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We present a new experimental platform for studying laboratory astrophysics that combines a high-intensity, high-repetition-rate laser with the Large Plasma Device at the University of California, Los Angeles. To demonstrate the utility of this platform, we show the first results of volumetric, highly repeatable magnetic field and electrostatic potential measurements, along with derived quantities of electric field, charge density and current density, of the interaction between a super-Alfvénic laser-produced plasma and an ambient, magnetized plasma.
Conventional commercial aircraft fuselages use all-aluminium semi-monocoque structures where the skin carries the external loads, the internal fuselage pressurisation and is strengthen using frames and stringers. Environmental and economic issues force aircraft designers to minimise weight and costs to keep air transport competitive and safe. But as metal designs have reached a high degree of perfection, extraordinary weight and cost savings are unlikely in the future. Carbon composite materials combined with lattice structures and the use of topology optimisation have the potential to offer such weight reductions. The EU FP7 project Advanced Lattice Structures for Composite Airframes (ALaSCA) was started to investigate this. This article present some of this research which has now led to the development of a new airframe concept which consists of: a load carrying inner skin; transverse frames; CFRP-metal hybrid stiffeners helically arranged in a grid configuration; insulating foam and an additional aerodynamic outer skin.
Experimental investigations of heavy-ion-generated shock waves in
solid, multilayered targets were performed by applying a Schlieren and
a laser-deflection technique. Shock velocity and the corresponding
pressures, temporal and spatial density profiles inside the material
compressed by multiple shock waves, and details of the shock dynamics
were determined. Important for equation-of-state and phase transition
studies, such experiments extend their relevance to inertial
confinement fusion and astrophysical fundamental research.
The final beam transport in the reactor chamber for heavy ion
fusion in preformed plasma channels offers many attractive
advantages compared to other transport modes. In the past few
years, experiments at the Gesellschaft für
Schwerionenforschung (GSI) accelerator facility have addressed
the creation and investigation of discharge plasmas, designed
for the transport of intense ion beams. Stable, self-standing
channels of 50 cm length with currents up to 55 kA were initiated
in low-pressure ammonia gas by a CO2-laser pulse
along the channel axis before the discharge is triggered. The
channels were characterized by several plasma diagnostics including
interferometry and spectroscopy. We also present first experiments
on laser-guided intersecting discharges.
The aim of the presented experiments is to study the transport
of a heavy ion beam in a high-current plasma channel. The discharge
is initiated in NH3 gas at pressures between 2 and
20 mbar by a line-tuned CO2 laser. A stable discharge
over the entire electrode gap (0.5 m) was achieved for currents
up to 60 kA. Concerning the ion beam transport, the magnetic
field distribution inside the plasma channel has to be known.
The ion-optical properties of the plasma channel have been
investigated using different species of heavy ions (C, Ni, Au,
U) with 11.4 MeV/u during six runs at the Gesellschaft für
Schwerionenforschungs-UNILAC linear accelerator. The high magnetic
field allowed the accomplishment of one complete betatron
oscillation along the discharge channel. The results obtained
up to now are very promising and suggest that, by scaling the
discharge gap to longer distances, the beam transport over several
meters is possible with negligible losses.
By the interaction of intense (1010
particles/500 ns) relativistic (∼300
MeV/amu) heavy ion beams with solid targets, large volumes
(several cubic millimeters) of strongly coupled plasmas are
produced at solid-state densities and temperatures of up to
1 eV, with relevance for equation-of-state (EOS) studies of
matter at high energy density and heavy ion-beam-driven inertial
confinement fusion (ICF). The time and space profile of the
ion beams, focused by the plasma lens to diameters of a minimum
of 0.5 mm in order to obtain specific energy depositions of
up to about 4 kJ/g, were measured to calculate the energy
deposition in the target. In the present work, the plasmas created
by ion beam interaction with cryogenic gas crystals and metallic
targets are studied, among other methods, by backlighting
shadowgraphy and electrical conductivity measurements. The
experiments are coupled with two-dimensional hydrodynamic simulations.
Discharge plasma channels have been investigated in recent
years at Gesellschaft für Schwerionenforschung–Darmstadt
(GSI) and at the Lawrence Berkeley National Laboratory in Berkeley,
California, in a number of experiments. A short summary of the
experimental work at Berkeley and GSI is given. Different
initiation mechanisms for gas discharges of up to 60 kA were
studied and compared. In the Berkeley experiments, laser ionization
of organic vapors in a buffer gas was used to initiate and direct
the discharge while at GSI, laser gas heating and ion-beam-induced
gas ionization were tested as initiation mechanisms. These three
initiation techniques are compared and the stability of the
resulting discharge channels is discussed. A discharge current
of 50 kA, a channel diameter well below 1 cm, a pointing stability
better than 200 μm, and MHD stability of more than 10 μs
have been demonstrated simultaneously in the recent experiments.
These parameters are sufficient or close to the requirements
of a reactor application depending on the details of the target
design. The experimental results show that transport channels
work with sufficient stability, reproducibility, and ion optical
properties for a wide pressure range of discharge gases and
The dynamics of low entropy weak shock waves induced by heavy
ion beams in solid targets was investigated by means of a schlieren
technique. The targets consist of a metallic absorber for the
beam energy deposition followed by a plexiglass block for optical
observations. Multiple waves propagating with supersonic velocities
at 15 kbar pressures were observed in the plexiglass, for pressures
of up to 70 kbar numerically calculated in the absorbers. Pressures
in the megabar ranges are predicted for a near future beam upgrade,
enabling studies of phase transition to metallic states of H,
Kr, and Xe.
Abundances of ammonia, hydrogen sulfide, water, methane and other hydrocarbons, noble gases and their isotopes, etc. were measured for the first time to the 22 bar level. The ratios of the heavy elements to hydrogen were found to be enriched by a factor of 2-3 relative to solar, implying a large influx of cold planetesimals into Jupiter.
The discovery by the Galileo Probe Mass Spectrometer that argon is enriched to the same extent as carbon and sulfur on Jupiter requires a revision of models for the formation of this giant planet. Evidently the excess heavy elements were carried to Jupiter in icy planetesimals that formed at temperatures ≤ 30 K. This result indicates that there is no original significance in the present position of Jupiter's orbit.
Macromolecular X-ray crystallography underpins the vigorous field of structural molecular biology having yielded many protein, nucleic acid and virus structures in fine detail. The understanding of the recognition by these macromolecules, as receptors, of their cognate ligands involves the detailed study of the structural chemistry of their molecular interactions. Also these structural details underpin the rational design of novel inhibitors in modern drug discovery in the pharmaceutical industry. Moreover, from such structures the functional details can be inferred, such as the biological chemistry of enzyme reactivity. There is then a vast number and range of types of biological macromolecules that potentially could be studied. The completion of the protein primary sequencing of the yeast genome, and the human genome sequencing project comprising some 105 proteins that is underway, raises expectations for equivalent three dimensional structural databases.
Diamond-like a-C:H films were obtained by reactive dc-magnetron sputtering from a glassy carbon target in an argon-hydrogen atmosphere. To our knowledge, this is the first time that glassy carbon is used as target material. The a-C:H films are transparent and hard. The a-C:H films can be used as protection and antireflection coatings on a-Si:H photoreceptors. The electrical, optical and structural properties of the a-C:H films are examined.
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