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Abstract Gravimetric data analysis and processing in the Guercif-Debdou-Mekkam regions representing the main domain of rifain foreland (Northeastern Morocco), enable to clarify the structure of the basement and identify areas of density contrast. The calculation of residual gravimetric (Rs) map shows the close relationship between the positive anomalies in the North of the Mekkam and Debdou areas and the uprising of the basement. However, the negatives anomalies are generated by the Hercynian granitic plutons formed by the interference of two anomalies with a maximum axis oriented NNE-SSW. At the border of the Southern one, the Soulouina granite outcrop in a small area, compared to the size of the attributed anomaly, which leads to the presence of a large, deep and thick granitic body. The keen analysis of the Rs map indicates that the buried granitic massifs extend over about 30 Km to the NNE under the Meso-Cenozoic cover. This result is confirmed by the presence of a metamorphic aureole close to the anomaly. A trial 3D modeling of gravity structures, using the USGS PFGRV3D program, shows a strong thickness of two granitic massifs. The SSW massif has a thickness of about 11 Km, while the NNE one is about 8 Km. The negative anomaly located at Mhirija village is correlated with the granitic apex of Alouana, generated by two granitic massifs buried at depth. It has the same contrast of density, age, and petrologic characteristics compared to than Soulouina, which indicates that they have the same behavior. In order to establish a new structural map of the study area, the horizontal gradient combined with lambertian reflectance applied to the Rs map was performed to delineate gravity inflection points, which overlaps with the vertical or the very steep-sided faults or any other surface limiting two compartments of different densities. The suggested faults reflect clearly the influence of Hercynian structural style. Last but not least, in this paper we propose a synthetic map displaying the lateral extension of Hercynian granites and the possible buried faults or non-mapped ones. Our final map represents an efficient and effective tool to help decision makers during mining exploration. Highlights • Analysis and processing of high gravimetric data of Guercif-Debdou-Mekkam regions. • Very fine interpretation of the different gravimetric anomalies. • Structural cartography of unmapped faults and their relation to geodynamic context. • 3D modeling of the negative anomaly located in the Mekkam region. [ABSTRACT FROM AUTHOR]

We present an approach that allows detecting all three components of the residual magnetic field inside shielding, based on the electron paramagnetic resonance (EPR) of spin-polarized K atoms. The residual field experienced by spin-polarized K atoms dominates Larmor precession frequency, the smaller the frequency is, the more benefits it has to realize spin-exchange relaxation-free (SERF) regime under a definite spin-exchange rate. The measurements are accomplished based on depopulation optical pumping and optically-detected peak of the K EPR spectrum. The EPR-based cross modulation method is employed to determine all three components of the residual field independently by modulating the frequency of transverse field and the strength of longitudinal field. The weighted averages of all measurements with the corresponding uncertainties are (9.60 ± 0.06) nT, (2.25 ± 0.03) nT, and (2.83 ± 0.17) nT along with the negative directions of their related axes, respectively. • Optically-detected electron paramagnetic resonance of spin-polarized potassium. • EPR-based cross modulation method used for detecting triaxial components of the magnetic field. • In-situ determination of residual magnetic field inside shielding. • Foundation for further measuring fetal magnetocardiogram (MCG) and magnetoencephalogram (MEG). [ABSTRACT FROM AUTHOR]

Abstract: We investigated the effect of adding magnetic shielding and applying of a compensation field to reduce the magnetic signal from unbound free markers. When the initial immunoassay system was used without the additional shielding box, the signal intensity of the liquid markers normalized by the weight of the Fe3O4 was 1/2700 of the dried markers. By installing the additional shielding box, the reduction factor was improved to 1/10,000. We successfully reduced the magnetic signal of the liquid marker further by applying a compensation field. The magnetic signal of the free marker obtained by applying a compensation field of −18nT was 1.4mΦ 0, which was close to the system noise level. Field compensation at the very local area just around the SQUID is sufficient for reducing of the magnetic signal from the free marker. [Copyright &y& Elsevier]

Residual magnetic field in a high temperature superconductor (HTS) magnet is a factor which should be avoided when the field of the magnet is being operated under a high uniformity and high accurate control. In this paper, the residual field in a Bi2223/Ag pancake magnet at 77 K is systematically studied. The amplitude of the residual field as a function of maximum charging current and the relaxation of the residual field are measured. For a magnet with an inner diameter of 60 mm, an outer diameter of 80 mm and a height of 30 mm, the maximum residual field is about 14.5 G after ramping the charging current up to 15 A, followed by dropping the current to zero. A simple model is proposed, from which the residual field can be estimated as along as the configurations of the magnet and the critical current (Ic) of the original short sample are given. [ABSTRACT FROM AUTHOR]

• A novel method to measure the residual field in a magnetic shield is proposed. • This method can eliminate both the Bolch-Siggert effect and the light effect. • This method can achieve a high measuring precision of 0.01 nT. Determining the residual field in a magnetic shield is essential in quantum measurement. However, it faces some problems which limit the measuring accuracy. In order to overcome the main problems for the measuring method based on magnetic resonance, a method which detects the electron paramagnetic resonance frequency of 133Cs atoms is reported. By using a rotating exciting magnetic field and choosing appropriate frequency of probe light, the influences of the Bloch-Siegert effect on the measurement of the residual field is eliminated, and by extracting the sums of the residual field and the fictitious field caused by light shifts under different pump light powers and using a second-degree polynomial fitting, the influences of light shifts on the measurement of the residual field is eliminated, thus the residual field is obtained accurately. The test results demonstrate that a high measuring accuracy of 0.01 nT can be achieved for this method. [ABSTRACT FROM AUTHOR]