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Study on the oxidation and release of gases in spontaneous coal combustion using a dual-species sensor employing laser absorption spectroscopy
摘要： Coal spontaneous combustion (CSC) is a common hazard in coal mines and a significant reason for the loss of coal in stockpiles and mines. To investigate the oxidation and release of gas due to of CSC, a miniature purpose-built laser-based sensor system capable of precise gas measurement and data processing was configured. A distributed feedback (DFB) diode laser with a central wavelength of 2.33 μm, in conjunction with a Herriot-type cell and wavelength modulation spectroscopy (WMS), was used for the simultaneous detection of methane (CH4) and carbon monoxide (CO) during coal combustion. The second-harmonic of WMS was applied to ensure sensor robustness and sensitivity with long-term performance for the system being evaluated by calculating the Allan-Werle deviations for the concentrations of CH4 and CO. The limits of detection (LoDs) for CH4 and CO were 0.05 ppm based on integration times of 120 s and 70 s, respectively. The dual-species sensor was employed for real-time and in situ investigations of coal samples for temperatures ranging from 85 °C to 200 °C and was considered suitable for integration into field monitoring equipment, especially for online early warning forecasting applications in CSC.
关键词： Wavelength modulation spectroscopy,Spontaneous coal combustion,Chemical inhibitor,Laser-based dual-species sensor,Self-heating oxidation
更新于2025-09-12 10:27:22
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in a hybrid trap
摘要： We report on the production of a 41K-87Rb dual-species Bose-Einstein condensate in a hybrid trap, consisting of a magnetic quadrupole and an optical dipole potential. After loading both atomic species in the trap, we cool down 87Rb first by magnetic and then by optical evaporation, while 41K is sympathetically cooled by elastic collisions with 87Rb. We eventually produce two-component condensates with more than 105 atoms and tunable species population imbalance. We observe the immiscibility of the quantum mixture by measuring the density profile of each species after releasing them from the trap.
关键词： Bose-Einstein condensate,immiscibility,hybrid trap,dual-species,sympathetic cooling
更新于2025-09-04 15:30:14
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A versatile dual-species Zeeman slower for caesium and ytterbium
摘要： We describe the design, construction, and operation of a versatile dual-species Zeeman slower for both Cs and Yb, which is easily adaptable for use with other alkali metals and alkaline earths. With the aid of analytic models and numerical simulation of decelerator action, we highlight several real-world problems affecting the performance of a slower and discuss effective solutions. To capture Yb into a magneto-optical trap (MOT), we use the broad 1S0 to 1P1 transition at 399 nm for the slower and the narrow 1S0 to 3P1 intercombination line at 556 nm for the MOT. The Cs MOT and slower both use the D2 line (62S1/2 to 62P3/2) at 852 nm. The slower can be switched between loading Yb or Cs in under 0.1 s. We demonstrate that within a few seconds the Zeeman slower loads more than 109 Yb atoms and 108 Cs atoms into their respective MOTs. These are ideal starting numbers for further experiments on ultracold mixtures and molecules.
关键词： caesium,Zeeman slower,dual-species,ytterbium,ultracold atoms,magneto-optical trap
更新于2025-09-04 15:30:14