Review of Scientific Instruments最新文献

We present a simple and easy-to-implement Graphics Processing Unit (GPU)-accelerated routine to numerically simulate the propagation of ultrashort and intense laser pulses as they interact with a medium. The routine is based on the solution of Maxwell's wave equation in the frequency domain with an extended Crank-Nicolson algorithm implemented in the Nvidia CUDA C++ programming language. The main advantages of our method are its significant speed-up factor and its ease of implementation, requiring only basic knowledge of CUDA and C++. In this article, we review the strong-field wave equations to be solved and their discretization and demonstrate how to implement a numerical solver for them on an Nvidia GPU. We show the results of the simulation of a near-infrared laser pulse propagating through a partially ionized atomic gas and discuss the performance of our GPU-accelerated scheme. Compared to a naïve central processing unit implementation of the same routine, our GPU-accelerated version is up to 198 times faster in standard regimes.

The compact torus (CT) injection device, widely known as a magnetized coaxial plasma gun, creates self-contained magnetic field structures, known as plasmoids, which exhibit high densities and velocities. Owing to its remarkable energy density, the CT injection device holds immense potential for tokamak core fueling, rendering it promising for future fusion reactor applications. This paper presents a novel algorithm, comprising a segmentation module based on the UNet neural network and a tracking module leveraging the simple online and real-time tracking (SORT) algorithm, developed for detecting and tracking plasmoids in visible images. The algorithm is specifically designed for the recently manufactured CT injection system of the EAST tokamak, known as EAST-CTI [Kong et al., Plasma Sci. Technol. 25(6), 065601 (2023)]. Our analysis reveals the presence of multiple plasmoids within the plasma flow ejected by the EAST-CTI system. The UNet convolutional neural network successfully detects these plasmoids, achieving a dice coefficient of 0.813 on the test dataset, indicating high accuracy. Meanwhile, a modified version of the SORT algorithm successfully tracks these plasmoids, demonstrating robust performance without false tracking or identity assignment errors. Overall, the developed algorithm offers critical insights into the evolution characteristics of CTs and meets the requirements of the EAST-CTI system's visible imaging diagnostics. This advancement creates a favorable environment for extensive data analysis using imaging data in future research endeavors.

To enhance meteorological detection methods, an atmospheric boundary layer detection system based on a rotary-wing unmanned aerial vehicle (UAV) was proposed. Computational fluid dynamics (CFD) was employed to model the surrounding airflow distribution during UAV hovering, thereby determining the optimal positions for sensor installation. A novel radiation shield was designed for the temperature sensor, offering both excellent radiation shielding and superior ventilation. To further improve temperature measurement accuracy, an error correction model based on CFD and neural network algorithms was designed. CFD was used to quantify the temperature measurement errors of the sensor under different environmental conditions. Subsequently, random forest and multilayer perceptron algorithms were employed to train and learn from the simulated temperature errors, resulting in the development of the error correction model. To validate the accuracy of the detection system, comparative experiments were conducted using the measurement values from the 076B temperature observation instrument as a reference. The experimental results indicate that the mean absolute error, root mean square error, and correlation coefficient between the experimental temperature errors and the algorithm-predicted errors are 0.055, 0.066, and 0.971 °C, respectively. The average error of the corrected temperature data is 0.05 °C, which shows substantial agreement with the reference temperature data. During UAV hovering, the average discrepancies between the temperature, humidity, and air pressure data of the detection system and the ground-based reference data are 0.6 °C, 1.6% RH, and 0.77 hPa, respectively.

Lock-in amplifiers are instrumental in the precise measurement of extremely small AC signals within high-noise environments. Traditionally, noise reduction in these instruments relies on infinite impulse response (IIR) filters, which can necessitate prolonged settling times to ensure the acquisition of accurate, statistically independent data. While moving average filters offer faster settling times, their non-monotonic frequency response may not be optimal for noise reduction. Conversely, IIR filters frequently realized as N-pole RC filters exhibit a monotonic frequency response conducive to effective noise reduction. This study presents a hybrid filter architecture that combines a short IIR filter with a longer moving average finite impulse response filter. The objective is to enhance noise reduction as quantified by the filter's equivalent noise bandwidth (ENBW). Theoretical analysis is provided to derive the step response, settling time, frequency response, and ENBW of the hybrid filter configuration. Design methodologies are outlined for hybrid filters that either match the settling time of an N-pole RC filter while achieving a lower ENBW or maintain the ENBW of an N-pole RC filter but with significantly faster settling time. The performance of the hybrid filter is validated through noise measurements of low-value resistors and thermal noise of larger resistors, with results compared to theoretical predictions.

Optothermal manipulation technologies trap and manipulate microparticles under a light-controlled temperature gradient. In this paper, we demonstrate the possibilities of optothermal trap, which is generated by an annular beam irradiating on an absorbing reflective film to capture the microparticles. The particles are subjected to thermal and optical gradient forces. First, we investigate the particle trapping near a non-absorbing reflective surface to understand the action of the optical force of annular beam. The results show that the optical force cannot trap the particles near a reflective surface. Second, an annular beam is generated by Gaussian beam shaping with the aid of axicons, which is then used to irradiate and heat a gold film to create an optothermal trap. The induced thermal gradient and thermal convection can bind the particles in the center of the annular spot. The trapping stiffness of the optothermal trap is 8.1 ± 2.9 fN/μm at a laser power of 100 mW.

According to the cross-distribution of four control points of the minimum zone circle, the four-point conditions that two control points on the circumscribed circle and two control points on the inscribed circle meet are proposed. Based on these conditions, a two-point method is proposed, which is suitable not only for the determination of two control points on the circumscribed circle but also for the determination of two control points on the inscribed circle. In the iterative process, redundant data points can be simply determined by using dichotomy in order to improve computational efficiency. Several examples have been carried out to validate the validity of the algorithm proposed.

The Testbed for Analysis of Permeation of Atoms in Samples (TAPAS) is an experimental setup for ion-driven permeation studies with a focus on investigating wall materials for nuclear fusion devices. A monoenergetic, mass-filtered high-intensity keV ion beam is focused and directed onto the permeation sample by electrostatic ion optics and decelerated to the desired ion energy by a dedicated set of apertures close to the sample. We were able to obtain ion energies as low as 170 eV/D with a D3+ ion beam with an ion flux density of the order of 1020 D/m2s on a beam-wetted area of ∼33 mm2. These conditions avoid sputtering of W targets by the ion beam and are representative of the particle flux and energy spectrum impinging on the first wall of a prospective nuclear fusion power reactor. Permeation samples can be heated up to 1000 K in an ultra-high vacuum. The design of the deceleration system, together with a high pumping speed in the loading chamber, ensures a low pressure of recycling hydrogen isotope molecules in front of the sample. In addition to ion-driven permeation, TAPAS provides a limited capability for gas-driven permeation at low pressures up to nearly 1 mbar. Permeating hydrogen isotopes are detected with a quadrupole mass spectrometer in the downstream ultra-high vacuum chamber. After a detailed description of the setup and calibration procedures for implanted particle flux, mass spectrometer, and neutral gas pressure, benchmark experiments on recrystallized, 50 μm thick tungsten foils are shown, demonstrating that diffusion-limited boundary conditions for permeation were reached.

The Lunar Environment heliospheric X-ray Imager (LEXI) is an instrument built to image x-rays from solar wind charge exchange in Earth's magnetosheath. Monitoring the position of the magnetopause at the inner boundary of the magnetosheath allows us to understand how magnetic reconnection regulates how energy from the solar wind is deposited into Earth's magnetosphere. LEXI is part of an upcoming lunar lander mission set to land in Mare Crisium. To repel unwanted charged particles, the instrument carries a permanent magnet array composed of 48 neodymium magnets. The array was designed to maximize charged particle deflection while minimizing stray magnetic fields, which could impact other instruments or spacecraft operation. A Runge-Kutta-based fully kinetic particle tracing model was created to evaluate the effectiveness of LEXI's unique charged particle deflector array. Combined with the other particle suppression measures of the instrument, including physical structures and filters, the simulations show proton and electron transmission to the LEXI detector is expected to be sufficiently reduced to allow successful imaging. The flexible simulation model can be generalized to be used in examining the magnetic deflector array effectiveness of other instruments whose signals could be compromised by unwanted charged particle contamination.

Laser-driven MeV x-ray radiography of dynamic, dense objects demands a small, high flux source of energetic x-rays to generate an image with sufficient quality. Understanding the multi-MeV x-ray spectrum underscores the ability to extrapolate from the current laser sources to new future lasers that might deploy this radiography modality. Here, we present a small study of the existing x-ray diagnostics and techniques. We also present work from National Ignition Facility-Advanced Radiographic Capability, where we deploy three diagnostics to measure the x-ray spectrum up to 30 MeV. Finally, we also discuss the needs and developments of two new diagnostics: a single crystal scintillator spectrometer and a fast decay activation.

An instrument for the simultaneous characterization of thin films by Raman spectroscopy and electronic transport down to 3.7 K has been designed and built. This setup allows for the in situ preparation of air-sensitive samples, their spectroscopic characterization by Raman spectroscopy with different laser lines and five-probe electronic transport measurements using sample plates with prefabricated contacts. The lowest temperatures that can be achieved on the sample are directly proven by measuring the superconducting transition of a niobium film. The temperature-dependent Raman shift and narrowing of the silicon F2g Raman line are shown. This experimental system is specially designed for in situ functionalization and optical spectroscopic and electron transport investigation of thin films. It allows for easy on-the-fly change of samples without the need to warm up the cryomanipulator.