March 28 of this year is the second Tibetan Serfs Emancipation Day. People of all nationalities in Tibet marked the day by hoisting the national flag and by singing and dancing. Smiles were on every face and a festive...March 28 of this year is the second Tibetan Serfs Emancipation Day. People of all nationalities in Tibet marked the day by hoisting the national flag and by singing and dancing. Smiles were on every face and a festive atmosphere pervaded the snowcovered plateau region.展开更多
In old Tibet, the local government (including individual officials), monasteries and feudal lords all engaged in trade. Without exception, they also lent money at usurious rates. Interest-based profits were a major so...In old Tibet, the local government (including individual officials), monasteries and feudal lords all engaged in trade. Without exception, they also lent money at usurious rates. Interest-based profits were a major source of their incomes. To exploit serfs, the Dalai Lama and the Tibetan local government established special agencies to handle money-lending matters. The agency established by the Dalai Lama for the purpose was called展开更多
Fifty years ago, on March 28, 1959, Zhou Enlai, Premier of the State Council of the People＇s Repubfic of China, promulgated a decree of the State Council, declanng the Tibet local government controlled by Tibet＇s fe...Fifty years ago, on March 28, 1959, Zhou Enlai, Premier of the State Council of the People＇s Repubfic of China, promulgated a decree of the State Council, declanng the Tibet local government controlled by Tibet＇s feudal aristocrats and upperstratum clergy dissolved on that day and resolving that the powers of the Tibet local government be exercised by the Preparatory Committee for the Founding of the Tibet Autonomous Region from that day on. This decision of great historic significance sounded the death knell of the feudal serf system in old Tibet, a theocratic system that was reactionary, corrupt and dark. The change of government cleared obstacles and created conditions for development and progress in Tibet. After that a broad democratic reform movement swept the plateau region. Under the leadership of the Communist Party of China, the one million serfs in Tibet buried the feudal serf system and won their emancipation,展开更多
Atomic spin gyroscopes are promising candidates for next-generation inertial navigation due to extremely high theoretical precision,relatively small size among atomic gyroscopes,and promising potential for miniaturiza...Atomic spin gyroscopes are promising candidates for next-generation inertial navigation due to extremely high theoretical precision,relatively small size among atomic gyroscopes,and promising potential for miniaturization.In particular,the spin-exchange relaxation-free(SERF)atomic gyroscope relies on optical pumping to polarize atoms,enabling rotation sensing through the Faraday optical rotation angle(FORA).However,fluctuations in atomic density introduce systematic errors in FORA measurements,limiting long-term stability.We present a data-driven decoupling method that isolates atomic density fluctuations from the FORA signal by modeling spatially resolved light absorption in the vapor cell.The model accounts for the spatial distribution of spin polarization in the pump-light interaction volume,density-dependent relaxation rates,wall-induced relaxation,and polarization diffusion,and is implemented within a finite-element framework.Compared to the conventional Lambert-Beer law,which assumes one-dimensional homogeneity,our approach captures the full threedimensional density and polarization distribution,significantly improving the accuracy of light absorption modeling.The resulting absorption-density maps are used to train a feedforward neural network,yielding a high-precision estimator for atomic density fluctuations.This estimator enables the construction of a decoupling equation that separates the density contribution from the FORA signal.Experimental validation shows that this method improves the bias instability atσ(100 s)of the gyroscope was improved by 73.1%compared to traditional platinum-resistance-based stabilization.The proposed framework is general and can be extended to other optical pumping-based sensors,such as optically pumped magnetometers.展开更多
Achieving the spin-exchange relaxation-free(SERF)state in atomic comagnetometers(ACMs)necessitates a stable and weak magnetic environment.This paper presents the design of a miniaturized permalloy magnetic shielding s...Achieving the spin-exchange relaxation-free(SERF)state in atomic comagnetometers(ACMs)necessitates a stable and weak magnetic environment.This paper presents the design of a miniaturized permalloy magnetic shielding spherical shell(MSSS)with minimal apertures,tailored to meet these requirements.By employing a combination of analytical solutions and finite element analysis(FEA),we achieved superior magnetic shielding while maintaining a compact form factor.The analytical solution for the shielding factor indicated that a four-layer permalloy sphere shell with optimized air gaps was necessary.A numerical analysis model of the MSSS was developed and validated using COMSOL software,confirming the suitability of the air gaps.The size,shape,and orientation of the openings in the perforated sphere shell were meticulously designed and optimized to minimize residual magnetism.The optimal structure was fabricated,resulting in triaxial shielding factors of 47619,52631,and 21739,meeting the anticipated requirements.A comparison of simulation results with experimental tests demonstrated the efficacy of the design methodology.This study has significant implications for ultrasensitive magnetic field detection devices requiring weak magnetic field environments,such as atomic gyroscopes,magnetometers,atomic interferometers,and atomic clocks.展开更多
The spin-exchange relaxation-free atomic gyroscope,with its exceptionally high theoretical precision,demonstrates immense potential to become the next-generation strategic-grade gyroscope.However,due to technological ...The spin-exchange relaxation-free atomic gyroscope,with its exceptionally high theoretical precision,demonstrates immense potential to become the next-generation strategic-grade gyroscope.However,due to technological noise,there is still a significant gap between its actual precision and theoretical precision.This study identifies the key factor limiting the precision of the SERF gyroscope as coupling noise.By optimizing the detection loop structure,a distinction between the dual-axis signals'response to optical and magnetic fields was achieved-where the optical errors responded similarly,while the response to magnetic noise was opposite.Based on the differences in the optical-magnetic response of the dual-axis signals,empirical mode decomposition was used to decompose the dual-axis gyroscope signals into multiple intrinsic mode functions,and Allan deviation analysis was applied to analyze the noise characteristics of the intrinsic mode functions over various periods.This study successfully reveals that optical errors caused by thermal-optical coupling and long-period magnetic noise induced by thermal-magnetic coupling are the dominant factors limiting the long-term stability of the SERF gyroscope.Based on these analyses,the study concludes that to achieve strategic-grade precision for the SERF gyroscope,it is essential to effectively address the noise issues caused by multi-physical field couplings.展开更多
SERF陀螺仪工作在无自旋交换弛豫(SERF)状态下,电子自旋和核子自旋强烈耦合。通过研究电子自旋与核子自旋的耦合方程,分析了泵浦激光的功率和气室温度对SERF陀螺仪磁场补偿的影响,并搭建了SERF陀螺仪实验平台系统进行验证。研究结果表明...SERF陀螺仪工作在无自旋交换弛豫(SERF)状态下,电子自旋和核子自旋强烈耦合。通过研究电子自旋与核子自旋的耦合方程,分析了泵浦激光的功率和气室温度对SERF陀螺仪磁场补偿的影响,并搭建了SERF陀螺仪实验平台系统进行验证。研究结果表明:原子核自旋补偿磁场正比于泵浦激光功率,泵浦激光功率在9.7 m W至105.6 m W的变化范围中,自旋补偿磁场的变化达到8.9 n T;气室温度在107.5℃至149.3℃变化范围中,自旋补偿磁场变化为4.5 n T,无明显的相关性,并且相对于气室温度的变化,补偿磁场对泵浦激光功率变化更加敏感。展开更多
在本文中再一次评述了四种量子磁力仪的基本原理、研究和开发方面的进展。四种量子磁力仪包括核子旋进磁力仪(质子磁力仪)、光泵磁力仪、超导磁力仪(SQUID)、SERF原子磁力仪。对于地球物理应用来说,德国、加拿大和其它国家的科学家研制...在本文中再一次评述了四种量子磁力仪的基本原理、研究和开发方面的进展。四种量子磁力仪包括核子旋进磁力仪(质子磁力仪)、光泵磁力仪、超导磁力仪(SQUID)、SERF原子磁力仪。对于地球物理应用来说,德国、加拿大和其它国家的科学家研制成功的全张量航空磁力梯度仪JESSY STAR,是最重要的一项技术突破。美国Seltzer S J和Romalis M V研制的无屏蔽SERF原子磁力仪具有构制另一种类型的全张量航空磁力梯度仪的潜力,如果实现,它将是磁力勘探另一项重要的技术突破。展开更多
文摘March 28 of this year is the second Tibetan Serfs Emancipation Day. People of all nationalities in Tibet marked the day by hoisting the national flag and by singing and dancing. Smiles were on every face and a festive atmosphere pervaded the snowcovered plateau region.
文摘In old Tibet, the local government (including individual officials), monasteries and feudal lords all engaged in trade. Without exception, they also lent money at usurious rates. Interest-based profits were a major source of their incomes. To exploit serfs, the Dalai Lama and the Tibetan local government established special agencies to handle money-lending matters. The agency established by the Dalai Lama for the purpose was called
文摘Fifty years ago, on March 28, 1959, Zhou Enlai, Premier of the State Council of the People＇s Repubfic of China, promulgated a decree of the State Council, declanng the Tibet local government controlled by Tibet＇s feudal aristocrats and upperstratum clergy dissolved on that day and resolving that the powers of the Tibet local government be exercised by the Preparatory Committee for the Founding of the Tibet Autonomous Region from that day on. This decision of great historic significance sounded the death knell of the feudal serf system in old Tibet, a theocratic system that was reactionary, corrupt and dark. The change of government cleared obstacles and created conditions for development and progress in Tibet. After that a broad democratic reform movement swept the plateau region. Under the leadership of the Communist Party of China, the one million serfs in Tibet buried the feudal serf system and won their emancipation,
基金supported by the Beijing Natural Science Foundation(Grant No.3252013)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300402)+1 种基金the National Natural Science Foundation of China(Grant No.61673041)Key Area Research and Development Program of Guangdong Province(Grant No.2021B0101410005)。
文摘Atomic spin gyroscopes are promising candidates for next-generation inertial navigation due to extremely high theoretical precision,relatively small size among atomic gyroscopes,and promising potential for miniaturization.In particular,the spin-exchange relaxation-free(SERF)atomic gyroscope relies on optical pumping to polarize atoms,enabling rotation sensing through the Faraday optical rotation angle(FORA).However,fluctuations in atomic density introduce systematic errors in FORA measurements,limiting long-term stability.We present a data-driven decoupling method that isolates atomic density fluctuations from the FORA signal by modeling spatially resolved light absorption in the vapor cell.The model accounts for the spatial distribution of spin polarization in the pump-light interaction volume,density-dependent relaxation rates,wall-induced relaxation,and polarization diffusion,and is implemented within a finite-element framework.Compared to the conventional Lambert-Beer law,which assumes one-dimensional homogeneity,our approach captures the full threedimensional density and polarization distribution,significantly improving the accuracy of light absorption modeling.The resulting absorption-density maps are used to train a feedforward neural network,yielding a high-precision estimator for atomic density fluctuations.This estimator enables the construction of a decoupling equation that separates the density contribution from the FORA signal.Experimental validation shows that this method improves the bias instability atσ(100 s)of the gyroscope was improved by 73.1%compared to traditional platinum-resistance-based stabilization.The proposed framework is general and can be extended to other optical pumping-based sensors,such as optically pumped magnetometers.
基金supported by Hefei National Laboratory,Innovation Program for Quantum Science and Technology(Grant Nos.2021ZD0300500 and 2021ZD0300503).
文摘Achieving the spin-exchange relaxation-free(SERF)state in atomic comagnetometers(ACMs)necessitates a stable and weak magnetic environment.This paper presents the design of a miniaturized permalloy magnetic shielding spherical shell(MSSS)with minimal apertures,tailored to meet these requirements.By employing a combination of analytical solutions and finite element analysis(FEA),we achieved superior magnetic shielding while maintaining a compact form factor.The analytical solution for the shielding factor indicated that a four-layer permalloy sphere shell with optimized air gaps was necessary.A numerical analysis model of the MSSS was developed and validated using COMSOL software,confirming the suitability of the air gaps.The size,shape,and orientation of the openings in the perforated sphere shell were meticulously designed and optimized to minimize residual magnetism.The optimal structure was fabricated,resulting in triaxial shielding factors of 47619,52631,and 21739,meeting the anticipated requirements.A comparison of simulation results with experimental tests demonstrated the efficacy of the design methodology.This study has significant implications for ultrasensitive magnetic field detection devices requiring weak magnetic field environments,such as atomic gyroscopes,magnetometers,atomic interferometers,and atomic clocks.
基金supported by Hefei National Laboratory,Innovation Program for Quantum Science and Technology(2021ZD0300400/2021ZD0300402)the Beijing Natural Science Foundation(3252013)the China Postdoctoral Science Foundation(2024T171116).
文摘The spin-exchange relaxation-free atomic gyroscope,with its exceptionally high theoretical precision,demonstrates immense potential to become the next-generation strategic-grade gyroscope.However,due to technological noise,there is still a significant gap between its actual precision and theoretical precision.This study identifies the key factor limiting the precision of the SERF gyroscope as coupling noise.By optimizing the detection loop structure,a distinction between the dual-axis signals'response to optical and magnetic fields was achieved-where the optical errors responded similarly,while the response to magnetic noise was opposite.Based on the differences in the optical-magnetic response of the dual-axis signals,empirical mode decomposition was used to decompose the dual-axis gyroscope signals into multiple intrinsic mode functions,and Allan deviation analysis was applied to analyze the noise characteristics of the intrinsic mode functions over various periods.This study successfully reveals that optical errors caused by thermal-optical coupling and long-period magnetic noise induced by thermal-magnetic coupling are the dominant factors limiting the long-term stability of the SERF gyroscope.Based on these analyses,the study concludes that to achieve strategic-grade precision for the SERF gyroscope,it is essential to effectively address the noise issues caused by multi-physical field couplings.
文摘SERF陀螺仪工作在无自旋交换弛豫(SERF)状态下,电子自旋和核子自旋强烈耦合。通过研究电子自旋与核子自旋的耦合方程,分析了泵浦激光的功率和气室温度对SERF陀螺仪磁场补偿的影响,并搭建了SERF陀螺仪实验平台系统进行验证。研究结果表明:原子核自旋补偿磁场正比于泵浦激光功率,泵浦激光功率在9.7 m W至105.6 m W的变化范围中,自旋补偿磁场的变化达到8.9 n T;气室温度在107.5℃至149.3℃变化范围中,自旋补偿磁场变化为4.5 n T,无明显的相关性,并且相对于气室温度的变化,补偿磁场对泵浦激光功率变化更加敏感。
文摘在本文中再一次评述了四种量子磁力仪的基本原理、研究和开发方面的进展。四种量子磁力仪包括核子旋进磁力仪(质子磁力仪)、光泵磁力仪、超导磁力仪(SQUID)、SERF原子磁力仪。对于地球物理应用来说,德国、加拿大和其它国家的科学家研制成功的全张量航空磁力梯度仪JESSY STAR,是最重要的一项技术突破。美国Seltzer S J和Romalis M V研制的无屏蔽SERF原子磁力仪具有构制另一种类型的全张量航空磁力梯度仪的潜力,如果实现,它将是磁力勘探另一项重要的技术突破。
