Deuterium-Deuterium Fusion Dynamics in Low-Density Molecular-Cluster Jets Irradiated by Intense Ultrafast Laser Pulses

Following the interaction of superintense, short pulse lasers and plasmas, ions can be accelerated to velocities sufficient to drive nuclear fusion reactions, in particular, by the process of Coulomb explosion of clusters [T. Ditmire et al., Nature (London) 398, 491 (1999)]. We show here how short bursts of neutrons can be produced using a jet of low-density deuterated methane clusters. Ion velocity distributions were simultaneously measured by a Thomson parabola mass spectrometer, demonstrating deuteron energies up to 120 keV. We show that, in such conditions, nuclear fusion will occur not only in the hot plasma core, but also in the cold outer region by collision processes.

Figure 1

Time of flight spectra of neutrons at two positions separated by 30 cm. The temporal width of the detection system is estimated to 10 ns.

Figure 2

Thomson parabola image of the ions resulting from the interaction. ${\mathrm{D}}^{+}$, ${\mathrm{C}}^{+}$, and ${\mathrm{C}}^{2+}$ ions are clearly visible.

Figure 3

Energy distributions of ${\mathrm{D}}^{+}$ and ${\mathrm{C}}^{+}$ ions measured by the Thomson parabola. The dashed line indicates a fit of the ${\mathrm{D}}^{+}$ distribution by a Maxwellian profile.

Figure 4

(a) Intensity dependence of the total neutron yield over $4\pi sr$; theoretical estimates assuming central plasma model (dashed line) and the lateral collision model (dotted line). (b) Most probable energies of the measured distributions of ${\mathrm{C}}^{+}$ and ${\mathrm{D}}^{+}$.