Review of Scientific Instruments最新文献

Since their discovery over 90 years ago, neutrons have become one of the premier tools in the study of the structure and dynamics of matter and materials. The main nuclear processes to generate a large number of free neutrons are fusion, fission, and spallation, which have been well established for using neutrons in broad areas of physics, material science, engineering, life sciences, and elsewhere. The vast majority of experiments that use neutrons as a probe require a directional, well-collimated beam of neutrons. Over the years, methods have been developed to deliver such neutron beams sufficiently, but it is still much desired to improve the efficiency of neutron sources. With the advent of high-powered lasers, laser-driven neutron sources suggest an attractive possibility. Laser photons can be converted to neutrons by accelerating particles (electrons, protons, and deuterons) and then either utilize hard x rays from, for example, electron acceleration to create photoneutrons or nuclear reactions, such as deuteron break-up. The maturity of such processes in recent years might have reached a state where such neutron sources are becoming useful and beneficial to the neutron community. In the present report, the current state-of-the-art of a laser-driven neutron source and its future development for neutron applications are presented, and existing sources are described. The basic physical principles of laser-driven neutron production and the current state-of-the-art of production techniques are outlined. The potential developments and the role of such sources in the landscape of neutron sources in the future are critically commented on.

Local shot noise spectroscopy with scanning tunneling microscopy (STM) has proven to be a powerful technique to investigate the electronic properties of quantum materials. It provides direct and non-invasive insight into the tunneling charge quanta or dynamics at the atomic scale. Due to the typically weak noise signal and the presence of low frequency spurious noise, local noise experiments require a high-resolution measurement amplifier. Here, we present a newly developed high-resolution noise amplifier that we implemented in three different STMs. Compared to our previous generation, we obtain more than a 20-fold improvement in the noise resolution, allowing us to resolve values of the effective charge as small as 0.01e. Our amplifier opens new possibilities for studying electronic properties in novel materials such as d-wave superconductors. In addition to this, it can give direct information about the local electron temperature in STM experiments.

The objective of the APEX (A Positron-Electron eXperiment) project is to magnetically confine and study positron-electron pair plasmas. For this purpose, a levitated dipole trap (APEX-LD) has been constructed. The magnetically levitated, compact (7.5-cm radius), closed-loop, high-temperature superconducting floating (F-)coil consists exclusively of a no-insulation rare-earth barium copper oxide winding pack, solder-potted in a gold-plated-copper case. A resealable in-vacuum cryostat facilitates cooling (via helium gas) and inductive charging of the F-coil. The 70-min preparation cycle reliably generates persistent currents of ∼60 kA-turns and an axial magnetic flux density of B0 ≈ 0.5 T. We demonstrate levitation times in excess of 3 h with a vertical stability of σz < 20 μm. Despite being subjected to routine quenches (and occasional mechanical shocks), the F-coil has proven remarkably robust. We present the results of preliminary experiments with electrons and outline the next steps for injecting positron bunches into the device.

Recent advances in ion diagnostics for laser-induced plasma experiments have improved system design and data analysis. Measuring charged particle emissions from laser-irradiated targets provides valuable insights into laser-matter interactions. Among real-time diagnostics, Time-of-Flight (TOF) detectors are reliable systems for analyzing particle beam properties such as kinetic energy and shot-to-shot reproducibility. Diamond-based detectors are ideal for TOF measurements due to their fast response time, radiation hardness, and low leakage current. However, TOF detectors lack particle discrimination. To overcome this, a Multi Filter Diamond Array (MFDA) was developed using six nominally identical single crystal diamond detectors paired with aluminum foils of different thicknesses to exploit particle stopping power differences. The MFDA was tested at the Prague Asterix Laser System during an experimental campaign in the framework of the FUSION project, and data analysis was performed. A cross-validation with other diagnostics, including a Thomson Parabola Spectrometer and CR-39 detectors, is also presented.

We report the development of a cryogenic powder filter that simultaneously offers high attenuation of radio frequency (RF) signals in the gigahertz range and minimized parasitic capacitance to ground. Conventional powder filters, which consist of a signal line passing through a metal powder-filled housing, attenuate high-frequency signals via the skin effect. However, these designs often suffer from significant parasitic capacitance between the signal line and the grounded chassis, which can compromise the performance of sensitive measurement setups by limiting their frequency bandwidth. In this work, we demonstrate that a multilayer powder filter design effectively achieves both high RF attenuation and reduced parasitic capacitance. This solution suppresses sample heating due to the unintentional intrusion of RF signals through the wiring, without degrading the performance of the measurement setup.

Lead zirconate titanate (PZT) bimorph mirrors are essential for performing multiple functions, such as beam shaping, wavefront correction, and dynamic focusing with adjustable beam sizes. They typically consist of a mirror substrate with PZT electrodes bonded to the substrate using a thin epoxy film. However, glue-bonded PZT mirrors exhibit low reproducibility in measurement results. One source of this variability is water absorption by the substrate's epoxy adhesive during wet fabrication processes, such as elastic emission machining (EEM), which leads to swelling and deformation. Additionally, longer deformable bimorph mirrors require larger PZT electrodes, further complicating their design and fabrication, particularly during bonding and ultraprecise metrology. To address these challenges, silver nanoparticles were employed to bond PZT elements to the silicon (Si) mirror, eliminating the need for epoxy glue. In this study, we developed an inorganic-glue-free PZT bimorph mirror with a length of 460 mm and 28 channels. The glue-free bonding method successfully ensured the high reproducibility of measurements after water immersion. This approach resulted in a shape error of only 0.41 nm root mean square after the figure correction process using an ultraprecise EEM process. Scanning acoustic tomography and basic response function tests confirmed the success of the bonding process, showing no critical voids. Furthermore, the shape changes induced by applying voltages to the PZT electrodes closely matched predictions obtained from simulations. These results demonstrate the reliability and precision of the proposed glue-free bonding technique, paving the way for improved performance of new PZT bimorph mirrors.

The world's strongest bio-based filament is currently produced from the wet spinning of cellulose nanofibrils. Such filaments could provide sustainable alternatives to currently available reinforcement fibers for high performance composites. Finding the weakest point of such filaments is of critical importance to their final application. However, what constitutes the weakest point in these filaments has yet to be determined with any certainty. Laser diffraction in conjunction with the Fraunhofer (single-slit) approximation could provide a rapid, nondestructive defectoscopy technique. Finding the thinnest point is the most accurate estimate of the breakpoint, with a mean distance-to-breakpoint of 1100 ± 200 μm, whereas the most precise determination of the weakest point is establishing which point is the least slit-like (48% of all cases). Combining width and propensity to be more or less slit-like was attempted to provide an accurate and precise metric ('the failure factor'). With an accuracy of 1000 ± 200 μm, this is the best possible estimate using the methodology presented here. The results indicate a need for further refinement of the method. Incorporating machine learning algorithms would increase reliability by circumventing the need for approximations. Performing high-resolution tomograms of the samples to take into account the cross-sectional circularity could be implemented as an additional in-depth secondary method. With the technique already presenting advantages in terms of speed and cost compared to other methods, e.g., electron microscopy, such instruments could be integrated into a production line, providing real-time defectoscopy and quality control.

Hefei Advanced Light Facility is a diffraction-limited synchrotron radiation light source in the soft x-ray range. The BL04 beamline needs micro-focusing spots for spatial and time-resolving experiments, and the Kirkpatrick-Baez mirror system is adopted as a post-focusing system. In this paper, a high-precision mirror bender with flexure mechanism modules has been designed to dynamically bend the flat mirror to an elliptical form. Given the required high surface accuracy, the mirror bender is optimized with the variable mirror profile. The bending moments can be applied independently on the bender ends, so the mirror can be bent to a different elliptical form, meeting the needs of focusing on different experimental stations. Based on the optomechanical design, the mirror bender can bend a 500 mm long flat mirror to an elliptical form with a small radius of curvature (∼400 m). When focused on the photo emission electron microscopy station, the residual slope error of the bent mirror surface is optimized to 7.2 nrad (rms). This work introduces the bender's optomechanical design and simulation process for verification. In addition, the machining and assembly errors' influence on the bending surface is evaluated and the influence of mirror substrate manufacturing errors on surface accuracy is systematically discussed. The tolerance requirements for mirror manufacturing are specified based on the analysis results. The optomechanical design and optimization for the bender provide a reference for subsequent engineering design.

To solve light loss from dead zones between Geiger-mode avalanche photodiode cells in silicon photomultipliers (SiPMs), this paper proposes a dead-zone light recovery scheme using focon/tapered fiber arrays. A microlens-like alignment method achieves precise fiber-SiPM integration. A multi-physics coupling simulation model compares light transmission and photoelectric response of original SiPM, tapered fiber-SiPM, and focon-SiPM under 13/25 μm cell sizes. Simulations show that under 300-1100 nm incident light, both structures significantly optimize SiPM performance: Tapered fibers boost average photocurrent by 70.19% and effective fill factor by 69.93% for 13 μm cells and 35.56%/33.84% for 25 μm cells. Focons show slightly lower improvements (68.77%/68.90% for 13 μm and 32.04%/30.84% for 25 μm). Neither scheme affects SiPM electrical stability. Tapered fibers excel in light recovery under small incident angles and wide bands, with applications in low-light detection (PET imaging, automotive light detection and ranging, and bioluminescence detection).

Perfect laser mode is required in many research fields such as quantum computing and precision measurement. Fiber optics provides a useful tool for maintaining a high quality laser when transmitting the laser over a long distance. Fiber link between modular structures of complicated optical paths increases the effectiveness and robustness of the optical experiment. It is a key element in coupling the laser into fiber with high efficiency in fiber optics applications. However, in confined or vacuum environments, such as spacecraft cabins, manual alignment is nearly impossible, highlighting the need for automated solutions. In this study, we experimentally investigated several automatic coupling algorithms, including the iterative scanning method and three global optimization algorithms. The results show that Bayesian optimization, by exploiting multidimensional control and high-precision actuation, enabled the coupling efficiency to reach its maximum of higher than 93% within 10 s. These algorithms provide repeatable and high-precision fiber alignment solutions for all-optical experiments under different conditions.