Model of neutron-production rates from femtosecond-laser–cluster interactions

Abstract

Solid deuterium clusters provide a new type of target for laser-matter interactions. We present a theory for the generation of laser driven Coulomb explosions that create a hot fusion-producing ion tail. We derive an initial distribution function for the exploded ions, for an arbitrary cluster-size distribution, and solve for the D-D neutron-production rate during the free expansion of these ions into a vacuum. We find good agreement between the theory and the experiment: the theory suggests an explanation for the observed saturation and drop in neutron yield beyond a definite cluster size, consistent with recent experiments by Ditmire ͓T. Ditmire et al., Nature 398, 489 ͑1999͔͒ and Zweiback ͓J. Zweiback et al., Phys. Rev. Lett. 84, 2634 ͑2000͒; J. Zweiback et al., Phys. Rev. Lett. 85, 3640 ͑2000͔͒.

Interaction of intense laser pulses with atomic clusters: Measurements of ion emission, simulations and applications

“…A detailed description of this work can be found in [69]. Modelling of the neutron yield within this Coulomb explosion picture has been carried out [70] providing good agreement with the experimental data, and a comparison with the case of a hydrodynamic cluster expansion is given in [71].…”

Coherently enhanced radiation reaction effects in laser-vacuum acceleration of electron bunches

“…Many different mechanisms play a role in laser-cluster interaction (Saalmann et al, 2006;Krainov & Smirnov, 2002) and it is beyond the scope of this paper to analyze this interaction in detail. Instead, we use a strongly simplified model of the cluster suggested by (Parks et al, 2001) to obtain order-of-magnitude estimates for the initial parameters of the electron bunch. Accordingly, at some point in the leading edge of the pulse the field strength becomes such that all atoms in the cluster are ionized almost instantaneously, changing the neutral cluster into a dense plasma ball.…”

“…The critical dimensionless field strength at which the electron bunch is liberated may be estimated as (Parks et al, 2001) a crit = 15 96…”

“…The time this takes is of the order t esc ∼ ω −1 p (Parks et al, 2001), so that the escaping electron bunch will have a velocity of approximately…”

“…The non-relativistic cluster model of (Parks et al, 2001) does not apply for such a large amount of charge. We assume a relativistic initial electron bunch velocity of β 0 = 0.9 instead, as is also indicated in (Liseykina et al, 2010).…”