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Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For selected: Download citations EndNote Ris BibTeX Toggle thumbnails Select A Yb optical clock with a lattice power enhancement cavity Chunyun Wang(王春云), Yuan Yao(姚远), Haosen Shi(师浩森), Hongfu Yu(于洪浮),Longsheng Ma(马龙生), and Yanyi Jiang(蒋燕义) Chin. Phys. B, 2024, 33 (3): 030601.   DOI: 10.1088/1674-1056/ad1986 Abstract （46）   HTML （0）    PDF （1444KB）（41）       Knowledge map    We construct a power enhancement cavity to form an optical lattice in an ytterbium optical clock. It is demonstrated that the intra-cavity lattice power can be increased by about 45 times, and the trap depth can be as large as 1400Er when laser light with a power of only 0.6 W incident to the lattice cavity. Such high trap depths are the key to accurate evaluation of the lattice-induced light shift with an uncertainty down to ~ 1×10-18. By probing the ytterbium atoms trapped in the power-enhanced optical lattice, we obtain a 4.3 Hz-linewidth Rabi spectrum, which is then used to feedback to the clock laser for the close loop operation of the optical lattice clock. We evaluate the density shift of the Yb optical lattice clock based on interleaving measurements, which is -0.46(62) mHz. This result is smaller compared to the density shift of our first Yb optical clock without lattice power enhancement cavity mainly due to a larger lattice diameter of 344 μm. Select Development of a monochromatic crystal backlight imager for the recent double-cone ignition experiments Chenglong Zhang(张成龙), Yihang Zhang(张翌航), Xiaohui Yuan(远晓辉), Zhe Zhang(张喆), Miaohua Xu(徐妙华), Yu Dai(戴羽), Yufeng Dong(董玉峰), Haochen Gu(谷昊琛), Zhengdong Liu(刘正东), Xu Zhao(赵旭), Yutong Li(李玉同), Yingjun Li(李英骏), Jianqiang Zhu(朱健强), and Jie Zhang(张杰) Chin. Phys. B, 2024, 33 (2): 025201.   DOI: 10.1088/1674-1056/ad1091 Abstract （80）   HTML （0）    PDF （2275KB）（58）       Knowledge map    We developed a monochromatic crystal backlight imaging system for the double-cone ignition (DCI) scheme, employing a spherically bent quartz crystal. This system was used to measure the spatial distribution and temporal evolution of the head-on colliding plasma from the two compressing cones in the DCI experiments. The influence of laser parameters on the x-ray backlighter intensity and spatial resolution of the imaging system was investigated. The imaging system had a spatial resolution of 10 μm when employing a CCD detector. Experiments demonstrated that the system can obtain time-resolved radiographic images with high quality, enabling the precise measurement of the shape, size, and density distribution of the plasma. Select Magnetic field regression using artificial neural networks for cold atom experiments Ziting Chen(陈子霆), Kin To Wong(黃建陶), Bojeong Seo, Mingchen Huang(黄明琛), Mithilesh K. Parit, Yifei He(何逸飞), Haoting Zhen(甄浩廷), Jensen Li, and Gyu-Boong Jo Chin. Phys. B, 2024, 33 (2): 026701.   DOI: 10.1088/1674-1056/ad0cc8 Abstract （75）   HTML （0）    PDF （958KB）（45）       Knowledge map    Accurately measuring magnetic fields is essential for magnetic-field sensitive experiments in areas like atomic, molecular, and optical physics, condensed matter experiments, and other areas. However, since many experiments are often conducted in an isolated environment that is inaccessible to experimentalists, it can be challenging to accurately determine the magnetic field at the target location. Here, we propose an efficient method for detecting magnetic fields with the assistance of an artificial neural network (NN). Instead of measuring the magnetic field directly at the desired location, we detect fields at several surrounding positions, and a trained NN can accurately predict the magnetic field at the target location. After training, we achieve a below 0.3% relative prediction error of magnetic field magnitude at the center of the vacuum chamber, and successfully apply this method to our erbium quantum gas apparatus for accurate calibration of magnetic field and long-term monitoring of environmental stray magnetic field. The demonstrated approach significantly simplifies the process of determining magnetic fields in isolated environments and can be applied to various research fields across a wide range of magnetic field magnitudes. Select A step to the decentralized real-time timekeeping network Fangmin Wang(王芳敏), Yufeng Chen(陈雨锋), Jianhua Zhou(周建华), Yuting Lin(蔺玉亭), Jun Yang(杨军), Bo Wang(王波), and Lijun Wang(王力军) Chin. Phys. B, 2024, 33 (1): 010702.   DOI: 10.1088/1674-1056/acfa88 Abstract （111）   HTML （0）    PDF （1954KB）（79）       Knowledge map    The composite time scale (CTS) provides an accurate and stable time-frequency reference for modern science and technology. Conventional CTS always features a centralized network topology, which means that the CTS is accompanied by a local master clock. This largely restricts the stability and reliability of the CTS. We simulate the restriction and analyze the influence of the master clock on the CTS. It proves that the CTS's long-term stability is also positively related to that of the master clock, until the region dominated by the frequency drift of the H-maser (averaging time longer than ～105 s). Aiming at this restriction, a real-time clock network is utilized. Based on the network, a real-time CTS referenced by a stable remote master clock is achieved. The experiment comparing two real-time CTSs referenced by a local and a remote master clock respectively reveals that under open-loop steering, the stability of the CTS is improved by referencing to a remote and more stable master clock instead of a local and less stable master clock. In this way, with the help of the proposed scheme, the CTS can be referenced to the most stable master clock within the network in real time, no matter whether it is local or remote, making democratic polycentric timekeeping possible. Select Design and simulation of an accelerometer based on NV center spin—strain coupling Lu-Min Ji(季鲁敏), Li-Ye Zhao(赵立业), and Yu-Hai Wang(王裕海) Chin. Phys. B, 2024, 33 (1): 017301.   DOI: 10.1088/1674-1056/ad09ab Abstract （113）   HTML （0）    PDF （1379KB）（42）       Knowledge map    The nitrogen-vacancy (NV) center quantum systems have emerged as versatile tools in the field of precision measurement because of their high sensitivity in spin state detection and miniaturization potential as solid-state platforms. In this paper, an acceleration sensing scheme based on NV spin—strain coupling is proposed, which can effectively eliminate the influence of the stray noise field introduced by traditional mechanical schemes. Through the finite element simulation, it is found that the measurement bandwidth of this ensemble NV spin system ranges from 3 kHz to hundreds of kHz with structure optimization. The required power is at the sub-μW level, corresponding to a noise-limited sensitivity of ${6.7\times }{{10}}^{{-5}}~{\rm g}/\sqrt {\rm Hz} $. Compared with other types of accelerometers, this micro-sized diamond sensor proposed here has low power consumption, exquisite sensitivity, and integration potential. This research opens a fresh perspective to realize an accelerometer with appealing comprehensive performance applied in biomechanics and inertial measurement fields. Select Performance optimization of scintillator neutron detectors for EMD in CSNS Xiaojie Cai(蔡小杰), Qian Yu(于潜), Chang Huang(黄畅), Bin Tang(唐彬), Shihui Zhou(周诗慧), Xiaohu Wang(王小胡), Xiuping Yue(岳秀萍), and Zhijia Sun(孙志嘉) Chin. Phys. B, 2023, 32 (11): 110701.   DOI: 10.1088/1674-1056/acd8a2 Abstract （115）   HTML （0）    PDF （3124KB）（71）       Knowledge map    Chinese Spallation Neutron Source (CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the engineering materials diffractometer (EMD) will be installed between 2019-2023. This instrument requires the neutron detectors with the cover area near 3 m2 in two 90° neutron diffraction angle positions, the neutron detecting efficiency is better than 40%@1 Å, and the spatial resolution is better than 4 mm×200 mm in horizontal and vertical directions respectively. We have developed a one-dimensional position-sensitive neutron detector based on the oblique 6LiF/ZnS(Ag) scintillators, wavelength shifting fibers, and SiPMs (silicon photomultipliers) readout. The inhomogeneity of the neutron detection efficiency between each pixel and each detector module, which caused by the inconsistency of the wave-length shifting fibers in collecting scintillation photons, needs to be mitigated before the installation. A performance optimization experiment of the detector modules was carried out on the BL20 (beam line 20) of CSNS. Using water sample, the neutron beam with Φ 5 mm exit hole was dispersed related evenly into the forward space. According to the neutron counts of each pixel of the detector module, the readout electronics threshold of each pixel is adjusted. Compared with the unadjusted detector module, the inhomogeneity of the detection efficiency for the adjusted one has been improved from 69% to 90%. The test result of the diffraction peak of the standard sample Si showed that the adjusted detector module works well. Select Ultrafast two-dimensional x-ray imager with temporal fiducial pulses for laser-produced plasmas Zheng-Dong Liu(刘正东), Jia-Yong Zhong(仲佳勇), Xiao-Hui Yuan(远晓辉), Ya-Peng Zhang(张雅芃), Jia-Wen Yao(姚嘉文), Zuo-Lin Ma(马作霖), Xiang-Yan Xu(徐向晏), Yan-Hua Xue(薛彦华), Zhe Zhang(张喆), Da-Wei Yuan(袁大伟), Min-Rui Zhang(张敏睿), Bing-Jun Li(李炳均), Hao-Chen Gu(谷昊琛), Yu Dai(戴羽), Cheng-Long Zhang(张成龙), Yu-Feng Dong(董玉峰), Peng Zhou(周鹏), Xin-Jie Ma(马鑫杰), Yun-Feng Ma(马云峰), Xue-Jie Bai(白雪洁), Gao-Yang Liu(刘高扬), Jin-Shou Tian(田进寿), Gang Zhao(赵刚), and Jie Zhang(张杰) Chin. Phys. B, 2023, 32 (11): 110702.   DOI: 10.1088/1674-1056/ace766 Abstract （101）   HTML （0）    PDF （1831KB）（62）       Knowledge map    It is challenging to make an ultrafast diagnosis of the temporal evolution of small and short-lived plasma in two dimensions. To overcome this difficulty, we have developed a well-timed diagnostic utilizing an x-ray streak camera equipped with a row of multi-pinhole arrays. By processing multiple sets of one-dimensional streaked image data acquired from various pinholes, we are capable of reconstructing high-resolution two-dimensional images with a temporal resolution of 38 ps and a spatial resolution of 18 μm. The temporal fiducial pulses accessed from external sources can advance the precise timing and accurately determine the arrival time of the laser. Moreover, it can correct the nonlinear sweeping speed of the streak camera. The effectiveness of this diagnostic has been successfully verified at the Shenguang-II laser facility, providing an indispensable tool for observing complex physical phenomena, such as the implosion process of laser-fusion experiments. Select Design and calibration of an elliptical crystal spectrometer for the diagnosis of proton-induced x-ray emission (PIXE) Yanlyu Fang(方言律), Dongyu Li(李东彧), Hao Cheng(程浩), Yuan Gao(高原), Ze-Qing Shen(申泽清), Tong Yang(杨童), Yu-Ze Li(李昱泽), Ya-Dong Xia(夏亚东), Yang Yan(晏炀), Sha Yan(颜莎), Chen Lin(林晨), and Xue-Qing Yan(颜学庆) Chin. Phys. B, 2023, 32 (11): 110703.   DOI: 10.1088/1674-1056/acf493 Abstract （75）   HTML （0）    PDF （1269KB）（51）       Knowledge map    Laser-driven proton-induced x-ray emission (laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spurted within nanoseconds and accompanied by strong electromagnetic pulses (EMP), so traditional multi-channel detectors are no longer applicable. In this work, we designed a reflective elliptical crystal spectrometer for the diagnosis of laser-PIXE. The device can detect the energy range of 1 keV-11 keV with a high resolution. A calibration experiment was completed on the electrostatic accelerator of Peking University using samples of Al, Ti, Cu, and ceramic artifacts. The detection efficiency of the elliptical crystal spectrometer was obtained in the order of 10-9. Select A combined magnetic field stabilization system for improving the stability of 40Ca+ optical clock Mengyan Zeng(曾孟彦), Zixiao Ma(马子晓), Ruming Hu(胡如明), Baolin Zhang(张宝林), Yanmei Hao(郝艳梅), Huaqing Zhang(张华青), Yao Huang(黄垚), Hua Guan(管桦), and Kelin Gao(高克林) Chin. Phys. B, 2023, 32 (11): 110704.   DOI: 10.1088/1674-1056/acf5d5 Abstract （112）   HTML （2）    PDF （5377KB）（149）       Knowledge map    Future applications of portable 40Ca+ optical clocks require reliable magnetic field stabilization to improve frequency stability, which can be achieved by implementing an active and passive magnetic field noise suppression system. On the one hand, we have optimized the magnetic shielding performance of the portable optical clock by reducing its apertures and optimizing its geometry; on the other hand, we have introduced an active magnetic field noise suppression system to further suppress the magnetic field noise experienced by the ions. These efforts reduced the ambient magnetic field noise by about 10000 times, significantly reduced the linewidth of the clock transition spectrum, improved the stability of the portable 40Ca+ optical clock, and created the conditions for using portable optical clocks in non-laboratory magnetic field environments. This active magnetic field suppression scheme has the advantages of simple installation and wide applicability. Select A cryogenic radio-frequency ion trap for a 40Ca+ optical clock Mengyan Zeng(曾孟彦), Yao Huang(黄垚), Baolin Zhang(张宝林), Zixiao Ma(马子晓), Yanmei Hao(郝艳梅), Ruming Hu(胡如明), Huaqing Zhang(张华青), Hua Guan(管桦), and Kelin Gao(高克林) Chin. Phys. B, 2023, 32 (11): 113701.   DOI: 10.1088/1674-1056/acc807 Abstract （90）   HTML （0）    PDF （2449KB）（54）       Knowledge map    A liquid-nitrogen cryogenic 40Ca+ optical clock is presented that is designed to greatly reduce the blackbody radiation (BBR) shift. The ion trap, the electrodes and the in-vacuum BBR shield are installed under the liquid-nitrogen container, keeping the ions in a cryogenic environment at liquid-nitrogen temperature. Compared with the first design in our previous work, many improvements have been made to increase the performance. The liquid-nitrogen maintenance time has been increased by about three times by increasing the volume of the liquid-nitrogen container; the trap position recovery time after refilling the liquid-nitrogen container has been decreased more than three times by using a better fixation scheme in the liquid-nitrogen container; and the magnetic field noise felt by the ions has been decreased more than three times by a better design of the magnetic shielding system. These optimizations make the scheme for reducing the BBR shift uncertainty of liquid-nitrogen-cooled optical clocks more mature and stable, and develop a stable lock with a narrower linewidth spectrum, which would be very beneficial for further reducing the overall systematic uncertainty of optical clocks. Select Performance of the merged APPLE-Knot undulator for soft x-ray beamline in medium energy ring Rui Cheng(成锐), Fa-Yuan Zhang(张发远), He-Ming Zha(查鹤鸣), and Shan Qiao(乔山) Chin. Phys. B, 2023, 32 (11): 114102.   DOI: 10.1088/1674-1056/acd924 Abstract （89）   HTML （0）    PDF （761KB）（48）       Knowledge map    APPLE-Knot undulator can effectively solve the on-axis heat load problem and is proven to perform well in VUV beamline and soft x-ray beamline in high energy storage ring. However, for soft x-ray beamline in a medium energy ring, whether the APPLE-Knot undulator excels the APPLE undulator is still a question. Here, a merged APPLE-Knot undulator is studied to generate soft x-ray in a medium energy ring. Its advantages and problems are discussed. Though the on-axis heat load of the APPLE-Knot undulator is lower in linear polarization modes compared to the APPLE undulator, its flux is lower. The APPLE-Knot undulator shows no advantage when only fundamental harmonic is needed. However, in circular polarization mode, the APPLE-Knot undulator shows the ability to cover a broader energy range which can remedy the notable shortcoming of the APPLE undulator. Select Measurement of the relative neutron sensitivity curve of a LaBr3(Ce) scintillator based on the CSNS Back-n white neutron source Jian Liu(刘建), Dongming Wang(王东明), Yuecheng Fu(甫跃成), Zhongbao Li(李忠宝), Han Yi(易晗), and Longtao Yi(易龙涛) Chin. Phys. B, 2023, 32 (10): 100703.   DOI: 10.1088/1674-1056/acca08 Abstract （96）   HTML （0）    PDF （2008KB）（61）       Knowledge map    A scintillator detector consisting of a LaBr3(Ce) (0.5%) scintillator, a photomultiplier tube (PMT), and an oscilloscope were used to study the neutron sensitivities of the LaBr3(Ce) scintillator at the China Spallation Neutron Source (CSNS) Back-n white neutron source in the double-bunch and single-bunch operation modes, respectively. Under the two operational modes, the relative neutron sensitivity curves of the LaBr3(Ce) scintillator in the energy regions of 1-20 MeV and 0.5-20 MeV were obtained for the first time. In the energy range of 1-20 MeV, the two curves were nearly identical. However the relative neutron sensitivity uncertainties of the double-bunch experiment were higher than those of the single-bunch experiment. The above results indicated that the single-bunch experiment's neutron sensitivity curve has a lower minimum measurable energy than the double-bunch experiment. Above the minimum measurable energy of the double-bunch experiment, there is little difference between the measured relative neutron sensitivity curves of the single-bunch and double-bunch experiments of the LaBr3(Ce) scintillator and those of other scintillators with a similar neutron response signal intensity. Select Current sensor based on diamond nitrogen-vacancy color center Zi-Yang Shi(史子阳), Wei Gao(高伟), Qi Wang(王启), Hao Guo(郭浩), Jun Tang(唐军), Zhong-Hao Li(李中豪), Huan-Fei Wen(温焕飞), Zong-Min Ma(马宗敏), and Jun Liu(刘俊) Chin. Phys. B, 2023, 32 (7): 070704.   DOI: 10.1088/1674-1056/acc3fe Abstract （192）   HTML （4）    PDF （1692KB）（300）       Knowledge map    High precision current measurement is very important for the calibration of various high-precision equipment and the measurement of other precision detection fields. A new current sensor based on diamond nitrogen-vacancy (NV) color center magnetic measurement method is proposed to realize the accurate measurement of current. This new current method can greatly improve the accuracy of current measurement. Experiments show that the linearity of the current sensor based on diamond NV color center can reach up to 33 ppm, which is superior to other current sensors and solves the problem of low linearity. When the range of input current is 5-40 A, the absolute error of the calculated current is less than 51 μA, and the relative error is 2.42×10-6 at 40 A. Combined with the research content and results of the experiment, the application of the current sensor in the field of current precision measurement is prospected. Select Measurement of remanent magnetic moment using a torsion pendulum with single frequency modulation method Min-Na Qiao(乔敏娜), Lu-Hua Liu(刘鲁华), Bo-Song Cai(蔡柏松), Ya-Ting Zhang(张雅婷),Qing-Lan Wang(王晴岚), Jia-Hao Xu(徐家豪), and Qi Liu(刘祺) Chin. Phys. B, 2023, 32 (5): 050702.   DOI: 10.1088/1674-1056/acae73 Abstract （199）   HTML （2）    PDF （972KB）（94）       Knowledge map    In TianQin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic properties. Here we present a single frequency modulation method based on a torsion pendulum to measure the remanent magnetic moment $m_{\rm r}$ of $1.1$ kg dummy copper test mass, and the measurement result is $(6.45\pm0.04(\rm{stat})\pm0.07(\rm{syst}))\times10^{-8} \rm{A\cdot m^2}$. The measurement precision of the $m_{\rm r}$ is about $0.9 \rm{nA\cdot m^2}$, well below the present measurement requirement of TianQin. The method is particularly useful for measuring extremely low magnetic properties of the materials for use in the construction of space-borne gravitational wave detection and other precision scientific apparatus. Select Three-dimensional color particle image velocimetry based on a cross-correlation and optical flow method Liang Shan(单良), Jun-Zhe Xiong(熊俊哲), Fei-Yang Shi(施飞杨), Bo Hong(洪波), Juan Jian(简娟), Hong-Hui Zhan(詹虹晖), and Ming Kong(孔明) Chin. Phys. B, 2023, 32 (5): 054702.   DOI: 10.1088/1674-1056/acb1ff Abstract （166）   HTML （5）    PDF （3190KB）（109）       Knowledge map    Rainbow particle image velocimetry (PIV) can restore the three-dimensional velocity field of particles with a single camera; however, it requires a relatively long time to complete the reconstruction. This paper proposes a hybrid algorithm that combines the fast Fourier transform (FFT) based co-correlation algorithm and the Horn-Schunck (HS) optical flow pyramid iterative algorithm to increase the reconstruction speed. The Rankine vortex simulation experiment was performed, in which the particle velocity field was reconstructed using the proposed algorithm and the rainbow PIV method. The average endpoint error and average angular error of the proposed algorithm were roughly the same as those of the rainbow PIV algorithm; nevertheless, the reconstruction time was 20% shorter. Furthermore, the effect of velocity magnitude and particle density on the reconstruction results was analyzed. In the end, the performance of the proposed algorithm was verified using real experimental single-vortex and double-vortex datasets, from which a similar particle velocity field was obtained compared with the rainbow PIV algorithm. The results show that the reconstruction speed of the proposed hybrid algorithm is approximately 25% faster than that of the rainbow PIV algorithm. Select Application of silicon carbide temperature monitors in 49-2 swimming-pool test reactor Guang-Sheng Ning(宁广胜), Li-Min Zhang(张利民), Wei-Hua Zhong(钟巍华), Sheng-Hong Wang(王绳鸿), Xin-Yu Liu(刘心语), Ding-Ping Wang(汪定平), An-Ping He(何安平), Jian Liu(刘健), and Chang-Yi Zhang(张长义) Chin. Phys. B, 2023, 32 (5): 056102.   DOI: 10.1088/1674-1056/acb41c Abstract （183）   HTML （2）    PDF （2103KB）（114）       Knowledge map    High purity SiC crystal was used as a passive monitor to measure neutron irradiation temperature in the 49-2 research reactor. The SiC monitors were irradiated with fast neutrons at elevated temperatures to 3.2×1020 n/cm2. The isochronal and isothermal annealing behaviors of the irradiated SiC were investigated by x-ray diffraction and four-point probe techniques. Invisible point defects and defect clusters are found to be the dominating defect types in the neutron-irradiated SiC. The amount of defect recovery in SiC reaches a maximum value after isothermal annealing for 30 min. Based on the annealing temperature dependences of both lattice swelling and material resistivity, the irradiation temperature of the SiC monitors is determined to be ～ 410 ℃, which is much higher than the thermocouple temperature of 275 ℃ recorded during neutron irradiation. The possible reasons for the difference are carefully discussed. Select A spin-based magnetic scanning microscope for in-situ strain tuning of soft matter Zhe Ding(丁哲), Yumeng Sun(孙豫蒙), Mengqi Wang(王孟祺), Pei Yu(余佩), Ningchong Zheng(郑宁冲), Yipeng Zang(臧一鹏), Pengfei Wang(王鹏飞), Ya Wang(王亚), Yuefeng Nie(聂越峰), Fazhan Shi(石发展), and Jiangfeng Du(杜江峰) Chin. Phys. B, 2023, 32 (5): 057504.   DOI: 10.1088/1674-1056/acbaee Abstract （169）   HTML （5）    PDF （4811KB）（120）       Knowledge map    We present a magnetic scanning microscope equipped with a nitrogen-vacancy (NV) center scanning probe that has the ability to mechanically tune the strain of soft matter in-situ. The construction of the microscope and a continuous strain-tuning sample holder are discussed. An optically detected magnetic resonance protocol utilized in the imaging is described. In order to show the reliability of this microscope, the strain conduction is estimated with finite element simulation, and x-ray diffraction is required for calibration when freestanding crystal films are under consideration. A magnetic imaging result is displayed to demonstrate the nano-scale imaging capability. The microscope presented in this work is helpful in studying strain-coupled magnetic physics such as magnetic phase transition under strain and strain-tuned cycloidal orientation tilting. Select Precision measurement and suppression of low-frequency noise in a current source with double-resonance alignment magnetometers Jintao Zheng(郑锦韬), Yang Zhang(张洋), Zaiyang Yu(鱼在洋),Zhiqiang Xiong(熊志强), Hui Luo(罗晖), and Zhiguo Wang(汪之国) Chin. Phys. B, 2023, 32 (4): 040601.   DOI: 10.1088/1674-1056/ac9361 Abstract （218）   HTML （3）    PDF （1068KB）（152）       Knowledge map    Low-noise high-stability current sources have essential applications such as neutron electric dipole moment measurement and high-stability magnetometers. Previous studies mainly focused on frequency noise above 0.1 Hz while less on the low-frequency noise/drift. We use double resonance alignment magnetometers (DRAMs) to measure and suppress the low-frequency noise of a homemade current source (CS) board. The CS board noise level is suppressed by about 10 times in the range of 0.001-0.1 Hz and is reduced to $100 \mathrm{nA/}\sqrt {\mathrm{Hz}} $ at 0.001 Hz. The relative stability of CS board can reach $2.2\times {10}^{-8}$. In addition, the DRAM shows a better resolution and accuracy than a commercial 7.5-digit multimeter when measuring our homemade CS board. Further, by combining the DRAM with a double resonance orientation magnetometer, we may realize a low-noise CS in the 0.001-1000 Hz range. Select Measurements of Majorana transition frequency shift in caesium atomic fountain clocks Jun-Ru Shi(施俊如), Xin-Liang Wang(王心亮), Fan Yang(杨帆), Yang Bai(白杨), Yong Guan(管勇), Si-Chen Fan(范思晨), Dan-Dan Liu(刘丹丹), Jun Ruan(阮军), and Shou-Gang Zhang(张首刚) Chin. Phys. B, 2023, 32 (4): 040602.   DOI: 10.1088/1674-1056/ac8344 Abstract （162）   HTML （2）    PDF （830KB）（80）       Knowledge map    The caesium atomic fountain clock is a primary frequency standard. During its operation, a Majorana transition frequency shift will occur once a magnetic field at some special locations along the atomic trajectory is singular. In this study, by developing a physical model, we analyzed the magnetic field requirements for atomic adiabatic transition and calculated the influence of the Majorana atomic transition on the atomic state via a quantum method. Based on the simulation results for the magnetic field in the fountain clock, we applied the Monte Carlo method to simulate the relationship between the Majorana transition frequency shift and the magnetic field at the entrance of the magnetic shielding, as well as the initial atomic population. Measurement of the Majorana transition frequency shift was realized by state-selecting asymmetrically populated atoms. The relationship between the Majorana transition frequency shift and the axial magnetic field at the entrance of the magnetic shielding was obtained. The measured results were essentially consistent with the calculated results. Thus, the magnetic field at the entrance of the magnetic shielding was configured, and the Majorana transition frequency shift of the fountain clock was calculated to be 4.57×10-18. Select Measurement of T wave in magnetocardiography using tunnel magnetoresistance sensor Zhihong Lu(陆知宏), Shuai Ji(纪帅), and Jianzhong Yang(杨建中) Chin. Phys. B, 2023, 32 (2): 020703.   DOI: 10.1088/1674-1056/aca5fe Abstract （347）   HTML （17）    PDF （1865KB）（98）       Knowledge map    Several critical clinical applications of magnetocardiography (MCG) involve its T wave. The T wave's accuracy directly affects the diagnostic accuracy of MCG for ischemic heart disease and arrhythmogenic. Tunnel magnetoresistance (TMR) attracts attention as a new MCG measurement technique. However, the T waves measured by TMR are often drowned in noise. The accuracy of T waves needs to be discussed to determine the clinical value of MCG measured by TMR. This study uses an improved empirical mode decomposition (EMD) algorithm and averaging to eliminate the noise in the MCG measured by TMR. The MCG signals measured by TMR are compared with MCG measured by the optically pumped magnetometer (OPM) to judge its accuracy. Using the MCG measured by OPM as a reference, the relative errors in time and amplitude of the T wave measured by TMR are 3.4% and 1.8%, respectively. This is the first demonstration that TMR can accurately measure the time and amplitude of MCG T waves. The ability to provide reliable T wave data illustrates the significant clinical application value of TMR in MCG measurement. page Page 1 of 2 Total 39 records First page Prev page Next page Last page