Spectral Analysis of the Light Flash Produced by a Natural Dolomite Plate Under Strong Shock

Transcription

1 Plasma Science and Technology, Vol.17, No.5, May 2015 Spectral Analysis of the Light Flash Produced by a Natural Dolomite Plate Under Strong Shock TANG Enling ( ) 1, XU Mingyang ( ) 1, ZHANG Qingming ( ) 2, SHI Xiaohan ( ) 1, WANG Meng ( ) 1, WANG Di ( ) 1, XIANG Shenghai ( ) 1,XIAJin( ) 1, HAN Yafei ( ) 1, ZHANG Lijiao ( ) 1,WUJin( ) 1, ZHANG Shuang ( ) 1, YUAN Jianfei ( ) 1 1 School of Equipment Engineering, Shenyang Ligong University, Shenyang , China 2 State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing , China Abstract In order to obtain the elemental compositions of the projectile and target materials during 2A12 aluminum projectile shot on a natural dolomite plate, three kinds of experiments have been conducted using a spectral acquirement system established on a two-stage light gas gun for impact velocities ranging from 2.20 km/s to 4.20 km/s, at the same projectile incidence angle of 30 o. Experimental results show that the elemental compositions of the projectile and target materials in the strong shock experiments have a good agreement with the original elemental compositions of the projectile and target. In addition, the relations between spectral radiant intensity and elemental compositions of the projectile and target materials have been obtained for different impact velocities, in which the spectral radiant intensity of the main elements in the material increases with increasing impact velocity, and more elements appear with increasing impact velocity since more energy would result from a higher velocity impact. Keywords: strong shock, light flash, spectral analysis, spectral radiant intensity PACS: Kw, Pa, Lc DOI: / /17/5/08 (Some figures may appear in colour only in the online journal) 1 Introduction Light flash is caused by emissions from a jet of shocked material which is thrown from the shock point. This phenomenon is under consideration for deep space exploration and missile defense applications. Spectral signatures created by a strong shock can be utilized as the basis for deep space exploration, which can characterize the elemental composition of the projectile and target materials. Experimental studies have shown that spectral radiation from a hypervelocity impact can be used to predict impact parameters related to the projectile and target materials [1 4]. In order to analyze physical phenomena associated with impact light flash in the impact event, the radiated energy is assumed to arise from high temperature metallic gas at the interface of the projectile and target interaction. Under the condition of high temperatures, the hot gas will be in a plasma state. The total radiation emitted from a unit volume of plasma is in local thermodynamic equilibrium, which contain atoms, ions and electrons [5 11]. Researchers have obtained an analytical model of iron and aluminum plasma. However, there are few researchers to study the spectrograph and elemental compositions of the projectile and target during hypervelocity impacts. In the paper, the authors have established a spectral acquirement system for light flash and conducted three kinds of experiments to acquire spectra for the light flash generated by a natural dolomite plate under strong shock. Relations between spectral radiant intensity and elemental compositions of the projectile and target materials have been obtained for different impact velocities. 2 Experimental and spectral acquirement systems Laboratory experiments were performed by twostage light gas gun at the Intense Dynamic Loading Research Center of Shenyang Ligong University. The experiments were carried out under near-vacuum conditions in a chamber large enough to allow free expansion of the impact plume and ejection without interference from the chamber walls. The two-stage light gas gun launched a sphere shaped 2A12 aluminum projectile. The projectile is separated from the sabot in the expansion chamber after flying a certain distance in the supported by National Natural Science Foundation of China (Nos , ), State Key Program of National Natural Science of China (No ), Program for Liaoning Excellent Talents in University of China (No. LR ) 409

2 expansion chamber, and then enters the chamber to impact the target. The optical probe of the spectral analyzer is pointed directly at the impact point, and spectral radiant intensity signals of different elements were acquired during the stage of the projectile interacting with the target. The spectral signals acquired were input to an Echelle Spectra Analyzer (ESA4000) via an optical fiber beam, which was made by LLA Instruments GmbH Company in Germany. ESA 4000 is a spectrometer system for simultaneous measurement of complex spectra within the entire UV/VIS-range. ESA 4000 consists of two units, the spectrograph and the electronic control system. It is available as an OEM item for integration into 19 racks for industrial applications. The standard configuration is the Lab version with the control unit in a table housing and a free accessible spectrograph for use in a laboratory. The spectra analyzer can perform spectral signals acquirement by an intensification charge-coupled device (ICCD) and optical grating, and the real-time data were input to the Industrial Personal Computer (IPC) via a data line. The schematic of the spectral measurement system for the light flash is shown in Fig. 1. Plasma Science and Technology, Vol.17, No.5, May Rectangular coordinate system and layout of the fiber probe In order to position the optical fiber probes, we used a Cartesian coordinate system (x, y, z) with the origin at the point of shock, where +z measures the height above the target surface, +y the distance in front of the shock point, and +x the distance away from the projectile line of flight in a right-handed sense. The optical fiber probe is placed away from the shock point, and directly pointed to the shock point. In the experiments, the Cartesian coordinates of the optical fiber probe are (0, 0, 90), respectively. Fig. 2 shows the layout of the target and the optical fiber probe in the chamber. Fig.2 The layout of the target and the optical fiber probe in the chamber 4 Experimental results and analysis Fig.1 Schematic of the spectral measurement system for the light flash 3 Laboratory experiments 3.1 Experimental basic parameters The material of the projectile is 2A12 aluminum, which is a solid sphere with a diameter of 4.6 mm. The target is a natural dolomite plate of 20 mm in thickness, which was produced in the mountain area in Xiuyan County of Liaoning province, China. The chemical composition of the 2A12 aluminum projectile includes silicon, iron, magnesium, manganese, copper, zinc, titanium, nickel and aluminum. The chemical composition of the natural dolomite plate is CaMg(CO 3 ) 2, the specific material component MgO accounted for 21%, CaO accounted for 31% and CO 2 accounted for 48%. Table 1 lists the basic experimental parameters. Fig. 3 shows the original relations between spectral radiant intensity and wavelengths for three kinds of impact parameters. One can see from Fig. 3 that the elemental compositions of the projectile and target materials were indeed obtained by strong shock light flash experiments, and include a lot of elements. These small peaks seem to reveal some elements, yet all of these small peaks can not show the elemental compositions of the projectile and target materials before comparison with standard elemental spectrographs. In order to clearly reveal the elemental compositions of the projectile and the target materials, the integral spectral signals must be cut into a lot of parts to obtain the real elemental compositions by comparison with standard elemental spectral graphs. In order to clearly identify the elemental compositions in different wavelength ranges, the spectral graph of the integral wavelength range was cut into four segments. Figs. 4-6 show spectral graph segments cut from the integral wavelength range from 250 nm to 870 nm during strong shock experimental shots , and , respectively. Table 1. Basic experimental parameters No. Impact velocity Impact angles Distance between shock point and Chamber pressure (km/s) ( o ) the optical fiber probe (mm) (Pa)

3 TANG Enling et al.: Spectral Analysis of the Light Flash Produced by a Natural Dolomite Plate Fig.3 (a) Original experimental spectral radiant intensity versus the wavelength in shot , (b) Original experimental spectral radiant intensity versus the wavelength in shot , (c) Original experimental spectral radiant intensity versus the wavelength in shot Fig.4 (a) Spectral graph segment cut from the integral wavelength range from 250 nm to nm in shot , (b) Spectral graph segment cut from the integral wavelength range from nm to nm in shot , (c) Spectral graph segment cut from the integral wavelength range from nm to nm in shot , (d) Spectral graph segment cut from the integral wavelength range from nm to nm in shot

4 Plasma Science and Technology, Vol.17, No.5, May 2015 Fig.5 (a) Spectral graph segment cut from the integral wavelength range from 250 nm to nm in shot , (b) Spectral graph segment cut from the integral wavelength range from nm to nm in shot , (c) Spectral graph segment cut from the integral wavelength range from nm to nm in shot , (d) Spectral graph segment cut from the integral wavelength range from nm to nm in shot Fig.6 (a) Spectral graph segment cut from the integral wavelength range from 250 nm to nm in shot , (b) Spectral graph segment cut from the integral wavelength range from nm to nm in shot , (c) Spectral graph segment cut from the integral wavelength range from nm to nm in shot , (d) Spectral graph segment cut from the integral wavelength range from nm to nm in shot

5 TANG Enling et al.: Spectral Analysis of the Light Flash Produced by a Natural Dolomite Plate One can see from Fig. 7(a) that the elemental compositions of the projectile and target materials contain silicon, iron, copper, magnesium, titanium and aluminum, for which the integral elemental spectrograph was cut into 26 segments. Furthermore, the percent contents of the weight for silicon, iron, copper, magnesium and titanium are given by the spectral graph, from which the percent contents are obtained as , , 36.22, and 1.885, respectively. One can see from Fig. 7(b) that the elemental compositions of the projectile and target materials contain iron and aluminum, for which the integral elemental spectrograph was cut into 26 segments. Furthermore, the percent contents of the weight for iron are given by the spectrograph, from which the percent contents is obtained as One can see from Fig. 7(c) that the elemental compositions of the projectile and target materials contain silicon, iron, zinc, chromium, titanium and aluminum, for which the integral elemental spectrograph was cut into twenty-six segments. Furthermore, the percent contents of the weight for silicon, iron, zinc, chromium, and titanium are given by the spectrograph, from which the percent contents are obtained as , , , and 0.204, respectively. Fig. 8 shows that the elemental compositions of the projectile and target can be obtained through acquirement of spectral signals by hypervelocity impact light flash experiments. Three kinds of experiments reveal that 2A12 aluminum contain silicon, iron, copper, magnesium, manganese, zinc, titanium, nickel and aluminum, which are the basic elemental compositions of 2A12 aluminum, and aluminum is the main element in 2A12 aluminum. The natural dolomite plate contains magnesium, calcium and carbonate, yet the calcium and carbonate elements can not be obtained. The authors think that the impact energy is not enough to destroy the chemical bond between calcium and carbonate. Furthermore, the spectral radiant intensity of the main element would increase with increasing impact velocity, and more elements appear with increasing impact velocity since more energy is emitted from a higher velocity impact. (a) The real elemental compositions of the light flash in shot , (b) The real elemental compositions of the light flash in shot , (c) The real elemental compositions of the light flash in shot Fig.7 The real elemental compositions of the light flash at different wavelengths and impact parameters Fig.8 (a) The relation between spectral radiant intensity and wavelength of elements in shot , (b) The relation between spectral radiant intensity and wavelength of elements in shot , (c) The relation between spectral radiant intensity and wavelength of elements in shot Conclusion Elemental compositions of the projectile and target can be obtained through acquirement of spectral signals by hypervelocity impact light flash experiments. 413

6 Plasma Science and Technology, Vol.17, No.5, May 2015 Experimental results certified that the elemental compositions of the projectile and target materials contain silicon, iron, copper, magnesium, manganese, zinc, titanium, nickel, calcium, carbonate and aluminum, and aluminum and magnesium are the main elements in the projectile and the target. The spectral radiant intensity of the main elements would increase with increasing impact velocity, and more elements appear with increasing impact velocity since more energy is emitted from a higher impact velocity. References 1 Bellot Rubio L R, Ortiz J L, Sada P V. 2000, The Astrophysical Journal, 82-83: Ortiz J L, Quesada J A, Aceituno J, et al. 2002, The Astrophysical Journal, 576: Schultz P H, Ernst C M, Anderson L B. 2005, Space Science Reviews, 117: Eichhorn G. 1976, Planetary and Space Sciences, 24: Artem eva N A, Kosarev I B, Nemtchinov I V, et al. 2001, Solar System Research, 35: Tang E L, Zhang Q M, Zhang J. 2009, Chinese Journal of Aeronautics, 22: Tang E L, Zhang Q M, Zhang J. 2008, Plasma Science and Technology, 10: Tang E L, Zhang Q M, Xiang S H, et al. 2012, International Journal of Applied Electromagnetics and Mechanics, 40: 85 9 Tang E L, Xu H J, Wang M, et al. 2014, International Journal of Applied Electromagnetics and Mechanics, 2: Tang E L, Xu H J, Wang M, et al. 2014, International Journal of Applied Electromagnetics and Mechanics, 2: Tang E L, Shi X H, Zhang Q M, et al. 2015, Internal Journal of Applied Electromagnetics and Mechanics, 47: 513 (Manuscript received 10 October 2014) (Manuscript accepted 19 November 2014) address of TANG Enling: tangenling@126.com 414