Featured Column — INSTRUMENTATION AND MEASUREMENT

    Chinese Physics B begins to accept and publish “Instrumentation and Measurement” papers in 2022. 

    The “Instrumentation and Measurement” paper is dedicated to publishing new developments in physical instrumentation, apparatuses, measurement techniques, and related measurement theory.

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    Frequency-modulated continuous-wave multiplexed gas sensing based on optical frequency comb calibration
    Linhua Jia(贾琳华), Xinghua Qu(曲兴华), and Fumin Zhang (张福民)
    Chin. Phys. B, 2024, 33 (9): 094201.   DOI: 10.1088/1674-1056/ad5980
    Abstract75)   HTML0)    PDF (3675KB)(25)      
    Laser absorption spectroscopy has proven to be an effective approach for gas sensing, which plays an important role in the fields of military, industry, medicine and basic research. This paper presents a multiplexed gas sensing system based on optical frequency comb (OFC) calibrated frequency-modulated continuous-wave (FMCW) tuning nonlinearity. The system can be used for multi-parameter synchronous measurement of gas absorption spectrum and multiplexed optical path. Multi-channel parallel detection is realized by combining wavelength division multiplexing (WDM) and frequency division multiplexing (FDM) techniques. By introducing nonlinear optical crystals, broadband spectrum detection is simultaneously achieved over a bandwidth of hundreds of nanometers. An OFC with ultra-high frequency stability is used as the frequency calibration source, which guarantees the measurement accuracy. The test samples involve H$^{13}$C$^{14}$N, C$_{2}$H$_{2}$ and Rb vapor cells of varying densities and 5 parallel measurement experiments are designed. The results show that the measurement accuracies of spectral absorption line and the optical path are 150 MHz and 20 μm, respectively. The scheme offers the advantages of multiplexed, multi-parameter, wide spectrum and high resolution detection, which can realize the identification of multi-gas components and the high-precision inversion of absorption lines under different environments. The proposed sensor demonstrates great potential in the field of high-resolution absorption spectrum measurement for gas sensing applications.
    Physics package based on intracavity laser cooling 87Rb atoms for space cold atom microwave clock
    Siminda Deng(邓思敏达), Wei Ren(任伟), Jingfeng Xiang(项静峰), Jianbo Zhao(赵剑波), Lin Li(李琳), Di Zhang(张迪), Jinyin Wan(万金银), Yanling Meng(孟艳玲), Xiaojun Jiang(蒋小军), Tang Li(李唐), Liang Liu(刘亮), and Desheng Lü(吕德胜)
    Chin. Phys. B, 2024, 33 (7): 070602.   DOI: 10.1088/1674-1056/ad4bc1
    Abstract111)   HTML2)    PDF (1341KB)(94)      
    This article proposes a new physics package to enhance the frequency stability of the space cold atom clock with the advantages of a microgravity environment. Clock working processes, including atom cooling, atomic state preparation, microwave interrogation, and transition probability detection, are integrated into the cylindrical microwave cavity to achieve a high-performance and compact physics package for the space cold atom clock. We present the detailed design and ground-test results of the cold atom clock physics package in this article, which demonstrates a frequency stability of $1.2 \times 10^{-12}$ $\tau^{-1/2}$ with a Ramsey linewidth of 12.5 Hz, and a better performance is predicted with a 1 Hz or a narrower Ramsey linewidth in microgravity environment. The miniaturized cold atom clock based on intracavity cooling has great potential for achieving space high-precision time-frequency reference in the future.
    Development of 400-μW cryogen-free dilution refrigerators for quantum experiments
    Xiang Guan(关翔), Jie Fan(樊洁), Yong-Bo Bian(边勇波), Zhi-Gang Cheng(程智刚), and Zhong-Qing Ji(姬忠庆)
    Chin. Phys. B, 2024, 33 (7): 070701.   DOI: 10.1088/1674-1056/ad3b87
    Abstract119)   HTML2)    PDF (3778KB)(122)      
    We have successfully developed cryogen-free dilution refrigerators with medium cooling power that can be applied to quantum experiments. Breakthroughs have been made in some key technologies and components of heat switches and dilution units. Our prototype has been running continuously and stably for more than 100 hours below 10 mK, with a minimum temperature of 7.6 mK and a cooling power of 450 μW at 100 mK. At the same time, we have also made progress in the application of dilution refrigerators, such as quantum computing, low-temperature detector, and magnet integration. These indicators and test results indicate good prospects for application in physics, astronomy, and quantum information.
    Imaging plate scanners calibration and the attenuation behavior of imaging plate signals
    Nan Bo(薄楠) and Nai-Yan Wang(王乃彦)
    Chin. Phys. B, 2024, 33 (6): 060701.   DOI: 10.1088/1674-1056/ad43d4
    Abstract51)   HTML1)    PDF (907KB)(55)      
    Based on previously reported work, we propose a new method for calibrating image plate (IP) scanners, offering greater flexibility and convenience, which can be extended to the calibration tasks of various scanner models. This method was applied to calibrate the sensitivity of a GE Typhoon FLA 7000 scanner. Additionally, we performed a calibration of the spontaneous signal attenuation behavior for BAS-MS, BAS-SR, and BAS-TR type IPs under the 20$\pm$1$^\circ$C environmental conditions, and observed significant signal carrier diffusion behavior in BAS-MS IP. The calibration results lay a foundation for further research on the interaction between ultra-short, ultra-intense lasers and matter.
    FPGA and computer-vision-based atom tracking technology for scanning probe microscopy
    Feng-Du Yu(俞风度), Li Liu(刘利), Su-Ke Wang(王肃珂), Xin-Biao Zhang(张新彪), Le Lei(雷乐), Yuan-Zhi Huang(黄远志), Rui-Song Ma(马瑞松), and Qing Huan(郇庆)
    Chin. Phys. B, 2024, 33 (5): 050705.   DOI: 10.1088/1674-1056/ad34cb
    Abstract91)   HTML2)    PDF (2432KB)(85)      
    Atom tracking technology enhanced with innovative algorithms has been implemented in this study, utilizing a comprehensive suite of controllers and software independently developed domestically. Leveraging an on-board field-programmable gate array (FPGA) with a core frequency of 100 MHz, our system facilitates reading and writing operations across 16 channels, performing discrete incremental proportional-integral-derivative (PID) calculations within 3.4 microseconds. Building upon this foundation, gradient and extremum algorithms are further integrated, incorporating circular and spiral scanning modes with a horizontal movement accuracy of 0.38 pm. This integration enhances the real-time performance and significantly increases the accuracy of atom tracking. Atom tracking achieves an equivalent precision of at least 142 pm on a highly oriented pyrolytic graphite (HOPG) surface under room temperature atmospheric conditions. Through applying computer vision and image processing algorithms, atom tracking can be used when scanning a large area. The techniques primarily consist of two algorithms: the region of interest (ROI)-based feature matching algorithm, which achieves 97.92% accuracy, and the feature description-based matching algorithm, with an impressive 99.99% accuracy. Both implementation approaches have been tested for scanner drift measurements, and these technologies are scalable and applicable in various domains of scanning probe microscopy with broad application prospects in the field of nanoengineering.
    High-frequency microwave cavity design for high-mass dark matter axion searches
    Chi Zhang(张驰), Jia Wang(王佳), Chunguang Li(李春光), Shiguang Chen(陈石广), Hang Cheng(程航), Liang Sun(孙亮), and Yun Wu(吴云)
    Chin. Phys. B, 2024, 33 (5): 054211.   DOI: 10.1088/1674-1056/ad34ca
    Abstract96)   HTML2)    PDF (1186KB)(71)      
    The haloscope based on the $\rm TM_{010}$ mode cavity is a well-established technique for detecting QCD axions. However, the method has limitations in detecting high-mass axion due to significant volume loss in the high-frequency cavity. Utilizing a higher-order mode cavity can effectively reduce the volume loss of the high-frequency cavity. The rotatable dielectric pieces as a tuning mechanism can compensate for the degradation of the form factor of the higher-order mode. Nevertheless, the introduction of dielectric causes additional volume loss. To address these issues, this paper proposes a novel design scheme by adding a central metal rod to the higher-order mode cavity tuned by dielectrics, which improves the performance of the haloscope due to the increased effective volume of the cavity detector. The superiority of the novel design is demonstrated by comparing its simulated performance with previous designs. Moreover, the feasibility of the scheme is verified by the full-wave simulation results of the mechanical design model.
    Microwave electrometry with Rydberg atoms in a vapor cell using microwave amplitude modulation
    Jian-Hai Hao(郝建海), Feng-Dong Jia(贾凤东), Yue Cui(崔越), Yu-Han Wang(王昱寒), Fei Zhou(周飞), Xiu-Bin Liu(刘修彬), Jian Zhang(张剑), Feng Xie(谢锋), Jin-Hai Bai(白金海), Jian-Qi You(尤建琦), Yu Wang(王宇), and Zhi-Ping Zhong(钟志萍)
    Chin. Phys. B, 2024, 33 (5): 050702.   DOI: 10.1088/1674-1056/ad1a8f
    Abstract130)   HTML2)    PDF (2052KB)(117)      
    We have theoretically and experimentally studied the dispersive signal of the Rydberg atomic electromagnetically-induced transparency (EIT) Autler-Townes (AT) splitting spectra obtained using amplitude modulation of the microwave (MW) electric field. In addition to the two zero-crossing points interval $\Delta f_{\text{zeros}}$, the dispersion signal has two positive maxima with an interval defined as the shoulder interval $\Delta f_{\text{sho}}$, which is theoretically expected to be used to measure a much weaker MW electric field. The relationship of the MW field strength $E_{\text{MW}}$ and $\Delta f_{\text{sho}}$ is experimentally studied at the MW frequencies of 31.6 GHz and 9.2 GHz respectively. The results show that $\Delta f_{\text{sho}}$ can be used to characterize the much weaker $E_{\text{MW}}$ than that of $\Delta f_{\text{zeros}}$ and the traditional EIT-AT splitting interval $\Delta f_{\text{m}}$; the minimum $E_{\text{MW}}$ measured by $\Delta f_{\text{sho}}$ is about 30 times smaller than that by $\Delta f_{\text{m}}$. As an example, the minimum $E_{\text{MW}}$ at 9.2 GHz that can be characterized by $\Delta f_{\text{sho}}$ is 0.056mV/cm, which is the minimum value characterized by the frequency interval using a vapor cell without adding any auxiliary fields. The proposed method can improve the weak limit and sensitivity of $E_{\text{MW}}$ measured by the spectral frequency interval, which is important in the direct measurement of weak $E_{\text{MW}}$.
    Design and implementation of the monochromator shielding for the cold neutron spectrometers XINGZHI and BOYA
    Jinchen Wang(汪晋辰), Juanjuan Liu(刘娟娟), Daye Xu(徐大业), Florian Grünauer, Lijie Hao(郝丽杰), Yuntao Liu(刘蕴韬), Hongxia Zhang(张红霞), Peng Cheng(程鹏), and Wei Bao(鲍威)
    Chin. Phys. B, 2024, 33 (5): 057801.   DOI: 10.1088/1674-1056/ad3629
    Abstract96)   HTML2)    PDF (3809KB)(78)      
    An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor. Via Monte Carlo simulations and careful mechanical designs, a shielding configuration has been successfully developed to satisfy safety requirements of below 3 μSv/h dose rate at its exterior, meanwhile fulfilling space, floor load and nonmagnetic requirements. Composite materials are utilized to form the sandwich-type shielding walls: the inner layer of boron carbide rubber, the middle layer of steel-encased lead and the outer layer of borated polyethylene. Special-shaped liftable shielding blocks are incorporated to facilitate a continuous adjustment of the neutron energy while preventing radiation leakage. Our work has demonstrated that by utilizing composite shielding materials, along with the sandwich structure and liftable shielding blocks, a compact and lightweight shielding solution can be achieved. This enables the realization of advanced neutron scattering instruments that provide expanded space of measurement, larger energy and momentum coverage, and higher flux on the sample. This shielding represents the first of its kind in neutron scattering instruments in China. Following its successful operation, it has been subsequently employed by other neutron instruments across the country.
    Probing the peripheral self-generated magnetic field distribution in laser-plasma magnetic reconnection with Martin—Puplett interferometer polarimeter
    Ya-Peng Zhang(张雅芃), Jia-Wen Yao(姚嘉文), Zheng-Dong Liu(刘正东), Zuo-Lin Ma(马作霖), and Jia-Yong Zhong(仲佳勇)
    Chin. Phys. B, 2024, 33 (4): 045206.   DOI: 10.1088/1674-1056/ad24db
    Abstract100)   HTML1)    PDF (943KB)(58)      
    Magnetic reconnection of the self-generated magnetic fields in laser-plasma interaction is an important laboratory method for modeling high-energy density astronomical and astrophysical phenomena. We use the Martin—Puplett interferometer (MPI) polarimeter to probe the peripheral magnetic fields generated in the common magnetic reconnection configuration, two separated coplanar plane targets, in laser-target interaction. We introduce a new method that can obtain polarization information from the interference pattern instead of the sinusoidal function fitting of the intensity. A bidirectional magnetic field is observed from the side view, which is consistent with the magneto-hydro-dynamical (MHD) simulation results of self-generated magnetic field reconnection. We find that the cancellation of reverse magnetic fields after averaging and integration along the observing direction could reduce the magnetic field strength by one to two orders of magnitude. It indicates that imaging resolution can significantly affect the accuracy of measured magnetic field strength.
    Building and characterizing a stylus ion-trap system
    Tai-Hao Cui(崔太豪), Ya-Qi Wei(魏雅琪), Ji Li(李冀), Quan Yuan(袁泉), Shuang-Qing Dai(戴双晴), Pei-Dong Li(李沛东), Fei Zhou(周飞), Jian-Qi Zhang(张建奇), Zhu-Jun Zheng(郑驻军), Liang Chen(陈亮), and Mang Feng(冯芒)
    Chin. Phys. B, 2024, 33 (4): 043701.   DOI: 10.1088/1674-1056/ad22d9
    Abstract131)   HTML2)    PDF (2720KB)(97)      
    Cold trapped ions can be excellent sensors for ultra-precision detection of physical quantities, which strongly depends on the measurement situation at hand. The stylus ion trap, formed by two concentric cylinders over a ground plane, holds the promise of relatively simple structure and larger solid angle for optical access and fluorescence collection in comparison with the conventional ion traps. Here we report our fabrication and characterization of the first stylus ion trap constructed in China, aiming for studying quantum optics and sensing weak electric fields in the future. We have observed the stable confinement of the ion in the trapping potential for more than two hours and measured the heating rate of the trap to be dε/dt=7.10±0.13 meV/s by the Doppler recooling method. Our work starts a way to building practical quantum sensors with high efficiency of optical collection and with ultimate goal for contributing to future quantum information technology.
    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
    Abstract138)   HTML3)    PDF (1444KB)(170)      
    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.
    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
    Abstract155)   HTML2)    PDF (2275KB)(112)      
    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.
    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
    Abstract140)   HTML1)    PDF (958KB)(97)      
    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.
    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
    Abstract189)   HTML1)    PDF (1954KB)(125)      
    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.
    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
    Abstract197)   HTML1)    PDF (1379KB)(115)      
    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.
    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
    Abstract137)   HTML0)    PDF (1269KB)(138)      
    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.
    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
    Abstract208)   HTML2)    PDF (5377KB)(224)      
    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.
    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
    Abstract138)   HTML0)    PDF (761KB)(94)      
    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.
    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
    Abstract195)   HTML2)    PDF (3124KB)(121)      
    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.
    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
    Abstract174)   HTML0)    PDF (1831KB)(119)      
    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.