Construction and Characterization of a Single Stage Dual Diaphragm Gas Gun

In the interest of studying the propagation of shock waves, this work sets out to design, construct, and characterize a pneumatic accelerator that performs high-velocity flyer plate impact tests. A single stage gas gun with a dual diaphragm breach allows for a non-volatile, reliable experimental testing platform for shock phenomena. This remotely operated gas gun utilizes compressed nitrogen to launch projectiles down a 14 foot long, 2 inch diameter bore barrel, which subsequently impacts a target material of interest. A dual diaphragm firing mechanism allows the 4.5 liter breech to reach a total pressure differential of 10ksi before accelerating projectiles to velocities as high as 1,000 m/s (1570-2240 mph). The projectile’s velocity is measured using a series of break pin circuits. The target response can be measured with Photon Doppler Velocimetry (PDV) and/or stress gauge system. A vacuum system eliminates the need for pressure relief in front of the projectile, while additionally allowing the system to remain closed over the entire firing cycle. Characterization of the system will allow for projectile speed to be estimated prior to launching based on initial breach pressure

The MEG detector for μ+→e+γ{\mu}+\to e+{\gamma} decay search

The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay \meg\ by using one of the most intense continuous $\mu^+$ beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus.Comment: 59 pages, 90 figure

The interaction of an electrothermal plasma with JA2 solid propellant

Electrothermal plasmas are being studied as an ignition mechanism for solid propellants in large caliber guns. Benefits of electrothermal plasma ignition over conventional primer charge ignition include a reduction of ignition delay and delay jitter (bootstrapping) and compensation for the variable burn rate of propellants at different initial temperatures. When JA2 solid propellant is exposed to plasma radiation alone, significant decomposition results. This radiative interaction is a possible mechanism that causes the bootstrapping and temperature compensation. In addition, the effects of plasma radiation exposure have the potential to increase the propellant burn rate. To characterize this radiation interaction, PLIF imaging of NO, a JA2 decomposition product, was conducted at the propellant surface. Also, simultaneous high speed video of the propellant surface and scattering of ejected particles has been performed. During the radiation interaction scattering particles and NO appeared between 100 and 150 µs after the beginning of the discharge and propagated away from the propellant surface. This ejected material appeared in identifiable structures that are irregular in shape and distribution. This suggests that the material was ejected at semi-discrete locations on the surface rather than diffused uniformly from the surface. During the plasma firing the propellant surface changed markedly by forming irregularly shaped decomposition structures that grew in size over the course of the discharge. No correlation was observed between the structure of the ejected material and the decomposition structures formed on the propellant surface during the discharge. After the plasma discharge, the propellant continued to react, with bubbles forming on the surface up to 9 ms after the discharge finished. These bubbles are probably the largest decomposition structures in images taken of the propellant surface minutes after radiation exposure. The delayed reaction of the propellant produced the majority of ejected particles after the plasma firing. This raises concerns that the potential burning rate increase by the effects of the radiation might not be completely realized in a plasma ignition event. Regions of the propellant exposed to plasma radiation could be consumed by the burning surface before all of the observed effects of the radiative interaction took place.Aerospace Engineering and Engineering Mechanic