Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session Y3: NT.1 Novel Techniques: Pulsed power/Magnetic Gauges |
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Chair: Jeremy Danielson, Los Alamos National Laboratory Room: Fifth Avenue |
Friday, July 12, 2013 9:15AM - 9:30AM |
Y3.00001: The Experimental Researching on Cylindrical Isentropic Compression by Ultrahigh Magnetic Field. Zhuowei Gu, Hao Luo, Hengdi Zhang, Shichao Zhao, Xiaosong Tang, Yanjin Tong, Zhenfei Song, Fuli Tan, Jianheng Zhao, Chengwei Sun The cylindrical isentropic compression by ultrahigh magnetic field (MC-1) is a kind of unique high energy density technique. It has characters like ultrahigh pressure and low temperature rising, and would have widely used in areas like high pressure physics, new material synthesis and ultrahigh magnetic field physics. The Institute of Fluid Physics, Chinese Academy of Engineering Physics (IFP, CAEP) has begun the experiment since 2011 and a primary experimental device had been set-up. In the experiments, a seed magnetic field of 5 Tesla were set-up first and compressed by a stainless steel liner which is driven by synchronous initiated high explosive. The internal diameter of the liner is 97 mm, and its thickness is 1.5 mm. The movement of liner was recorded optically and a typical turning-around character was observed. From the photograph results the liner was compressed smoothly and evenly and its average velocity was about 5-6 km/s. In the experiment a maximum axial magnetic field of 540 Tesla has been recorded and its response magnetic pressure is more than 100 GPa. The MC-1 process was numerical simulated by 1D MHD code MC11D and the simulations are in accord with the experiments. The isentropic compression of some gas materials were also numerical simulated and some valuable results were obtained and discussed. [Preview Abstract] |
Friday, July 12, 2013 9:30AM - 9:45AM |
Y3.00002: Optical Diagnostics For High Power Pulsed Underwater Electrical Discharge Characterization Julien Deroy, Gilles Avrillaud, Michel Boustie, Alain Claverie, Ekaterina Mazanchenko, David Assous, Alexander Chuvatin In order to evaluate the behavior of a high power pulsed underwater electrical discharge, and especially characterize the pressure generated by such a discharge, we implemented several optical diagnostics. We first observed directly the expansion of the plasma produced by the dielectric breakdown of the water between the electrodes and the resulting gaseous pulsating bubble. This observation led to an estimate of the pressure inside the bubble with respect to time. We then visualized the propagation of the pressure wave generated by the discharge with shadowgraphy and Schlieren set-up. The obtained velocity was then used to evaluate the theoretical maximum pressure at the pressure front. Finally, we measured the velocity induced by the pressure wave on a thin aluminum disk with a heterodyne velocimeter and used numerical simulation to obtain a temporal form of pressure. These methods and results can be used to develop and assess performances of processes using underwater electrical discharges to generate pressure waves such as electrohydraulic forming. [Preview Abstract] |
Friday, July 12, 2013 9:45AM - 10:00AM |
Y3.00003: Effects observed when using metallic flyers and barriers with the embedded particle velocity gauge technique Michael Goff, Gareth Appleby-Thomas, Malcolm Burns, Paul Hazell, Rick Gustavsen, Chris Stennet A number of experiments were carried out using a modified version of the standard particle velocity gauge technique in plate impact experiments with inert targets. Unusually these utilised metallic flyer plates. Traditional methodology advises against the use of metallic flyers/barriers with this technique, additional conductive objects moving in the magnetic field produce perturbations in the output gauge voltage. This body of work investigated the causes of the perturbation effect, methods of minimising its magnitude and possible post-processing correction methods. In experiments with Al flyers, perturbations on the order of 15\% of signal strength were observed. While the magnitude of the voltage traces were distorted, key features such as shock impact could still be observed, and shock trackers were still effective. Mitigating techniques such as laminated flyers and were tried and reduced the perturbation effect, but adversely affected the shock input produced. The case of metallic barriers was also examined and similar effects observed. This study has indicated that while a coarse empirical correction is possible, uncertainty in the validity of the correction would preclude against the use of metallic flyers in experiments where high fidelity data is required. [Preview Abstract] |
Friday, July 12, 2013 10:00AM - 10:15AM |
Y3.00004: Magnetic gauge for free surface velocities due to rock blasts Yecheskel Ashuach, Itai Gissis, Chen Avinadav We developed a simple magnetic gauge for measuring free surface velocities of rock materials in the range of 0.1-20 m/s. The gauge consists of two elements: a NdFeB magnet and a pick-up coil. The coil is attached to the free surface at the point of interest. The magnet is placed a few centimeters away from the coil on its central axis, intact from the rock. Rock surface movement due to blast loading induces current in the coil due to change of the magnetic flux. The coil velocity is deduced from the measured current using a computational code. The gauge was tested and validated in a set of free-falling experiments. We present velocity measurements from various blast experiments in limestone and reinforced concrete, using both the magnetic gauge and a Doppler interferometer. The results obtained from the two measurement techniques were in good agreement during a few milliseconds. The magnetic gauge is cheap and very simple to operate, and therefore favorable for mapping the velocity distribution at multiple points of interest on the surface. [Preview Abstract] |
Friday, July 12, 2013 10:15AM - 10:30AM |
Y3.00005: A New Diagnostic for Shock Experiments: Pulse Correlation Reflectometry Terry Salyer Based on the conceptually simple principle of time domain reflectometry, the pulse correlation reflectometry technique allows for the determination of shock position as a function of time along a diagnostic cable. Once the electrical pulse speed of the cable is accurately known (via calibration), the current shock position may be determined by measuring the two-way transit time of an interrogation pulse reflected off the electrical short created by the crushed cable at the shock position. Due to electrical pulse dispersion within the cable, a pulse correlation analysis method is required to achieve the positional accuracy required for small-scale shock experiments. To further increase the positional accuracy, a method of multiplexing several pulses within the cable allows for more frequent interrogation of the dynamic shock front. With a high frequency pulser and a high bandwidth digitizer, the new technique can acquire far more data than typical fiducial pins, effectively providing a near continuous shock position measurement. Initial experiments along explosively driven surfaces indicate excellent agreement with pin and streak camera data, while yielding a several order of magnitude increase in data with an order of magnitude reduction in fielding time, complexity, and cost. [Preview Abstract] |
Friday, July 12, 2013 10:30AM - 10:45AM |
Y3.00006: The method to improve accuracy and informativeness of shock-wave study of solids by means of electric explosion of foils Ivan Smirnov, Yuri Sudenkov The experimental technique using the phenomenon of electric explosion of foils for generation of shock waves in solids will be presented. The developed setup allows to carry out the study of deformation and fracture processes in materials under high-speed loading with the pulse duration of 0.5-1 $\mu $s and pressures up to 20 GPa. As well as for any methods of impact loading, the traditional technique of application of electrical explosion of foils does not allow to register exact parameters of loading pulse. However the use of symmetry of the foil explosion makes it possible to register with sufficient accuracy both the initial parameters of the shock wave, and the shock wave output to the sample free surface. The results of application of such technique in studies of elastic-plastic processes and spall strength of metals will be shown. [Preview Abstract] |
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