MeV 3He Particles Research Articles

Double folding analysis of 3He elastic and inelastic scattering to low lying states on 90Zr, 116Sn and 208Pb at 270 MeV

The experimental data on elastic and inelastic scattering of 270 MeV 3He particles to several low lying states in 90Zr, 116Sn and 208Pb are analyzed within the double folding model (DFM). Fermi density distribution (FDD) of target nuclei is used to obtain real potentials with different powers. DF results are introduced into a modified DWUCK4 code to calculate the elastic and inelastic scattering cross sections. Two choices of potentials form factors are used; Woods Saxon (WS) and Woods Saxon Squared (WS2) for real potential, while the imaginary part is taken as phenomenological Woods Saxon (PWS) and phenomenological Woods Saxon Squared (PWS2). This comparison provides information about the similarities and differences of the models used in calculations.

Light output and energy resolution of CsI, YAG, GSO, BGO and LSO scintillators for light ions

The light output and energy resolution for the scintillators CsI(Tl), YAG(Ce), GSO(Ce), BGO and LSO(Ce) have been measured with 1H, 2H and 3He ions in the energy region ∼ 3–20 MeV/nucleon using photodiodes for the light readout. A very good energy resolution of ∼ 0.62% for 45 MeV 3He-particles has been obtained for CsI. The YAG(Ce), GSO(Ce) and LSO(Ce) crystals are non-hygroscopic, have fast decay time as main component and are well suited for experiments with high counting rates and strict timing requirements. The LSO crystal gives the best energy resolution, but reveals strong quenching for heavy ions. The GSO crystal is a good candidate for operation in UHV environment and has high stopping power, short decay time (56 ns) and moderate quenching.

A study of the ( 3He, p) reaction on 60Ni

The ( 3He, p) reaction has been studied on 60Ni using a beam of 33 MeV 3He particles. Angular distributions of outgoing protons have been measured for twelve levels including the ground-state analogue of 62Ni covering an excitation energy of 4.55 MeV over range θ lab = 12.5°–115° (maximum). A microscopic DWBA analysis has been carried out using the spectroscopic amplitudes derived from the two-body matrix elements given by Koops and Glaudemans based on the modified surface delta interactions.

A study of the (3He,α) reaction on 60Ni

The (3He, alpha ) reaction on 60Ni has been studied using a beam of 33 MeV 3He particles. Angular distributions have been measured for twenty-two levels, including five analogues, up to Ex approximately=10.5 MeV over the angular range 12.5 degrees -115 degrees (lab) in steps of 2.5 degrees . DWBA analysis was carried out using the code DWUCK4 with non-locality and finite range corrections introduced in the local energy approximation. The large angle data call for the incorporation of exact finite range including target recoil and the angular distributions were re-analysed using the full finite range DWBA code DWUCK5. Spectroscopic factors have been extracted.

Measurement of oxide-layer thickness of internal granules in high-purity aluminium

High-purity aluminium samples and mixtures containing different amounts of alumina were irradiated by 13 MeV3He particles. The aim of the investigation was to determine the oxide-layer thickness on the surface of internal aluminium granules. Measurement was carried out by determining the bulk oxygen concentration in the samples, and calculating the oxide-layer thickness, by using model conditions about the microstructure of the aluminium samples.

Excitation functions of 3He- and α-particle induced nuclear reactions on natural krypton: Production of 82Sr at a compact cyclotron

Excitation functions have been measured for natKr( 3He, xn) 82,83,85m,85g,87mSr and natKr( 3He, pxn) 81,82m,83,84m,84g,86Rb reactions over the energy range of 10–33 MeV and for natKr(α, xn) 82,83,85m,85g,87mSr and natKr(α, pxn) 81,82m,83,84,86Rb processes from 10 to 25 MeV. Cross section data and calculated thick target yields show that for the production of 82Sr in this energy region the 3He-particle induced process is more suitable than the alpha-induced process. A high current gas target was constructed to test the 82Sr-production yield under actual production conditions using 36 MeV 3He-particles. A thick target yield of 1.49 μCi (55 kBq)/μAh was achieved using natural krypton. The 82Kr( 3He, 3n) 82Sr process is technically feasible for production and, if long parasitic irradiations could be carried out, the method would be of considerable interest for use at a medium-sized cyclotron.

Strong-absorption model analysis of3He scattering

Angular distributions of 25 and 41 MeV3He particles elastically scattered from a number of nuclei are analysed in terms of the three-parameter strong-absorption model of Frahn and Venter. Best-fit parameter values are obtained which give the nuclear interaction radius and surface diffuseness. Data on inelastic scattering leading to the lowest 2+ state in a few nuclei are studied giving the quadrupole deformation parameter β2.

Nearside-farside analysis of elastic scattering of polarized 3He

An exact decomposition of the scattering amplitudes into the nearside and farside components has been performed for the elastic scattering of 33 MeV 3He particles by nuclei. Calculations have been carried out for 40Ca, 54Fe, 89Y, 90,91Zr, 207,208Pb and 209Bi and compared with the available cross section and polarization data. In particular the behaviour of the vector analysing powers is examined. Calculations of the interference between the nearside and farside components demonstrate that the interference plays a significant role in certain mass/energy regions. Regions where the scattering is dominated by the nearside component are discussed.

Elastic and inelastic scattering of 270 MeV3He particles from58Ni,90Zr,116Sn and208Pb

Differential cross-section angular distributions for the elastic scattering of 270 MeV3He particles from58Ni,90Zr,116Sn and208Pb have been measured. Optical model analysis of the cross-sections has yielded the optical model parameters for3He particles at 270 MeV. Angular distributions have also been measured for the inelastic excitation of the low-lying levels in the above mentioned nuclei. A collective model analysis using the distorted wave Born approximation (DWBA) of these cross-sections with the distorted waves generated by the optical model parameters determined from the elastic scattering analysis, has yielded the reduced transition probability (B(EL)) values consistent with those reported in the literature.

Energy dependence of the elastic scattering 40Ca( 3He, 3He) in the energy range 10.0 to 18.0 MeV

Differential cross sections for the elastic scattering of 18, 16, 14, 12 and 10 MeV 3He particles by 40Ca were measured and analyzed in terms of the optical model with volume imaginary and real spin-orbit potentials. Angular distributions have been measured in 5° steps between 25° and 175°. Four sets of optical model parameters were established and in two of these, sets A and B, systematic variations with energy of the real, volume imaginary and spin-orbit potentials were obtained. The geometrical parameters were not varied as a function of energy. The effect of the matching radius R M on the optical model calculations, was investigated. It was found that the matching radius should be calculated using the geometrical parameters of the potential that yields the largest value for R M according to the receipe R M = R + 7 a where R is the nuclear radius and a is the diffuseness.

Nuclear Structure Studies with Pick-up Reactions on Even Tellurium Nuclei: The 126Te (d,t)125Te and the 126Te (3He,α)125Te Reactions

The level structure of 125Te up to an excitation energy of ∼ 2.2 MeV has been investigated by the (d, t) and (3He, α) reactions with beams of 17 MeV deuterons and 24 MeV 3He particles. Angular distributions were recorded and analyzed with standard DWBA calculations. Spectroscopic factors were deduced. Anomalous angular distributions and cross sections of some low-lying and weakly excited positive parity states are explained using CCBA calculations. A new level, probably ½+, is observed at 538 keV.

Ion beam characterization of the GaAs–GaAs oxide interface for plasma and anodic oxides

Ion beam channeling has been used to measure the effects of oxide growth and annealing on the substrate at the GaAs–GaAs oxide interface. Plasma and anodic oxides have been grown on 〈100〉 GaAs substrates, and the oxides were removed with an etch in hydrofluoric acid. The substrates were then examined with a beam of 1.5 MeV 3He particles channeled down the 〈100〉 axis. The resultant Ga and As surface peaks can be resolved with Rutherford backscattering and are a measure of the Ga and As at the substrate–oxide interface. Anodic oxides grown by the constant-current method (50 μA) show no change from virgin material at the interface; however, annealing of the oxide prior to its removal results in As enhancement at the surface (?2.0 monolayers). Plasma oxides grown by direct immersion in an rf plasma show As enhancement at the interface without annealing. When grown in a fluorinated plasma, the data show an enhanced Ga surface peak consistent with a thicker interface and modified composition of the substrate. The differential measurements were made with a precision of ±0.2 monolayer.

Elastic scattering of 119 MeV 3He particles and energy and mass-number dependence of optical potential parameters

The elastic scattering of 119 MeV 3He particles by 12C, 27Al, 58,60,62,64Ni, 59Co, 90,92Zr and 89Y has been investigated over a wide angular range in order to study the mass-number dependence of the optical potential and odd-even differences in the elastic scattering. The elastic scattering cross sections have been analyzed in terms of the optimal model. The data, except for 12C, 27Al and 59Co, were fitted with r R = 1.21 fm, a R = 0.76 fm and r I = 1.17 fm, fixed at the average values. The following formulae were obtained for the three remaining parameters by combining with the energy dependence of the parameters (90–120 MeV) obtained previously: V=111.4−0.173E+ Z A 1 3 +14.9 N−Z A ( MeV) W D =24.8−0.028E ( MeV) , a I=0.754+0.78 N−Z A ( fm) The depths of the valleys of the angular distribution in the case of 59 Co(I = 7 2 ) are considerably shallower than those for Ni isotopes, while the depths in the case of 89 Y(I = 1 2 ) are nearly the same as those for Zr isotopes. Thus it may be concluded that the odd-even differences are attributed to the scattering from the quadrupole moment of the odd- A nucleus (if I > 1 2 ).

Inelastic scattering of 108.5 MeV 3He particles at very small momentum transfer to the giant monopole resonance of 90Zr and 208Pb

Inelastic scattering spectra from the ( 3He, 3He′) reaction at 108.5 MeV have been measured down to 1.85° scattering angle on 90Zr and 208Pb, allowing a giant monopole resonance study in these nuclei. DWBA analysis is reported.

Optical model analysis of the elastic scattering of 45 MeV 3He particles on 1p shell nuclei

Angular distributions of elastically scattered 3He particles from the 1p shell nuclei 6Li, 7Li, 9Be, 10B, 11B, 12C and 16O were measured by using a 45 MeV 3He beam. The absolute differential cross section data obtained were analysed in terms of the standard optical model. Using the fact that the rms radius of the 1p shell nuclei is nearly constant a simple folding model allows finding an optical potential family whose real potential depth varies linearly with the target mass. The best fits exhibit a normalized volume integral of about 400 MeV · fm 3 for the real potential. From the best-fit parameters a mean parameter set is deduced which varies smoothly with the target mass A T. The average parameter set compares well with the systematics found for heavier nuclei.

Elastic scattering of 90–120 MeV 3He particles and an unambiguous optical potential

Abstract The elastic scattering of 109.2 MeV 3 He particles by 40 Ca, 58 Ni, 90 Zr and 116 Sn has been investigated over a wide angular range. The elastic scattering cross sections have been analyzed in terms of the optical model. The data for each nucleus studied were sufficient to eliminate the discrete ambiguity in the strength of the optical potential; the unique potential which fits the data has a real well depth of about 100 MeV and a corresponding volume integral per nucleon pair of about 310 MeV · fm 3 . The elastic scattering of 3 He particles by 58 Ni has been further measured at bombarding energies of 89.3 and 118.5 MeV, and the incident-energy dependence of the optical potential of 3 He particles for 58 Ni was obtained.

Projectile break-up and the continuum spectra of the (3He, d) reaction

Deuteron continuum spectra induced by 70,90 and 110 MeV 3He particles have been measured for a number of target nuclei. Each spectrum shows a broad bump at forward angles, the peak energy of which is about 23 of the incident 3He energy and the cross section is nearly proportional to the radius of the target nucleus. The results are compared with projectile break-up calculations reflecting the internal deuteron momentum distribution in 3He. The good fit of the calculations shows that the continuum bump originates mainly from the projectile break-up process, and the mass number dependence of the cross section indicates that such a break-up reaction occurs at the peripheral region of the target nucleus.

Determination of the composition of NbTi films by elastic scattering of 3He

The chemical composition of NbTi superconducting films was determined by the elastic scattering of 3.0 MeV 3He particles. It is shown that film composition analysis can be carried out on NbTi films up to 8000 Å thick using values of the energy loss parameter [ S]. The accuracy of the determination of the chemical composition by this method is of the order of 0.2 at.%.

Chemical composition and structure of cathode- sputtered CdTe thin films

A chemical composition analysis of cathode-sputtered CdTe thin films by elastic scattering of 3.0 MeV 3He particles is presented. The vacuum conditions during deposition have a marked influence on the composition of the sputtered CdTe thin films, as is shown by the presence of up to 2 at.% of the operating gas argon and an oxygen contamination in the films of up to 2.5 at.%. The atomic concentration of the basic cadmium and tellurium components in the films is strictly constant and is the same as in the target from which the films were deposited. The films consist of fibres oriented perpendicular to the substrate crystallites, with either the cubic or the hexagonal structure. The diameter of the crystallites (0.1–0.3μm) is constant throughout the film thickness.

Elastic and inelastic scattering of 17.5 and 40.0 MeV 3He particles from 11B

The 3He scattering cross sections have been measured at 17.5 and 40.0 MeV from the ground state and first four excited levels of 11B. The results are analysed with the SCA assuming 11B to be a symmetric rotator and including the K-band mixing introduced by the Coriolis force. A systematic attempt is made to deduce the hexadecapole moment and the sign of the quadrupole deformation of 11B.