531 research outputs found
Introducing the Fission-Fusion Reaction Process: Using a Laser-Accelerated Th Beam to produce Neutron-Rich Nuclei towards the N=126 Waiting Point of the r Process
We propose to produce neutron-rich nuclei in the range of the astrophysical
r-process around the waiting point N=126 by fissioning a dense
laser-accelerated thorium ion bunch in a thorium target (covered by a CH2
layer), where the light fission fragments of the beam fuse with the light
fission fragments of the target. Via the 'hole-boring' mode of laser Radiation
Pressure Acceleration using a high-intensity, short pulse laser, very
efficiently bunches of 232Th with solid-state density can be generated from a
Th layer, placed beneath a deuterated polyethylene foil, both forming the
production target. Th ions laser-accelerated to about 7 MeV/u will pass through
a thin CH2 layer placed in front of a thicker second Th foil closely behind the
production target and disintegrate into light and heavy fission fragments. In
addition, light ions (d,C) from the CD2 production target will be accelerated
as well to about 7 MeV/u, inducing the fission process of 232Th also in the
second Th layer. The laser-accelerated ion bunches with solid-state density,
which are about 10^14 times more dense than classically accelerated ion
bunches, allow for a high probability that generated fission products can fuse
again. In contrast to classical radioactive beam facilities, where intense but
low-density radioactive beams are merged with stable targets, the novel
fission-fusion process draws on the fusion between neutron-rich, short-lived,
light fission fragments both from beam and target. The high ion beam density
may lead to a strong collective modification of the stopping power in the
target, leading to significant range enhancement. Using a high-intensity laser
as envisaged for the ELI-Nuclear Physics project in Bucharest (ELI-NP),
estimates promise a fusion yield of about 10^3 ions per laser pulse in the mass
range of A=180-190, thus enabling to approach the r-process waiting point at
N=126.Comment: 13 pages, 6 figure
Learning Outcomes of an Educational Leadership Cohort Program
Over the past three decades, demands on public schools have increased dramatically with a direct impact on the expectations of principals
Efficient ion acceleration by collective laser-driven electron dynamics with ultra-thin foil targets
Experiments on ion acceleration by irradiation of ultra-thin diamond-like
carbon (DLC) foils, with thicknesses well below the skin depth, irradiated with
laser pulses of ultra-high contrast and linear polarization, are presented. A
maximum energy of 13MeV for protons and 71MeV for carbon ions is observed with
a conversion efficiency of > 10%. Two-dimensional particle-in-cell (PIC)
simulations reveal that the increase in ion energies can be attributed to a
dominantly collective rather than thermal motion of the foil electrons, when
the target becomes transparent for the incident laser pulse
Dynamics of Nanometer-Scale Foil Targets Irradiated with Relativistically Intense Laser Pulses
In this letter we report on an experimental study of high harmonic radiation
generated in nanometer-scale foil targets irradiated under normal incidence.
The experiments constitute the first unambiguous observation of odd-numbered
relativistic harmonics generated by the component of the
Lorentz force verifying a long predicted property of solid target harmonics.
Simultaneously the observed harmonic spectra allow in-situ extraction of the
target density in an experimental scenario which is of utmost interest for
applications such as ion acceleration by the radiation pressure of an
ultraintense laser.Comment: 5 pages, 4 figure
Giant half-cycle attosecond pulses
Half-cycle picosecond pulses have been produced from thin photo-conductors,
when applying an electric field across the surface and switching on conduction
by a short laser pulse. Then the transverse current in the wafer plane emits
half-cycle pulses in normal direction, and pulses of 500 fs duration and 1e6
V/m peak electric field have been observed. Here we show that single half-cycle
pulses of 50 as duration and up to 1e13 V/m can be produced when irradiating a
double foil target by intense few-cycle laser pulses. Focused onto an
ultra-thin foil, all electrons are blown out, forming a uniform sheet of
relativistic electrons. A second layer, placed at some distance behind,
reflects the drive beam, but lets electrons pass straight. Under oblique
incidence, beam reflection provides the transverse current, which emits intense
half-cycle pulses. Such a pulse may completely ionize even heavier atoms. New
types of attosecond pump-probe experiments will become possible.Comment: 5 pages, 4 figures, to be presented at LEI2011-Light at Extreme
Intensities and China-Germany Symposium on Laser Acceleratio
Recommended from our members
Contemporary Issues in Translantic Relations
This report summarises the interdisciplinary seminar hosted by the Jean Monnet Chair in Transatlantic Relations at City Law School and the Institute for the Study of European Law (ISEL). The event consisted of three sessions: The Transatlantic Relationship; Transatlantic Defence, Security and Civil Liberties; Transatlantic and Global Trade. It examined topical issues in transatlantic relations across a range of subjects and issues, from trade, security and data, to defence. The seminar reflected upon the state of the art in transatlantic relations, with speakers from a broad variety of disciplines and practice. It considered inter alia: How should we understand the future of ‘American First’ at the end of the Trump Presidency? What is the current state of the US-Sino tech war and what are its implications for EU-US relations? How do UK-US relations impact upon this equation, in light of the Huawei 5G affair? What is the future of the EU-UK-US triangle in international security, where the EU loses the heft of one of its largest members? Will the UK increasingly align in sectoral fields to the US? What do the negotiation objectives of the EU-US and UK-US indicate to us about the future of the special partnerships? With the world’s largest sanctions regimes, the EU and US will pose a challenge for the UK to alignment purposes- will it inevitably be the EU first? What are its implications for a more significant FTA between the respective parties? How does the rise of the EU as a global data actor influence contemporary politics? Has the US succeeded in taming the global mobility of its social media giants through taxation threats? How does a multilateralist such as the EU deal with the future of American First after the next US election and the development of the uncertain path of Global Britain? Does Churchill’s call for a United States of Europe with the UK outside but closely aligned within the Commonwealth of Nations have any resonance going forward? In any field at all? What developments in the breakdown of the WTO DS system can occur with the aid of the EU, US and UK? Is the US sincere about its reform? Can Global Britain survive a shift outside of the EU without a WTO DS
Theory of laser ion acceleration from a foil target of nanometers
A theory for laser ion acceleration is presented to evaluate the maximum ion
energy in the interaction of ultrahigh contrast (UHC) intense laser with a
nanometer-scale foil. In this regime the energy of ions may be directly related
to the laser intensity and subsequent electron dynamics. This leads to a simple
analytical expression for the ion energy gain under the laser irradiation of
thin targets. Significantly, higher energies for thin targets than for thicker
targets are predicted. Theory is concretized to the details of recent
experiments which may find its way to compare with these results.Comment: 22 pages 7 figures. will be submitted to NJ
Laser Ion Acceleration: Status and Perspectives for Fusion
High power short-pulse lasers presently reach peak powers of a few hundred Terawatts up to a
Petawatt, and routinely reach focal intensities of 1018 - 1021 W/cm2 . These lasers are able to produce various secondary radiation, from relativistic electrons and multi-MeV/nucleon ions to high-energetic X-rays and γ-rays. In many laboratories world-wide large efforts are presently devoted to a rapid development of this novel tool of particle acceleration, targeting nuclear, fundamental and high-field physics studies as well as various applications. Based on the Radiation Pressure Acceleration mechanism, laser-accelerated ion beams can be generated with solid-state density, thus exceeding beams from conventional accelerators by about 14 orders of magnitudes. This opens the perspective of a novel reaction scheme called ’f ssion-fusion’, where in a first step f ssion is induced both in laser-accelerated f ssile projectiles from a ’production target’ and in a second ’reaction target’ again from f ssile material hit by the accelerated projectiles. Due to the unprecedented ion density, (neutron-rich) light f ssion fragments from projectile and target can fuse again, forming extremely exotic species approaching the region of the N = 126 waiting point of the r-process.
Within the next 5 years a new EU-funded large-scale research infrastructure (ELI: Extreme Light Infrastructure) will be constructed, with one of its four pillars exclusively devoted to nuclear physics based on high intensity lasers (ELI-Nuclear Physics, to be built in Magurele/Bucharest). Studies of laser-induced nuclear reactions like the ’f ssion-fusion’ mechanism will be amongst the experimental f agship projects pursued there
Recommended from our members
Investigating the impact of poverty on colonization and infection with drug-resistant organisms in humans: a systematic review
Background
Poverty increases the risk of contracting infectious diseases and therefore exposure to antibiotics. Yet there is lacking evidence on the relationship between income and non-income dimensions of poverty and antimicrobial resistance. Investigating such relationship would strengthen antimicrobial stewardship interventions.
Methods
A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Ovid, MEDLINE, EMBASE, Scopus, CINAHL, PsychINFO, EBSCO, HMIC, and Web of Science databases were searched in October 2016. Prospective and retrospective studies reporting on income or non-income dimensions of poverty and their influence on colonisation or infection with antimicrobial-resistant organisms were retrieved. Study quality was assessed with the Integrated quality criteria for review of multiple study designs (ICROMS) tool.
Results
Nineteen articles were reviewed. Crowding and homelessness were associated with antimicrobial resistance in community and hospital patients. In high-income countries, low income was associated with Streptococcus pneumoniae and Acinetobacter baumannii resistance and a seven-fold higher infection rate. In low-income countries the findings on this relation were contradictory. Lack of education was linked to resistant S. pneumoniae and Escherichia coli. Two papers explored the relation between water and sanitation and antimicrobial resistance in low-income settings.
Conclusions
Despite methodological limitations, the results suggest that addressing social determinants of poverty worldwide remains a crucial yet neglected step towards preventing antimicrobial resistance
- …