3He Nuclei Research Articles

Differential Cross Section of Electron Scattering From 3He and 3H Nuclei with Considering Pionic Contribution

The excess pion inside the nucleus could change not only nucleons structure function, but also electron scattering cross section from nuclei. In this paper, we calculate pionic contribution in nuclear structure functions of 3He and 3H nuclei and the differential cross sections of electron scattering from these nuclei. At first, we calculate the Fermi motion and binding energy contribution as an important nuclear medium effect in scattering cross sections and then we add pionic contribution to structure functions and differential cross sections of electron scattering from these nuclei that the Fermi motion and binding energy are considered.

Double antikaonic nuclear clusters in antiproton-3He annihilation at J-PARC

We search for double anti-kaon nuclear bound states in the \(\bar p\) annihilation reaction in 3He nuclei at rest. In view of the strongly attractive \(\bar K N\) interaction, the existence of nuclear clusters with more than one K − has been predicted theoretically. The double anti-kaon production in elementary antiproton annihilation at rest is forbidden because of the negative Q-value; however, a double anti-kaon nuclear bound state, such as K − K − pp, with deep binding energy would enable double anti-kaon production in the nuclei. In order to investigate the K − K − pp production in the \(\bar p + ^3{\rm He} \to K^+ + K^0 + X~(X = K^-K^-pp)\) channel, the produced K − K − pp cluster is identified both using missing mass spectroscopy via the K + K0 channel with a Λ-tag, and invariant mass analysis of the expected decay particles from the K − K − pp cluster such as ΛΛ. We propose to perform the experiment at the existing K1.8BR beam line at J-PARC with the E15 spectrometer.

Experimental studies of few-body systems at MAMI

Few-body experiments at the Mainz Microtron were focused on a number of selected topics. Double-polarization experiments to determine the neutron electric form factor Gen have been performed using both deuterium and polarized helium-3 targets. The structure of 3He has been studied in the reactions 3H e e(ee,e′n) and 3H e e(ee,e′p) with large (transversal) missing momenta and in quasi-elastic electron scattering. Electromagnetically induced two-nucleon knockout has been investigated in order to study the role of correlated nucleon-nucleon motion in the nucleus. Measurements of the (e,e′pn) reaction on 3He and 16O were performed for the first time. A triple-polarization experiment of type 3H e e(ee,e′ep)d has been performed, where, in addition, the spin of the knocked out proton is analyzed. This measurement provides information on the spin-dependent momentum distribution of proton-deuteron clusters in the 3He nucleus. Hence, by tagging the outgoing deuteron spin-polarized 3He might also serve as an effective polarized proton target for electron scattering experiments. Moreover, in inclusive 3,4He(e,e′) measurements at low momentum transfer, the effect of 3-body-forces has been studied.

The COMBAS fragment separator

The basic ion-optical characteristics of the COMBAS fragment separator are analyzed. The momentum distributions of radioactive 6He, 8He, and 9Li nuclei obtained in the reaction 11B (33 A MeV, where A is the mass number of a particle) + 9Be (332.6 mg/cm2) have been investigated in forward-angle measurements on the COMBAS fragment separator. The momentum and angular (horizontal) acceptances of the COMBAS separator have been measured using the 6He, 8He, and 9Li beams. It has been ascertained that the images of the 6He, 8He, and 9Li nuclear beams in final achromatic focus of the separator Fa approximately twofold exceed the size of the beam on a producing target (input focus F0), at which the primary beam has a diameter of 6 mm. The intensities of 6He, 8He, and 9Li beams obtained at a 5-μA intensity of the primary 11B beam are 6.9 × 105, 2 × 104, and 4.7 × 105 particles/s, respectively. These values are sufficient for use in spectroscopic measurements. It is proposed that time-of-flight analysis of nuclear reaction products at the exit from the COMBAS separator will be used not only to measure the energy of transported particles over the whole operating range of the momentum acceptance, but also to identify them by mass A and charge Z without loss of these particles. The problem of reducing the count rates of detectors and further improvement of their energy resolution for detected particles can be solved by placing a high-resolution magnetic spectrometer past the second target accepting the secondary radioactive nuclear beams.

One-nucleon exchange and the effective local potential in nucleus-nucleus scattering

The influence of one-nucleon exchange on the local nucleus-nucleus potential is investigated using the resonating group method. Neutron scattering on 4He and 16O nuclei is examined in detail. The results are compared to microscopic calculations.

A study of the ground-state energy of 4He with nucleon–nucleon potentials

Ground-state properties are evaluated for the finite nucleus 4He starting from realistic nucleon–nucleon interactions within the framework of the Green’s function approach. For the sake of comparison, the same calculations are performed using the Brueckner–Hartree–Fock approximation. For that purpose four high-quality modern nucleon–nucleon interactions represented in momentum space are employed: the Argonne V18, CD-Bonn, Bonn A and N 3LO potentials. In these potentials, the effects of charge dependence are taken into account. Additional binding energy is obtained from the inclusion of the hole–hole scattering term within the framework of the Green function approach. It has been shown that the Green function results agree well with the results obtained by accurate methods for few-nucleon systems such as the Faddeev–Yakubovsky calculation. In this study, a comparison of the calculated ground-state energies, obtained by using the Green function approach and different nucleon–nucleon potentials, with experimental values is carried out. The results show good agreement between the calculated values and the experimental ones.

Precision measurement of the η-mass at COSY-ANKE

Measurements on the mass of the η-meson performed at different experimental facilities over the last decade have resulted in very precise results but differ by up to 0.5 MeV/c2 i e, more than eight standard deviations. In order to clarify this situation a new high precision measurement of the dp → 3Heη reaction was conducted at the COoler SYnchrotron – COSY – of the Forschungszentrum Jülich using the ANKE magnetic spectrometer, with the aim to achieve a mass resolution of Δm < 50 keV/c2. In order to measure the η meson mass with high accuracy through the dp → 3Heη reaction, both the momentum of the circulating deuteron beam in COSY as well as of the emitted 3He nucleus has to be determined with high precision. The experimentally achieved resolution for the momenta of the 3He nuclei and the beam deuterons will allow to reach the envisaged η-meson mass resolution.

Holographic 3He and 4He nuclei

The potential energy of 3He and 4He nuclei has been studied using the AdS/CFT correspondence. We consider a holographic picture for 3He and 4He nuclei and obtained their potentials using the holographic nucleon–nucleon potential. Then we calculate the binding energies of the nuclei by these potentials. Also, we obtain the energy of some excited states for the 4He nucleus. Similar calculations show that there is no excited state for the 3He nucleus. Our results are in good agreement with the experimental data.

Calculating the characteristics of neutron-deuteron and proton-deuteron systems in a two-body potential model

3H and 3He nuclei are considered in a two-body model (3H = n + d; 3He = p + d). Two independent approaches are used: in the first, interaction is described by the folding potential, while NN potentials are taken in the Hulthen form with allowance for violations of isotopic invariance. The second approach features phenomenological Hulthen and Yukawa Nd potentials used as Nd interaction. In both approaches, the binding energies, vertex constants, and asymptotic normalization coefficients in the N+d channel are calculated.

Optimised adiabatic fast passage spin flipping for 3He neutron spin filters

We describe here a method of performing adiabatic fast passage (AFP) spin flipping of polarized 3He used as a neutron spin filter (NSF) to polarize neutron beams. By reversing the spin states of the 3He nuclei the polarization of a neutron beam can be efficiently reversed allowing for the transmission of a neutron beam polarized in either spin state. Using an amplitude modulated frequency sweep lasting 500ms we can spin flip a polarized 3He neutron spin filter with only 1.8×10−5 loss in 3He polarization. The small magnetic fields (10–15G) used to house neutron spin filters mean the 3He resonant frequencies are low enough to be generated using a computer with a digital I/O card. The versatility of this systems allows AFP to be performed on any beamline or in any laboratory using 3He neutron spin filters and polarization losses can be minimised by adjusting sweep parameters.

Toward describing one-nucleon exchange in nucleus-nucleus scattering

The effect of one-nucleon exchanges on the potential of nucleus-nucleus interaction is considered on the basis of the resonating-group method. Corrections to the folding-model potential are obtained in the semiclassical approximation. Neutron scattering on 4He nuclei is considered as a model example.

Short-pulse ECR: A source of multiply charged ions

Extensive investigation is now under way in CERN (European Organization for Nuclear Research) in the framework of the Beta Beam project with the aim of gaining insight into neutrino oscillations. It is suggested that the decay of 6He nuclei produce neutrino beams accelerated to an energy on the order of 100 GeV/nucleon. To this end, it is necessary to generate short-pulse (30–100 μs) beams of multiply charged ions of this isotope. Conventional ECR-based ion sources seem to be inappropriate for this purpose, since the plasma density grows slowly (for more than a millisecond) in this case compared with the desired pulse duration. A design concept of a short-pulse ECR-based source of multiply charged ions is proposed. In experiments with pumping at frequencies of 37.5 and 75.0 GHz, pulses as short as ∼50 μs were obtained. Good agreement between theory and experiments is demonstrated.

Sub-barrier fusion of two-neutron halo nuclei

The tunneling of composite systems, where breakup may occur during the barrier penetration process, is considered in connection with the fusion of halo-like radioactive, neutron- and proton-rich nuclei, on heavy targets. The large amount of recent and new data clearly indicates that breakup hinders the fusion at energies near and below the Coulomb barrier. However, clear evidence for enhancement due to halo properties seems to over ride the breakup hindrance at lower energies, owing, to a large extent, to the extended matter density distribution. In particular we report here that at sub-barrier energies the fusion cross section of the Borromean two-neutron halo nucleus 6He with the actinide nucleus 238U is significantly enhanced as compared to the fusion of a similar projectile with no halo. This conclusion differs from that of the original work, where it was claimed that no such enhancement ensues. This sub-barrier fusion enhancement is also observed in the 6He+209Bi system.

In-situ Polarized 3He-Based Neutron Polarization Analyzer for SNS Magnetism Reflectometer

We report here the construction and neutron transmission test results of an in-situ polarized 3He-based neutron polarization analyzer system for the Magnetism Reflectometer at the Spallation Neutron Source, Oak Ridge National Laboratory. The analyzer uses the Spin-Exchange Optical Pumping method to polarize the 3He nuclei of a cell of 3He gas. Polarized neutrons scattered from the sample are intercepted by the polarized 3He gas which strongly absorbs neutrons in one spin-state while allowing most neutrons in the other spin-state to pass through. To maintain a stable analyzing efficiency during an experiment, the 3He gas is continuously polarized in-situ on the instrument. Neutron transmission measurements showed that 73% 3He polarization was reached in this setup.

Ab initiocoupled-cluster approach to nuclear structure with modern nucleon-nucleon interactions

We perform coupled-cluster calculations for the doubly magic nuclei 4He, 16O, 40Ca and 48Ca, for neutron-rich isotopes of oxygen and fluorine, and employ "bare" and secondary renormalized nucleon-nucleon interactions. For the nucleon-nucleon interaction from chiral effective field theory at order next-to-next-to-next-to leading order, we find that the coupled-cluster approximation including triples corrections binds nuclei within 0.4 MeV per nucleon compared to data. We employ interactions from a resolution-scale dependent similarity renormalization group transformations and assess the validity of power counting estimates in medium-mass nuclei. We find that the missing contributions due to three-nucleon forces are consistent with these estimates. For the unitary correlator model potential, we find a slow convergence with respect to increasing the size of the model space. For the G-matrix approach, we find a weak dependence of ground-state energies on the starting energy combined with a rather slow convergence with respect to increasing model spaces. We also analyze the center-of-mass problem and present a practical and efficient solution.

Elastic Scattering of 6He + p at 82.3 MeV/nucleon

Differential cross sections for the elastic scattering of halo nucleus 6He on proton target were measured at 82.3 MeV/u. The experimental results are well reproduced by optical model calculations using global potential KD02 with a reduction of the depth of real volume part by a factor of 0.7. A systematic analysis shows that this behavior might be related to the weakly bound property of unstable nuclei.

Energy levels of light nuclei [formula omitted

A compilation of experimental and theoretical information is presented on the mass 3 systems 3n, 3H, 3He and 3p. Emphasis is on advances since the previous evaluation Tilley et al. (1987) [1987TI07] such as, (1) detailed calculations of the vector and tensor analyzing powers for neutron and proton scattering by deuterium which led to the discovery of the still unresolved analyzing power puzzle, (2) the wide spread use of polarized 3He targets which allowed for the experimental study of sum rules among other things and (3) the ability to include the Coulomb interaction in three-body calculations. As stated in the 1987 evaluation and is still the case, there is no firm evidence for either excited states of 3H or 3He nuclei or for the existence of the trineutron or triproton.

Measurement of the polarization correlation parameter C nn in the pp elastic scattering with an unpolarized proton target and an unpolarized 1-GeV proton beam

The polarization correlation parameter Cnn in the elastic proton-proton scattering was for the first time measured with a high statistical accuracy at 1 GeV using an unpolarized proton beam incident on an unpolarized proton target. Both outgoing protons from the reaction were detected in coincidence by means of a two-arm focusing magnetic spectrometer installed at nonsymmetric angles corresponding to the center-of-mass scattering angle Θcm = 62.25°. The correlation parameter Cnn, as well as polarizations P1 and P2 of the secondary protons, were measured by means of multiwire proportional chamber polarimeters placed at the focal planes of each spectrometer arm. The obtained data are compared with the predictions of the phase-shift analysis. The connection with the experiment on Cnn and polarization measurements in the (p, 2p) reaction on 4He and other light nuclei in similar kinematics is discussed

Non-linearity of recoil pulse height events in He-3 tubes

Regarding neutron spectrometry, energy calibration of a He-3 counter was performed for neutron energies up to about 7 MeV, for various operating voltages in the proportionality region. Full-energy peak position is linearly correlated with neutron energy, while the position of the 3He recoil peak deviates from a linear response, especially in the lower energy region. By means of the linear full-energy peak calibration, recoil peak energies are found to be significantly lower than those resulting from the kinematics of the reaction. The pulse-height loss is attributed to initial recombination. Using the Bragg curve of the recoiling nucleus in the counter gas mixture, it is determined that the pulse-height loss corresponds to a constant portion, 33.5±1.3 %, of the fraction of energy deposited by a 3He nucleus traversing the gas mixture with a stopping power higher than 450 eV/μm. The energy calibration equation for the recoil peaks is derived using the following: (i) the range-energy relation and the stopping power function for a 3He nucleus in the gas mixture where the coefficients of both functions were determined via Monte Carlo calculations, and (ii) the experimentally determined recombination coefficient.

Investigation of 6He yield in 7Li(γ, p) reaction with 22 MeV electron beam

The possibility of producing exotic 6He nuclei in the 7Li(γ, p) reaction with 22 MeV electron beam at the MT-25 microtron in the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research (FLNR JINR), is studied. The 6He yield from the Li2CO3 target made up 6 × 105 s−1 per 1 μA of the electron beam current. The obtained result is quite promising, taking into account the further improvement of the target unit, the possibility of using another lithium compound, and the increase in the target material temperature and the electron beam current up to 20 μA. The application of this approach for the further production of a monochromatic beam of accelerated 6He nuclei with an intensity on the order of 107 s−1 would make a large number of experiments on investigating the structure of this nucleus and the mechanisms of nuclear reactions with its participation feasible. This method for obtaining 6He nuclei may turn out to be one of the most optimal (and inexpensive) currently available.