Nuclear fragmentation by tunneling

Fragmentation of nuclear system by tunneling is discussed in a molecular dynamics simulation coupled with imaginary time method. In this way we obtain informations on the fragmenting systems at low densities and temperatures. These conditions cannot be reached normally (i.e. above the barrier) in nucleus-nucleus or nucleon-nucleus collisions. The price to pay is the small probability of fragmentation by tunneling but we obtain observables which can be a clear signature of such phenomena.Comment: Phys.Rev.C (submitted

On The Expansion and Fate Of The Universe

The evolution of the universe from an initial dramatic event, the Big-Bang, is firmly established. Hubble's law [1] (HL) connects the velocity of galactic objects and their relative distance: v(r)=Hr, where H is the Hubble constant. In this work we suggest that HL is not valid at large distances because of total energy conservation. We propose that the velocity can be expanded in terms of their relative distance and produce a better fit to the available experimental data. Using a simple 'dust' universe model, we can easily calculate under which conditions an (unstable) equilibrium state can be reached and we can estimate the values of the matter present in the universe as well as the 'dark energy'. We do not need to invoke any 'dark energy', its role being played by the kinetic correction. The resulting picture is that the universe might reach an unstable equilibrium state whose fate will be decided by fluctuations: either collapse or expand forever

Density and Temperature of Bosons from Quantum Fluctuations

A method to determine the density and temperature of a system is proposed based on quantum fluctuations typical of Bosons in the limit where the reached temperature T is close to the critical temperature $T_c$ for a Bose condensate at a given density $\rho$. Quadrupole and particle multiplicity fluctuations relations are derived in terms of $\frac{T}{T_c}$. This method is valid for weakly interacting infinite and finite Boson systems. As an example, we apply it to heavy ion collisions using the Constrained Molecular Dynamics (CoMD) approach which includes the Fermi statistics. The model shows some clusterization into deuteron and ${\alpha}$ clusters which could suggest a Bose condensate. However, our approach demonstrates that in the model there is no Bose condensate but it gives useful informations to be tested experimentally. We stress the differences with methods based on classical approximations. The derived 'quantum' temperatures are systematically higher than the corresponding 'classical' ones. The role of the Coulomb charge of fragments is discussed

Deuteron-induced reactions generated by intense Lasers for PET isotope production

We investigate the feasibility of using laser accelerated protons/deuterons for positron emission tomography (PET) isotope production by means of the nuclear reactions $^{11}$B($p,n$)$^{11}$C and $^{10}$B($d,n$)$^{11}$C. The second reaction has a positive Q-value and no energy threshold. One can, therefore, make use of the lower energy part of the laser-generated deuterons, which includes the majority of the accelerated deuterons. The $^{11}$C produced from the reaction $^{10}$B($d,n$)$^{11}$C is estimated to be 7.4 $\times$ 10$^{9}$ per laser-shot at the Titan laser at Lawrence Livermore National Laboratory. Meanwhile a high-repetition table top laser irradiation is estimated to generate 3.5 $\times$ 10$^7$ $^{11}$C per shot from the same reaction. In terms of the $^{11}$C activity, it is about 2 $\times$ 10$^4$ Bq per shot. If this laser delivers kHz, the activity is integrated to 1 GBq after 3 minutes. The number is sufficient for the practical application in medical imaging for PET.Comment: 17 pages, 4 figure

Hydrodynamic Scaling Analysis of Nuclear Fusion driven by ultra-intense laser-plasma interactions

We discuss scaling laws of fusion yields generated by laser-plasma interactions. The yields are found to scale as a function of the laser power. The origin of the scaling law in the laser driven fusion yield is derived in terms of hydrodynamic scaling. We point out that the scaling properties can be attributed to the laser power dependence of three terms: the reaction rate, the density of the plasma and the projected range of the plasma particle in the target medium. The resulting scaling relations have a predictive power that enables estimating the fusion yield for a nuclear reaction which has not been investigated by means of the laser accelerated ion beams.Comment: 11 page