Review of Scientific Instruments最新文献

This study developed and validated an adaptive treatment control system based on affine transformation for accelerator-based boron neutron capture therapy. Accelerator-based boron neutron capture therapy is a form of targeted radiotherapy that uses boron-10 to label tumor cells. When these boron-rich cells interact with neutrons, they produce high-linear energy transfer alpha particles and lithium-7 particles, effectively destroying the tumor cells with precision. The newly developed treatment control system integrates real-time stereoscopic x-ray imaging technology, enabling dynamic adjustments to the treatment plan by continuously monitoring changes in tumors and surrounding tissues. To optimize treatment accuracy, the system employs an affine transformation algorithm, ensuring precise dose delivery and accurate patient positioning. Positioning test results demonstrate that the system excels in its core functionality of ensuring patient positioning accuracy, significantly improving treatment adaptability while minimizing damage to healthy tissues. In addition, the study introduces the accelerator-based boron neutron capture therapy device independently designed and constructed by Lanzhou University. This includes a detailed description of the system's architecture, algorithms, and the principles behind its safety interlock functions. Spatial positioning tests of the device confirmed its high overall positioning accuracy, validating the system's reliability and highlighting its potential for broader applications in cancer treatment.

An optically accessible prechamber-equipped constant volume combustion chamber (CVCC) has been designed and installed at the University of Minnesota to investigate turbulent jet ignition and reacting flows. The CVCC features an optically accessible windowed prechamber, allowing the extensive study of the combustion physics inside the prechamber. The prechamber is also modular, allowing multiple internal geometries and nozzle configurations. Two pairs of optical windows in the main combustion chamber, along with a bottom window axisymmetrically viewing the prechamber nozzle, provide exceptional optical accessibility. Optical techniques such as schlieren imaging and chemiluminescence, along with laser diagnostics, can be employed to gain a fundamental understanding of turbulent jet ignition chemistry. The CVCC is designed to withstand a maximum combustion pressure of 100 bars. Multiple standardized and custom ports on the main chamber allow various fueling techniques and sensor integration. The performance and reliability of the CVCC were demonstrated through prechamber and main chamber visualization studies of nanosecond spark-assisted turbulent jet ignition. The optically accessible prechamber-CVCC setup, therefore, provides a platform for highly detailed combustion analysis.

An instrument employing passive microrheology has been developed for measuring the viscosity of liquids at high temperatures. The viscometer features a dark-field optical microscope, a custom high temperature laser transmission furnace, and flame-sealed capillaries containing microsphere suspensions of test liquids. The Brownian trajectories of individual microspheres were captured in long image sequences and analyzed for their mean square displacement, which provides viscosity via the Stokes-Einstein-Sutherland relation. The viscometer was validated at room temperature with glycerol-water mixtures and at high temperature with water and molten nitrate salt. The measured viscosity was in good agreement with the literature values of each liquid across all temperatures studied (20-450 °C). The measured diffusion coefficient and liquid viscosity achieved <1% and 2%-3.3% uncertainty, respectively, where the latter was limited by the coefficient of variation of the microsphere size distribution. The viscometer could reach temperatures of up to 760 °C, <1 mL sample sizes, high throughput capability with ≈1 min acquisition time, and low cost sample vessels. Importantly, the viscometer recovers the dynamic viscosity without requiring knowledge of either material properties nor a calibration liquid.

Utilizing the Zeeman Faraday effect in atomic vapor cells, a novel setup is introduced both for laser intensity stabilization and laser intensity modulation. The method is based on the closed loop control of the polarization rotation angle of the laser light in an atomic vapor cell for adjustment of the laser intensity. Characterizing the implemented setup, it is shown that more than 30 dB attenuation of the optical fluctuation is achieved in the frequency range from DC to 1 kHz. Meanwhile, the laser intensity could be efficiently locked to a modulating voltage signal, which results in amplitude modulation of the laser beam. We believe that this simple method could be effectively used in different atomic physics experiments, including the stabilization of the laser intensity in applications where near resonance frequency sweeping is required or applications that contain optical modulation of lasers in lock-in detection schemes.

This paper introduces a novel high-performance millimeter-wave diplexer, engineered using a suspended microstrip line and rectangular waveguide, achieving operational bandwidths spanning DC to 40 and 70-110 GHz. The low-pass filter section features a tunable compact microstrip resonant cell based on elliptic filter technology, significantly enhancing transition band suppression. The ability to adjust transition bandwidth and suppression performance through modifications of open-circuit stubs exemplifies the filter's tunability. Distinct from traditional millimeter-wave diplexers, this design incorporates low insertion loss, excellent return loss, and high isolation while offering reconfigurability. This reconfigurability makes the diplexer adaptable for constructing various millimeter-wave applications, including mixers, providing a versatile platform for future technology integrations. The simulation results demonstrate that the diplexer achieves an insertion loss of less than 0.5 dB, a return loss greater than 15 dB, and isolation exceeding 40 dB. In addition, it has a fractional bandwidth exceeding 48.7%, making it suitable for advanced millimeter-wave communication systems and meeting the rigorous standards required for modern diplexer implementations.

We describe a broadband ferromagnetic resonance spectrometer for scientific and educational applications with a frequency range of up to 30 GHz. It is built with components available off-the-shelf, utilizes 3D printed parts for sample holders and support structures, and requires little assembly. A PCB design for the grounded coplanar waveguide (GCPW) is presented and analyzed. We further include a software suite for command-line or script driven data acquisition, a graphical user interface, and a graphical data analysis program. The capabilities of the system design are demonstrated with measurements on ferromagnetic thin films with a thickness of 1 nm. All designs and scripts are published under the GNU GPL v3.0 license.

The symmetry and compactness of the structure has a considerable impact on the properties of piezoelectric motors, including step size, threshold voltage, and effective length. This is particularly evident in motors driven by the inertia principle. Asymmetric and eccentric designs have been observed to result in greater deflections and wobbling during operation, which in turn leads to additional energy loss derived from the energy generated by piezoelectric deformation and further impedes enhancements in overall compactness. In order to address this issue, we present an inertial piezoelectric motor that offers high stability and adaptive symmetry in this paper. The motor's structure ensures that the four edges of the sliding shaft always remain tangent to the inner wall of the piezoelectric tube, thereby achieving a uniform distribution of pressure and friction while ensuring the motor's self-satisfying symmetry and coaxial alignment. The effective length of the piezoelectric motor is only 9 mm, which is just 30% of the length of a conventional inertial piezoelectric motor, exemplifying a remarkably high degree of compactness. With a step size ranging from 0.1 to 1 μm at room temperature and a threshold voltage of about 30 V, these motors are small, simple, and extremely compact, demonstrating significant potential for applications in scanning tunneling microscopes used in narrow and confined spaces.

Linear transformer driver (LTD) is one of the promising technologies for the next-generation petawatt Z-pinch facility. Mismatch between the driver and load can cause energy reflections, resulting in more energy being dissipated in the LTD and causing damage to the devices. An equivalent circuit model based on a 12-stage LTD facility under different operating conditions was established and validated through experimental results over a relatively long time (∼2 μs). Then, circuit simulations were carried out to explore energy distribution under various load impedances, particularly focusing on the reflected energy to the LTD. The simulation results were used to predict capacitor lifetimes in discharge bricks, analyze output gap electric field strengths, and evaluate protective measures for LTD devices. The results with constant load impedance indicate that a near-matched load impedance can dissipate over 83% of the energy in the load region upon its first arrival, significantly higher than that in short-circuit or open-circuit scenarios (less than 1%). However, in practical experiments, the dynamic load is often closer to a short-circuit condition, resulting in LTD devices operating under more strenuous conditions. This is characterized by faster discharge frequencies (f > 1 MHz), higher voltage reversal factors (Q > 2), and stronger electric field strengths across output gaps (>40 kV/cm), all of which may lead to insulation failures or reduced lifetime of LTDs. Increasing the length of the coaxial water transmission line is expected to enhance device longevity and reduce insulation failure risks, offering valuable insights into optimizing design of LTD-based facility.

Recognition and execution of motor imagery play a key role in brain-computer interface (BCI) and are prerequisites for converting thoughts into executable instructions. However, to date, data acquired through commonly used electroencephalography (EEG) methods are very sensitive to motion interference, which will affect the accuracy of the data classification. The emerging functional near-infrared spectroscopy (fNIRS) technique, while overcoming the drawbacks of EEG's susceptibility to interference and difficulty in detecting motor signals, has less publicly available data. In this paper, we designed a motor execution and imagery experiment based on a wearable fNIRS device to acquire brain signals and proposed a modified Kolmogorov-Arnold network (named SE-KAN) for recognizing fNIRS signals corresponding to the task. Due to the small number of subjects in this experiment, the Wasserstein generative adversarial network was used to enhance the data processing. For the fNIRS data recognition task, the SE-KAN method achieved 96.36 ± 2.43% single-subject accuracy and 84.72 ± 3.27% cross-subject accuracy. It is believed that the dataset and method of this paper will help the development of BCI.