Review of Scientific Instruments最新文献

High-sensitivity and wide-bandwidth magnetometers are crucial for both terrestrial and space-based geophysical applications. In this work, we present an electronics design tailored for a helium optically pumped magnetometer (He-OPM) operating under ambient geomagnetic field conditions. The proposed design features low noise and fast response, which are critical for achieving high bandwidth and high sensitivity in He-OPMs. In addition, a phase compensation method is introduced to reduce phase errors introduced by the signal transmission path, including electronic delays, thereby improving measurement accuracy. The system performance is evaluated in a laboratory environment using a frequency-stabilized laser and effective magnetic shielding. Experimental results demonstrate that the influence of the electronics on measurement accuracy is below 40 pT per 1 μT, and the system achieves a bandwidth of 650 Hz. Under an applied magnetic field of ∼0.65 μT, the He-OPM achieves a sensitivity of 620fT/Hz@1Hz in closed-loop operation.

We present a novel polarization-based spectroscopic method developed for measuring the radial component of the magnetic field, Br, in an imploding magnetized-plasma column. The method is based on the combined effects of the Zeeman splitting and the Doppler shift. In the experiment, we use imploding oxygen plasma with a pre-embedded axial magnetic field Bz. Due to the axial non-uniformity of the plasma implosion and the field compression, the Bz lines are bent radially. We measure the magnitude and direction of B⃗ along the radial coordinate; the magnitude is found to constitute a substantial fraction of the total B⃗ in the compressed plasma. The measurements extend the capabilities of spectroscopic diagnostics in magnetized plasmas, enabling a deeper understanding of the plasma dynamics (such as plasma rotation) and the energy flow in plasmas under high-current pulses.

Optical absorption spectroscopy of halide molten salts enables the determination of the valence state and coordination properties of transition and rare-earth metals, as well as actinides which are present in these melts. However, a serious challenge arises from the highly corrosive behavior of the molten halides. Thus, the application of quartz cuvettes, commonly used for optical absorption spectroscopy as containers for liquid samples, is significantly limited because quartz can be easily dissolved by the melt. Herein, to overcome these issues, we present the design and verification results of a custom spectrophotometry system integrated into a glovebox, allowing for optical absorption measurements based on reflection registration geometry. Such registration geometry allows for utilizing a Pt or glassy carbon crucible as a container for the melt, with the Pt-Rh mirror on its bottom, which remains stable in numerous molten media. The absorption process occurs during vertical light transmission through the melt layer located above the mirror. The beam reflected back by the mirror and re-passed through the melt is detected by a spectrometer. An induction furnace provides the possibility for experiments at temperatures up to 2000 K. Integrating the system into a glovebox allows for convenient operation with materials under a controlled, pure inert atmosphere, which is crucial for halide melts. Verification was performed on KMnO4, PS-7 optical glass, and (LiF-NaF-KF)eut-2 mol. % NdF3 melt. The designed system is promising for measurements of highly corrosive (e.g., fluorides), highly hygroscopic (e.g., LiCl), and high-temperature (e.g., silicates) melts.

An accurate measurement of electrical resistivity of iron (Fe) and Fe-alloy systems at high temperatures and high pressures is essential for understanding the dynamics inside the metallic cores of planetary bodies. Many experimental studies have been carried out on the electrical resistivity of Fe and Fe-alloy compositions using both powder samples and wire samples with different experimental designs, and discrepancies in the measured values still persist. In this study, we evaluated multiple experimental designs using the four-wire method with Fe powder samples to assess the influence of sample geometry, melting, and contact materials on measured resistivity values in a large-volume multi-anvil press. Three configurations with varying sample diameters and geometrical constraints were tested at 5 GPa and beyond the melting temperature of Fe, revealing significant uncertainties due to deformation, especially in the molten state. These results indicate that electrical resistivity measurements with powder samples should be taken as the upper bound unless sample geometry is well preserved. Further experiments examined the effect of disk materials (Pt, W, and Re), with results indicating that higher resistivity materials, such as Re, may introduce larger discrepancies in measured values. With a geometric correction derived from previous room-temperature resistivity data, the agreement of resistivity values between wire and powder samples improves significantly. A two-step approach was then suggested for future experiments with powder samples to reduce uncertainties in resistivity measurements.

To provide rapid gas injection for the plasma gun developed at the CUE of ShanghaiTech University, a new fast gas valve activated by eddy currents has been designed and tested on an experimental facility. A 7075 aluminum flyer plate is used to control the gas injection process. A saucer spring is designed to provide pre-compression force and back force on the flyer plate. Four displacement sensors are installed vertically to the flyer plate to measure distances at four equally distributed points. A capacitance diaphragm gauge is used to measure pressure changes in the vacuum chamber. The main characteristics of the fast gas valve are as follows: (1) the open-close time (the opening to complete closure time) is less than 230 μs, with a minimum value of 102 μs; (2) a saucer spring is designed to provide pre-compression force on the flyer plate, which demonstrates better performance than conventional spiral springs; (3) the gas mass dispensed by the fast gas valve is highly stable, with an average variation of less than 1%; (4) the maximum variation in displacements at the four measuring points on the flyer plate is less than 7%. The fast gas valve has been tested with argon gas on the plasma gun and has shown good performance.

A hierarchical multi-access scheme is proposed for stable frequency dissemination in fiber-optic ring networks. The system features primary and secondary nodes, where a phase-locked loop at the primary site suppresses fiber-induced noise to generate a high-stability signal. Secondary nodes receive optical signals from the local and primary sites, applying third-order mixing to generate stable frequency outputs. This design ensures continuous operation even in case of single-node failures and efficiently addresses varying user requirements with limited resources. Experimental validation on a 220 km fiber-optic ring network demonstrates frequency instabilities of 2.65 × 10-14 @ 1 s and 4.58 × 10-17 @ 10 000 s at the primary site and 1.48 × 10-14 @ 1 s and 4.02 × 10-16 @ 10 000 s as well as 1.56 × 10-14 @ 1 s and 9.70 × 10-16 @ 10 000 s at two intermediate nodes. The scheme provides a robust foundation for stable frequency distribution in metropolitan fiber-optic networks.

Molecular jet expansions are critical for producing cold molecular beams for gas-phase molecular spectroscopy. Notably, most of the operating instruments in this class of experiments rely on pulsed valves with intrinsic temperature limits that significantly constrain the efficient vaporization of less volatile compounds. Here, we present and benchmark the Thermally Insulating Nozzle (TINo), a new pulsed nozzle design that supports substantially higher vaporization temperatures without compromising valve integrity. As a proof of concept, we integrated TINo into a chirped-pulse Fourier transform microwave spectrometer and recorded the rotational spectrum of 1,8-naphthalimide, a molecule of interest with a melting point of 300 °C. The enhanced signal-to-noise ratio enabled the detection of both the parent species and the singly substituted 13C isotopologues in natural abundance. TINo opens a viable path toward acquiring laboratory spectra of otherwise inaccessible molecular libraries via jet-cooled molecular spectroscopy.

With the growing trend of seeking resources, the significance of infrastructure construction in the upper part of soils has become increasingly prominent. Studying the geotechnical characteristics of soils is crucial for the safe operation of geotechnical projects and the efficient deep-resource development. The cone penetration test (CPT) indirectly measures the geotechnical properties of soils. However, Parkin and Lunne pointed out that the CPT data obtained solely on site cannot be reliably converted into soil mechanical parameters. It is difficult to obtain undisturbed samples of soils for laboratory tests (such as triaxial and pedometric tests), thus making it impossible to accurately obtain their mechanical parameters, resulting in a lack of comparison in the interpretation of in situ CPT data. Furthermore, due to the differences in testing procedures, experimental equipment, and soil types among various regions, the data and findings from CPT cannot be generalized into universal principles to guide engineering practices. CPT calibration chamber (CCC) testing, as an effective method to establish the correlation between laboratory measurements of soil and its in situ mechanical properties, holds significant research value for soils where undisturbed samples cannot be retrieved (such as cohesion-less sands and silty soils without plasticity). This paper first reviews the characteristics of large and small CCC equipment for different types of soil. It then discusses the boundary effect encountered in the interpretation of CCC test data and general solutions and summarizes the proposed empirical relationships based on CCC test data for geotechnical parameters. Finally, it outlines future directions for CCC equipment and data interpretation methods.

A low-noise, high-speed optical detector module is characterized and successfully commissioned for the measurement of high-frequency, low-intensity beam emission on Wendelstein 7-X (W7-X). An ultra-narrow bandpass optical filter is employed to selectively transmit the desired emission line while suppressing broadband plasma background emissions. Carbon density fluctuations are investigated by observing the carbon C-VI emission line (n = 8 → 7, λ ∼ 529 nm), arising from charge exchange (CX) between the neutral beam atoms and the intrinsic carbon population. We present the characterization of the optical detector module and experimental measurements of carbon density fluctuations using available fibers on W7-X. The initial performance of the detector is presented in both active and passive CX measurements of intrinsic carbon density fluctuations. The low frequency dynamics of fluctuation is observed in response to the neutral beam and the pellet injection, demonstrating that the optical detector module is capable of providing a sufficient signal level with an adequate signal-to-noise ratio. In the upcoming OP2.4 campaign, this optical detector module will be adapted for use in a beam emission spectroscopy system by replacing the optical bandpass filter with one centered at 654 nm (90% transmission: 653-655.3 nm), which facilitates two-dimensional measurements of ion gyro-scale turbulence on W7-X.

For the first time, the full prototype of the ITER Hard X-Ray (HXR) monitor (HXRM) system has been successfully tested in a tokamak environment during the experimental campaign in the ADITYA Upgrade tokamak located at the Institute for Plasma Research. Unlike conventional HXR diagnostic systems operating in the existing tokamaks, the ITER HXRM is uniquely designed for robustness. In the HXRM system, the UV (Ultraviolet) photons from the scintillator are guided by the optical components to the PMT (Photomultiplier Tube). This approach introduces significant optical attenuation that has a direct impact on the characteristics of the PMT signal. As a result, digital pulse processing algorithms and the I&C (Instrumentation and Control) electronics need reconsideration to work correctly. The initial validation of the HXRM system design was carried out in the laboratory at the Department of Microelectronics and Computer Science, Lodz University of Technology, where the full prototype of the ITER HXRM system was established. The laboratory test validated the design considerations and aided the development of the I&C components. However, the functionality of the system has never been tested in the tokamak environment. The HXRM prototype setup was integrated into the ADITYA Upgrade tokamak and operated during plasma discharges. The data obtained from the plasma discharge allowed verification of the I&C electronics and methodology of the signal transmission, as well as validation of the developed PMT signal simulations. Several test configurations have been tested on the ADITYA Upgrade tokamak, and the preliminary results and observations are reported herein.