Alameda Applied Sciences Corporation (United States)

A gas-puff z-pinch experimental platform has been developed for the 0.5–1-MA, 100–250-ns MAIZE pulsed power facility at the University of Michigan. The experiment consists of a nozzle and fast-valve assembly, which is integrated into the pulsed power circuit and forms a gas load in the center of the pulsed power device. The capacitors that form the pulsed power device discharge through the gas, forcing it to pinch on axis. Such a gas-puff z-pinch is afflicted by various instabilities, the mitigation of which is achieved by imploding multiple concentric shells of gas with increasing gas density toward the center of the pinch and imploding high mass number gases onto low mass number gases. These constraints suggested the development of a triple-nozzle system with an outer shell, inner shell, and central jet. A voltage-driven thin-shell model was used to inform the design of the gas-puff nozzles’ radii and gas pressures in the fast valve. The hardware was developed based on this point design. The MAIZE transmission lines were redesigned to accommodate the new hardware. Systems that support the gas-puff experiment include a gas manifold that supplies the nozzles with gas; a driver that pulses the valve to opened and closed states; and a logic circuit that provides a signal if and only if the gas-puff load successfully forms, to trigger MAIZE and the diagnostics. These were all constructed, tested, and integrated into the experiment. Additional diagnostics were also developed and fielded: a 2-D interferometer, a four polycrystalline diamond (PCD) detector array with Ross filter pairs, and neutron bubble detectors. Characteristic results from the first z-pinch experiments conducted with this gas-puff system are presented. The system demonstrates an x-ray energy output of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$720~\pm ~50$ </tex-math></inline-formula> J per pulse and a neutron output of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(4.9 \pm 0.5) \times 10^{8}$ </tex-math></inline-formula> neutrons per pulse. Notably, this system has enabled shot rates of over 30 z-pinch experiments per day on MAIZE.

Results on coordinated experiments and MHD simulations on the axial phase sheath dynamics of dense plasma focus are presented. The aim of this effort is to use a repetitively fired dense plasma focus (DPF) to gather data from 100's to 1000's of shots per gas load, so as to better refine numerical codes. The experimental results will feed fully 3D simulations of DPF devices, adding new capabilities to the GORGON code.

Alameda Applied Sciences Corporation (AASC) grows Nb thin films via Coaxial Energetic Deposition (CED) from a cathodic arc plasma. The plasma from the cathode consists exclusively of 60-120eV Nb ions (Nb+ and Nb2+) that penetrate a few monolayers into the substrate and enable sufficient surface mobility to ensure that the lowest energy state (crystalline structure with minimal defects) is accessible to the film. AASC is coating 1.3 GHz SRF cavities using a graded anode to ensure uniform film thickness in the beam tube and elliptical regions. Copper cavities are centrifugal barrel polished and electropolished (done for us by the Fermilab Technical Division, Superconducting RF Development Department and by Thomas Jefferson National Accelerator Facility (JLAB)) before coating, to ensure good adhesion and improved film quality. The Nb coated copper cavities will undergo RF tests at JLAB and at Fermilab to measure Qo vs. E.

Argon gas puffs have produced 330 kJ ± 9% of x-ray radiation above 3 keV photon energy in fast z-pinch implosions, with remarkably reproducible K-shell spectra and power pulses. This reproducibility in x-ray production is particularly significant in light of the variations in instability evolution observed between experiments. Soft x-ray power measurements and K-shell line ratios from a time-resolved spectrum at peak x-ray power suggest that plasma gradients in these high-mass pinches may limit the K-shell radiating mass, K-shell power, and K-shell yield from high-current gas puffs.

In previous experiments, using a RF plasma generator at low power, we have grown diamond like carbon films (DLC), using a hydrocarbon plasma, without the use of a catalyzer precursor[1]. In order to better understand the relationship between the properties of the resulting DLC films and the RF plasma parameters, we have performed detailed optical emission spectroscopy (OES) observations of RF hydrocarbon plasmas, under identical conditions to those used for DLC films growth. The experiments were performed in a low power capacitively coupled RF (13.6 MHz) plasma generator, operating at 30 W. Working gases were acetylene and hydrogen. The optical emission of the RF plasma was recorded, under different operational conditions, with a spectrometer, and an f-f light collection arrangement was used to achieve spatial resolution. The relative emission of the different molecular species was found to depend on the C2H2:H2 flow ratio. Based on the OES observations, we present a description of plasma conditions in a low power RF hydrocarbon plasma reactor.

The Spectra Optia apheresis system is a newer centrifugation-based device that in comparison with the COBE Spectra includes features that enhance procedure automation and usability. In this FDA-approved three-center two-arm observational study we characterized the performance of the Spectra Optia for collection of MNCs and CD34+ cells from nonmobilized and granulocyte-colony stimulating factor (G-CSF) mobilized healthy donors, respectively. There were a total of 15 evaluable subjects in each arm. Key performance indicators included collection efficiency of MNCs/CD34+ cells, product purity and cellular viability. For nonmobilized donors, median MNC collection efficiency, platelet collection efficiency, product hematocrit and granulocyte contamination were 57%, 12%, 4%, and 1.7%, respectively. For mobilized donors, median MNC collection efficiency, CD34+ cell collection efficiency, platelet collection efficiency, product hematocrit and granulocyte contamination were 61%, 77%, 19%, 4%, and 15%, respectively. Average WBC viability in the mobilized products was 99%. There was one severe (grade 3) adverse event related to citrate toxicity. This study demonstrates that the Spectra Optia can be used for safe and efficacious collection of MNCs, and results obtained are in line with expectations on collection efficiency and product characteristics. Adverse events were limited to those that are well documented in the stem-cell mobilization and leukapheresis process. As of the time of this writing, FDA 510(k) approval for use of the Spectra Optia device for MNC collection was achieved in the US based partly on the results of this study.

Summary form only given. Short burst, ultrafast laser pulses interact intensely with matter to generate beams of secondary radiation such as coherent x-rays via high harmonic generation, electron bunches via laser wakefield acceleration, and protons via laser-driven ion acceleration. These secondary radiation sources have applications in biological imaging, medical diagnostics and treatment, and nondestructive evaluation. The emerging field of laser-plasma acceleration (LPA) has demonstrated electron accelerators with unprecedented electric field gradients. Supersonic, highly collimated gas jets and gas-filled capillary discharge waveguides are two primary targets of choice for LPA. A new LPA accelerated beam energy record of >2 GeV has been recorded using the Texas Petawatt laser (150 J) focused into a 7 cm He gas cell. The electron beams were highly-collimated (<;1 mrad divergence), containing high charge (>1 nC), and had a broad energy spectrum (peaked at ~2 GeV, with electrons up to 2.4 GeV). A fast opening and closing gas valve is essential to a LPA. This paper describes a fast valve (developed under a DOE SBIR grant) that opens in <;100μs, closes in <;400μs and can run (in cooled mode) at ~10Hz rep-rates at pressures as high as 1000psia. Recently we have designed advanced versions of the nozzle to create ~10-15mm long supersonic gas jets with tailored density gradients to test the concept of phase locking in an LPA. Dense gas jets with high concentrations of clusters are also of interest for such ultra-fast laser interactions. Development of a dense cluster jet using our ultra-fast opening/closing valve is also described.

Laboratory astrophysics is a novel approach to study different types of astrophysical phenomena by the means of carefully scaled laboratory experiments. Particularly, the formation of highly supersonic, radiatively cooled plasma jets for the study of protostellar jets is an active area of research at present. At Imperial College London, different experimental configurations allow producing plasma flows which are scalable to protostellar jets. The plasma is produced by introducing a ∼1.4 MA, 250 ns current pulse from the MAGPIE generator into a load. By varying the geometry of the load it is possible to study different regions of interest in the jet. For instance, the effect of magnetic fields in the launching and collimation of the jet, and the propagation of the jet far away from the launching region as it interacts with the ambient medium. Two main experiments can address such regions of interest: radial wire arrays and radial foils. By using a radial wire array it is possible to produce a jet driven by a predominant toroidal magnetic field on the axis of a magnetic "bubble", which expands with velocities up to ∼300 km/s. In a radial foil the wires are replaced by a continuous disk allowing to produce a hydrodynamic jet, i.e. a jet in which magnetic fields are not dynamically significant. With this particular configuration it is possible to introduce a neutral gas above the foil in order to study jet-ambient interactions. Experimental results from different diagnostics will be presented together with 3-D MHD simulations using the GORGON code.

We have recently demonstrated unprecedentedly high values of RRR (up to 542) in thin-films of pure Nb deposited on a-plane sapphire and MgO crystal substrates. The Nb films were grown using a vacuum arc discharge struck between a reactor grade Nb cathode rod (RRR~30) and a coaxial, semi-transparent Mo mesh anode, with a heated substrate placed just outside it. The substrates were pre-heated for several hours prior to deposition at different temperatures. Low pre-heat temperatures (<300°C) and deposition temperatures (<300°C) give low RRR (<50) films, whereas higher pre-heat (700°C) and coating temperatures (500°C) give RRR=214 on a-sapphire and RRR=542 on MgO. XRD (Bragg-Brentano scans and Pole Figures), EBSD and SIMS data reveal several features: (1) on asapphire, higher temperatures show better 3D registry for epitaxial growth of Nb; the crystal structure evolves from textured, polycrystalline (with twins) to single-crystal; (2) on MgO, there is a transition from {110} planes to {100} as the temperature is increased beyond 500°C. The dramatic increase in RRR (from ~10 at <300°C to ~500 at >600°C) is correlated with better epitaxial crystal structure in both a-sapphire and MgO substrate grown films. However, the SIMS data reveal that the most important requirement for high-RRR Nb films on either substrate is the reduction of impurities in the film, especially hydrogen. The hydrogen content in the MgO grown films is 1000 times lower than in bulk Nb tested as a reference from SRF cavity grade Nb. This result has potential implications for SRF accelerators. Coating bulk Nb cavities with an MgO layer followed by our CEDTM deposited Nb films, might create superior SRF cavities that would avoid Q-slope and operate at higher peak fields. This research was supported by Department of Energy grants DE-SC0004994 and DE-FG02-08ER85162.