Fusion Generated Fast Particles by Laser Impact on Ultra-Dense Deuterium: Rapid Variation with Laser Intensity

Abstract

Nuclear fusion D?D processes are studied by nanosecond pulsed laser interaction with ultra-dense deuterium. This material has a density of 10 29 cm -3 as shown in several previous publications. Laser power is \2 W (0.2 J pulses) and laser intensity is \10 14 W cm -2 in the 5-10 lm wide beam waist. Particle detection by time-offlight energy analysis with plastic scintillators is used. Metal foils in the particle flux to the detector remove slow ions, and make it possible to convert and count particles with energy well above 1 MeV. The variation of the signal of MeV particles from D?D fusion is measured as a function of laser power. At relatively weak laser-emitter interaction, the particle signal from the laser focus varies as the square of the laser power. This indicates collisions in the ultra-dense deuterium of two fast deuterons released by Coulomb explosions. During experiments with stronger laser-emitter interaction, the signal varies approximately as the sixth power of the laser power, indicating a plasma process. At least 2 9 10 6 particles are created by each laser pulse at the maximum intensity used. Our results indicate break-even in fusion at a laser pulse energy of 1 J with the same focusing, in approximate agreement with theoretical results for ignition conditions in ultra-dense deuterium. Radiation loss at high temperature will however require higher laser energy at break-even.

MeV particles from laser-initiated processes in ultra-dense deuterium D(−1)

“…It is difficult to distinguish between n and p generated signals in the scintillator, but since the sensitivity to protons is much larger than to neutrons, the main part of the signal observed is due to protons (and deuterons) [2]. A distinction between n and p may be found by using very thick foils, but the TOF information needed for the particle identification is then lost.…”

“…Nuclear fusion reactions can be caused by laser-initiated release of fast D atoms in ultra-dense deuterium D(−1) [1,2]. The density of this material is close to 10 29 cm −3 or 140 kg cm −3 as shown in several publications [3][4][5][6][7][8][9][10].…”

“…From this high density it is concluded that multiple-scattering events will take place of particles released with high energy from fusion reactions and Coulomb explosions (CE) as observed in refs. [1,2]. This scattering will strongly modify the results relative to a low-density case.…”

“…It is expected that such processes will be much easier to initiate in D(−1) [11,12], allowing the use of much weaker lasers for initiation of nuclear fusion. Recently, the number of fast particles released from D(−1) was found to increase rapidly with laser pulse energy [2].…”

Accelerator-based neutron source using a cold deuterium target with degenerate electrons

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] The findings suggest that deuterium clusters in a condensedmatter state exhibit both superfluid and superconducting characteristics at room temperature and below atmospheric pressure. Ultra-dense deuterium (UDD) was reported in Refs.…”