Observation and Control of Shock Waves in Individual Nanoplasmas
Abstract not provided
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Engineering topics
Petrov, G M
Publications and source records attributed to Petrov, G M.
Generation of high-energy (>15 MeV) neutrons using short pulse high intensity lasers
A roadmap is suggested and demonstrated experimentally for the production of high-energy (>15 MeV) neutrons using short pulse lasers. Investigation with a 3D Monte Carlo model has been employed to quantify the production of energetic neutrons. Numerical simulations have been performed for three nuclear reactions, d(d,n){sup 3}He, {sup 7}Li(d,n){sup 8}Be, and {sup 7}Li(p,n){sup 7}Be, driven by monoenergetic ion beams. Quantitative estimates for the driver ion beam energy and number have been made and the neutron spectra and yield in the ion propagation direction have been evaluated for various incident ion energies. In order to generate neutron fluence above a detection limit of 10{sup 6} neutrons/sr, either {approx}10{sup 10} protons with energy 20-30 MeV or comparable amount of deuterons with energy 5-10 MeV are required. Experimental verification of the concept with deuterons driven by the Titan laser (peak intensity 2 Multiplication-Sign 10{sup 19} W/cm{sup 2}, pulse duration of 9 ps, wavelength 1.05 {mu}m, and energy of 360 J) is provided with the generation of neutrons with energy of up to 18 MeV from {sup 7}Li(d,n){sup 8}Be reactions. Future research will focus on optimized schemes for ion acceleration for production of high-energy neutrons, which will involve efficient target design, laser parameter optimization, and converter material.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Production of neutrons up to 18 MeV in high-intensity, short-pulse laser matter interactions
The generation of high-energy neutrons using laser-accelerated ions is demonstrated experimentally using the Titan laser with 360 J of laser energy in a 9 ps pulse. In this technique, a short-pulse, high-energy laser accelerates deuterons from a CD{sub 2} foil. These are incident on a LiF foil and subsequently create high energy neutrons through the {sup 7}Li(d,xn) nuclear reaction (Q = 15 MeV). Radiochromic film and a Thomson parabola ion-spectrometer were used to diagnose the laser accelerated deuterons and protons. Conversion efficiency into protons was 0.5%, an order of magnitude greater than into deuterons. Maximum neutron energy was shown to be angularly dependent with up to 18 MeV neutrons observed in the forward direction using neutron time-of-flight spectrometry. Absolutely calibrated CR-39 detected spectrally integrated neutron fluence of up to 8 x 10{sup 8} n sr{sup -1} in the forward direction.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Comparison of bulk and pitcher-catcher targets for laser-driven neutron production
Laser-driven d(d, n)-{sup 3}He beam-target fusion neutron production from bulk deuterated plastic (CD) targets is compared with a pitcher-catcher target scheme using an identical laser and detector arrangement. For laser intensities in the range of (1-3) x 10{sup 19} W cm{sup -2}, it was found that the bulk targets produced a high yield (5 x 10{sup 4} neutrons per steradian) beamed preferentially in the laser propagation direction. Numerical modeling shows the importance of considering the temperature adjusted stopping powers to correctly model the neutron production. The bulk CD targets have a high background target temperature leading to a reduced stopping power for the deuterons, which increases the probability of generating neutrons by fusion. Neutron production from the pitcher-catcher targets was not as efficient since it does not benefit from the reduced stopping power in the cold catcher target. Also, the inhibition of the deuteron acceleration by a proton rich contamination layer significantly reduces the pitcher-catcher neutron production.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
A generalized implicit algorithm for multi-dimensional particle-in-cell simulations in Cartesian geometry
An implicit multi-dimensional particle-in-cell (PIC) code is developed to study the interaction of ultrashort pulse lasers with matter. The algorithm is based on current density decomposition and is only marginally more complicated compared to explicit PIC codes, but it completely eliminates grid heating and possesses good energy conserving properties with relaxed time step and grid resolution. This is demonstrated in a test case study, in which high-energy protons are generated from a thin carbon foil at solid density using linear and circular polarizations. The grid heating rate is estimated to be 1-10 eV/ps.
36 MATERIALS SCIENCE↗
Neutron production from ultrashort pulse lasers using linear and circular polarization
An implicit 2D3V particle-in-cell code is used to study proton and deuteron acceleration from an ultrathin CD foil with thickness between 20 and 200 nm using linear and circular polarization. The proton and deuteron beams drive nuclear fusion reactions from converter foils in a pitcher-catcher set-up. The neutron yield for three representative reactions d - d, d - Li, and p - Li has been calculated analytically using the total neutron production cross section and ion stopping power. For linear polarization, maximum normalized neutron yield of Y{sub d-d}=3.4x10{sup 6}, Y{sub d-Li}=3.2x10{sup 7}, and Y{sub p-Li}=6.8x10{sup 6} neutrons/J laser energy has been calculated at the optimum foil thickness of 50 nm. For circular polarization, the optimum foil thickness is 20 nm, for which the corresponding neutron yields are Y{sub d-d}=1.9x10{sup 6}, Y{sub d-Li}=2.0x10{sup 7}, and Y{sub p-Li}=2.7x10{sup 6}, respectively. The laser polarization strongly affects the neutron production; for our regime, i.e., intensity I=1x10{sup 21} W/cm{sup 2}, pulse duration {tau}{sub FWHM}=30 fs, and laser energy {epsilon}{sub laser}=3.8 J, both the conversion efficiency of laser energy into ion kinetic energy and neutron yield are higher for linear polarization. Only for ultrathin ({approx}20 nm) foils in the radiation pressure acceleration regime, circular and linear polarizations yield comparable results.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗