Investigation of fusion yield from exploding deuterium-cluster plasmas produced by 100-TW laser pulses

Abstract

When clusters of deuterium are irradiated with an intense, ultrafast laser pulse, the clusters explode, generating ions with kinetic energies high enough to produce nuclear-fusion events. Here we present experimental measurements of the dependence of the fusion yield of an exploding deuterium-cluster plasma on pulse energy up to the 10-J level for incident pulse durations of 100 fs and 1 ps. These energies correspond to peak vacuum intensities of 2 ϫ 10 20 and 2 ϫ 10 19 W/cm 2 , respectively. We also present measurements of the resulting plasma ion spectra that possess features indicative of a Coulomb explosion and discuss the yield scaling and its relation to previous findings based on the differences in laser focal geometry and pulse duration.

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

“…If something induced a breakup of clusters causing a drop in average ion energy at the highest intensities, it certainly did not appreciably affect the Coulomb nature of the expansion at the optimum intensity of 2.8×10 16 W/cm 2 . It has been speculated that once the laser field is intense enough to strip all electrons from a given cluster, the cluster would also experience total outer ionization for electric fields of even greater intensity, resulting in similar ion kinetic energies [12,21]. According to our measurements, this was not the case and much less energetic ions (∼3 keV) were produced at the highest laser intensities near 1×10 18 W/cm 2 .…”

“…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].…”

“…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.…”

Efficient neutron generation from solid-nanoparticle explosions driven by DPSSL-pumped high-repetition rate femtosecond laser pulse

“…A number of experiments [1][2][3][4][5] demonstrated the possibility of laser-driven fusion using pure D 2 or CD 4 clusters. In these works, multi-keV deuterium ions were generated by Coulomb explosion of a few nanometres clusters.…”

Fusion neutron detector calibration using a table-top laser generated plasma neutron source

“…We have explored an alternate avenue for calibration of a detector by exploiting the technique of driving fusion by irradiating atomic clusters to drive nuclear fusion between hot deuterons from neighboring cluster explosions [14,15]. Cluster fusion sources are capable of yields up to 10 5 fusion neutrons per Joule of incident laser energy using pure deuterium clusters [14,16]. In addition Grillon et al [17] demonstrated that even higher ion energies can be achieved from deuterated methane clusters.…”