A detailed description of a 10.16 cm gas gun that has been designed and installed at Washington State University is presented. The design velocity is 1.5 mm/μsec; the maximum velocity achieved to date is 0.9 mm/μsec with an 1100 g projectile. Angular misorientation of the projectile with respect to the target surface is consistently below 0.5 mrad. Brief descriptions of ancillary instrumentation and equipment are also given.
An experimental facility was developed to obtain real-time, quantitative, x-ray diffraction data in laboratory plate impact experiments. A powder gun, to generate plane wave loading in samples, was designed and built specifically to permit flash x-ray diffraction measurements in shock-compression experiments. Spatial resolution and quality of the diffracted signals were improved significantly over past attempts through partial collimation of the incident beam and the use of two-dimensional detectors to record data from shocked crystals. The experimental configuration and synchronization issues are discussed, and relevant details of the x-ray system and the powder gun are described. Representative results are presented from experiments designed to determine unit cell compression in shock-compressed LiF single crystals subjected to both elastic and elastic-plastic deformation, respectively. The developments described here are expected to be useful for examining lattice deformation and structural changes in shock wave compression studies.
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An experimental method was developed to measure the pressure-time profile of a liquid in a reverberation or multiple-shock experiment. Profiles, with peak pressures to 30 kbars, were measured for carbon disulfide using shorted quartz gauges (25.4 mm diameter by 3.15 mm thick); these gauges formed the back surfaces of cells which contained the carbon disulfide. Sapphire plates were used both as impactors and as the front surfaces of the cell. Up to six pressure steps were clearly observed in the quartz-gauge output. Measured pressure-time profiles were compared to profiles calculated with available equations of state. The experiments agreed well with profiles predicted with an equation of state proposed by Sheffield [J. Chem. Phys. 79, 1981 (1983)]. Calibration experiments were performed to characterize both the initial current response and the subsequent current ramping of the shorted quartz gauges used in this study.
The response of shorted quartz gauges, 1.27 cm in diameter and 0.32-cm thick, to impact loading has been examined. Of particular interest was the increase in current with time, commonly referred to as current ramping. Data on the initial current jump from the present work and from earlier studies have been fitted using a piezoelectric current coefficient, k=(1.92+8.25×10−3σ) ×10−8 C/cm2/kbar. This fit, good to within ±2%, is valid to 40 kbar. The current ramping coefficient α was found to be linear with stress and was fitted over the same stress range as α=0.195+8.24×10−3σ, where σ is in kbar and α is in μs−1. Procedures to use the current and ramping calibration are described.
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