Fusion neutron yield from a laser irradiated heavy water spray

The fusion neutron yield from a laser irradiated heavy water D2O spray target was studied. Heavy water droplets of about 150 nm diameter in the spray were exposed to 35 fs laser pulses at an intensity of 1 1019 W cm2. Due to the 10 50 times bigger size of the spray droplets compared to usual cluster sizes, deuterons are accelerated to considerably higher kinetic energies of up to 1 MeV. Neutrons are generated by the deuterons escaping from the plasma and initiating a fusion reaction within the surrounding cold plume of the spray jet. For each 0.6 J of laser pulse energy, 6 amp; 61620;103 neutrons are produced by about 1011 accelerated deuterons. This corresponds to a D d,n reaction probability of about 6 amp; 61620;10 8. Compared to cluster targets, the reaction probability in the spray target is found to be two orders of magnitude larger. This finding apparently is due to both the considerably higher deuteron energies and the larger effective target thickness in the spray target. The measured neutron yield per accelerated deuteron i.e., the D d,n reaction probability , is employed to compare and extrapolate the neutron emission characteristics from different target arrangement

Explosion characteristics of intense femtosecond laser driven water droplets

An efficient acceleration of energetic ions is observed when small heavy water droplets of 20 mm diameter are exposed to ultra fast 40 fs Ti Sa laser pulses of up to 1019 W cm2 intensity . Quantitative measurements of deuteron and neutron spectra were done, allowing to analyze the outward and inward directed deuteron acceleration from the droplet. Neutron spectroscopy based on the D d,n fusion reaction was accomplished in four different spatial directions. The energy shifts of those fusion neutrons produced inside the exploding droplet reflect a remaining deuteron acceleration inside the irradiated droplet along the axis of the incident laser beam. The overall neutron yield of the microdroplets is as a result of the dominant outward directed acceleration of the deuterons with 1200 neutrons shot relatively small. Relying on the explosion like acceleration of such spherical droplet targets we have developed a new spray target consisting of heavy water micro spheres with diameters of 150 nm.. Both the high deuteron energies of up to 1 MeV resulting from the irradiation intensity of 1019 W cm2 as well as the collisions between the deuterons and the surrounding spray delivered about one order of magnitude more neutrons than the single droplet system . The 6 103 neutrons per laser pulse from the spray can be attributed to an efficient deuteron release from a significantly smaller laser excited volume as from deuterium cluster target

Interatomic and Intermolecular Coulombic Decay

Interatomic or intermolecular Coulombic decay (ICD) is a nonlocal electronic decay mechanism occurring in weakly bound matter. In an ICD process, energy released by electronic relaxation of an excited atom or molecule leads to ionization of a neighboring one via Coulombic electron interactions. ICD has been predicted theoretically in the mid nineties of the last century, and its existence has been confirmed experimentally approximately ten years later. Since then, a number of fundamental and applied aspects have been studied in this quickly growing field of research. This review provides an introduction to ICD and draws the connection to related energy transfer and ionization processes. The theoretical approaches for the description of ICD as well as the experimental techniques developed and employed for its investigation are described. The existing body of literature on experimental and theoretical studies of ICD processes in different atomic and molecular systems is reviewed

Permeable marine sediments: overturning an old paradigm

Sandy sediments, which cover about 70% of continental shelves and most beaches, are often thought of as geochemical deserts that harbor no life because they are usually poor in organic matter and other reactive substances. Based on the belief that significant reactions and fluxes and a dynamic ecology require large standing stocks of reactants and organic matter, sandy sediments are neglected.

Permeable marine sediments: overturning an old paradigm

Sandy sediments, which cover about 70% of continental shelves and most beaches, are often thought of as geochemical deserts that harbor no life because they are usually poor in organic matter and other reactive substances. Based on the belief that significant reactions and fluxes and a dynamic ecology require large standing stocks of reactants and organic matter, sandy sediments are neglected