247 research outputs found
Borane (BmHn), Hydrogen rich, Proton Boron fusion fuel materials for high yield laser-driven Alpha sources
No full textWe propose for the first time, a new fuel-material for laser-driven Proton Boron (P-B) fusion nuclear reactions. We propose, Hydrogen rich, Borane (BmHn) materials as fusion fuel as compared to Boron Nitride (BN) presently used. We estimate more than 10-fold increase in the yield of nuclear fusion reactions, and Alpha-prticle flux, when, for example Ammonia Borane (BNH6) laser-target material will be used compared to the state of the art normalized flux ∼108 Alphas/sr/J from BN targets. BNH6 contains ∼1000× higher concentration of Hydrogen compared to BN. We report the manufacture of the first solid-pellets Ammonia Borane laser-targets. To obtain high Flux Alpha sources from repetitive lasers we propose new BNH6 target geometries: liquid (molten) droplets/jets; or translated tape- or disc-targets coated with BNH6 powder. Targets would be irradiated in low pressure, ambient buffer gas. To enhance the fusion/Alpha yield of ultra-high intensity PetaWatt laser-target interaction we propose nano- and micro-structured Borane targets. As applications, we propose to use the Alpha-driven nuclear reactions inside the laser-driven Borane targets for new schemes to produce short-lived medical radioisotopes. Such laser-driven radioisotope beamlines would be installed directly in hospitals. Borane materials, like Diborane (6), B2H6, are also proposed as nuclear-fuels for laser-driven Proton-Boron fusion energy generation. The high dilution of Boron in Hydrgen B/H = 33% would need to be further enahnced to B/H < 15% to cut radiation losses from the hot and dense fusion pellet
Review of HPLSE special issue on target fabrication
No full textIn 2017 the journal High Power Laser Science and Engi- neering produced a Special Issue on Target Fabrication. The scope of the special issue was to span the latest developments and reviews on topics related to their deployment on ultra-high-energy/power laser facilities. The topics invited for inclusion were:
• Target assembly
• Novel characterization techniques
• Target solutions for high repetition rate targets • Cryogenic target development
• Novel material fabrication
• Precision micro-machining
• Target debris studies
Although this was not meant as an exhaustive list. As is usual with a Special Issue of this type Guest Editors were invited to lead in sourcing articles. These editors were: Paul Fitzsimmons, General Atomics, USA; Chris Spindloe, STFC Rutherford Appleton Laboratory, UK; Professor Yuji Fukuda, Kansai Photon Science Institute, Japan; and Profes- sor Kai Du, China Academy of Engineering Physics, China. The field of target fabrication is very diverse, often being led by the fundamental research priorities of the national laboratories across the world. Submissions for the special issue covered the invited topics and also branched out into broader areas and capabilities. Papers described research on: techniques for the production of targets for inertial confinement fusion (ICF), micro-assembly, liquid targets[10] , systems for delivery of targets at high repetition rates, fundamental target fabrication processes, low density materials and metrology methods. In addition, there were three important review papers that give an excellent snapshot of the current capabilities across the world.journal articl
Effect of defocusing on picosecond laser-coupling into gold cones
No full textThis work was supported in part by DTRA under Basic Research Award No. HDTRA1-10-10077.Here, we show that defocusing of the laser in the interaction of a picosecond duration, 1.053 μm wavelength, high energy pulse with a cone-wire target does not significantly affect the laser energy coupling efficiency, but does result in a drop in the fast electron effective temperature. This may be beneficial for fast ignition, since not only were more electrons with lower energies seen in the experiment but also the lower prepulse intensity will reduce the amount of preplasma present on arrival of the main pulse, reducing the distance the hot electrons have to travel. We used the Vulcan Petawatt Laser at the Rutherford Appleton Laboratory and gold cone targets with approximately 1 mm long, 40 μm diameter copper wires attached to their tip. Diagnostics included a quartz crystal imager, a pair of highly oriented pyrolytic graphite crystal spectrometers and a calibrated CCD operating in the single photon counting regime, all of which looked at the copper Kα emission from the wire. A short pulse optical probe, delayed 400 ps relative to the main pulse was employed to diagnose the extent of plasma expansion around the wire. A ray-tracing code modeled the change in intensity on the interior surface of the cone with laser defocusing. Using a model for the wire copper Kα emission coupled to a hybrid Vlasov-Fokker-Planck code, we ran a series of simulations, holding the total energy in electrons constant whilst varying the electron temperature, which support the experimental conclusions.Peer reviewe
Investigation of laser plasmas relevant to shock ignition at PALS
No full textWe present the results of an experiment concerning laser-plasma interaction in the regime relevant to shock ignition. The interaction of high-intensity frequency tripled laser pulse with CH plasma preformed by lower intensity pre-pulse on fundamental wavelength of the kJ-class iodine laser was investigated in the planar geometry in order to estimate the coupling of the laser energy to the shock wave or parametric instabilities such as stimulated Raman or Brillouin scattering, or to the fast electrons. First the complete characterization of the hydrodynamic parameters of preformed plasma was made using crystal spectrometer to estimate the electron temperature and XUV probe to resolve the electron density profile close to the critical density region. The other part of the experiment consisted of the shock chronometry, calorimetry of the back-scattered light and hard X-ray spectrometry to evaluate the coupling to different processes. The preliminary analysis of the measurements showed rather low energy transfer of the high-intensity pulse to back-scattered light (> 5%) and no traces of any significant hot electron production were found in the X-ray spectra. © 2011 SPIE
Characterisation of the oxide effects on aluminium opacity targets
No full text 900 nanometre thick aluminium strips were produced by the Target Fabrication Group for an experiment at the Central Laser Facility. They were specified to be supported horizontally at either end across an 800 micron void and to be 500 microns in height. The production method used a Parylene (C 8 H 8 ) supporting layer which was removed by oxygen plasma etching. This process resulted in a problematic contaminant layer that caused substantial increase to the absorption of X-rays in the laser campaign. The contaminant layer was characterised by optical microscopy and Scanning Electron Microscopy. Energy Dispersive X-ray Spectroscopy was able to detect a high relative abundance of carbon and oxygen in the plastic etched strips when compared to control samples. It has been shown that partially etched Parylene can form carboxylic groups with a ratio of 4:1 carbon to oxygen atoms. This effect was observed and exacerbated by the sample geometry not in sufficient contact with the grounded chamber baseplate causing charging and therefore insufficient hydrogen abstraction in the plasma. An alternative production method produced strips that were not as flat over the open area as the previous method but had no significant contaminant layer. This process involved coating a release layer of sodium chloride before the aluminium strips. When lowered into water, the salt dissolves in water and the strips are suspended on the surface tension, allowing the strips to be picked onto the mount. Each target required measuring for form using a white light interferometer where around half were within specification. </p
Experimental investigation of fast electron propagationin laser compressed cylindrical targets
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Automated production of high rep rate foam targets
No full textManufacturing low density targets in the numbers needed for high rep rate experiments is highly challenging. This report summarises advances from manual production to semiautomated and the improvements that follow both in terms of production time and target uniformity. The production process is described and shown to be improved by the integration of an xyz robot with dispensing capabilities. Results are obtained from manual and semiautomated production runs and compared. The variance in the foam thickness is reduced significantly which should decrease experimental variation due to target parameters and could allow for whole batches to be characterised by the measurement of a few samples. The work applies to both foil backed and free standing foam targets.Peer reviewe
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