Magnetothermodynamics In SSX: Measuring The Equations Of State Of A Compressible Magnetized Plasma

Magnetothermodynamics is the study of compression and expansion of magnetized plasma with an eye toward identifying equations of state (EOSs) for magneto-inertial fusion experiments. We present recent results from Swarthmore Spheromak Experiment (SSX) experiments on the thermodynamics of compressed magnetized plasmas called Taylor states. In these experiments, we generate twisted flux ropes of magnetized, relaxed plasma accelerated from one end of a 1.5-m-long copper flux conserver and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. The instances of ion heating during compression are identified by constructing a pressure-volume diagram using measured density, temperature, and volume of the magnetized plasma. While we only measure compression up to 30%, we speculate that if higher compression ratios could be achieved, the compressed Taylor states could form the basis of a new kind of fusion engine. The theoretically predicted magnetohydrodynamic (MHD) and double-adiabatic [Chew-Goldberger-Low (CGL)] EOSs are compared to experimental measurements to estimate the adiabatic nature of the compressed plasma. Since our magnetized plasmas relax to an equilibrium described by MHD, one might expect their thermodynamics to be governed by the corresponding EOS. However, we find that the MHD EOS is not supported by our data. Our results are more consistent with the parallel CGL EOS suggesting that these weakly collisional plasmas have most of their proton energy in the direction parallel to the magnetic field

Magnetothermodynamics In SSX: Measuring The Equations Of State Of A Compressible Magnetized Plasma

Magnetothermodynamics is the study of compression and expansion of magnetized plasma with an eye toward identifying equations of state (EOSs) for magneto-inertial fusion experiments. We present recent results from Swarthmore Spheromak Experiment (SSX) experiments on the thermodynamics of compressed magnetized plasmas called Taylor states. In these experiments, we generate twisted flux ropes of magnetized, relaxed plasma accelerated from one end of a 1.5-m-long copper flux conserver and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. The instances of ion heating during compression are identified by constructing a pressure-volume diagram using measured density, temperature, and volume of the magnetized plasma. While we only measure compression up to 30%, we speculate that if higher compression ratios could be achieved, the compressed Taylor states could form the basis of a new kind of fusion engine. The theoretically predicted magnetohydrodynamic (MHD) and double-adiabatic [Chew-Goldberger-Low (CGL)] EOSs are compared to experimental measurements to estimate the adiabatic nature of the compressed plasma. Since our magnetized plasmas relax to an equilibrium described by MHD, one might expect their thermodynamics to be governed by the corresponding EOS. However, we find that the MHD EOS is not supported by our data. Our results are more consistent with the parallel CGL EOS suggesting that these weakly collisional plasmas have most of their proton energy in the direction parallel to the magnetic field

Spheromak Experiment Using Separate Guns For Formation And Sustainment

An experiment is described that incorporates the use of separate magnetized plasma guns for formation and sustainment of a spheromak. It is shown that energy coupling efficiency approaches unity if the gun and spheromak are of comparable size. A large gun should be able to operate at lower current and therefore lower voltage. In addition, it is expected that a gun matched to the size of the spheromak will cause less perturbation to the equilibrium. It is proposed to use a smaller gun for spheromak formation and a large, efficient gun for sustainment. The theoretical basis for the experiment is developed, and the details of the experiment are described. A prediction of the equilibrium magnetic flux surfaces using the EFIT code is presented

SSX MHD Plasma Wind Tunnel

A new turbulent plasma source at the Swarthmore Spheromak Experiment (SSX) facility is described. The MHD wind tunnel configuration employs a magnetized plasma gun to inject high-beta plasma into a large, well-instrumented, vacuum drift region. This provides unique laboratory conditions approaching that in the solar wind: there is no applied background magnetic field in the drift region and has no net axial magnetic flux; the plasma flow speed is on the order of the local sound speed (M ~ 1), so flow energy density is comparable to thermal energy density; and the ratio of thermal to magnetic pressure is of order unity (plasma β ~ 1) so thermal energy density is also comparable to magnetic energy density. Results presented here and referenced within demonstrate the new capabilities and show how the new platform is proving useful for fundamental plasma turbulence studies

In situ poly(urea-formaldehyde) microencapsulation of dicyclopentadiene

Microencapsulated healing agents that possess adequate strength, long shelf-life, and excellent bonding to the host material are required for self-healing materials. Ureaformaldehyde microcapsules containing dicyclopentadiene were prepared by in situ polymerization in an oil-in-water emulsion that meet these requirements for self-healing epoxy. Microcapsules of 10-1000 ??m in diameter were produced by appropriate selection of agitation rate in the range of 200-2000 rpm. A linear relation exists between log(mean diameter) and log(agitation rate). Surface morphology and shell wall thickness were investigated by optical and electron microscopy. Microcapsules are composed of a smooth 160-220 nm inner membrane and a rough, porous outer surface of agglomerated urea-formaldehyde nanoparticles. Surface morphology is influenced by pH of the reacting emulsion and interfacial surface area at the core-water interface. High yields (80-90%) of a free flowing powder of spherical microcapsules were produced with a fill content of 83-92 wt% as determined by CHN analysis.published or submitted for publicationis peer reviewe

An Analysis of the Statistics of the Hubble Space Telescope Kuiper Belt Object Search

We calculate statistical limits to the detection of Kuiper belt objects in the Hubble Space Telescope (HST) data of Cochran et al., in which they report the discovery of a population of Halley-sized objects in Pluto-like orbits. Detection of a population of faint objects in these data is limited by the number of false objects that appear owing only to random noise; the number of real objects must exceed the uncertainty in the number of these false objects for the population to be observable. We determine the number of false objects expected owing to random noise in the data of Cochran et al. by measuring the pixel-to-pixel noise level in the raw HST data and propagating this noise through the detection method employed by Cochran et al. We find that the uncertainty in the number of false objects exceeds by 2 orders of magnitude the reported number of objects detected by Cochran et al. The detection of such a population of Halley-sized Kuiper belt objects with these data is therefore not possible