Experimental Study On Deuterium-deuterium Fusion Reaction In Laser Plasma Environment

With the rapid development of the intense laser technology,laser nuclear physics,a new interdisciplinary of laser plasma physics and nuclear physics,has received con-siderable attention.The ultra-intense and ultra-short laser interacting with matter will produce an extreme plasma environment with high temperature,high density and high pressure.Laser-induced plasma,an extreme environment created in labs,provides a new platform to study nuclear reactions in astronomical environments.Due to the elec-tron screening effect,the cross section measured by method of traditional accelerator beam target experiment needs to be modified before it can be used in the nuclear astro-physical reaction network calculation,but the cross section correction is very uncertain.In the research of astrophysical processes,using high-intensity laser to generate plasma environment to induce nuclear reaction has received considerable attention.Deuterium-deuterium(DD)fusion reaction is not only an important reaction in the process in the primordial nucleosynthesis,but also an important reaction in controlled nuclear fusion reactor.This thesis mainly studied DD fusion reaction in the plasma environment pro-duced by high-power laser device and new methods for measuring the products of laser plasma experiment.CR-39 is common detector in laser-induced nuclear physics.The track on CR-39 is related to the type and energy of incident particles and etching conditions.This thesis studied the response of CR-39 for particles(protons,? particles and carbon ions)pro-duced by accelerators and radioactive sources,and calibrated the relationship between track diameter and particle energy.The main conclusions are as follows:1.the a particles and carbon ions are more suitable for chemical etching at etching condition of 98?,6.25 mol/1 NaOH,and the advantage is that the etching time is obviously shortened.For a particle,when the particle energy is more than 2 MeV,the track diameter difference between each energy point at 98? is larger than that at 70?.The greater the difference between tracks,the more advantageous it is to use tracks to distinguish particles with different energies.For carbon ion,the track diameters in the energy range of 10 MeV to 30 McV,are not related to the energy at two etching conditions.For proton,due to 6 MeV and 8 MeV proton tracks can be etched at low temperature,but not at 98?,proton tracks of enengy above 6 MeV are more suitable for etching at 70?.Comparing the track diameters of three kinds of particles at two etching conditions,using 98? etching particle tracks,the protons track,a particles track and carbon ions track can be distinguished by controlling the etching time.2.we measured the bulk etching rate of CR-39 at etching temperature of 98?,combined with the data in other temperature,fitted the relationship between bulk etching rate and temperature,and found that the bulk etching rate increased exponentially with temperature.A 4H-SiC detector is developed for laser plasma experiment,which has the ad-vantages of radiation resistance,high temperature resistance and fast response.We use SiC detector to measure the time-of-flight signal of ions accelerated by high-intensity laser,and measure the electromagnetic pulse signal(EMP)and proton time-of-flight signal produced by the interaction between laser and target.Among them,EMP is the ion take-off time signal,and the ion arrival detector is the termination time signal.The maximum proton energy accelerated by TNSA is about 30 MeV.What's more,there is no feasible method to analyze the time of flight signal into accurate proton energy spectrum.In addition,the on-line particle separation method is not used in the experi-ment,so the simple time-of-flight detector can not identify the particles and analyze the energy spectrum.For this reason,we have designed an array diamond position sensitive detector combined with Thomson parabola spectrometer(TPS),to solve this problem in the future experiment.The DD fusion reaction was experimentally investigated at the ShengGuang-II Up-date laser facility.The fusion reaction was realized in a complete plasma environment by using eight nanosecond lasers to directly symmetrically ablate a Deuterated polyethy-lene(CD2)target with a thickness of tens to hundreds of microns.The important exper-imental conclusions are as follows:1.According to the characteristics of DD fusion products,two pieces of CR-39 and an aluminum film are combined to form a range filter spectrometer(RFS),which realizes that the first piece of CR-39 behind the aluminum film is used to measure primary DD protons and the second piece of CR-39 is used to measure secondary D3He protons.At the same time,the track diameter distribution data of CR-39,coated aluminum films with the same thickness were calibrated with 3 MeV protons,which provides a basis for analyzing the experimental results of laser-induced DD fusion2.We measured the 3 MeV protons produced by the primary DD reaction by uti-lizing the range filter spectrometer,and its yields was about 106-107.Meanwhile primary 2.45 MeV DD neutrons and secondary DT neutrons were measured by using scintillator detector based on time-of-flight method,in which the yield of 2.45 MeV neutron was about 107,which can be verified with the primary 3 MeV DD proton yield,which is consistent with those experiment results of neutron yields on the same type of laser facilities in the world.