Fusion neutron and ion emission from deuterium and deuterated methane cluster plasmas

Abstract

Experiments on the interaction of intense, ultrafast pulses with large van der Waals bonded clusters have shown that these clusters can explode with substantial kinetic energy and that the explosion of deuterium clusters can drive nuclear fusion reactions. Producing explosions in deuterated methane clusters with a 100 fs, 100 TW laser pulse, it is found that deuterium ions are accelerated to sufficiently high kinetic energy to drive deuterium nuclear fusion. From measurements of cluster size and ion energy via time of flight methods, it is found that these exploding deuterated methane clusters exhibit higher ion energies than explosions of comparably sized neat deuterium clusters, in accord with recent theoretical predictions. From measurements of the plume size and peak density, the relative contribution to the fusion yield from both beam target and intrafilament fusion is discussed.

High repetition-rate neutron generation by several-mJ, 35 fs pulses interacting with free-flowing D2O

“…We demonstrate a conversion efficiency of laser energy into 2.45 MeV neutrons of ∼ 10 −8 , which is comparable to previous experiments that utilized tabletop systems 8,16,17,[19][20][21] .…”

Optimization of the neutron yield in fusion plasmas produced by Coulomb explosions of deuterium clusters irradiated by a petawatt laser

“…After compression, the pulse continued in vacuum, directed to reflect off the f /40 spherical mirror that focuses the 22 cm diameter flat-top beam to a 200 μm diameter focal spot in the target chamber with a Rayleigh length of 2 cm. This created a relatively large interaction volume compared with previous experiments [1,3,[9][10][11][12][13][14] to increase neutron yields [16]. The spherical mirror could be translated along the laser propagation direction to adjust the distance between the optical focus and the position of the cluster-producing nozzle.…”

“…At high enough laser intensity, almost all of the electrons are removed from the cluster on a time scale short relative to the ion motion. What remains is a highly charged cluster of ions at liquid density, which promptly explodes by Coulomb repulsion.In experiments with peak laser intensities of 10 16 -10 18 W/cm 2 , deuterium ions with average kinetic energies up to about 10 keV have been observed, which were energetic enough to drive DD fusion events in a plasma with an average ion density near 10 19 cm −3 [9][10][11][12]. DD fusion can also occur when energetic ions collide with cold atoms in the background gas jet [13].…”

High Intensity Femtosecond XUV Pulse Interactions with Atomic Clusters

“…This ion distribution peaks at around 80 eV and has a tail that extends out toward 600 eV. We can calculate the spectrum from Coulomb exploding clusters by convolving the spectrum of a single Coulomb exploding cluster with a log-normal cluster size distribution, a procedure which has been shown to model accurately the explosions of deuterium clusters irradiated by high intensity 800 nm laser pulses [4]. The calculated spectrum for Coulomb exploding clusters with <N> =30,000 (and Z ~1) is illustrated in figure 5.…”

“…At high intensity, the electric field of the laser strips electrons from the cluster by tunnel and barrier suppression ionization, and electrons confined to the vicinity of the cluster by spacecharge forces further ionize the cluster to high charge states by collisional ionization [1]. If the laser field is strong enough, a condition satisfied if the ponderomotive potential of the laser is greater than the surface binding potential of the ionized cluster, the laser field strips the cluster of its electrons and the charged cluster explodes by Coulomb explosion [4]. On the other hand, if the clusters are large and the ions highly charged, space charge forces retain electrons within the cluster body, resulting in a "nanoplasma" which explodes by hydrodynamic forces [1].…”