The fast ignition concept has been conceived as an alternative to other approaches for nuclear fusion energy. In the fast ignitor scenario a high-energy particle beam, driven by an ultrashort pulse laser, is deposited into a pre-compressed deuterium-tritium (DT) fuel capsule and creates a 'hot spot' with temperature and density parameters suitable for ignition, approximately 10 kiloelectron volts (keV).
Initially, the easiest path for ignition was taken using electrons, but it was soon recognized that numerous problems such as instabilities exists. The next logical step was to use ions, more specifically, protons. Subsequent experiments demonstrated that protons could be accelerated to relevant energies with conversion efficiencies of 5 to 10 percent and they were proposed as an alternative to relativistic electrons. However, the number of protons required for fast ignition is in order of magnitude two times greater than that of light ions that have a conversion efficiency of laser energy into ions of up to 25 percent.
"Presently, all efforts in the direction of fast ignition focus entirely on protons, but this continues to be plagued by problems," said Dr. Jack Davis. "Our research strongly indicates that the use of light ions, heavier than protons, in the lithium to aluminum range is a path in the right direction for ignition."
For ions of the appropriate range, the beam energy can be deposited directly in the fuel, with high efficiency. In general, ion beams offer the advantage of more localized energy deposition, improved beam focusing, straight line trajectory while traversing the DT fuel, maximum energy deposition at the end of their range and suppression of the various kinds of instabilities.
The Ion stopping power — the gradual energy loss of fast particles as they pass through matter — results in a quadratic increase in the required ion kinetic energy relative to atomic number, but a decreasing number of these ions is needed to deliver the fast ignition hot spot energy, translating into a decreased irradiated spot size on the coupling target. The ionization density (number of ions per unit of path length) produced by a fast charged particle along its track increases as the particle slows down. It eventually reaches a maximum called the Bragg peak close to the end of its trajectory. After that, the ionization density dwindles quickly to insignificance.
Other considerations such as tailoring the ion energy and angular distribution, which are responsible for ion beam focusing and energy density deposition in time and space, may turn out to be more important for the practical realization of the fast ignition.
Daniel Parry | EurekAlert!
Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie
Seeing the quantum future... literally
16.01.2017 | University of Sydney
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction