Review of Scientific Instruments最新文献

Acoustically levitated droplets in the nanoliter to microliter range are studied in various fields. The volume measurements of these are conventionally done using image analysis. A precision-produced calibration sphere is often used to calibrate the recording equipment, which is time-consuming and expensive. This paper describes a self-calibrating method to measure the volumes of acoustically levitated droplets as a versatile and low-cost alternative. The distance between two levitated droplets in a horizontally oriented acoustic trap is processed via real-time or recorded frame data using image analysis. To assist in setting the cavity length for the acoustic trap, a simulation of the acoustic field is utilized based on the temperature in the trap, thereby also predicting the distance between the central nodes used to determine the scale factor. The volumes of the spheroidal-shaped levitated droplets can then be calculated from the pixel data. We use a modified version of the well-known TinyLev, and our method has been tested with two types of transducer packing. Its accuracy for volume measurements has been verified in comparison with the standard calibration sphere technique. Self-calibration of the system is demonstrated by changing the camera zoom during data collection, with negligible effects on measured volume. This is something that could not be achieved with conventional static methods.

A new quasi-optical (QO) Electron Cyclotron Emission (ECE) transmission system has been established on the HL-3 tokamak, which includes a focusing QO mirror combination and a long-distance transmission line. This system was developed to meet the requirements for poloidal spatial resolution and the high signal-to-noise ratio needed for magnetohydrodynamic (MHD) instability studies using ECE on the HL-3. The QO mirror combination was installed inside the vacuum chamber for focusing. Laboratory test results, theoretical calculations, and synthetic ECE simulation results indicate that the Gaussian beam can meet the spatial resolution requirements for the accurate measurement of the MHD instability on the q = 1/2/3 surfaces, corresponding to the poloidal mode numbers m = 3/6/9. This includes good diagnostic poloidal spatial resolution for the important 2/1 and 3/2 modes. At the front end of the transmission line, a high-efficiency mode converter was designed to transition the TE10 mode to the HE11 mode for input into the transmission line, with an insertion loss of less than 1.5 dB. A 30 m long-distance corrugated oversized waveguide was constructed, with transmission losses ranging from 6 to 10 dB in the 60-120 GHz range. Polarization adjustment results show that the polarization offset and geometric spatial polarization angle change consistently, which can provide a reference for polarization adjustment in other complex structured transmission lines. The newly established ECE QO transmission system will provide strong support for future physics research involving ECE on the HL-3.

Many current and upcoming laser facilities used to study high-energy-density (HED) physics and inertial fusion energy (IFE) support operating at high rep-rates (HRRs) of ∼0.1-10 Hz, yet many diagnostics, target-fielding strategies, and data storage methods cannot support this pace of operation. Therefore, established experimental paradigms must change for the community to progress toward rep-rated operation. To this end, we introduce the General Atomics LAboratory for Developing Rep-rated Instrumentation and Experiments with Lasers, or GALADRIEL, to serve as a test bed for developing and benchmarking the engineering science advancements required for HRR experiments. GALADRIEL was constructed from the ground up around a commercial 1 TW (∼25 mJ in ∼25 fs at 800 nm) laser with diverse experimental applications in mind. Assembly of the basic framework of GALADRIEL concluded with commissioning shots generating ∼1-4 MeV electrons via laser-wakefield acceleration (LWFA) using a nitrogen gas jet. Subsequent LWFA experiments operated at 1 Hz, utilized instrument feedback for optimization, and stored all data in a custom-built NoSQL database system. From this database called MORIA, or the MOngodb Repository for Information Archiving, data are retrievable via individual files or en masse by query requests defined by the user. GALADRIEL focuses on outstanding questions in engineering science, including targetry, diagnostics, data handling, environmental and materials studies, analysis and machine learning algorithm development, and feedback control systems. GALADRIEL fills a niche presently missing in the US-based user-facility community by providing a flexible experimental platform to address problems in engineering science relevant to rep-rated HED and IFE experiments.

Downhole instrumentation requires more and more accuracy of MEMS inertial sensors. However, in measurement while drilling, temperature drift phenomenon of the sensor will have a cumulative impact on the drill pipe attitude solution. After experimental testing, the output response of the accelerometer had strong local linear and global nonlinear characteristics. In this paper, we proposed a temperature compensation model based on tent chaotic mapping and sparrow search algorithm optimized back propagation (BP) neural network (Tent-SSA-BPNN). Sparrow search algorithm (SSA) was optimized by tent chaotic mapping, which was utilized to improve the uniformity and search ability of SSA populations. Then, the improved SSA was used to optimize the weight and bias parameters of the BP neural network for constructing the temperature compensation model. Finally, the trained compensation model is integrated into the microprogram control unit for real-time compensation testing. The experimental results show that after sacrificing a small amount of sampling frequency, the compensation model proposed in this article has good global compensation performance, and the mean absolute percentage error is reduced from 2% to 0.2% compared to the original output. The mean absolute error and root mean square error of the improved compensation model are all reduced compared to the pre-improved BP compensation model. This temperature-compensated modeling method has a reference value for low-cost and high-precision modeling in high temperature environments, while greatly saving time cost and measurement costs.

Research on evaluating weapon systems, building structures, and personnel protection has attracted considerable attention due to the high incidence of blast accidents. The explosively driven shock tube is an affordable and replicable method for investigating high pressure blast waves and extreme shock environments. A newly constructed large caliber explosively driven shock tube with an inner diameter of 2.5 m and a length of 18 m has been documented and characterized in this paper. It is capable of providing a peak pressure of at least 5.49 MPa in the test section with 160 kg of TNT charges. The tube can produce an overpressure that is significantly higher than conventional shock tubes, which expands the capability to simulate a high overpressure blast load. A two-dimensional axisymmetric simulation model has been developed, validated, and calibrated for the characterization of the flow field inside the shock tube. The influence of the charge mass on the overpressure, arrival time, and positive impulse was discussed, and the planarity of the shock wave was also quantitatively characterized. To aid in designing further shock experiments and applications, a physics-based prediction model was developed using the dimensional analysis.

The design of a compact 2 × 2 diamond matrix with independent and redundant pixels optimized for the spectrometric neutron camera of the SPARC tokamak is presented in this article. Such a matrix overcomes the constraints in dynamic range posed by the size of a single diamond sensor while keeping the ability to perform energy spectral analysis, marking a significant advancement in tokamak neutron diagnostics. A charge pre-amplifier based on radio frequency amplifiers based on InGaP technology transistors, offering up to 2 GHz bandwidth with high robustness against radiation, has been developed. A first single-channel device has been tested and proven to provide a fast signal development time of 20-25 ns, necessary to mitigate pileup effects while offering precise energy measurements. As the diamond sensors may suffer from polarization effects due to the trapping of charges at the diamond/metal interface, a periodical bias inversion can guarantee optimal performance. To facilitate that, a reversible high voltage power supply has been developed. The ongoing development of data acquisition equipment and real-time processing algorithms based on programmable gate arrays further enhances the neutron camera's capabilities.

To improve the performance of studless tires on ice surfaces, the mechanism of liquid film removal must be elucidated. In this study, an experimental system is developed to simulate the running conditions of a studless tire, and the microscopic liquid film flow generated between the rubber surface and glass is observed to evaluate the liquid thickness distribution. Liquid film removal by micropores on foamed rubber samples is investigated by visualizing the liquid thickness in the micropores. The proposed system enables variations in the pressure and sliding velocity between the rubber and glass. The liquid thickness in the micropores is measured using laser-induced fluorescence, and the effects of pressure and sliding velocity on the thickness are examined. Water penetrates the micropores on the rubber sample surface, and different liquid thicknesses are obtained for each pore. The amount of liquid penetrating the pores is affected to a greater extent by the sliding velocity than by the pressure. Therefore, liquid penetration is more strongly influenced by the hydrodynamic effect of the increasing inertia of the liquid under high sliding velocities than by the elastic deformation of the pore.

A permanently available molecular-beam injection setup for controlled molecules (COMO) was installed and commissioned at the small quantum systems (SQS) instrument at the European x-ray free-electron laser (EuXFEL). A b-type electrostatic deflector allows for pure state-, size-, and isomer-selected samples of polar molecules and clusters. The source provides a rotationally cold (T ≈ 1 K) and dense (ρ ≈ 108 cm-3) molecular beam with pulse durations up to 100 µs generated by a new version of the Even-Lavie valve. Here, a performance overview of the COMO setup is presented along with characterization experiments performed both with an optical laser at the Center for Free-Electron-Laser Science and with x rays at EuXFEL under burst-mode operation. COMO was designed to be attached to different instruments at the EuXFEL, in particular, the SQS and single particles, clusters, and biomolecules (SPB) instruments. This advanced controlled-molecules injection setup enables x-ray free-electron laser studies using highly defined samples with soft and hard x-ray FEL radiation for applications ranging from atomic, molecular, and cluster physics to elementary processes in chemistry and biology.

The MAJIS (Moons and Jupiter Imaging Spectrometer) instrument is an imaging spectrometer on-board the JUICE (JUpiter ICy moons Explorer) spacecraft. MAJIS covers the spectral range from 0.5 to 5.54 μm with two channels [visible-near infrared (VISNIR) and IR]. A comprehensive campaign of on-ground MAJIS calibration was conducted in August and September 2021 in the IAS (Institut d'Astrophysique Spatiale, CNRS/Université Paris-Saclay) facilities. In this article, we present the results relevant for the radiometric calibration of MAJIS. Due to the specific characteristics of the MAJIS detectors (H1RG from Teledyne), an extensive detector characterization campaign was implemented for both the VISNIR and IR detectors before integration so as to validate readout procedures providing precision and accuracy. The characterization also provided critical information on linearity and operability as a function of the integration time and operating temperature. The radiometric calibration of the integrated MAJIS instrument focused on the determination of the instrument transfer function in terms of DN output per unit of radiance for each MAJIS data element as a function of its position in the field of view of MAJIS and its central wavelength. The radiometric calibration of the VISNIR channel required a specific procedure due to stray light at short wavelengths. Observations of an internal calibration source during calibration and after launch (April 14, 2023) showed that there were minor changes in both the VISNIR and IR channels. The instrument transfer functions to be used in flight have been updated on this basis.