Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session D4: Geophysics and Planetary Science I: Vaporization and Ionization |
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Chair: Seiji Sugita, University of Tokyo Room: Renaissance Ballroom C |
Monday, June 27, 2011 2:00PM - 2:15PM |
D4.00001: Uncertainties in the Shock Devolatilization of Hydrated Minerals Sarah Stewart, Richard Kraus, Ralph Milliken, Nicholas Tosca Controlled recovery of hydrated minerals subjected to planar shock loading is challenging because of the large volume required for equilibrium outgassing upon shock release. Significant differences in recovery capsule design confound straightforward interpretation of existing data on shock modification of hydrated minerals. We present results from new experiments on nontronite (a smectite clay observed on Mars) and identify major issues in the interpretation of recovered samples. Most previous work assumes that the first shock pressure step in a ring-up configuration is the most important factor in the interpretation of shock modification. By comparing experiments with similar first shock steps but different final shock states, this work demonstrates the need for a deeper understanding of the thermodynamics of ring-up experiments in order to be able to interpret the results in terms of an equivalent single shock loading pressure for planetary applications. At high shock pressures, vented capsules are essential in order to characterize the structural alteration upon shock release. We have developed a recovery method and validation test that allows us to address the major issues and technical tradeoffs with shock recovery experiments on volatile materials. [Preview Abstract] |
Monday, June 27, 2011 2:15PM - 2:30PM |
D4.00002: Flyer acceleration by high-power laser and impact experiments at velocities higher than 10 km/s T. Kadono, T. Sakaiya, Y. Hironaka, T. Watari, K. Otani, T. Sano, T. Fujiwara, T. Mochiyama, M. Arakawa, S. Takasawa, A.M. Nakamura, K. Kurosawa, T. Hamura, S. Ohno, S. Sugita, T. Matsui, H. Nagatomo, S. Fujioka, K. Shigemori Impact velocity of meteorites on planetary and satellite surfaces at the final stage of planetary accretion becomes more than 10 km/s. Recently, we have developed a macroscopic (larger than 0.1 mm) flyer acceleration technique to velocities more than 10 km/s using high-power lasers. In this presentation, we show that higher impact velocities than 10 km/s can be achieved using sheet flyers with a diameter of 0.6 mm and a thickness of 0.03 - 0.05 mm and spherical projectiles with a diameter of 0.1 - 0.3 mm, and that various impact experiments are carried out using this technique. [Preview Abstract] |
Monday, June 27, 2011 2:30PM - 2:45PM |
D4.00003: Direct measurement of chemical composition of SO$_{x}$ in impact vapor using a laser gun Sohsuke Ohno, Toshihiko Kadono, Kosuke Kurosawa, Taiga Hamura, Tatsuhiro Sakaiya, Seiji Sugita, Keisuke Shigemori, Yoichiro Hironaka, Takeshi Watari, Takafumi Matsui The SO$_{3}$/SO$_{2}$ ratio of the impact vapor cloud is a key parameter for understanding the environmental perturbation caused by the impact-induced SO$_{x}$ and the killing mechanism of. the mass extinction at the K-Pg boundary. We conducted hypervelocity impact experiments using a high-speed laser gun (GEKKO XII-HIPER, ILE, Osaka University) and measured the chemical compositions of the SO$_{x}$ released from CaSO$_{4}$. The experimental result indicates that SO$_{x}$ are dominated by SO$_{3}$. It implies that the SO$_{x}$ generated by the K-Pg impact would have been also dominated by SO$_{3}$, because the SO$_{3}$/SO$_{2}$ ratio of natural planetary scale impact vapor clouds would have been larger than that of the experimental result of this study. [Preview Abstract] |
Monday, June 27, 2011 2:45PM - 3:00PM |
D4.00004: Determining the Liquid-Vapor Curve of Silica with Mbar Shock and Release Experiments R.G. Kraus, S.T. Stewart, D.C. Swift, C.A. Bolme, R.F. Smith, S. Hamel, B. Hammel, D.K. Spaulding, D.G. Hicks, J.H. Eggert, G.W. Collins The liquid-vapor curve of most materials is an elusive part of the phase diagram because static techniques cannot reach the high temperatures and pressures near the critical point. Dynamic shock and release experiments are currently the best method for probing states up to and over the critical point. Shock-induced vaporization is an important process in the geosciences, e.g., it is key to testing the giant impact hypothesis for the formation of the Moon. We use shock and release experiments to probe the liquid-vapor curve of SiO$_{2}$, the dominant phase in Earth's crust. At Janus, 1-3 Mbar planar supported shock waves were driven through alpha-quartz by direct laser ablation. The temperature of the fluid released to the liquid-vapor curve is measured using a streaked optical pyrometer, and the average density of the mixed phases is derived from stagnation against aluminized LiF windows after uniaxial expansion across different gap distances. The results of our temperature and density measurements compare favorably with a recent model for the vapor curve of silica; however, our calculated entropy on the Hugoniot is significantly higher than in previous work. Hence, we revise the criteria for vaporization of silica during planetary impact events. [Preview Abstract] |
Monday, June 27, 2011 3:00PM - 3:15PM |
D4.00005: Time-resolved spectroscopic observations of shock-induced silicate ionization K. Kurosawa, T. Kadono, S. Sugita, K. Shigemori, Y. Hironaka, N. Ozaki, T. Sakaiya, A. Shiroshita, Y. Cho, S. Fujioka, S. Tachibana, T. Vinci, S. Ohno, R. Kodama, T. Matsui We present the results of shock vaporization experiments with natural silicates at Osaka University. Our goal is to understand the roles of hypervelocity impacts on the origin of the Moon, atmospheres and life. The EOS is the key to investigate such problems because the EOS controls energy partitioning. Thus, we conducted time-resolved spectroscopic observations of shock-heated diopsides to investigate the energy partitioning process. We observed the change in emission spectrum from shock-heated diopside from a blackbody radiation to a number of atomic/ionic emission lines, suggesting that we directly observed the shock-induced vaporization/ionization of natural silicates. The obtained peak shock temperatures are significantly lower than a theoretical prediction. Our results indicate that the electrons may play the important role on energy partitioning as an energy reservoir via ionization (endothermic) and electron recombination (exothermic). The EOS including such electron behavior is expected to be required for the understanding of impact-related phenomena. [Preview Abstract] |
Monday, June 27, 2011 3:15PM - 3:30PM |
D4.00006: Linear TOF mass spectrometers as a tool for the investigation of impact ionisation plasma Anna Mocker, Theresa Johnson, Eberhard Gruen, Klaus Hornung, Sir Jonathan Hillier, Sascha Kempf, Zoltan Sternovsky, Ralf Srama Impact physics plays an important role in a variety of field such as investigation of matter at extreme conditions, shock waves in solids or even planetology and cosmic dust research. Impact ionisation is a key part of impact physics, playing an increasingly important role at small scales. Linear TOF mass spectrometry provides an opportunity for investigating the thermodynamical properties, e.g. the velocity distribution, of the charged particles within an impact plasma. To relate the dynamical parameters of individual particle impacts with the properties of the resulting plasma, a comprehensive programme of impact experiments under well known experimental conditions for a wide variety of impact parameters is needed. For this suitable solar system analogue dust particles are accelerated to hypervelocity speeds, an activity performed at the MPI for Nuclear Physics in Heidelberg, Germany. Here a 2 MV Van de Graaff accelerator accelerates charged micron and submicron-sized dust particles to speeds in excess of 80 km/s. [Preview Abstract] |
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