Review of Scientific Instruments最新文献

The first measurements made with a prototype Faraday cup fast ion loss detector (FC-FILD) on the Wendelstein 7-X (W7-X) device are presented and shown to be consistent with lost neutral beam fast ions. The FC-FILD is a small form factor, energy resolving detector designed to be mounted inside the first wall armor tiles of W7-X. Such mounting will allow for a future detector array to be installed, which has been shown to be critical for demonstrating improved fast ion confinement with plasma beta (β = 2μ0p/B2). The prototype diagnostic is composed of a movable armature with a water cooled diagnostic head, mimicking the first wall armor tile cooling structure. The movement of the armature allows for assessment of different detector positions relative to the plasma edge. Measurements of lost fast ions in the low shear magnetic configuration are correlated with neutral beam blips and the neutral beam energy spectrum. Analysis of the rise time of the signals presents a timescale much faster than the energy or particle confinement time and of the order of the predicted neutral beam fast ion slowing down time. Simulations predict a larger signal amplitude than measured, and possible reasons for this are discussed. Finally, a redesigned aperture is presented, which allows for fast ions to reach the detector in a larger set of magnetic configurations.

With extensive use of natural gas energy, various gas accidents occur frequently. Reasonable odorization of natural gas is an effective way to detect gas leakage in time and avoid gas explosions. Therefore, it is necessary to realize the identification and concentration detection of natural gas odorants to ensure early warning without degrading the gas quality. Given the cross-interference effect of electrochemical gas sensors and the poor accuracy of conventional analysis methods, this paper proposed a method based on principal component analysis and the K-nearest neighbor algorithm to realize gas recognition. In addition, the backpropagation-AdaBoost model combined with an electrochemical sensor array was employed to estimate the concentration of tetrahydrothiophene, an odorant in natural gas. The natural gas from the Chenghua district of Chengdu was used as the gas source to verify the reliability of the method. The experimental results show that the gas recognition rate reaches 90.17%, and the tetrahydrothiophene concentration detection average relative error reduced to 3.37%. The results demonstrate that the method can effectively improve the prediction accuracy and reduce the impact of cross-interference on the detection of tetrahydrothiophene. The method can provide technical support for natural gas odorant detection with great engineering significance for solving gas safety problems.

Ultrafast transmission electron microscopy (UTEM) has gained wide applications in the nanoscale dynamics with femtosecond, even attosecond, resolution. The instrument development is still in progress to satisfy the various applications. At Nankai University, we built an UTEM with a laser-driven Schottky field emitter based on a field emission TEM (Talos200i) of Thermo Fisher Scientific. This study comprehensively examines the performance of the UTEM, including the continuous mode and ultrafast photoemission mode. The investigation focuses on optimizing brightness, temporal resolution, energy dispersion, and stability in ultrafast photoemission mode, achieving a temporal resolution of ∼200 fs and an energy dispersion of 0.7 eV with excellent stability through careful adjustments of laser parameters and equipment settings. In scanning transmission electron microscopy mode, the beam size of the photoemission mode is ∼1.4 nm at specific settings with potential for further improvement. As application examples, we illustrate the results of photoinduced structural dynamics of gold film and MoS2 thin flake by ultrafast electron diffraction. We also report the polarization dependent optical interference pattern characterized by the photoinduced near field microscopy effect in a silicon thin film sample prepared by the focused ion beam method. These findings provide valuable insights for researchers aiming to leverage the UTEM's capabilities for advanced electron microscopy applications and pave the way for future advancements in UTEM technology.

Aiming at fully utilizing the spatial resolution of a fast charge exchange recombination spectroscopy (CXS) system, a full-image operation scenario is newly developed. A data analysis procedure is presented. Calibration using a white light source and a neon-enclosed hollow cathode lamp is performed, which provides vertical-stripe separation, horizontal-pixel vs wavelength conversion, and stripe sensitivity. Data from fast and slow CXS systems are compared, providing qualitatively equivalent emission spectra in the same time-integration duration. An asymptotically decreasing trend of noise level with respect to the amount of ensemble averaging (time integration) is confirmed for the fast CXS system. Radial profiles of emission intensity, ion temperature, and toroidal velocity obtained from slow and fast CXS systems are compared, and reasonable agreement is found.

We demonstrate the use of steady-state thermoreflectance (SSTR) as a technique for characterizing mirror surfaces. Due to the enhanced sensitivity of thermoreflectance compared to reflectance, SSTR provides the ability to assess the physical and chemical characteristics as well as the uniformity of thin films and coatings much more rapidly than common metrological methods such as x-ray photoelectron spectroscopy. The use of this technique is demonstrated on AlF3-passivated Al surfaces produced using a process developed for the fabrication of far ultraviolet reflectors. However, since SSTR is thermal in nature, this technique negates the need for a priori knowledge of the optical properties of the material. This is emphasized by interrogating both homogeneous and non-uniform AlF3 films.

Heavy ion synchrotron accelerators rely on intense pulsed beams of highly charged ions. The production of these pulsed beams from an electron cyclotron resonance (ECR) ion source is predominantly achieved through the afterglow mode. However, the influence of microwave parameters on the characteristics of afterglow beams in high-frequency, high-power, and large plasma-volume ion sources remains unexplored. Recently, a series of experiments have been conducted with a third-generation superconducting ECR ion source. The effects of key microwave parameters, including the power level and pulse length of the secondary microwave source, as well as the RF-off time of the primary microwave radiation, on xenon afterglow beam currents are systematically examined. The experimental results and conclusions derived from the data are presented in this article.

A two-color pyrometer is presented that enables detection of a temperature rise with temporal resolution of 17.5 ns. It is geared toward extreme environments where fast electrical electron pulses or currents may push the temperature of a metal surface to melt on a 100 ns time scale. The developed pyrometer, which utilizes an internal gain of 100x, has been tested for SS304 surfaces subjected to an intense electron beam in vacuum. The two-color pyrometer is calibrated using a quasi-calibration method by heating a graphite disk and measuring this temperature with a FLIR TG297 thermal camera. The quasi-calibration method supports the pyrometer to be within 3% accuracy of absolute temperature. The measured temporal temperature profile of the SS304 surface was derived from the pyrometer output data through a detailed gray-body analysis utilizing empirical emissivity data from publicly available literature.

Human-computer collaboration serves as a high-quality method to achieve optimal decisions in the workplace. However, there are relatively few existing papers that focus on how to effectively aggregate the viewpoints of different individuals. Contemporary research suggests that decision confidence bears a positive correlation with decision accuracy, thereby indicating that it can serve as a weighting parameter for aggregating viewpoints. This paper endeavors to quantitatively estimate decision confidence through the application of electroencephalogram (EEG). In this paper, we designed an animal recognition task to measure different decision confidence levels. The success of the task design was demonstrated by the comparison result of behavioral data and EEG at different confidence levels. In addition, then a neural network called channel attention based thinker-invariant DenseNet was proposed to predict confidence levels, with an average accuracy of 77.84%, higher than the results of existing models. Moreover, the regions of the brain associated with decision confidence, found by visualizing the channel attention module of our model, are consistent with existing studies.

This paper proposes a piezoelectric energy harvester using asymmetric clamping to improve output performance. The piezoelectric ceramics have a greater degree of deformation and a shorter response time during squeezing under the effect of the rectangular baffles, resulting in a higher voltage output than that from the structure without baffles. When the piezoelectric beams have rectangular baffles on both sides and the length is 8 mm, the prototype provides a high output voltage over a wide range, and the open-circuit peak-peak voltage is 60.8 V, which is 3.49 times that of the structure without baffles. The strength of the prototype and its feasibility in practice are verified by observing the brightness of the same number of LEDs; it shows great promise for powering microelectronic devices.

A microfluidic device has been designed to electrically measure average intercellular connectivity in a cell monolayer. This proof-of-concept design uses elastomeric microvalves to isolate cells across three microfluidic chambers, creating a direct microscale analog of benchtop sucrose gap physiology rigs. The device operation has been verified for normal rat kidney cells (NRK-49F) using a chemical gap junction blocker, 2-aminoethoxydiphenyl borate (2-APB). At 410 Hz, the system measured an averaged network impedance magnitude between 730 and 930 kΩ and demonstrated the ability to distinguish a significant increase of 6.51 kΩ and 0.464° due to 2-APB perfusion.