The paper by Belyaev et al. [Phys. Rev. E 72, 026406 (2005)] reported the first experimental observation of alpha particles produced in the thermonuclear reaction 11 B(p, α) 8 Be induced by laser-irradiation on a 11 B polyethylene (CH2) composite target. The laser used in the experiment is characterized by a picosecond pulse duration and a peak of intensity of 2×10 18 W/cm 2 . We suggest that both the background-reduction method adopted in their detection system and the choice of the detection energy region of the reaction products are possibly inadequate. Consequently the total yield reported underestimates the true yield. Based on their observation, we give an estimation of the total yield to be higher than their conclusion, i.e., of the order of 10 5 α per shot. The observations of the thermonuclear reactions in a high-power laser pulse irradiated target is one of the hottest topics [1,2,3,4,5,6,7]. The most investigated reaction is D (d, n) 3 He with a Q-value of 3.26 MeV. There have been studies using different characteristics of lasers irradiation on a wide variety of targets, solid CD 2 plastic [2,5,6], D 2 -gas [4] and deuterium-clusters [1]. Since the reactions produce monochromatic neutrons, the spectroscopy of these neutrons gives important information on the ion acceleration mechanism in the laser-induced plasma.In the experiment recently carried out by a Russian group the yield of 10 3 α-particles has been reported [7], for the first time, in the laser-irradiation of a 11 B+CH 2 composite target. Their experiment is important for a deep understanding of the ion acceleration mechanism in the laser-matter interaction. The experiment has been carried out by using a "Neodymium" laser facility with the pulse energy of up to 15 J, a laser wave length of 1.055 µm, and a pulse duration of 1.5 ps. Before the main pulse, there are three pre-pulses with relative intensities 10 −4 , 10 −3 and 10 −8 , with ps durations for the former two and with 4 ns duration for the last one.The laser beam has been focused on the solid target at an oblique incidence of 40 degrees to the target normal. CR-39 track detectors covered with 11 and 22 µm thick aluminum foils have been used to count the yield of α-particles from the reaction 11 B(p, α) 8 Be. The reaction induces three-particles decay. Either through the 8 Be ground state (α 0 ):with the reaction Q-value = 8.59 MeV or through the 8 Be excited state (α 1 ):(2) * Electronic address: kimura@lns.infn.it; Also at Dipartimento di Fisica e Astronomia dell'Universita' di Catania, via Santa Sofia, 64, 95123 Catania, Italy with the reaction Q-value = 5.65 MeV and a large width of 1.5 MeV [8,9,10]. This is followed by the decay of the excited state (α 12 ):and a reaction Q-value = 3.028 MeV. It is known that the main channel of the reaction is the second [11,12] and only 1 % of the reaction products are α 0 from the reaction (1). Using energy and momentum conservation laws, the α 0 and α 1 have kinetic energies:where E is the center-of-mass incident energy in the case of the c...
We discuss a quantum effect in the diffusion process by developing a theory, which takes the finite curvature of the potential field into account. The transport coefficients of our theory satisfy the well-known fluctuation-dissipation theorem in the limit of Markovian approximation in the cases of diffusion in a flat potential and in a potential well. For the diffusion along a potential barrier, the diffusion coefficient can be related to the friction coefficient by an analytic continuation of the fluctuation-dissipation theorem for the case of diffusion along a potential well in the asymptotic time, but contains strong non-Markovian effects at short times. By applying our theory to the case of realistic values of the temperature, the barrier curvature, and the friction coefficient, we show that the quantum effects will play significant roles in describing the synthesis of superheavy elements, i.e., the evolution from the fusion barrier to the conditional saddle, in terms of a diffusion process. We especially point out the importance of the memory effect, which increases at lower temperatures. It makes the net quantum effects enhance the probability of crossing the conditional saddle.
Two different methods have been employed to determine the plasma temperature in a laser-cluster fusion experiment on the Texas Petawatt laser. In the first, the temperature was derived from time-of-flight data of deuterium ions ejected from exploding D(2) or CD(4) clusters. In the second, the temperature was measured from the ratio of the rates of two different nuclear fusion reactions occurring in the plasma at the same time: D(d,(3)He)n and (3)He(d,p)(4)He. The temperatures determined by these two methods agree well, which indicates that (i) the ion energy distribution is not significantly distorted when ions travel in the disassembling plasma; (ii) the kinetic energy of deuterium ions, especially the "hottest part" responsible for nuclear fusion, is well described by a near-Maxwellian distribution.
The plasma astrophysical S factor for the 3He(d,p)4He fusion reaction was measured for the first time at temperatures of few keV, using the interaction of intense ultrafast laser pulses with molecular deuterium clusters mixed with 3He atoms. Different proportions of D2 and 3He or CD4 and 3He were mixed in the gas target in order to allow the measurement of the cross section for the 3He(d,p)4He reaction. The yield of 14.7 MeV protons from the 3He(d,p)4He reaction was measured in order to extract the astrophysical S factor at low energies. Our result is in agreement with other S factor parametrizations found in the literature.
In the last decade, the availability in high-intensity laser beams capable of producing plasmas with ion energies large enough to induce nuclear reactions has opened new research paths in nuclear physics. We studied the reactions 3He(d, p)4He and d(d,n)3He at temperatures of few keV in a plasma, generated by the interaction of intense ultrafast laser pulses with molecular deuterium or deuterated-methane clusters mixed with 3He atoms. The yield of 14.7 MeV protons from the 3He(d, p)4He reaction was used to extract the astrophysical S factor. Results of the experiment performed at the Center for High Energy Density Science at The University of Texas at Austin will be presented
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.