Design and Construction of a Superconducting Gravimeter Prototype

Xing, Hongtao; Hu, Xinning; Cui, Chunyan; Wang, Hao; Niu, F.; Zhang, Yuan; Wang, Luzhong; Wang, Qiuliang; Hao, Xiaohua; Liu, Ming; Chen, Xiao; Yang, Yan

doi:10.1109/tim.2022.3147885

“…The raw output of the prototype is the feedback voltage associated with the force required to hold the test mass in a stable position, which is proportional to the current in the feedback coil, and converted to gravity by a linear calibration factor. This coefficient was estimated from electromagnetic excitation or solid tide observations (Huang et al , 2022). In addition to the gravity data, the prototype recorded the tilt and room temperature.…”

Section: Methodsmentioning

confidence: 99%

“…To realize the localization of superconducting gravimeters and promote the research by China in high-accuracy gravity fields, the Institute of Electrical Engineering, Chinese Academy of Sciences (IEECAS) has successfully developed a superconducting gravimeter prototype (hereafter referred to as “prototype”) (Huang et al , 2022). The gravity sensor of this prototype consists of two superconducting coils and a superconducting sphere, in which a certain proportion of current is passed into the coils, and a negative gradient magnetic field (Xu et al , 2015) forms at the superconducting sphere and holds it stably.…”

Section: Introductionmentioning

confidence: 99%

“…The gravity sensor of this prototype consists of two superconducting coils and a superconducting sphere, in which a certain proportion of current is passed into the coils, and a negative gradient magnetic field (Xu et al , 2015) forms at the superconducting sphere and holds it stably. A change in gravitational acceleration causes the sphere to move up and down vertically, and high-accuracy gravitational acceleration data can be obtained by reading the voltage signal corresponding to this displacement using a differential capacitor bridge (Huang et al , 2022).…”

Section: Introductionmentioning

confidence: 99%

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Study on room-temperature effect of a superconducting gravimeter prototype

Xing

¹

,

Hu

²

,

Niu

³

et al. 2022

SR

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0

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Purpose This study aims to reveal the room-temperature effect of a superconducting gravimeter prototype, which will guide its subsequent optimization to improve its gravimetric measurement accuracy. Design/methodology/approach Without leveling, the prototype output signal, tilt data and room temperature were measured under steady operating conditions. After analyzing the correlations of the three data sets, the residuals of the prototype’s output signal were compensated using the tilt data and the geodynamic effects (ocean tide loading, atmospheric loading and the gravitational effect of polar motion) were then corrected. Findings The remaining residuals after correction may be caused by small tilt variations that are due to the sensor chamber temperature and radiation shield temperature changes. These small tilt variations were submerged in the tilt signal noise. Although the peak-to-peak noise of the tiltmeter does not exceed 15 µrad, it can still produce gravimetric deviations above 60 µGal when the prototype is significantly tilted. Originality/value This study analyzes in detail the room-temperature effect of a superconducting gravimeter prototype, introduces the tilt effect of the relative gravimeters to compensate for the gravimetric deviations and emphasizes that the improvement of fine leveling and the accuracy of the tiltmeter are key requirements for the prototype to perform high-accuracy gravity measurement tasks.

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“…The simulation modeling requires the consideration of different aspects (a) Considering that the superconducting gravimeter sensor electromagnetic structure is rotational axisymmetric [23][24][25], a two-dimensional model is required.…”

Section: Model Constructionmentioning

confidence: 99%

Numerical simulation of AC losses in superconducting gravimeter

Xing¹,

Hu²,

Cui³

et al. 2022

Supercond. Sci. Technol.

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The annual drift of μGal level is an important indicator of superconducting gravimeters, which helps geophysicists to clarify the weak geophysical signals. In this paper, a finite element simulation model of the superconducting gravimeter sensor is developed based on the H formulation for evaluating the contribution of the excitation AC losses and the AC losses under operating conditions to the superconducting gravimeter’s drift. The model combines the H formulation and the heat transfer module of COMSOL Multiphysics software to calculate the AC losses of the superconducting gravimeter’s test mass and obtain the distribution images of the test mass’s temperature due to the AC losses-induced heating. The overall temperature rise of the test mass is obtained by assuming that it heats up uniformly and thus combines the temperature dependence factor (10 μGal/mK) of the superconducting gravimeter to derive the instrument drift induced by AC losses. Then, the long-term drift due to excitation losses can reach 0.847 μGal/year, while the operating losses can be 0.45 μGal/year or even less, according to the simulation. In addition, this paper discusses the effects of the parameters (index number, critical electric field and critical current density) in the E-J power law introduced by the H formulation on the AC loss evaluation. It is concluded that the AC losses are sensitive to the critical current density, and increasing the test mass’s critical current density helps enhance the stability of the superconducting gravimeter.

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“…In the Gravity Probe B (GP-B) experiment aiming at testing the fundamental predictions of Einstein's theory of general relativity, there are four gyroscopes each comprising a fused silica sphere coated with 1.25 µm thick superconducting Nb [10], which are the heart of the instrument and critical to the success of the nearly 48 year GP-B mission [11,12]. Superconducting spherical shells, typically 2.5 cm diameter Nb, are also the basic elements of superconducting gravimeters [13], which use the levitation of the hollow superconducting sphere to measure the gravity change with high precision and have been deployed to study a wide variety of geophysical phenomena [14,15].…”

Section: Introductionmentioning

confidence: 99%

Properties of superconducting MgB₂ spherical shells deposited on 2 mm and 1 mm diameter Si₃N₄ spheres

Xu¹,

Sun²,

Zhao³

et al. 2023

Supercond. Sci. Technol.

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Superconducting spherical shells may not only provide an appealing platform for exploring superconductivity in three-dimensional (3D) geometries with curved surfaces, but also be practically applied in important fields, such as in gyroscopes and gravimeters. In inertial confinement fusion (ICF), the perturbation on the target capsule caused by traditional contact support methods is recognized as one of the major contributors to performance degradation in ICF implosions. It was proposed recently that coating the capsule with a thin superconducting MgB2 spherical shell to realize non-contact support by means of magnetic levitation at the required temperatures ∼ 20 K might offer a promising solution to this longstanding problem. To simulate the coating of ICF capsules, we deposited MgB2 spherical shells onto polycrystalline Si3N4 spheres (diameter d = 2 mm and 1 mm) via a hybrid physical–chemical vapour deposition technique. For both diameters, the spherical shells, of about 1 µm in thickness and covering the whole spheres completely, were polycrystalline with thin plate-shaped MgB2 crystallites oriented randomly and closely connected. The spherical shells exhibited superconducting transition at a zero resistance temperature T c z e r o of 38.5–39.4 K in four-probe resistance measurements and ideal diamagnetism at low temperatures in magnetization measurements, suggesting the good crystallinity and homogeneity of the shells. The upper critical field H c 2 , the irreversibility field H i r r and the lower critical field H c 1 were characterized and showed similar magnitudes and temperature dependencies for the d = 2 mm and 1 mm shells, yielding H i r r of 7–8 T and H c 1 of 7–12 mT at 20 K. The superconducting critical current density J c values, evaluated from the magnetization hysteresis loops, were 1.8 × 10 6 A cm−2 and 8.5 × 10 4 A cm−2 at 20 K under zero and 2 T applied field, respectively, for the d = 1 mm shell. The occurrence of small flux jumps was observed at low temperatures up to 12 K and in low fields below 0.3 T. The results demonstrate the feasibility of fabricating MgB2 spherical shells with properties applicable to potential areas employing magnetic levitation such as in ICF and that MgB2 spherical shells may be exploited as an experimental system to study superconductivity in 3D curvilinear geometry.

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Design and Construction of a Superconducting Gravimeter Prototype

Cited by 6 publications

References 17 publications

Study on room-temperature effect of a superconducting gravimeter prototype

Study on room-temperature effect of a superconducting gravimeter prototype

Numerical simulation of AC losses in superconducting gravimeter

Properties of superconducting MgB₂ spherical shells deposited on 2 mm and 1 mm diameter Si₃N₄ spheres

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Design and Construction of a Superconducting Gravimeter Prototype

Cited by 6 publications

References 17 publications

Study on room-temperature effect of a superconducting gravimeter prototype

Study on room-temperature effect of a superconducting gravimeter prototype

Numerical simulation of AC losses in superconducting gravimeter

Properties of superconducting MgB2 spherical shells deposited on 2 mm and 1 mm diameter Si3N4 spheres

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Product

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Properties of superconducting MgB₂ spherical shells deposited on 2 mm and 1 mm diameter Si₃N₄ spheres