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A brief review of antimatter production
Yu-Gang Ma, Jin-Hui Chen, Liang Xue
Frontiers of Physics. 2012, 7 (6 ): 637-646.
https://doi.org/10.1007/s11467-012-0273-9
In this article, we present a brief review of the discoveries of kinds of antimatter particles, including positron (e ˉ ), antiproton (p ˉ ), antideuteron (d ˉ ) and antihelium-3 (H e ˉ 3 ). Special emphasis is put on the discovery of the antihypertriton(3 Λ H ˉ ) and antihelium-4 nucleus (H e ˉ 4 , or α ˉ ) which were reported by the RHIC-STAR experiment very recently. In addition, brief discussions about the effort to search for antinuclei in cosmic rays and study of the longtime confinement of the simplest antimatter atom, antihydrogen are also given. Moreover, the production mechanism of anti-light nuclei is introduced.
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Multi-element analysis by ArF laser excited atomic fluorescence of laser ablated plumes: Mechanism and applications
Yue Cai, Po-Chun Chu, Sut Kam Ho, Nai-Ho Cheung
Frontiers of Physics. 2012, 7 (6 ): 670-678.
https://doi.org/10.1007/s11467-012-0264-x
A new multi-element analysis technique based on laser-excited atomic fluorescence was reviewed. However, the one-wavelength-one-transition constraint was overcome. Numerous elements were induced to fluoresce at a single excitation wavelength of 193 nm. This was possible provided that the analytes were imbedded in dense plumes, such as those produced by pulsed laser ablation. The underlying mechanism of the technique was explained and corroborated. Analytical applications to metals, plastics, ceramics and their composites were discribed. Detection limits in the ng/g range and mass limits of atto moles were demonstrated. Several real-world problems, including the analysis of paint coating for trace lead, the non-destructive analysis of potteries and ink, the chemical profiling of electrode–plastic interfaces, and the analysis of ingestible lead colloids were discussed.
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Recent progress on the application of LIBS for metallurgical online analysis in China
Feng-Zhong Dong, Xing-Long Chen, Qi Wang, Lan-Xiang Sun, Hai-Bin Yu, Yun-Xian Liang, Jing-Ge Wang, Zhi-Bo Ni, Zhen-Hui Du, Yi-Wen Ma, Ji-Dong Lu
Frontiers of Physics. 2012, 7 (6 ): 679-689.
https://doi.org/10.1007/s11467-012-0263-y
Recent progress on the application of laser-induced breakdown spectroscopy (LIBS) for metallurgical analysis particularly achieved by Chinese research community is briefly reviewed in this article. The content is mainly focused on the progress in experimental research and calibration methods toward LIBS applications for metallurgical online analysis over the past few years. Different experiment setups such as single-pulse and double-pulses LIBS schematics are introduced. Various calibration methods for different metallic samples are presented. Quantitative results reported in the literature and obtained in the analysis of various samples with different calibration methods are summarized. At the last section of this article, the difficulties of LIBS application for molten metal analysis in a furnace are discussed.
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Recent progress on laser-induced breakdown spectroscopy for the monitoring of coal quality and unburned carbon in fly ash
LeiZhang (张雷), Zhi-YuHu (胡志裕), Wang-Bao Yin (尹王保), Dan Huang (黄丹), Wei-Guang Ma (马维光), Lei Dong (董磊), Hong-Peng Wu (武红鹏), Zhi-Xin Li (李志新), Lian-Tuan Xiao (肖连团), Suo-Tang Jia (贾锁堂)
Frontiers of Physics. 2012, 7 (6 ): 690-700.
https://doi.org/10.1007/s11467-012-0259-7
Our recent progress on developments of laser-induced breakdown spectroscopy (LIBS) based equipments for on-line monitoring of pulverized coal and unburned carbon (UC) level of fly ash are reviewed. A fully software-controlled LIBS equipment comprising a self-cleaning device for on-line coal quality monitoring in power plants is developed. The system features an automated sampling device, which is capable of elemental (C, Ca, Mg, Ti, Si, H, Al, Fe, S, and organic oxygen) and proximate analysis (Q ad and A ad) through optimal data processing methods. An automated prototype LIBS apparatus has been developed for possible application to power plants for on-line analysis of UC level in fly ash. New data processing methods are proposed to correct spectral interference and matrix effects, with the accuracy for UC level analysis estimated to be 0.26%.
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Detection of explosives with laser-induced breakdown spectroscopy
Qian-Qian Wang, Kai Liu, Hua Zhao, Cong-Hui Ge, Zhi-Wen Huang
Frontiers of Physics. 2012, 7 (6 ): 701-707.
https://doi.org/10.1007/s11467-012-0272-x
Our recent work on the detection of explosives by laser-induced breakdown spectroscopy (LIBS) is reviewed in this paper. We have studied the physical mechanism of laser-induced plasma of an organic explosive, TNT. The LIBS spectra of TNT under single-photon excitation are simulated using MATLAB. The variations of the atomic emission lines intensities of carbon, hydrogen, oxygen, and nitrogen versus the plasma temperature are simulated too. We also investigate the time-resolved LIBS spectra of a common inorganic explosive, black powder, in two kinds of surrounding atmospheres, air and argon, and find that the maximum value of the O atomic emission line SBR of black powder occurs at a gate delay of 596 ns. Another focus of our work is on using chemometic methods such as principle component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) to distinguish the organic explosives from organic materials such as plastics. A PLS-DA model for classification is built. TNT and seven types of plastics are chosen as samples to test the model. The experimental results demonstrate that LIBS coupled with the chemometric techniques has the capacity to discriminate organic explosive from plastics.
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Major elements analysis in bituminous coals under different ambient gases by laser-induced breakdown spectroscopy with PLS modeling
Zhe Wang, Ting-Bi Yuan, Siu-Lung Lui, Zong-Yu Hou, Xiong-Wei Li, Zheng Li, Wei-Dou Ni
Frontiers of Physics. 2012, 7 (6 ): 708-713.
https://doi.org/10.1007/s11467-012-0262-z
Three major elements, carbon, hydrogen, and nitrogen, in twenty-four bituminous coal samples, were measured by laser-induced breakdown spectroscopy. Argon and helium were applied as ambient gas to enhance the signals and eliminate the interference of nitrogen from surrounding air. The relative standard deviation of the related emission lines and the performance in the partial least squares (PLS) modeling were compared for different ambient environments. The results showed that argon not only improved the intensity, but also reduced signal fluctuation. The PLS model also had the optimal performance in multi-element analysis using argon as ambient gas. The root mean square error of prediction of carbon concentration decreased from 4.25% in air to 3.49% in argon, while the average relative error reduced from 4.96% to 2.98%. Hydrogen line demonstrated similar improvement. Yet, the nitrogen lines were too weak to be detected even in an argon environment which suggested the nitrogen signal measured in air come from the breakdown of nitrogen molecules in the atmosphere.
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Study on parameters influencing analytical performance of laser-induced breakdown spectroscopy
Yong Zhang, Yun-Hai Jia, Jin-Wen Chen, Xue-Jing Shen, Lei Zhao, Chun Yang, Yong-Yan Chen, Yong-Hui Zhang, Peng-Cheng Han
Frontiers of Physics. 2012, 7 (6 ): 714-720.
https://doi.org/10.1007/s11467-012-0267-7
Lens-to-sample distances, delay time, atmospheric condition, laser pulse energy, etc. had obvious effects on the analytical performance of laser-induced breakdown spectroscopy. In this paper, these parameters are investigated in greater detail and we will explain how they have influences on the analytical performance. The results show that the focal plane under the sample surface can improve precision and detection limit, and the delay time should be decided according to sensitivity and accuracy. Spectral line intensity is stronger in argon than helium, nitrogen and air gas environment. Pulse energy should exceed energy threshold (about 50 mJ) which can generate plasma, and the energy should not exceed about 300 mJ to avoid plasma shielding. Under optimum parameters, concentration relative standard deviation of C, Si, Mn, P, S, Ni, and Cr for low-alloyed steel (sample number 11278) which were measured 11 times is 2.37%, 2.18%, 2.23%, 7.8%, 9.34%, 1.92%, and 2.13%, respectively. And the detection limit of C, Si, Mn, P, S, Ni, and Cr for pure steel is 0.0045%, 0.0072%, 0.0069%, 0.0027%, 0.0024%, 0.0047%, and 0.0024%, respectively.
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