We describe the performance of a second-harmonic interferometer (SHI) to measure, on an optical path exceeding 12 m, the electron plasma density of two plasmoids formed in separate theta-pinch chambers and then merged in a central compression chamber after undergoing acceleration and compression. The excellent mechanical stability and a time resolution better than 50 ns suggest the application of SHI, especially in pulsed plasma devices with limited optical accesses.
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http://dx.doi.org/10.1364/ol.37.003855 | DOI Listing |
Anal Chem
January 2025
School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, Liaoning, China.
A cantilever-enhanced fiber-optic photoacoustic (PA) spectrophone is reported for trace gas detection at a low-pressure environment. A cantilever-based fiber-optic Fabry-Perot (F-P) interferometer (FPI) is utilized for simultaneous measurement of air pressure and PA pressure. Since the cantilever resonance frequency follows air pressure linearly, the fundamental frequency intensity modulation (1-IM) technique is applied to scan the frequency response of the solid PA signal from tube wall absorption for tracking the cantilever resonance frequency in real time.
View Article and Find Full Text PDFNat Commun
October 2024
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.
A Second-Harmonic Dispersion Interferometer (SHDI) is assembled to measure the two-dimensional, line-integrated density profile of a pulsed-plasma jet using probe-beam diameters well beyond the 1 mm diameters typically used in such instruments. An initial prototype demonstrated the technique using 7 mm beam diameters, which are now increased to 35 mm diameter using two types of beam expanders: an achromatic-beam expander (ABE) or a reflective-beam expander (RBE). ABEs were found to add a periodic background to the measured-phase image with a magnitude of the order of Δϕ ∼ 2π radians, compared to the background phase noise level in the system configured without beam expanders at Δϕbg ∼ 0.
View Article and Find Full Text PDFRev Sci Instrum
July 2024
Department of Physics, Lund University, P.O. Box 118, 22100 Lund, Sweden.
We present a novel, interferometric, two-color, high-order harmonic generation setup based on a turn-key Ytterbium-doped femtosecond laser source and its second harmonic. Each interferometer arm contains a spatial light modulator with individual capabilities to manipulate the spatial beam profiles and to stabilize the relative delay between the fundamental and the second harmonic. In addition, separate control of the relative power and focusing geometries of the two color beams is implemented to conveniently perform automated scans of multiple parameters.
View Article and Find Full Text PDFUltrasonics
March 2024
Shanghai Key Laboratory of Intelligent Sensing and Detection Technology, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China.
The traditional nonlinear ultrasonic technique, as typified by the second-harmonic generation and the frequency mixing response, can be employed to identify and characterize the micro-damage. However, the research on micro-damage characterization using nonlinear Lamb wave imaging technique remains an ongoing challenge and is rarely reported. A method called standardized amplitude difference is proposed for nonlinear feature enhancement, and further for fatigue crack imaging based on the wavefield data.
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