Source: http://www1.jinr.ru/Preprints/prepr_2016_eng.html
Timestamp: 2019-04-20 18:28:15+00:00

Document:
Didyk A. Yu., Gulbekyan G. G., Myshinskiy G. V.
Natural xenon at an initial pressure of 250 bar in a special chamber (XeHPC) was irradiated for 60 h 16 min (2.17· 105 s) by braking γ-rays with a threshold energy of 10 MeV at the electron accelerator MT-25 at an average intensity of the beam of 20–22 µA. With increase in temperature the pressure in the steady state at the beginning of exposure grew up to 270 bar. After opening of the XeHPC both internal chambers with all the structures and particles, but without gas, were measured using a γ-germanium detector. Visual inspection of the inner chambers showed visible dense greenish-yellow coating of significant thickness formed on their surfaces. X-ray microprobe analysis (RMPA) and SEM studies allowed us to determine the composition of the synthesized particles.
In this paper an investigation of solutions of quasi-stationary states in the framework of the Schroedinger equation with complex energies with piecewise constant potentials for various values of the parameters of the potential is conducted. Quasi-levels are found for the under- and above-barrier cases. For the given potential barrier heights the number of under-barrier quasi-levels for the double-barrier potential is more than for the single-barrier potential. The calculations show that the real part of the energy varies smoothly and the imaginary part of the energy changes irregularly when changing the parameters of the potential.
The photoinjector electron beam quality dramatically depends on the laser driver beam quality. For laser beam diagnostics a "virtual cathode" system was realized at the JINR LHEP photogun bench. The system allows one to image laser beam profile at the cathode. The AVINE software complex developed in DESY Zeuthen is being used for imaging. Equipment for emittance measurement using the slit method was installed. The original emittance calculation software EmCa was created and tested with the laser beam.
Bogolubov N.N. (Jr.), Soldatov A.V.
Non-equilibrium properties of a model system comprised of a subsystem of magnetic moments strongly coupled to a selected Bose field mode and weakly coupled to a heat bath made of a plurality of Bose field modes were studied on the basis of non-equilibrium master equation approach combined with the approximating Hamiltonian method. A variational master equation derived within this approach is tractable numerically and can be readily used to derive a set of ordinary differential equations for various relevant physical variables belonging to the subsystem of magnetic moments. Upon further analysis of the thus obtained variational master equation, an influence of the macroscopic filling of the selected Bose field mode at low enough temperatures on the relaxation dynamics of magnetic moments was revealed.
This paper presents an artificial neural network method for long-term prediction of the thermal dynamic parameters of primary coolant circuit of the IBR-2M reactor. The main goal is to predict the temperature and liquid sodium flow rate through the core and thermal power. It is shown that the prediction can reduce three times the effects of slow reactivity fluctuations in power and decrease the requirements for the automatic power stabilization system. Nonlinear autoregressive neural network (NAR) with local feedback connection has been considered. The results of prediction error ~ 5% coincide with the experimental ones.
Batgerel B., Nikonov E.G., Puzynin I.V.
A new procedure for constructing symplectic numerical schemes for solving the Hamiltonian systems of equations is proposed. A method for symmetrization of the obtained symplectic numerical schemes is suggested. The numerical schemes constructed by the above procedure conserve the energy of a system on the large interval of numerical integration for relatively large integration step in comparison with the Verlet method which is usually used for solving equations of motion in molecular dynamics. Results of numerical experiments are given. These results show the main advantages of the obtained symmetric symplectic numerical schemes of the third order of accuracy for the integration step for the Hamiltonian systems of equations in comparison with numerical schemes of the Verlet method of the second order of accuracy.
Mokrov Yu. V., Morozova S. V.
The calculated results of the research correspondence of the indication of dosimeter based on the 10В counter with polyethylene moderator to the ambient dose equivalent behind the U-400M are presented. It was shown that the instrument can be used to measure the ambient dose with the uncertainty 25 % in radiation monitoring at LNR cyclotrons. Value of correction coefficient for this dosimeter behind the cyclotron shield is 0.9.
Pepelyshev Yu.N., Popov A. K., Sumkhuu D.
Parameters of the IBR-2M reactor power feedback (PFB) are estimated based on the analysis of power transients caused by deliberate square wave reactivity when the pulsed reactor operates in the self-regulation mode. The PFB of the IBR-2M is described by three linear first-order differential equations. Two components of the PFB are responsible for the negative feedback and one, for the positive. The overall feedback is negative, i.e., it has a stabilizing effect for the operation of the reactor. The slowest negative component of the PFB is probably caused by heating of the fuel. Periodically repeated in the process of exploitation, estimation of the PFB parameters is one of the methods to ensure safety operation of the reactor.
Didyk A. Yu. et al.
up to 620 bar and then dropped to 550 bar. After opening of the XeHPC both of the internal chambers with all the structures, but without gas, were measured using a γ-germanium detector (Canberra) during 15 h each for measurement of the background and short-lived isotopes. During a visual inspection of the interior surfaces of the XeHPC inner assembly, a visible coating of substantial thickness and greenish-yellowish color was observed. The research carried out by scanning electron microscopy (SEM) and X-ray micro-probe analysis (XMPA) allowed us to determine the elemental composition of synthesized particles.
The safeguarding of a nuclear reactor during the operation process is one of the most significant tasks. The difficulty is in the necessity to use nondestructive methods. One of such perspective methods is the neutron noise diagnostics of a nuclear reactor. Possibility of the noise diagnostics by the new method of norms of positive definite Toeplitz correlation matrices is studied. The advantage of this method is its purely mathematical nature; no model of the process is employed. The neutron noise analysis of the IBR-2M pulse energy has been carried out by the represented method. Both the static state and dynamic state of the reactor have been studied. Frequency analysis of unstable components of the reactor noise has been carried out. The main unstable components of the neutron noise are frequencies of 0.8 and 1.6 Hz, which are conditional on the vibration of the movable reflector blades of the reactivity modulator. The results of this diagnostics have been compared with the results of the classical spectral analysis.
Volkov V.V., Cherepanov E.A., Kalandarov Sh.A.
A new approach to the interpretation of the process of spontaneous fission of heavy nuclei is suggested. It is based on nuclear physics data which are obtained in heavy ion collisions. The process of spontaneous fission consists of three sequential stages: clusterization of the valent nucleons of a heavy nucleus into a light nucleus-cluster, which leads to the formation of a dinuclear system; evolution of the dinuclear system which proceeds by nucleon transfer from the heavy to light nucleus; and decay of the dinuclear system from the equilibrium configuration into two fragments.
Yamauchi Yu., Apel P. Yu.
We study the adsorption of anionic surfactant, sodium dodecyl diphenyloxide disulfonate (SDDD) on three types of polyethylene terephthalate (PET) substrates from aqueous solutions of SDDD of different concentrations. Neutral electrolyte (KCl) was added to the solutions to vary the ionic strength. Three types of substrates were used: 1) original PET film; 2) etched nonporous film, obtained from pristine film by chemical etching and bearing negative charge on the surface; 3) etched porous membranes, fabricated from pristine film by ion irradiation and subsequent chemical etching. The membranes have negative charge on the flat surface and on the inner pore walls. The comparison shows that the negative charge on the flat surface has weak effect on adsorption of the anionic surfactant, and the SDDD adsorption on the inner walls of pores is much weaker than on flat surface, even if the pore radius is significantly larger than the Debye length. This «exclusion» effect strongly depends on ionic strength of solution.
Tsulaia M. I. et al.
We study the adsorption of anionic surfactant, sodium dodecyl diphenyloxide disulfonate (SDDD) on three types of polyethylene terephthalate (PET) substrates from aqueous solutions of SDDD of different concentrations. Neutral electrolyte (KCl) was added to the solutions to vary the ionic strength. Three types of substrates were used: 1) original PET film; 2) etched nonporous film, obtained from pristine film by chemical etching and bearing negative charge on the surface; 3) etched porous membranes, fabricated from pristine film by ion irradiation and subsequent chemical etching. The membranes have negative charge on the flat surface and on the inner pore walls. The comparison shows that the negative charge on the flat surface has weak effect on adsorption of the anionic surfactant, and the SDDD adsorption on the inner walls of pores is much weaker than on flat surface, even if the pore radius is significantly larger than the Debye length. This “exclusion” effect strongly depends on ionic strength of solution.
Cerium-doped lanthanum cobaltite perovskites (La1-xCexCoO3 with x = 0, 0.2, 0.4) were prepared by the sol-gel method (calcined for 5 h at 750ºC) and characterized by X-ray diffraction (XRD), X-ray absorption (XAS), energy-dispersive X-ray spectroscopy (EDS), and BET surface area analysis. The results showed that the cerium doping promoted the structural transformation of LaCoO3 from rhombohedral into the cubic structure. High specific surface area and small crystallite size are achieved at x = 0.2. The XAS results confirmed the formation of compound La1-xCexCoO3.
Artoshina O. V. et al.
Thin films of TiO2, Ag, Ag-TiO2, Cu-TiO2 deposited on the surface of polyethyleneterephthalate track membranes (TM) were investigated. Metals and oxide deposition was carried out by the method of vacuum reactive sputtering with application of a planar magnetron. The microstructure of samples was studied by the scanning and transmission electron microscopy (TEM) techniques. The elemental composition of coatings was investigated using energy-dispersive spectroscopy. For the identification of phase structure, X-ray diffraction phase analysis was used at various temperatures, and the XRD crystal structure patterns of the samples were obtained by the selected area electron diffraction (SAED) in TEM analysis. It was found that titanium dioxide on the TM surface can be present in three forms: nanocrystals of tetragonal anatase with impurity of rhombic brookite and the so-called X-ray amorphous TiO2. Cubical Cu2O was identified in TM metallized by copper. Optical properties of composite membranes and films were investigated by the method of absorption spectroscopy. Calculation of energies of the direct and indirect allowed optical transitions was carried out based on the analysis of absorption spectra of the studied composite membranes.
Gustova M. V., Maslov O. D., Sabelnikov A. V.
The paper reports on the possibility of using TEVA resin (TRISKEM company), made on the basis of the Aliquat-336 extractant (a quaternary ammonium salt), for the isolation and concentration of 236Pu. The 236Pu isotope was produced as a result of the photonuclear reaction 237Np(γ, n) 236mNp → (β–)236Pu using the linebreak MT-25 microtron at FLNR, JINR. Plutonium-236 was separated on the TEVA resin from 237Np target. Products of (γ, f) photonuclear reactions, daughter products of 236Pu and 237Np, fragments of 237Np(γ, n) (237Np, 232U, 228Th, 233Pa, 137Cs, etc.) induced fission were also separated. The content of the actinide elements in 236Pu was less than 10-6 Bq/Bq.
Azorskii N. I. et al.
A device for fabricating thin-wall (straw) drift tubes using polyethylene terephthalate film 36 µm thick by ultrasonic welding is described together with the technique for controlling their quality. The joint width amounts to 0.4–1.0 mm. The joint breaking strength is 31.9 kg/mm2 The argon leakage from a tube of volume 188.6 cm3 under a pressure gradient of 1.0 atm does not exceed 0.3 · 10-3cm3min, which is mainly related to the absence of metallization in the joint vicinity. The high strength, the low tensile creep due to the absence of glued layers, and the small value of gas leakage make the new tubes capable of reliable and long-term operation in vacuum, which is confirmed by the operation of 7168 straw tubes for two years in the NA62 experiment.
Babkin V. A. et al.
A new specialized setup “MPD test beam” was created at the extracted beam of the Nuclotron to carry out methodical research and testing detectors for the MPD experiment at the NICA collider. The setup is described in detail. Results of the test of fast detectors for the MPD TOF system are presented as an example of the setup operation.
Кiselev М. А., Zemlyanaya Е. V.
On the basis of the separated form factors method (SFF), the analysis of data on the small-angle neutron scattering (SANS) on polydispersed population of unilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC) in heavy water with dimethyl sulfoxide (DMSO) is carried out. It is shown that the growth of DMSO molar fraction in water from 0 to 15&percnt; leads to increase of thickness of the bilayer to values of the repeat distance of multilamellar membranes of DPPC, which means a dehydration of the intermembrane space and steric contact of the neighbor bilayers of DPPC at a DMSO molar fraction of 15&percnt;.
Omelyanenko M. M. et al.
The described pulse-mode current power supply has been designed and fabricated for the magnetic field measurement system of superconducting magnets for accelerators. The power supply is based on a current regulator with pass transistor bank in linear mode. The output current pulses (0–100 A) are produced by using the energy of preliminary charged capacitor bank (5–40 V), which is charged additionally after each pulse. There is no AC-line frequency and harmonics ripple in the output current, the relative noise level is less than –100 dB (or 10–5 of RMS value (it is defined as the ratio of output RMS noise current to the maximal output current 100 A within the operating bandwidth, expressed in dB).
Vu D. C. et al.
The developed in Dubna practical model of the cascade gamma decay of neutron resonance allows one, from the fitted intensities of the two-step cascades, to obtain parameters both of level density and of partial widths of emission of nuclear reaction products. In the presented variant of the model a part of phenomenological representations is minimized. Analysis of new results confirms the previous finding that dynamics of interaction between Fermi- and Bose-nuclear states depends on the form of the nucleus. It also follows from the ratios of densities of vibrational and quasi-particle levels that this interaction exists at least up to the binding neutron energy and probably differs for nuclei with varied parities of nucleons.
Kabdrakhimova G. D. et al.
The analysis of the experimental excitation functions of the total cross sections of nuclear reactions 6He+Si and 4He+Si in the energy range 5–50 MeV/A and a brief overview of the techniques by which experimental data were obtained have been presented. Detailed attention is given to the description of experiments conducted with beams of radioactive nuclei of the accelerators of FLNR JINR. Analysis of experimental data was performed using the semi-microscopic optical model.
Alexandrov V. S. et al.
The analysis of results of the magnetic measurements executed on a breadboard model of the focusing solenoid of accelerating section of accelerator LUE-200, and results of numerical modelling of dynamics of a beam in accelerating system of the linear accelerator with the account of the possible errors admitted in focusing fields of the linac are presented.
Sumbaev A. P., Kukarnikov S. I.
Results of designing and manufacturing of the focusing solenoid of the first accelerating section of the electron linear accelerator with a S-band traveling wave — the driver of the the IREN facility, a pulse resonant neutrons source, are considered. Requirements to parametres of the solenoid with the account of necessity of minimisation of heterogeneity of a magnetic field at edges and in the area occupied with an electron beam are formulated. Results of calculations, a design and results of measurements of magnetic fields of the solenoid after its installation on a regular place on the linac are presented.
Aksenov V. L. et al.
A physical model of high-flux neutron source based on subcritical (kef = 0,96) two-stage booster, managed by proton accelerator with energy of 600 MeV and 0.3 MW beam power, is offered. It is shown that the thermal neutron flux will be comparable to the flux density in the European Spallation Source (ESS), proton beam power of which is 5 MW. Due to a short pulse the neutron diffraction experiments on the proposed source will be almost an order of magnitude more efficient than in ESS.
In the present work, we formulate and give the mathematical foundation of the amplitude functions method. This method is adopted for solving the radial problem of two-dimensional scattering of a quantum particle by the sum of the Coulomb potential and a central short- or long-range potential.
Morozov V. A., Morozova N. V.
An autocorrelation method is developed for determining the composition and decay time of scintillators. It also allows studying the spatial distribution of nuclear radiation and controlling the amount of the admixture introduced in the scintillators. The decay time is measured in the range from a few nanoseconds to microseconds. It is found that the decay time increases in plastic scintillators with a wave shifter and a Gd admixture.
The multiparticle production process in π–C interactions at 40 GeV/с has been studied on cumulative number nc. Local values of temperature, pressure, volume, and energy density in the interaction region are determined as a function of the cumulative number. This analysis gives us an opportunity of studying a space-time picture and the phase transition process at high energies.
The two-dimensional scattering of a slow quantum particle by the superposition of the Coulomb and short-range potential is studied. The analysis of low-energy asymptotics of all radial wave-functions, partial phase-shifts and cross-sections is given. Two methods for calculation of the scattering length and effective radius are proposed.
Khushvaktov J. H. et al.
The natural uranium assembly, QUINTA, was irradiated with 6-GeV deuterons. The 232Th samples were placed at the central axis of the setup QUINTA. The spectra of gamma rays emitted by the activated 232Th samples have been analysed, and more than one hundred nuclei produced have been identified. For each of those products, reaction rates have been determined. The ratio of the weight of produced 233U to that of 232Th is presented. Experimental results were compared with the results of Monte Carlo simulations by the FLUKA code.
Molokanova L. G. et al.
photon) of PEN films under the influence of UV radiation were evaluated. The feasibility of production of asymmetric pores in PEN films via controlled photo-oxidative degradation was demonstrated.
Marachev A. A. et al.
For the IBR-2M pulsed reactor, characterized by a high level of reactivity fluctuations and, as a consequence, of a power pulse amplitude, two variants of an automatic regulator (AR) are considered. Both variants satisfy the criterion of a minimum probable standard deviation of the amplitude of the future pulse on the basis of information obtained in the previous momenta. The difference between the AR variants is registered in the data. Since perturbations of reactivity in the process of reactor operation contain random and regular components, transient processes in these types of reactivity are considered for both AR variants. It is shown that the variant of AR accepted in the IBR-2M, where earlier data is given less weight, is more preferable than the variant where the information obtained from a fixed number of the last pulses is given the greatest weight, and the earlier information is not considered at all.
Pepelyshev Yu. N., Popov A. K., Sumkhuu D.
Based on the analysis of the power transient processes caused by the intentional square-wave reactivity in the IBR-2 and IBR-2M reactors with burnup of 800–900 MW ¢erdot; day, the fast power feedback structure is substantiated. Due to the differences in the geometry of the reactor cores and fuel structure, symmetrical oscillations of reactivity induced asymmetrical power fluctuations in the IBR-2 reactor and symmetrical ones in the IBR-2M. The analysis of the measured pulse response of the reactor feedback at a nominal power of 2 MW shows that the IBR-2M is more stable in comparison with the IBR-2. A margin of the perturbation amplitude to the stability boundary of the IBR-2M is almost twice that at the IBR-2. A margin on the phase shift between the perturbing reactivity and power is large enough for both reactors. It can be expected that the operation time of the IBR-2M in the existing nominal mode with a power of 2 MW and a flow of coolant through the core of 100 m3/h before the oscillatory instability is longer than at the IBR-2.
Belyaev A. V. et al.
At measurements performed in experimental particle physics, for every particle taking part in collision or decay, kinematical parameters such as momentum and exit angles are fixed individually. Due to measurement errors the conservation laws of energy and momentum are violated in this set of kinematical parameters. The procedure of ''kinematical fitting'', which was developed as early as the sixties of the 20th century, makes values of kinematical parameters more precise, eliminates violations of the conservation laws and makes smaller errors in parameters.
Belyaev A. V., Jerusalimov A. P., Troyan A. Ju.
At studying particle interactions we often have no particle identification. In this case the task of defining the true channel arises. One of the important numerical instruments which is used to determine the true channel of a reaction is the procedure of &quout;kinematical fitting&quout;, which for each of the tested combinations calculates the value of the functional χ2 (≥s; 0). In this work it is proposed to use the obtained χ2 -values to attribute a specific weight to every combination. Thus, in the proposed method all combinations (with their weight) which were successfully fitted take part in the forming of channels of a reaction. The Kolmogorov criterion that has been applied to χ2-distributions, obtained with two described methods, gives a better agreement between the experimental distributions and theoretical ones when the weight method is used.
The possibility of working welded straw tubes in vacuum is considered. The behavior of straw in a vacuum is considered in the framework of the cylindrical shells theory. A solution to the equilibrium state equation for a straw tube describing its behavior under the effect of pre-tensioning and internal pressure is provided. The analysis of the solution shows that the rotation of self-supporting straws is due to the moment acting on the unfixed ends. The estimation of strain caused by the overpressure is made. An original technique of measurement of straw Poisson's ratio is presented and its dependence on tension is investigated. The effect of the temperature and the deformation rate on the mechanical properties of straw is considered with polybutylene terephthalate as an example. The optimum temperature range for the long-term straw operation in the experiment is specified.
Arsenyev N. N. et al.
Starting from the Skyrme interaction SLy5, we study the effect of phonon--phonon coupling on the low-energy electric dipole response in 40–48Ca. This effect leads to the fragmentation of the E1 strength to a low energy and improves the agreement with available experimental data.
Sushenok E. O., Severyukhin A. P.
Starting from the T45 Skyrme interaction with tensor terms, the properties of the β-decay of 72-80Ni are studied. We take into account the effect of unpaired neutron and proton on the ground state properties of odd-odd and even-odd nuclei. It is shown that the calculated Qβ values and the $\beta$-decay half-lives are in a reasonable agreement with experimental data.
Sushenok E. O. et al.
A finite rank separable approach(FRSA) based on the quasiparticle random phase approximation with Skyrme interactions has been extended to describe charge-exchange excitation modes. The central and tensor residual interaction in the both particle-hole and particle-particle channel and the coupling between one- and two-phonon configurations are taken into account in the framework of the FRSA model. The calculation scheme of the β-delayed multi-neutron emission of the neutron-rich nuclei is presented.
Maslova V. A., Kiselev M. A.
Sodium cholate is a bile acid salt and is used as a biological detergent. The mixed systems of sodium phospholipidcholate are used to study the self-assembly process of the formation of micelles and micellar systems. Micelles composed of a mixture of a phospholipidsodium cholate are used as carriers of drugs through the skin. We have studied the structure of micelles of sodium cholate by small-angle neutron scattering. It was established that the average radius of sodium cholate micelles was (10.14 &pm; 0.01) Å in the sodium cholate concentration range from 25 to 100 mM.
Glonti L. N. et al.
Microscope studies of thin-wall drift tubes (straws) of a new type for the NA62 drift chambers have shown that under certain conditions they are semitransparent and, when illuminated by directional light, allow their anode wires to be observed in both transmitted and reflected light. These tubes are supposed to be used in other experiments as well. In this work, new results of the calibration measurements performed with an accuracy of about ∼ &pm;1-2 μm using the UIM-23 microscope are presented. It is also shown that the measurements can in principle be automated. The first semiautomatic measurements accurate to about ∼ &pm;0.003 μm are reported, which are made under the MBS-type microscope with a digital eyepiece. The proposed method is much simpler than the methods based on radioactive or X-ray radiation.
By assumption, a charged quantum particle moves in the space of dimension d = 2,3,&mldr; and is scattered by a fixed Coulomb center. The expansions of the wave-functions and all radial wave-functions of this particle over integer powers of the wave number and the Bessel functions of real order are derived. It is proven that the finite sums of these expansions are the asymptotics of the wave-functions in the low-energy limit.
Piecewise polynomial approximation (PPA) is widely used in digital technology and data processing. Within the framework of the Basic Element Method (BEM), optimization of the solution of PPA problems is achieved on the basis of the functional relationship between basis functions and applying formulas to calculate the coefficients depending on parameters of the three-point grid. The results of optimization and comparison with the results of the respective Maple-procedures are illustrated by examples of the 12th-order BEM-approximation.
Dmitrieva S. O. et al.
The work is dedicated to the determination of the origin of archaeological finds from medieval glass using the method of neutron activation analysis(NAA). Among such objects we can discover things not only produced in ancient Russian glassmaking workshops but also brought from Byzantium. The authors substantiate the ancient Russian origin of the medieval glass bracelets of pre-Mongol period, found on the ancient Dubna settlement. The conclusions are based on the data about the glass chemical composition obtained as a result of NAA of ten fragments of bracelets at the IBR-2 reactor, FLNP, JINR.
The results of readout correction for albedo dosimeters DVGN-01 with using of a spherical albedo system are presented. The measurements were carried out behind the neutron generator ING-27. On the base of the presented results the correction coefficients were recommended for individual radiation control at the neutron generator ING-27.
The upper limit of the thermal neutron flux density is obtained for fission pulsed sources for beam researches. Three types of possible configurations are considered: multiplying target at a proton accelerator (booster), a booster with a reactivity modulation (superbooster), and a pulsed reactor. Comparison with other high-flux sources, both operating and under construction, is done.
Lukyanov S. M. et al.
The study of inelastic scattering and multi-nucleon transfer reactions was performed by bombarding a 9Be target with a 3He beam at the incident energy of 30 MeV. Angular distributions for 9Be(3He, 4He) 8Be, 9Be(3He, 6Li) 6Li, 9Be(3He, 7Li)5Li, and 9Be(3He, 7Be) 5He reaction channels were measured. Experimental angular distributions for the corresponding ground states (g.s.) were analyzed within the framework of the optical model, the coupled-channel approach and the distorted-wave Born approximation. The contributions of different exit channels have been determined confirming that the (α + 5He) configuration plays an important role. The configuration of 9Be consisting of two bound helium clusters (3He + 6He) is significantly suppressed (less than 3%), whereas the two-body configurations (&nscr; + 8Be) (69%) and (α + 5He) (25%) including unbound 8Be and 5He are found more probable.

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