STUDY OF THE REACTIONS BETWEEN LIGHT NUCLEI IN THE ASTROPHYSICAL ENERGY REGION USING THE PLASMA HALL ACCELERATOR

STUDY OF THE REACTIONS BETWEEN LIGHT NUCLEI IN THE ASTROPHYSICAL ENERGY REGION USING THE PLASMA HALL ACCELERATOR Vyach.M.Bystritsky1, Vit.M.Bystritskii2, L.D.Butakov 3, V.V.Gerasimov1, G.N.Dudkin3, A.R Krylov1, B.A.Nechaev3, V.M.Padalko3, S.S.Parzhitskii1, A.V.Petrov3, N.M.Polkovnikova3, J.Wozniak4 Joint Institute for Nuclear Research, Dubna, Russia; Department of Physics and Astronomy, University of California, Irvine, USA; 3Federal State Scientific Institution "Scientific Research Institute of Nuclear Physics ",Tomsk, Russia; Faculty of Physics and Applied Computer Science, AGH, University of Science and Technology, Cracow, Poland Abstract Using the plasma accelerator based on the pulse Hall ion source, the first measurements of the astrophysical S-factor of the d+d3He + n reaction were performed for deuteron energies 9.1 and 9.9 keV The observed values of the S-factor and effective cross sections ~dd for dd reaction are in agreement with the results obtained by us earlier in the experiments at liner plasma accelerators (in a configuration of both direct and inverse Z-pinch) The preliminary results have confirmed the fact that the proposed technique can be effective to study nuclear reactions between light nuclei in the astrophysical energy region I Introduction Interest in studying reactions between light nuclei (pd , dd, d3He and d6Li reactions) in the region of astrophysical energies 2-12 keV is caused by a possibility of verifying symmetries in strong interactions, determining the contribution to interaction from exchange currents, checking the standard Solar model [1] Research of the given processes in the indicated energy region is rather problematic since intensity of the beams of the accelerated particles produced by classical accelerators are extremely low (I  1012 – 1013 1/s ), and cross sections of nuclear reactions in the astrophysical energy region are extremely small (10-39 - 10-33 сm2) An impetus to the current intensive study of reactions between light nuclei has become the possibility of using for these purposes pulsed high-current plasma accelerators and energy-precise linear ion accelerators of energy 4-100 keV [2-4] Plasma accelerators with the liner plasma formation in the direct and inverse Z-pinch configuration allowed quantitative information on the astrophysical S-factors and effective cross sections of the pd and dd reactions (pd3He + ; dd3He + n) in the ultralow energy region to be obtained for the first time [2,4] The results obtained for the first time have confirmed the fact that the proposed technique can be effectively used to study nuclear reactions in the astrophysical energy region It is necessary to note that highly accurate measurement of cross sections of the pd, dd and d3He reactions with the use of the plasma in the Z-pinch configuration is rather problematic The absence of reproducibility of the experimental conditions from "shot" (the act of the accelerator operation) to "shot" caused by the specificity of the work of accelerators of this class imposes certain restrictions on accuracy of measurement of parameters of the investigated processes This stimulated development of alternative methods for formation of intense charged-particles beams in the ultralow energy region For further research of reactions with light nuclei we developed and built a pulsed ion source with the closed Hall current allowing acceleration of plasma ions H +, D + and 3He + in the energy range 2-12 keV In this work the preliminary results of measuring the astrophysical S-factor and effective cross sections for the dd reaction in the experiment at the created accelerator Measurement method Experimental determination of the astrophysical S-factor and effective cross section of the dd reactions is based on measurement of the neutron output and parameterization of the dependence of the cross section reaction ~dd on the deuteron collision energy: S (E )  N nexp  ~ ~dd  N nexp / N d nt  n l , (2)  e  2 , (1) N d nt  n f ( E )dE  dx  E ( E , x ) 0 exp where N n is the yield of the detected neutrons, Nd is the number of deuterons hit in the target, Z1 = Z2 = is the deuteron charge,  = md is the reduced mass of the colliding particles, n t is the deuteron density of the target, (E) = Z1Z2e (µ/E)1/2 , n is the efficiency of the neutron registration, E are the collision energies of deuterons with the target nuclei after passage of a target layer of thickness x , E is the average energy of the deuteron collision, f (E) is the energy ~ distribution of the deuterons hitting the target, l is the effective target thickness defined from the ~ tot expression N n ( l ) 0.9 N ntot ( N n is the yield of neutrons from the dd reaction in the case of an the infinitely thick target) Experimental procedure The experimental setup (Fig.1) includes the plasma accelerator on the basis of the Hall ion source, a solid-state CD2 target from installed in the accelerator chamber, two detectors for detection of 2.5 MeV neutrons, diagnostic equipment for collecting information on parameters of the accelerated-ion flow generation process, an electrostatic multigrid mass-spectrometer of charged particles for measurement of the deuteron energy distribution The CD2 solid-state target was of the 25 cm2 area Neutrons were detected by two detectors of thermal neutrons, each being an assembly of 10 proportional 3He counters [5] Current of accelerated ions at the output of the Hall source was measured by means of the Rogovsky belt, and the current density in various sections of the beam hitting the target surface was determined with the collimated Faraday cylinders The energy distribution of ions was measured by our electrostatic multigrid mass-spectrometer of the charged particles whose operation was based on the braking potential method Analysis of the results Figure shows the energy distribution of deuterons measured by the mass-spectrometer during data taking in the experiment on the study of the dd reaction Using the function describing the given energy distributions, the values describing the experimental conditions (E d =9.10.3 keV, Ed =9.90.3 keV, FWHM =1.3 keV, N d (9.1) = (4.10.5)·1014, Nd (9.9) = (7.950.3)·1014 , nt exp exp =(8.000.08)·1022, n =(1.270.11)10-2, N n (9.1)=4 and N n (9.9) = 12), and formulas (1) and (2) we determined the values of the astrophysical S-factor and the effective dd-reaction cross: spectrometer, (4) 3He detector of thermal neutrons Fig Experimental setup: (1) Hall ion source plasma accelerator, (2) CD2 deuterium target, (3) electrostatic mass Fig Deuteron energy distribution ~ ~ S (4.7) = (31.916.9 3.2) keV b,  dd (4.3 < Ecoll