Microplastics are an emerging marine pollutant, and their negative impacts on the photosynthetic efficiency of marine photoautotrophs are gradually endangering marine ecosystems and biota. To analyze and solve the impact of microplastic particles on light propagation in the ocean, the investigation of radiative properties of microplastic particles is essential. The extinction and absorption coefficients of polyamide-12 (PA12) with different particle concentrations are experimentally measured using transmission and integration methods in the spectral range of 200 to 1100 nm. The extinction and absorption cross sections are obtained from the measured extinction and absorption coefficients. The measured PA12 absorption peaks, located at 692, 728, 764, 835, and 940 nm, correspond to the vibrational absorption of methylene groups (-CH 2 ) and amide groups (CO-NH). The scattering albedo of PA12 is mostly above 0.7 in the visible spectral, indicating that PA12 is a scattering dominated medium. The measured radiative properties of PA12 provide optical parameters for determining the radiative transfer containing microplastics.

The field null configuration of a poloidal magnetic field is one of the critical conditions for achieving Ohmic breakdown during the initial discharge of a new tokamak. The issue of the Ohmic breakdown on the NanChang Spherical Tokamak (NCST) is still not solved satisfactorily although plasma currents of about 2 kA were found. Hence, a removable three-dimensional magnetic probe (RTMP) system consisting of 25 magnetic probes was designed, calibrated, and constructed on the NCST to evaluate the field null inside a vacuum vessel. After repeated tests, the RTMP system exhibited outstanding performance in terms of accuracy and stability with errors of about 1%. Meanwhile, the RTMP system successfully measured the toroidal field (TF) coil ripples at the magnetic axis. During experiments, the stray field arising from the TF coil implied a strong link between the flexible connection of the TF coil and the Ohmic breakdown on the NCST. After the field null was effectively modified by using a new flexible connection of the TF coil and controlling the induced current in the poloidal field coil, the NCST tokamak reproducibly obtained 20 kA plasma current with the limiter configuration during the plasma current flat-top phase.