MeV 58Ni Research Articles

Beta decay of 50Ni

The very neutron-deficient isotope 50Ni was produced in fragmentation reactions between a \(650\cdot\) A MeV 58Ni beam and a 9Be target. For the first time the decay of this nucleus was investigated, leading to the determination of the half-life as 12+3-2 ms and the branching ratio for \(\beta\)-delayed proton emission of (\(70\pm 20\))%.

Coulomb excitation and structure of the rotational bands in 231Pa

The level structure of 231Pa was investigated by Coulomb excitation using 148 MeV 32S and 255, 260 and 261 MeV 58Ni projectiles and the NORDBALL detector array. The 1/2[530] ground-state rotational band was excited up to spin 39/2 −. The 3/2[651] band, established up to spin 37/2 +, was observed to be populated apart from direct Coulomb excitation by the de-excitation of the 1/2[530] band. The 1/2[400] band could be followed up to spin 23/2 +. Weak excitation of the bands 5/2[642], 5/2[512], 3/2[532] and 3/2[521] was seen up to spins 11/2 +, 15/2 −, 9/2 − and 9/2 −, respectively. Matrix elements were extracted from the γ-ray yields with the help of the semi-classical Coulomb-excitation least-squares search code GOSIA. The level scheme and transition intensities were analyzed in the framework of the quasiparticle-plus-phonon model including Coriolis-coupling (QPMC).

Particle emission time sequence in intermediate energy heavy ion reactions

The CHIC Collaboration has performed a series of simultaneous pp, np and nn fermion interferometry experiments in order to study the space-time evolution of the emission sources in intermediate energy heavy ion reactions. Furthermore, when correlations of non-identical particles are available, additional model independent information on the emission chronology of the particles is obtained. In this contribution, after reviewing the method to determine the order of emission of non-identical particles, we discuss the emission chronology of neutrons and protons from the E/A = 45 MeV 58Ni + 27Al reaction and from the E/A = 60 MeV 36Ar + 27Al reaction, shown here for the first time.

Laser-guided, intersecting discharge channels for the final beam transport in heavy-ion fusion

Ion-beam transport in space charge neutralizing discharge channels has been proposed for the final focus and chamber transport in a heavy-ion fusion reactor. A driver scenario with two-sided target illumination requires a system of two intersecting discharges to transport beams of the same charge from opposite sides towards the fusion target. In this article we report on experiments on the creation of free-standing, intersecting high-current discharge channels. The discharges are initiated in ammonia gas (NH3) in a metallic chamber by two perpendicular CO2-laser beams, which resonantly heat and subsequently rarefy the gas along the laser paths before the breakdown. These low density channels guide the discharges along the predefined paths and also around the 90° angles without any mechanical guiding structures. In this way stable X-, T-, and L-shaped discharges with currents in excess of 40 kA, at pressures of a few mbar were created with a total length of 110 cm. An 11.4 A MeV Ni+1258 beam from the UNILAC (Universal Linear Accelerator) linear accelerator was used to probe the line-integrated ion-optical properties of the central channel in a T-shaped discharge.

Recent results on fast intermediate velocity electron production induced by 19+ 45 A MeV 58Ni highly charged ions on thin solid targets

In order to study the emission of energetic electrons induced by the impact of swift heavy ions on thin solid targets, we carried out a series of experiments at the superconducting cyclotron of the Catania Laboratori Nazionali del Sud. We report results on a recent experiment where electron–electron coincidences were measured in a forward ring by bombarding a thin carbon target of 7.4 μg/cm2 with 19+ 45 AMeV 58Ni beam. The velocity1–velocity2 bidimensional plot is dominated by events in which the two detected electrons have a velocity close to the beam velocity 9.03 cm/ns (convoy electrons). The remaining small fraction of coincidences has still a convoy electron and a second electron having either a velocity almost twice the beam velocity 16.5 cm/ns (binary encounter, BE electrons) or a velocity of about 12.7 cm/ns intermediate between BE and convoy velocities (IV electrons). We interprete this last intermediate component as due to in-flight de-excitation of highly excited n+58Ni ions by Auger electrons. Although less distinct, we observe also an intense peak close to the convoy velocity peak, centered at ≈9.7 cm/ns, corresponding to electrons emitted with an energy of only about ≈170 eV in the projectile rest frame of reference.

Possibility to deduce the emission time sequence of neutrons and protons from the neutron-proton correlation function.

Experimental information has been derived from the neutron-proton correlation function in order to deduce the time sequence of neutrons and protons emitted at 45 degrees in the E/A = 45 MeV 58Ni + 27Al reaction.

Optical absorption studies in heavy ion irradiated polymers

Heavy ion induced modification in optical absorption studies of the polymers Polypropylene and Polyimide have been carried out to investigate the potential for improvements in their conductivity properties. The polymers were irradiated to four different doses of 140 MeV 28Si and 100 MeV 58Ni ion beams. The optical absorption studies were carried out by UV-Vis spectroscopy. The shift in the absorption edges were correlated to the optical band-gap by Tauc's expression. A decrease in optical band-gap has been observed in the irradiated polymers, but the effect of 58Ni ions were more pronounced in decreasing the band-gap in the polymers.

Monte-Carlo simulation of the charged particle detector used in the NORDBALL γ-ray spectrometer

The NORDBALL silicon detector array for detecting light charged particles emitted in fusion evaporation reactions was simulated with the Monte-Carlo method. The data from the reaction of 261 MeV 58Ni ions with 50Cr nuclei in a 4.8 mg/cm 2 thick target was used to adjust the simulation parameters. Relative population of residual nuclei in the reaction was determined, by comparing the intensities of γ-rays.

Synergistic effects of hydrogen and helium on microstructural evolution in vanadium alloys by triple ion beam irradiation

In fusion materials, irradiation of 14 MeV neutrons produces He and H atoms at a high generation rate. The objective of this study is to clarify synergistic effects of He and H on microstructural evolution in pure vanadium and two vanadium alloys including candidate ternary alloy V–5Cr–5Ti. The specimens are irradiated with 12 MeV Ni3+ ions at 873 K with simultaneous implantation of 1 MeV He+ and 350 keV H+ ions. Helium and hydrogen implantation ratios are independently controlled at two different He/dpa and H/dpa rates. Dual beam irradiation with heavy ions and He ions or H ions, and single beam irradiation experiments are also performed. Triple beam irradiation strongly enhances growth of cavities and swelling in pure vanadium compared with those under dual beam irradiation with He and single beam irradiation, whereas simultaneous implantation of H without He does not affect cavity growth and swelling. In V–5Cr–5Ti alloy, no cavities are detected without implantation of He. However, Ni, He and H triple beam irradiation is found to enhance swelling. These results are discussed in terms of dislocation and cavity evolution in the irradiated vanadium alloys.

Quantitative long-range-order measurement and disordering efficiency estimation in ion-irradiated bulk Ni3Al using cross-sectional conventional transmission electron microscopy

Irradiation-induced disordering of bulk Ni3Al under 6 MeV Ni2+ irradiation is studied at room temperature. A self-consistent long-range-order quantification method for ion-irradiated intermetallics is presented using cross-sectional sample preparation and conventional transmission electron microscopy in selected area diffraction depth profiling mode. This method, which does not require the full assessment of dynamic diffraction image simulation information, is unique to precisely measure long-range-order as a function of depth or dose for a single total fluence. The disordering efficiency constant ε is estimated in the range 10.0±0.7/dpa for a total fluence of 1014 cm−2.

Properties of carbon films produced from polyimide by high-energy ion irradiation

The changes of composition and structure of polyimide films due to irradiation-induced carbonization were studied by surface characterization techniques and electric resistance measurement. Polyimide (C22H10N2O5)n film specimens were irradiated with 4 MeV Ni3+ ions for the fluences from 3.5×1012 cm−2 to 1.0×1016 cm−2. After irradiation with the fluence of 1.0×1016 cm−2, the ratios of N/C and O/C decreased from 0.089 and 0.244 to 0.018 and 0.086, respectively. Though the absolute quantities of bond types were not clear, the portion of carbon–carbon bonds was obviously increased from 0.62 to more than 0.82. The generation of dispersed carbonized areas in the irradiated polyimide film was also suggested by Raman spectroscopy, electric resistance measurement and elastic recoil detection (ERD) analysis.

Ion Irradiation Effects on Polymers and Fabrication of Carbon Alloy

The changes of composition and structure of polyimide films due to high-energy irradiation and high-dose implantation were studied by surface characterization techniques and the electric resistance measurement. Polyimide (C22H10N2O5) n film specimens were irradiated with 4 MeV Ni3+ ions for the fluences from 3.5×1012cm-2 to 1.0×1016cm-2. After irradiation with the fluence of 1.0×1016cm-2, the ratios of N/C and O/C decreased from 0.089 and 0.244 to 0.018 and 0.086, respectively. The generation of amorphous carbon areas dispersed in the irradiated polyimide film was suggested by Raman spectroscopy and electric resistance measurement. Nano-sized metallic particles were produced in the films by 130 keV silver ion implantation. The diameter of the particles was about 5 nm for the specimen implanted with 1×1016cm-2 and it increased with the implantation dose. On the other hand, no particles were observed in the specimen implanted with tungsten ion.

Excited state population effect of 60 MeV 58Ni 18+ ions penetrating thin carbon foils

Measurements of the charge fractions F( q) of 60 MeV 58Ni 18+ traversing thin carbon foils in dependence on their thickness show a non-trivial behavior. Particularly, the charge fraction of the analysed charge state 18+ has a minimum for foil thickness below 1.9 μg/cm 2 . This behavior can be interpreted by fast electron capture into high shells and a slow depopulation and excitation of innershells.

Anomalous ac susceptibility behaviour in ion-irradiated YBa2Cu3O7-δ epitaxial thin films

Abstract Epitaxial thin films of YBa2Cu3O7-δ, prepared by the low-pressure rf-magnetron sputtering technique, have been irradiated with 100 MeV 58Ni ions at a dose exceeding 1012 ions cm−2 at 77 K. Low-field magnetic ac-susceptibility measurements (X ac −T ) are performed before and after the irradiation to study the irradiation-induced effects in the films. A superconducting transition accompanied by an anomalous change in the X ac −T response. that is a positive susceptibility peak just below the transition temperature, is seen for the first time in the ion-irradiated films. This ion-irradiation-induced positive-susceptibility trait has been attributed to the paramagnetic Meissner effect. It is proposed that the ion irradiation at higher fluences leads to the formation of a π junction through the partial removal of oxygen ions in the chain sites and results in the observed extrinsic paramagnetic Meissner effect.

High-spin studies of the neutron deficient nuclei 103In, 105In, 107In, and 109In

High-spin states of the isotopes 103,105,107,109In have been investigated using in-beam γ-ray spectroscopic methods. Results from three different experiments are presented. Targets of 54Fe, 50Cr, and 92Mo were bombarded by a 270 and 261 MeV 58Ni beam and by a 95 MeV 19F beam, respectively. Reaction channel separation was achieved with a charged-particle detector array and in the first two experiments also with a 1π neutron detector system. As a result of these experiments the level schemes of 103,105,107,109In were significantly extended. Excited states of these odd- A indium isotopes are discussed within the framework of the nuclear shell model and the hole-core coupling scheme. The systematics of excited states of light odd- A indium isotopes is also discussed.

Limits in elastic recoil detection analysis with heavy ions

Severe alterations of the sample by the ion beam limits the detectable concentrations in elastic recoil detection analyses (ERDA). Therefore, sputtering and effusion yields were determined and an enhancement was found in comparison to collisional theory. The sputter yield ranges from 650 carbon atoms per incident 120 MeV 197Au ion to about 2500 for hydrogen of a hydrogenated polycrystalline c-BN layer for 60 MeV 58Ni ions, and up to several millions of CH x for organic materials using 60 MeV 127I ions. In addition plural scattering and secondary reactions limit sensitivity, especially when probing materials which mainly contain light elements. The actual limits in ERD with respect to depth resolution and sensitivity are discussed in terms of these principle effects and those induced by the used detection systems.

PIXE analysis of heavy elements in silicon using MeV heavy ion beams

Detection limits of heavy elements such as Fe or Cu near the surface of silicon was investigated by PIXE using slow heavy ions (<90 keV/amu). Fe atoms were implanted in silicon at 343 keV energy to a dose of 1 × 10 13−1 × 10 15Fe/cm 2 and Cu was introduced in silicon to the dose of 5 × 10 14Cu/cm 2. PIXE spectra were obtained by 5.2 MeV 58Ni 3+ and 74Ge 3+ beams in order to enhance the yield of Fe or Cu K X-ray by MO process. The results were compared with those obtained by a 2 MeV proton beam. In the case of slow heavy ion impact, bremsstahlung background above 5 keV was much lower than that of protons. Moreover, Fe Kα X-ray production in Fe implanted silicon was enhanced by using the 5.2 MeV 58Ni 3+ beam. As a result, the detection limit of Fe in silicon was successfully improved. However, Cu Kα X-ray production in Cu contaminated silicon was not so enhanced by using the 5.2 MeV 74Ge 3+ beam and the detection limit could not be improved.

Charge state dependence of the stopping power of 1 MeV/A 58Ni ions

The dependence of the energy loss of 60 MeV 58Ni ions on the incident and analysed charge state was measured in thin carbon foils with a Q3D magnetic spectrograph. The surface contamination of the carbon foils was determined by elastic scattering of 12 MeV protons and included in the analysis of the energy loss data. Five incident charge states between qin = 8+ and qin = 18+ were selected. A reduction of the stopping power in the first few atomic layers is observed for low incident charge states and an enhancement for high ones with the transition occurring at qin ≈ 13.5. The results are discussed in terms of a reduction of the dynamic screening of the effective charge of the projectiles at the target surface.

Study of hydrogen in DLC film by ERDA with 58Ni ions

The content of hydrogen and its depth profile in diamond like carbon (DLC) films deposited by the microwave plasma deposition technique is determined by Elastic Recoil Detection Analysis (ERDA) using 85 MeV 58Ni ions. Simultaneous detection of hydrogen and carbon recoils provided a method to determine the relative number of hydrogen: carbon atoms without using a standard H sample for quantitative calibration.

Charge state dependence of the stopping power of 1 Mev/A 58Ni-ions in thin carbon foils

Energy loss and energy straggling of 60 MeV 58Ni ions in ultrathin carbon foils (0.8 to 30 μg/cm 2) have been measured with a Q3D magnetic spectrograph in dependence on the incident and analysed charge state of the ions. The stopping power in the first few atomic layers deviates significantly from the value in larger depths and can be scaled with the square of the incident charge state q. For larger depths the stopping power coincides with the tabulated value for all measured charge states. From this difference in the stopping power an average charge state q = 15.5 for the Ni-ions inside the bulk can be estimated in a first approximation. With the average charge state behind carbon foils being q = 17.6 the ion has to lose two electrons on average when leaving the target, e.g. by Auger processes. The energy straggling of the Ni-ions can be approximated by the known formula of Bohr. Nevertheless the systematics of the dependence on the incident and analysed charge state indicates that charge changing events contribute a significant amount to the energy straggling.