Time-of-flight of He ions from laser-induced processes in ultra-dense deuterium D(0)

• Time-of-flight studies have been made of ejection of massive particles from laser-induced fusion in ultra-dense deuterium D(0). Ion peaks are observed with energies from 1.4 MeV u−1 down to 50 keV u−1.
• The ion peaks are interpreted as due to collisionally delayed 4He and 3He (initially with normal fusion energies) and to p and D scattered off the He ions.
• Collisions of 4He with D4 ultra-dense clusters are also observed.
• Thermal distributions of neutrons are found at temperatures of 80–600 MK, showing fusion temperature of the plasma.

Time-of-flight (TOF) energy measurements of ions from pulsed laser-induced processes in ultra-dense deuterium D(0) have been accomplished. The scintillation detector is a fast plastic scintillator preceded by a thin Al foil, with photo-multiplier detection of the scintillations. Signal is normally observed only when the laser focus is moved over the target, which means that the process is critically dependent on the state of the D(0) layer. Ions require up to 1 MeV u−1 to penetrate through the Al foil and the observation of a signal in this setup proves directly that nuclear processes take place. Most TOF peaks agree with 4He ions ejected with 3.5–3.6 MeV energy in the D + D nuclear fusion process. These ions are further delayed by collisions with deuterium atoms or ultra-dense deuterium clusters. All probable collision processes of 4He and 3He are observed. T emission is not observed, as expected due to the large reaction rate for T + D. To exclude that after-pulses in the photo-multipliers can give a similar signal, two flight lengths, two photo-multipliers with several mounting methods, several optical filters, and both oscilloscope and pulse-counting detection methods have been employed to study the TOF distributions.

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