Review of Scientific Instruments最新文献

Controlled nucleation and growth of thin films and nanostructured surfaces is one of the fundamental challenges and intriguing aspects of nanomaterials for researchers and manufacturers. The unique properties exploited in the application of nanomaterials rely on controlling the mechanism underlying their synthesis, i.e., the nucleation and growth. Several approaches have been adopted for controlled synthesis of nanomaterials. Herein, we report on the design and building of a pressure controlled vacuum chamber to process thin films under controlled pressure/temperature using xenon flashlamp photonic curing. We built a UV-vis pressure-controlled chamber (PCC) and demonstrated the processing of thin films at pressures varying from 1 to 3.5 atm in different gas environments ranging from inert to reactive gases. Our results showed that the processing of thin films under controlled pressure changes the nano-morphology of thin film growth. The successful implementation of the PCC for photothermal processing of thin films makes it a promising route to control the nucleation and growth of nanomaterials under various conditions for large scale-controlled synthesis of nanomaterials.

This paper presents new type of dual mode sensor for dielectric characterization. The design uses the even mode of the resonator for measuring the dielectric constant of a sample under test. For the odd mode, two identification (ID) transmission lines are loaded such that we obtain four ID combinations (00, 01, 10, and 11). By proper design procedure, the even mode resonances are insensitive to the ID resonator loading, whereas the odd mode resonances are insensitive to the sample characteristics. The dielectric constant and loss tangent are successfully measured with this sensor.

Laser-driven particle acceleration and related laser-matter interaction experiments require an ultrashort pulse laser with high temporal contrast. Here, we presented a plasma mirror (PM) temporal contrast enhancement system implemented at the SG-II 5PW laser facility, with a comprehensive investigation of spatiotemporal properties and physical applications. Key performance parameters of a PM were successfully obtained through single-shot online measurement by combining a spatiotemporally overlapped chirped pulse method. At a 45° incidence angle, the plasma reflectivity reached 84% for S-polarization and 48% for P-polarization, while the focal spot maintained excellent quality and the temporal contrast was improved by two orders of magnitude. The PM system was further applied in proton acceleration experiments under both polarization configurations. Supported by corresponding physical diagnostics, a significant reduction in optimum target thickness from 8 to 0.8 μm was achieved-clear evidence of effective pre-pulse suppression. Additionally, the PM and target installation were evaluated using a triple laser-damaged imaging method, based on the analysis of the three PM damage spots.

Ultrasonic phased array is based on acoustic levitation technology for non-contact manipulation of particles and has a wide range of applications in the fields of biology, micro-assembly, and chemical engineering. However, most current ultrasonic phased arrays are limited by their structure, making it difficult to achieve non-contact transport of microparticles. Therefore, in order to achieve non-contact transport of microparticles, this study proposed an ultrasonic transport system. This system uses an ultrasonic phased array as the end effector and realizes the spatial transport of particles through a multi-degree-of-freedom robotic arm. The experimental results indicate that the ultrasonic transport system proposed in this study can achieve non-contact transport of microparticles. The ultrasonic transport system proposed in this study has a simple structure and small size and can be integrated as an independent non-contact operation module into experimental platforms in different fields, which is expected to promote the application of acoustic manipulation.

We report the design and implementation of the first operational compact platform for strong-field terahertz (THz) pump-ultrafast x-ray probe measurements, which were previously accessible only at large-scale accelerator-based facilities, such as SLAC. Femtosecond laser-driven THz and x-ray sources are optimized by appropriately tuning the chirp of the driving laser pulses to maximize their generation efficiencies. The intense THz pump pulse generated via laser optical rectification in organic crystals delivers peak fields of up to 3 MV/cm and covers the spectral range of 0.1-3 THz. The ultrafast x-ray probe pulse is produced via ultraintense femtosecond laser interactions with tape-like copper foils, yielding a flux of around 105 copper Kα photons/pulse impinging on the sample at a repetition rate of 100 Hz. The spatial overlap and temporal synchronization of THz and x-ray pulses are achieved with the aid of an auxiliary near-infrared laser pulse. THz pump-x-ray probe measurements on the ultrafast structural phase transition of vanadium dioxide are performed as an example to demonstrate the capability of the platform. Such an all-optical tabletop platform enables the selective excitation and control and in situ high-temporal-resolution detection of ultrafast lattice structural dynamics, offering a unique tool for the study of ultrafast materials science and non-equilibrium physics.

We present the combination of a broadband terahertz time-domain spectroscopy system (0.1-8 THz), a diamond anvil cell (DAC) capable of generating high pressure conditions of up to 10 GPa, and a cryostat reaching temperatures as low as 10 K. This combination allows us to perform equilibrium and time-resolved THz spectroscopy measurements of a sample while continuously tuning its temperature and pressure conditions. In this study, the procedures and characterizations necessary to carry out such experiments in a tabletop setup are presented. Due to the large modifications of the terahertz beam as it goes through the DAC, standard terahertz time-domain spectroscopy analysis procedures are no longer applicable. New methods to extract the pressure dependent material parameters are presented, both for samples homogeneously filling the DAC sample chamber as well as for bulk samples embedded in pressure media. Different pressure media are tested and evaluated using these new methods, and the obtained material parameters are compared to literature values. Time resolved measurements under pressure are demonstrated using an optical pump-THz probe scheme.

High-voltage (HV) DC power supplies, defined here as sources providing DC output in the kilovolt range (typically a few to a few tens of kilovolts), are critical in scientific and industrial applications that demand low ripple, high efficiency, precise voltage regulation, and low stored energy. Achieving these requirements is challenging due to the significant parasitic elements of HV high-frequency transformers, such as leakage inductance (Lleak), reflected winding capacitance (Cp), and magnetizing inductance (Lp), which increase circulating currents and reduce efficiency. To address these challenges, this work proposed an optimal design methodology for a fourth-order LCLC resonant converter that gainfully integrates Lleak, Cp, and Lp into the resonant tank circuit. A steady-state analysis and design methodology is developed to ensure unity power factor (UPF) operation, soft-switching in entire load range (ZCS turn-onturn-off), and load-independent constant voltage output characteristics. In addition, a kVA/kW size optimization technique is presented to minimize stored reactive power at the optimal quality factor (Qs,opt=1/γ, where γ = Lp/Ls denotes the magnetizing to series inductance ratio. A scaled down -5 kV prototype validates the proposed research, demonstrating UPF operation, soft-switching, a peak efficiency of 97.26%, and ∼6.4% voltage regulation at 20% load, thereby confirming the validity of the theoretical analysis.

Circular dichroism spectroscopy is known to provide important insights into the interplay of different degrees of freedom in quantum materials, and yet spectroscopic study of the optoelectronic responses of quantum materials to structured optical fields, such as light with finite spin and orbital angular momentum, has not yet been widely explored, particularly at cryogenic temperature. Here, we demonstrate the design and application of a novel instrument that integrates scanning spectroscopic photocurrent measurements with structured light of controlled spin and orbital angular momentum. For structured photons with wavelengths between 500 and 700 nm, this instrument can perform spatially resolved photocurrent measurements of two-dimensional materials or thin crystals under magnetic fields up to ±14 T, at temperatures from 400 K down to 3 K, with either spin angular momentum ±h or orbital angular momentum ± ℓh (where ℓ = 1, 2, 3… is the topological charge), and over a (35 × 25) μm2 area with ∼1 μm spatial resolution when coupling with a f = 75 mm objective lens at 3 K. These capabilities of the instrument are exemplified by magneto-photocurrent spectroscopic measurements of monolayer 2H-MoS2 field-effect transistors, which not only reveal the excitonic spectra but also demonstrate monotonically increasing photocurrents with increasing |ℓ| and excitonic Zeeman splitting and an enhanced Landé g-factor due to the enhanced formation of intervalley dark excitons under magnetic field. These studies thus demonstrate the versatility of the scanning photocurrent spectrometry for investigating excitonic physics, optical selection rules, and optoelectronic responses of novel quantum materials and engineered quantum devices to structured light.

Levitated optical mechanical systems have demonstrated excellent force and impulse sensitivity and are currently being developed for the creation of non-classical states of motion in these new quantum systems. An important requirement in the design of these systems is the ability to independently control and cool all three translational degrees of freedom. Here, we describe the design and implementation of a stable and robust 3D velocity feedback cooling scheme with particular emphasis on creating minimal crosstalk between the independent oscillatory modes when cooling.