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.

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within nanoseconds and accompanied by strong electromagnetic pulses (EMP), so traditional multi-channel detectors are no longer applicable.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.

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.

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.

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.

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.

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.

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.

We report a design and implementation of a field-programmable-gate-arrays (FPGA) based hardware platform, which is used to realize control and signal readout of trapped-ion-based multi-level quantum systems. This platform integrates a four-channel 2.8 Gsps@14 bits arbitrary waveform generator, a 16-channel 1 Gsps@14 bits direct-digital-synthesis-based radio-frequency generator, a 16-channel 8 ns resolution pulse generator, a 10-channel 16 bits digital-to-analog-converter module, and a 2-channel proportion integration differentiation controller. The hardware platform can be applied in the trapped-ion-based multi-level quantum systems, enabling quantum control of multi-level quantum system and high-dimensional quantum simulation. The platform is scalable and more channels for control and signal readout can be implemented by utilizing more parallel duplications of the hardware. The hardware platform also has a bright future to be applied in scaled trapped-ion-based quantum systems.

Anti-Stokes/Stokes Raman peak intensity ratio was used to infer sample temperatures, but the influence factors of system correction factors were not clear. Non-contact in-situ anti-Stokes/Stokes temperature calibration was carried out for up to 1500 K based on six different samples under two excitation light sources (±50 K within 1000 K, ±100 K above 1000 K), and the system correction factor γ was systematically investigated. The results show that the correction factor γ of anti-Stokes/Stokes thermometry is affected by the wavelength of the excitation light source, Raman mode peak position, temperature measurement region and other factors. The anti-Stokes/Stokes thermometry was applied to the laser-heating diamond anvil cell (LHDAC) experiment to investigate the anharmonic effect of hBN under high temperature and high pressure. It is concluded that the strong anharmonic effect caused by phonon scattering at low pressure gradually changes into the predominance of localized molecular lattice thermal expansion at high pressure.

We present a compact injection-locking diode laser module to generate 671 nm laser light with a high output power up to 150 mW. The module adopts a master-slave injection-locking scheme, and the injection-locking state is monitored using the transmission spectrum from a Fabry-Pérot interferometer. Beat frequency spectrum measurement shows that the injection-locked slave laser has no other frequency components within the 150-MHz detection bandwidth. It is found that without additional electronic feedback, the slave laser can follow the master laser over a wide range of 6 GHz. All the elements of the module are commercially available, which favors fast construction of a complete 671-nm laser system for the preparation of cold ⁶Li atoms with only one research-grade diode laser as the seeding source.

The energy-resolved neutron imaging spectrometer (ERNI) will be installed in 2022 according to the spectrometer construction plan of the China Spallation Neutron Source (CSNS). The instrument requires neutron detectors with the coverage area of approximately 4 m² in 5° -170° neutron diffraction angle. The neutron detection efficiency needs to be better than 40% at 1 Å neutron wavelength. The spatial resolution should be better than 3 m mm×50 mm in the horizontal and vertical directions respectively. We develop a one-dimensional scintillator neutron detector which is composed of the ⁶LiF/ZnS (Ag) scintillation screens, the wavelength-shifting fiber (WLSF) array, the silicon photomultipliers (SiPMs), and the self-designed application-specific integrated circuit (ASIC) readout electronics. The pixel size of the detector is designed as 3 m mm×50 mm, and the neutron-sensitive area is 50 m mm×200 mm. The performance of the detector prototype is measured using neutron beam 20# of the CSNS. The maximum counting rate of 247 kHz, and the detection efficiency of 63% at 1.59 Å are obtained. The test results show that the performance of the detector fulfills the physical requirements of the ERNI under construction at the CSNS.

The accurate analysis of the elemental composition plays a crucial role in the research of functional materials. The emitting characteristic x-ray fluorescence (XRF) photons can be used for precisely discriminating the specified element. The detection accuracy of conventional XRF methodology using semiconductor detector is limited by the energy resolution, thus posing a challenge in accurately scaling the actual energy of each XRF photon. We adopt a novel high-resolution x-ray spectrometer based on the superconducting transition-edge sensor (TES) for the XRF spectroscopy measurement of different elements. Properties including high energy resolution, high detection efficiency and precise linearity of the new spectrometer will bring significant benefits in analyzing elemental composition via XRF. In this paper, we study the emph{L}-edge emission line profiles of three adjacent rare earth elements with the evenly mixed sample of their oxide components: terbium, dysprosium and holmium. Two orders of magnitude better energy resolution are obtained compared to a commercial silicon drift detector. With this TES-based spectrometer, the spectral lines overlapped or interfered by background can be clearly distinguished, thus making the chemical component analysis more accurate and quantitative. A database of coefficient values for the line strength of the spectrum can then be constructed thereafter. Equipped with the novel XRF spectrometer and an established coefficient database, a direct analysis of the composition proportion of a certain element in an unknown sample can be achieved with high accuracy.

We report a new design of microwave source for X-band electron paramagnetic resonance spectrometer. The microwave source is equipped with a digital automatic frequency control circuit. The parameters of the digital automatic frequency control circuit can be flexibly configured for different experimental conditions, such as the input powers or the quality factors of the resonator. The configurability makes the microwave source universally compatible and greatly extends its application. To demonstrate the ability of adapting to various experimental conditions, the microwave source is tested by varying the input powers and the quality factors of the resonator. A satisfactory phase noise as low as -135 dBc/Hz at 100-kHz offset from the center frequency is achieved, due to the use of a phase-locked dielectric resonator oscillator and a direct digital synthesizer. Continuous-wave electron paramagnetic resonance experiments are conducted to examine the performance of the microwave source. The outstanding performance shows a prospect of wide applications of the microwave source in numerous fields of science.

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.

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.

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.

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.

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.

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.