Reactions In Inverse Kinematics Research Articles

Pionic Fusion Study of the halo analogue state6Li

The isobaric analogue state of the ground state of the halo nucleus6He,6Li* has been studied in a pionic fusion experiment at the CELSIUS storage ring facility in Uppsala, Sweden. This was the first of two proposed experiments with the aim to study the high momentum part of the wave functions of the halo nuclei6He and6Li (0+, T=1). The Li nuclei were produced in inverse kinematics reactions with alpha particles incident on a deuterium cluster jet target. The6Li ions were detected in a zero-degree spectrometer situated in the fourth quadrant of the CELSIUS ring. The measurement was done for three different beam energies corresponding to 5.4, 2.2 and 1.5 MeV above threshold in the c.m. The cross-sections slowly increase with beam energy from 95 nb at the lowest energy to about 250 nb at 5.4 MeV above threshold.

Measurement of the 1H(6He,6Li)n reaction in inverse kinematics.

The $^{1}\mathrm{H}(^{6}\mathrm{He}, ^{6}\mathrm{Li})n$ reaction was studied at 0\ifmmode^\circ\else\textdegree\fi{} with the NSCL A1200 fragment separator in the energy loss mode. A $^{6}\mathrm{He}$ secondary beam at $\frac{E}{A}=93$ MeV was used to measure the Gamow-Teller and Fermi strengths between the ground state of $^{6}\mathrm{He}$ and the ground and excited states of $^{6}\mathrm{Li}$, in inverse kinematics. At 0\ifmmode^\circ\else\textdegree\fi{} the ground-state cross section is measured to be $\frac{d{\ensuremath{\sigma}}_{\mathrm{GS}}}{(d\ensuremath{\Omega})}=43\ifmmode\pm\else\textpm\fi{}16$ mb/sr, which is dominated by systematic error in the secondary beam flux. The ratio of Gamow-Teller to Fermi strength is not sensitive to this error and is found to be (87\ifmmode\pm\else\textpm\fi{}6)% of that expected from ($p, n$) systematics and $\ensuremath{\beta}$ decay. Angular distributions have been measured between 0\ifmmode^\circ\else\textdegree\fi{} and 10\ifmmode^\circ\else\textdegree\fi{} in the center of mass.

6Li-vector+12C inelastic scattering at 30 and 50 MeV.

A complete set of analyzing powers (AP`s), {ital iT}{sub 11}, {ital T}{sub 20}, {ital T}{sub 21}, and {ital T}{sub 22}, for 50 MeV {sup 12}C({sup 6}Li(vector),{sup 6}Li) elastic scattering and inelastic scattering to the {sup 12}C(2{sup +}, 4.44 MeV), {sup 12}C(0{sup +}, 7.65 MeV), and {sup 12}C(3{sup {minus}}, 9.64 MeV) states over the center-of-mass (c.m.) angular range 10{degree}{endash}115{degree} is reported. In addition, cross sections for the excited states 3{sup +}(2.18 MeV), 2{sup +}(4.31 MeV), and 1{sup +}(5.65 MeV) of {sup 6}Li were measured by using the inverse-kinematics reaction {sup 6}Li({sup 12}C,{sup 12}C) at 100 MeV. A combined analysis of the new 50 MeV data and previous 30 MeV data has been carried out using the coupled-channels (CC) code FRESCO. The CC calculations use an optical potential with double-folded (DF) real central, Woods-Saxon imaginary central, and Thomas real spin-orbit (SO) potentials. Calculations include reorientation terms and coupling to the first three excited states of {sup 6}Li and the first two nonzerospin states of {sup 12}C. The {sup 6}Li coupling strengths were fixed by the measured {sup 6}Li excited-state cross sections. The elastic-scattering cross sections and A.P.`s are described well. The need for an explicit SO potential is apparent in the elasticmore » and inelastic-scattering AP`s {ital iT}{sub 11}, more so at 30 MeV than at 50 MeV. The rank-2 AP`s up to 50{degree} c.m. arise mainly from ground-state reorientation effects. The DF potential normalization constant {ital N} approaches unity for the 50 MeV data. At both energies, the {sup 12}C(2{sup +}) cross sections are underestimated at large angles, and the description of the {sup 12}C(3{sup {minus}}) cross sections is poor in detail. The {sup 12}C(3{sup {minus}}) AP`s and the {sup 12}C(2{sup +}) {ital iT}{sub 11} are not reproduced at either energy. {copyright} {ital 1996 The American Physical Society.}« less

Study of the decay of hot nuclei formed inLa139-induced reactions atEA=45MeV by a hybrid dynamical-statistical calculation

The reactions {sup 139}La + {sup 27}Al and {sup 139}La + {sup 65}Cu at {ital E}/{ital A} = 45 MeV have been modeled by combining a Boltzmann-Nordheim-Vlasov dynamical model calculation with a statistical sequential binary decay model code. For the reaction {sup 139}La + {sup 27}Al, the major features of the experimental data are adequately described by the model calculations. These features include the inclusive fragment cross sections and the total charge and source velocity distributions of multiple fragment events. Other finer features, such as charge-Dalitz plots and the branching ratios between events of different multiplicity, are not reproduced by the calculation. The failure of the calculations is even greater for the reaction {sup 139}La + {sup 65}Cu, in which only the source velocity distributions of multiple fragment events are reproduced. Because the source velocity can be a measure of how much of the target is incorporated into the projectile in inverse kinematics reactions, this suggests that the earliest stages of the reaction, described by the dynamical calculation, are adequately characterized by the model. It is the later stages of the reaction, when fragments are emitted, where the model calculation appears to fail. However, there are some indications that statisticalmore » decay in the reaction {sup 139}La + {sup 65}Cu has occurred, whether by sequential binary decays or some type of prompt multifragmentation. {copyright} {ital 1996 The American Physical Society.}« less

Coulomb excitation of 174Hf K-isomer. γ-ray spectroscopy with high-spin isomer beam

A new experimental technique utilizing a high-spin isomer beam (HSIB) has been developed. The HSIB of 174Hf was produced by the 9Be( 170Er, 5 n) 174Hf reaction in inverse kinematics. By using the HSIB, the Coulomb excitation of the K π = 8 − isomer in 174Hf was measured. The γ-rays from the 9 − level, which is the first excited state built on the isomer, were observed as well as the cascade γ-rays of the ground-state rotational band. From the measured γ-ray yield, a value of 2 ± 1 e 2b 2 was extracted for the B( E2: 8 − → 9 −). This is the first experiment of γ-ray spectroscopy by means of the HSIB-induced secondary reactions.

Proton evaporation time scales from longitudinal and transverse two-proton correlation functions.

Two-proton correlation functions for the inverse kinematics reaction $^{129}\mathrm{Xe}$${+}^{27}$Al at E/A=31 MeV have been reanalyzed to search for differences between longitudinal and transverse correlations indicative of emission from a long-lived composite system. Evidence for such differences is found when tight angular cuts are applied in the compound nucleus rest frame and when the correlation functions are constructed by the event mixing technique.

Multifragment events in the reaction 58Ni+27Al at 15.8 MeV/nucleon.

Intermediate mass fragment (IMF) production was studied in the inverse kinematics reaction [sup 58]Ni+[sup 27]Al at 15.8 MeV/nucleon bombarding energy using the Heavy Ion Light Ion (HILI) detector. Exit channels with up to 4 IMFs have been observed. The three-body events can be ascribed to different production mechanisms: (i) incomplete momentum transfer with projectile spectator breakup, (ii) sequential fission following a deep inelastic reaction, and (iii) fast sequential fission (i.e., with Coulomb final-state interaction) in competition with a prompt breakup out of a toroidal configuration. The identified ternary reaction mechanisms, covering an extremely wide dynamic range, could be observed simultaneously; a subgroup of events is compatible with an instantaneous breakup of a highly excited nuclear system.

Application of inverse kinematics to 1H + 23Na → 12C + 12C using a thick target

Some experimental techniques used in the measurement and analysis of inverse kinematic reactions are described and applied to a kinematically complete

High-spin isomers and high-spin isomer beams

Yrast traps were found in N=83 isotones, 144Pm and 145Sm, by using inverse kinematic reactions, 14N(136Xe, 6n)144Pm and 16O(136Xe, 7n)145Sm. Their probable spin-parities are (27+) and (492+), respectively. Excitation energies of these isomers are 7.5 and 8.7 MeV Reaction products were transported by a gas filled recoil ion separation system and collected at 6 m down stream of the primary target position . The possible utilization of these high-spin isomers as secondary beams are discussed.

Energy partition in near-barrier strongly damped collisions 58Ni+208Pb.

Neutron spectra from the inverse-kinematics reaction $^{58}\mathrm{Ni}$${+}^{208}$Pb at ${\mathit{E}}_{\mathrm{lab}}$/A=6.65 MeV have been measured in coincidence with nickel-like fragments. Neutron emission patterns for net pickup and stripping channels have been analyzed in terms of sequential evaporation from fully accelerated projectile-like and target-like fragments. Like at higher energies, these patterns suggest an absence of appreciable correlations between net mass transfer and excitation energy division for strongly damped collisions, at the present near-barrier energy. The overall multiplicities, as well as energy spectra and angular distributions of neutrons, are well reproduced by simulation calculations, assuming an energy division always in favor of the heavy fragment.

A large solid angle high resolution recoil mass spectrometer for use with radioactive beams at GAMMASPHERE

A large solid angle, high resolution, recoil mass spectrometer has been designed for use with heavy ion beams from the Holifield Heavy Ion Facility at Oak Ridge National Laboratory. The design has been coordinated with the GAMMASPHERE detector project such that the spectrometer will operate with this 110-element germanium detector array at its target or focal plane positions with minimum loss of gamma ray solid angle. The spectrometer has been designed with the specific intention of using inverse kinematic reactions. The use of inverse kinematics tremendously enhances the capabilities of the spectrometer and selected examples will be discussed including the use of low intensity radioactive beams.

A large-solid-angle high-resolution recoil mass spectrometer optimized for use with Gammasphere

A large-solid-angle, high-resolution, recoil mass spectrometer has been designed for use with heavy ion beams from the Holifield heavy-ion facility at Oak Ridge National Laboratory. The design has been coordinated with the Gammasphere detector project such that the spectrometer will operate with this 110-element germanium detector array at its target or focal-plane positions with minimum loss of gamma-ray solid angle. The spectrometer has been designed with the specific intention of using inverse kinematic reactions, and the special problems that this entails and their solutions are discussed. The use of inverse kinematics tremendously enhances the capabilities of the spectrometer and selected examples will be discussed.

The superconducting magnet components of the large acceptance QQD spectrometer ALAD/sup i/N

A magnetic spectrometer system for the investigation of projectile fragmentation and nuclear reactions in inverse kinematics consists of independent elements for focusing (two superconducting quadrupole magnets) and momentum analysis (one superconducting dipole magnet as its major component). The dipole magnet consists of two superconducting solenoid coils symmetric to the midplane with pole pieces at room temperature outside the coil vacuum chambers and a large iron yoke to return the magnetic flux. The most important parameters are summarized. Optimizations with the 3-dimensional magnet program TOSCA yielded a total current of 4*10/sup 6/ A which produces a central field of 4.2 T in the dipole magnet with H-shaped iron yoke; the stored energy is approximately=21 MJ. The force acting between the iron plates is approximately=1.5*10/sup 6/ MPa. The forces were estimated with the two-dimensional computer code POISSON. The authors review design considerations for the coils, special requirements demanded of the superconductor, and quench protection for the magnet. >