM) was taken as our research object. On the basis of the equivalent surface current method, we proposed an improved equivalent analytical algorithm with a trapezoidal side length unit. The equivalent analytical model of the magnetic induction vector of the two-dimensional air gap was established, and the air gap magnetic field of the trapezoidal Halbach array coreless PMLSM was calculated. At the same time, we analyzed the influence of the bottom angle α of a trapezoidal permanent magnet equivalent width coefficient αw, pole height coefficient αh, and air gap height coefficient αg on the amplitude (Bpeak) and total harmonic distortion (THDB) of the central magnetic field in the air gap. The results show that α and αw have a significant influence on the Bpeak and THDB of the central magnetic field air gap. With the synergy of α and αw, we identified the “flux convergence” effect, which makes the maximum range of Bpeak α > 90° and αw < 0.5. We also found the “equilateral” effect, which causes the minimum region of THDB to change linearly. The calculation results of the improved equivalent surface current analytical model established in this paper agree with those verified by the finite element method. The calculation is convenient, and the accuracy of the result is high. This research provides a new method for analyzing the air gap magnetic field of a permanent magnet with a nonrectangular cross-section and lays a theoretical foundation for optimizing the PMLSM pole model.

Vector unmixing of multicomponent palaeomagnetic data

SUMMARYPalaeomagnetic investigations often encounter multiple magnetization components, where secondary processes have obscured, partially overprinted or completely replaced the original (primary) remanent magnetization. Identification and separation of primary and secondary magnetizations are generally carried out with principal component analysis of stepwise demagnetization data. However, rocks may contain multiple generations of magnetic minerals with overlapping unblocking ranges that complicate the discrimination of components when applying best-fitting line procedures. Developing a method to differentiate and quantify contributions of overlapping magnetic components using directional data is therefore highly desirable. This paper presents a method to unmix stepwise demagnetization data using an inverse modelling approach. We show that the method is capable of accurately resolving two or three magnetic components with overlapping or superimposed unblocking spectra as well as quantifying absolute component contributions. The method depends on accurate identification and selection of end-member components prior to analysis; in doing so, the method can help palaeomagnetists understand how magnetization components combine to explain their data. We show that the dilution of one component by more than ca. 25 per cent from another component can result in linear demagnetization curves that decay to the origin on orthogonal plots, but whose best-fitting direction can significantly deviate from both end-members. The efficacy of the method is demonstrated through examples of demagnetization data from hematite and/or magnetite-bearing sandstones from China. This method can be broadly applied to all multicomponent magnetization problems in palaeomagnetism.

Characteristics Analysis of an Electromagnetic Actuator for Magnetic Levitation Transportation

In this article, an electromagnetic actuator is proposed to improve the driving performance of magnetic levitation transportation applied to ultra-clean manufacturing. The electromagnetic actuator mainly includes the stator with the Halbach array and the mover with a symmetrical structure. First, the actuator principle and structure are illustrated. Afterward, in order to select a suitable secondary structure and analyze the characteristics of the actuator, the electromagnetic characteristics of actuators with different secondary structures are analyzed by the finite element method (FEM). Analysis results show that the actuator adopting the secondary structure with a Halbach array will increase the electromagnetic force and working stability. The secondary with the three-section Halbach array is selected for the electromagnetic actuator. Then, the influence of secondary permanent magnet (PM) thickness on the electromagnetic force is analyzed by FEM. The results indicate that the increase in PM thickness will lead to increased electromagnetic force and decreased utilization ratio of PM. Finally, a prototype of an electromagnetic actuator is built, and experiments are implemented. The correctness of the theoretical analysis and the effectiveness of the electromagnetic actuator are verified by experimental results.

LATE PALEOZOIC REMAGNETISATION AS AN INDEPENDENT INDICATOR OF TECTONIC PROCESSES IN THE SOUTHERN URALS

Analysis of secondary magnetization components (Late Paleozoic remagnetization) makes it possible to trace the formation of the Southern Urals folded system. The paper presents new data on the Late Paleozoic remagnetization of rocks in the Southern Urals. The results of the paleomagnetic study of rocks in various structural zones of the Southern Urals, obtained since 2009, were revised and supplemented again to identify the remagnetization component. Combined analysis of the newly obtained results and previously published data on Late Paleozoic remagnetization shows that in the western segment of the western slope of the South Urals the intermediate-temperature magnetization component (ITC) was acquired prior to or at the initial stages of deformation. In contrast, the ITC observed in the eastern segment arose after folding. In the western part of the Magnitogorsk zone in Devonian-age rocks, the average for all sites is post-folding. Deformations here occurred long before the final stage of the development of the Urals, most likely in late Devonian — early Carboniferous. In the Magnitogorsk-Bogdanovsky graben, in the early Carboniferous rocks, ITC has arisen during the process of deformation or shortly before it and at its initial stages. The Late Paleozoic remagnetisation identified in the paleomagnetic records is regional in nature and probably reflects a collisional event of the final stage of the evolution of the Ural Paleocean. Collision processes which occurred in the Southern Urals from the Late Devonian until the Late Permian time had undoubtedly left their trace in the western structures (in present-day coordinates). Within the passive margin of Baltica the collision resulted in the formation of a lateral series of fold-and-thrust structures. They started from the Main Uralian Fault westward, with possible gradual termination of this process towards the Pre-Uralian Foredeep. Paleomagnetic results of this research work support these assumptions.

Matuyama–Brunhes geomagnetic reversal record and associated key tephra layers in Boso Peninsula: extraction of primary magnetization of geomagnetic fields from mixed magnetic minerals of depositional, diagenesis, and weathering processes

We report paleomagnetic records of Matuyama–Brunhes geomagnetic polarity reversal and associated key tephra layers from the Early–Middle Pleistocene marine sedimentary succession in the Boso Peninsula. The outcrop is in Terasaki, Chiba, Japan and ~ 25 km northeast of the Chiba section. The sediment succession consists of a massive siltstone layer of the Kokumoto Formation, Kazusa Group. A tephra layer was identified in the middle of the outcrop with chemical composition comparable to that of the Byk-E tephra layer from the Chiba section defining the base of the Chibanian Stage. Oriented paleomagnetic samples were collected at intervals of 1–10 cm from the siltstone. To identify the primary remanent magnetization, progressive alternating field demagnetization (PAFD) and progressive thermal demagnetization (PThD) were conducted on pilot samples. Identification of primary magnetization with PAFD was not successful, especially for reversely magnetized samples. In addition, magnetization during PThD showed sharp drops around 175 °C, which decreased gradually between 175 °C and ~ 300 °C, and became unstable above ~ 350 °C. To extract the primary remanent magnetization while avoiding laboratory alteration by heating, a PThD up to 175 °C followed by PAFD was conducted. Combined analysis of remagnetization circles enables extraction of primary magnetization with improved reliability. Rock magnetic experiments were conducted during stepwise heating to understand the magnetic minerals involved and to evaluate the influence of laboratory heating. During heating, FORC-PCA revealed significant changes of magnetic minerals at 200 °C, 400 °C, 450 °C and 550 °C. Rock magnetic analyses and electron microscopy indicate that titanomagnetite/magnetite are magnetic minerals contributing to primary remanent magnetization. Greigite was also identified preserving secondary magnetizations during sub-seafloor diagenesis. The presence of feroxyhyte is suggested as secondary magnetization through the weathering of pyrite by exposure to the air after the Boso Peninsula uplift. The correlation of relative paleointensity with the Chiba section provides an age model with sedimentation rates of 30 cm/kyr and 18 cm/kr for the intervals above and below the Byk-E tephra. VGP latitudes are highly consistent with those from the Chiba section based on the age model, which assigns the main directional swing from reversed to normal polarities as 772.8 ± 0.5 ka.Graphical

Paleomagnetic Constraints From South Georgia on the Tectonic Reconstruction of the Early Cretaceous Rocas Verdes Marginal Basin System of Southernmost South America

AbstractSouth Georgia exists as a microcontinent along the North Scotia Ridge ∼1,700 km east of Cape Horn. The tectonostratigraphic units of South Georgia have long been correlated with those of the Fuegian Andes of southernmost South America. Accordingly, South Georgia has been regarded as a continuation of the Late Jurassic–Early Cretaceous Rocas Verdes marginal basin system, formerly situated south of Burdwood Bank and east of Cape Horn. To test this, paleomagnetic analysis of samples from the Larsen Harbour Complex, Drygalski Fjord Complex, and Annenkov Island Formation of South Georgia showed that 21 sites yield a mean direction of D = 328.5°, I = −62.1° (a95 = 3.5°) and a paleomagnetic pole at 068.2°E, 67.2°N, A95 = 4.7°. The consistency of directions and strong polarity bias, plus indications of a negative differential tilt test, point to a secondary magnetization acquired in the Late Cretaceous. Comparison of predicted versus observed directions for South Georgia relative to stable South America indicate 27.2 ± 11.2° of counter‐clockwise rotation (and 10.5° ± 4.5° of northward tilting) since the acquisition of magnetization. These results are consistent with paleomagnetic studies from the Fuegian Andes and support a paleoposition of the South Georgia microcontinent south of Burdwood Bank as strongly indicated by the geologic evidence. Partitioning this rotation between oroclinal bending during the Rocas Verdes basin collapse in the Late Cretaceous and left‐lateral translation along the North Scotia Ridge is not possible on paleomagnetic grounds, but the co‐linearity of Andean structures between the restored microcontinent and Tierra del Fuego indicates the former.

Application of Vector Spherical Harmonics to the Magnetization of Mars' Crust

AbstractMars has a magnetic field originating in its strongly magnetized crust that holds clues to the planet's interior. We apply vector spherical harmonic decomposition to simple candidate magnetic structures to separate the parts responsible for the anomalies from those that remain invisible. A uniform magnetic layer produces no anomalies: spatial variations are essential although secondary magnetization does produce a weak field that might reflect the primordial dynamo field. A hemispheric layer produces anomalies confined to the equator rather than the observed hemispheric difference. A uniformly magnetized crust with variable thickness determined from gravity and topography produces a crustal field with large anomalies at the major impact crater sites that are not observed. These anomalies are not present if the magnetic layer lies deeper than the crater floor. We conclude that decomposing magnetizations in this way is a useful tool in the interpretation of Martian magnetic anomalies.

Paleomagnetism as a geochronological gauge for deformational events: Insights from the Najd-related Nugrus Shear Zone, Northern Nubian Shield

Abstract The Nugrus Shear Zone (NSZ) of southern central Egypt is a major ductile shear structure with controversial origins. It lies east of the Hafafit Gneissic Complex (HGC) and separates the Central and South Eastern Desert terranes of Egypt. The NSZ has been correlated with the Najd Fault system in Saudi Arabia, and shares orientation and kinematic characteristics with the Najd fault. Previous microstructural studies of the NSZ and HGC have concluded a polydeformation history for the Nugrus area, involving early NW-ward thrusting, followed by NW-SE transcurrent shearing. This contribution reports a combined rock magnetic and palaeomagnetic study of the shear zone and wallrocks that gives a conclusive evidence for the previously mentioned tectonic scenario. Furthermore, the palaeopoles obtained correlate well with the available geochronologically dated poles from Northern Africa, leading to inferred ages for the deformation and thermal events of the area. These ages confirm the previous proposed tectonic models. Three components of Natural Remanant Magnetization (NRM) direction (CA, CB and CD) are identified. Component CA represents the Characteristic Remanent Magnetization (ChRM). Components CB and CD are considered to be secondary magnetization. CA is consistent with arc-related deformation and magmatism at ∼ 700–680 Ma. CB and CD represent the protracted Najd-related shear deformation and transpression at ∼ 650–550 Ma.

Seafloor Magnetism Under Hydrothermal Alteration: Insights From Magnetomineralogy and Magnetic Properties of the Southwest Indian Ridge Basalts

AbstractTitanomagnetites in mid‐ocean ridge basalt (MORB) experience variable post crystallization alterations associated with seafloor tectonic and environmental processes. Compared to low‐temperature oxidation, seafloor hydrothermal alteration is thought to be more destructive but its magnetic aftermaths are insufficiently documented. Here we present comprehensive rock magnetic and electron microscopic analyses of fresh and hydrothermally‐altered MORBs dredged from the Longqi and Yuhuang hydrothermal fields, Southwest Indian Ridge. We observe large variations in magnetic properties of fresh MORBs, originated from relative proportions of nano‐scale single‐domain to vortex state and micron‐scale vortex to multi‐domain state dendritic titanomagnetites. Progressive hydrothermal alteration produces secondary magnetite through recrystallization of exsolved and dissolved Fe from primary titanomagnetite. Exsolution is evident by a dual Verwey transition signature and coexisting Ti‐poor titanomagnetites and sphenes in partially chloritized basalts. A schematic model is proposed to explain the variations in magnetomineralogy and magnetic properties with progressive hydrothermal alteration. Intermediate hydrothermal alteration products retain a secondary chemical remanent magnetization (CRM) which is related to the long‐term magnetization variations in oceanic basalts. The established framework allows characterizing MORB hydrothermal alteration and ultimately contributes to resolving the complexity of seafloor magnetism.

A cryogen-free, semi-automated apparatus for bullet-dynamic nuclear polarization with improved resolution.

In dissolution-dynamic nuclear polarization, a hyperpolarized solid is dissolved with a jet of hot solvent. The solution is then transferred to a secondary magnet, where spectra can be recorded with improved sensitivity. In bullet-dynamic nuclear polarization this order is reversed. Pressurized gas is used to rapidly transfer the hyperpolarized solid to the secondary magnet, and the hyperpolarized solid is dissolved only upon arrival. A potential advantage of this approach is that it may avoid excessive dilution and the associated signal loss, in particular for small sample quantities. Previously, we have shown that liquid-state NMR spectra with polarization levels of up to 30 % may be recorded within less than 1 s after the departure of the hyperpolarized solid from the polarizing magnet. The resolution of the recorded spectra however was limited. The system consumed significant amounts of liquid helium, and substantial manual work was required in between experiments to prepare for the next shot. Here, we present a new bullet-DNP (dynamic nuclear polarization) system that addresses these limitations.