研究目的
To measure the attenuation of air suspended particles using terahertz and visible light, assess visibility in THz compared to visible range, estimate scattering strength and particle density, and characterize the refractive index of sand grains and glass beads for evaluating THz imaging performance in brownout conditions.
研究成果
The method successfully determines the refractive indices of sand grains (1.67 ± 0.02) and glass beads (2.54 ± 0.05) using simultaneous THz and visible attenuation measurements with Mie theory. These values are consistent with literature for bulk materials. The approach is effective for evaluating THz imaging performance in brownout conditions, though absorption effects are minimal and not quantifiable with current precision. Future work should test other sand types and improve setup for higher density measurements.
研究不足
The absorption coefficient of particles is not measurable with current setup accuracy; it has a weak effect on extinction but cannot be precisely determined. Particle density fluctuations and spectrometer noise introduce errors. The method assumes constant particle size distribution and negligible absorption, which may not hold in all cases. Real brownout conditions might have higher densities or different compositions, requiring further validation.
1：Experimental Design and Method Selection:
The experiment uses a dual-measurement setup with a THz time-domain spectrometer (THz-TDS) and a visible laser diode to measure attenuation through particle suspensions. Mie theory is applied to analyze scattering properties and deduce refractive indices and densities.
2：Sample Selection and Data Sources:
Calibrated sand grains and glass beads with known size distributions are suspended in air within a 3D-printed chamber. Particle size distributions are estimated using image processing.
3：List of Experimental Equipment and Materials:
THz-TDS (MenloSystems TERA K15), 1560 nm femtosecond laser, photoconductive antennas, ammeter, 650 nm laser diode (Apinex), photodiode (BPW24R by Vishay), oscilloscope (PicoScope), diaphragm, fan, cellophane tape, 3D-printed chamber, sand grains, glass beads.
4：Experimental Procedures and Operational Workflow:
THz pulses are generated and detected using photoconductive antennas with a femtosecond laser. The laser diode beam is transmitted through the same sample. Attenuation is measured by comparing intensities with and without particles, using Beer-Lambert law. Data is acquired over time to average fluctuations.
5：Data Analysis Methods:
Fourier transform of time-domain signals, ratio of transmitted to reference intensities, application of Mie theory to compute extinction cross-sections and efficiencies, and statistical averaging over acquisitions to determine refractive indices and densities.
独家科研数据包，助您复现前沿成果，加速创新突破
获取完整内容
