H. Takeda

High resolution beam line for the Grand Raiden spectrometer.

Abstract We have designed and constructed a new beam line which can accomplish both lateral and angular dispersion matching with the Grand Raiden spectrometer. In dispersive mode, lateral and angular dispersions of the beam line are b 16 =37.1 m and b 26 =−20.0 rad , respectively, to satisfy matching conditions for Grand Raiden. In achromatic mode, the beam line satisfies the double achromatic condition of b16=b26=0. The magnifications of the beam line are (Mx,My)=(−0.98,0.89) and (−1.00,−0.99) for dispersive and achromatic modes, respectively. In the commissioning experiments, we have succeeded to separate the first excited 2+ state of 168Er with E x =79.8 keV clearly from the ground state in the (p,p′) reaction. We achieved energy resolutions of ΔE=13.0±0.3 and 16.7±0.3 keV in full width at half-maximum for 295 and 392 MeV protons, respectively. These energy resolutions agree with the resolving power of Grand Raiden for an object size of about 1 mm .

Isoscalar giant dipole resonance in 208Pb via inelastic α scattering at 400 MeV and nuclear incompressibility

The isoscalar giant dipole resonance (ISGDR) in Pb-208 has been investigated with inelastic a-scattering of 400 MeV at extremely forward angles, including 0degrees. Energy spectra, virtually free from instrumental background, have been obtained and the ISGDR strength distribution has been extracted using a multipole-decomposition analysis (MDA). A difference-of-spectra approach yields the same ISGDR centroid energy as with MDA. These results lead to a value for nuclear incompressibility that is consistent for both the isoscalar dipole and monopole modes

Polarization transfer observables for proton inelastic scattering from 12C at 0

Abstract Polarization transfer (PT) observables in the 12 C (p,p′) reaction at 0° for 392 MeV protons have been measured. The excitation strengths are decomposed into the spin-flip part and the non-spin-flip part by using the obtained PT observables. The PT observables for excitation of the 1+, T=0 and 1+, T=1 states are compared with distorted wave impulse approximation calculations. The strength ratios of the isoscalar spin-dependent term to the isovector tensor term and the isovector tensor term to the isovector spin-dependent term are reasonably consistent with the Franey and Love interaction.

Proton elastic scattering from tin isotopes at 295-MeV and systematic change of neutron density distributions

Crosssectionsand analyzing powersforproton elasticscattering from 116;118;120;122;124 Sn at295 M eV havebeen m easured fora m om entum transferofup to about3.5 fm 1 to deducesystem atic changesofthe neutron density distribution. W e tuned the relativistic Love-Franey interaction to explain the proton elastic scattering ofa nucleuswhosedensity distribution iswellknown.Then, weapplied thisinteraction todeducetheneutron density distributionsoftin isotopes.Theresultof ouranalysisshowstheclearsystem aticbehaviorofagradualincreasein theneutron skin thickness oftin isotopeswith m assnum ber.

Compressional-mode giant resonances in deformed nuclei

Abstract Background-free inelastic scattering spectra have been obtained for the Sm isotopes with 400xa0MeV α particles at forward angles (including 0°) to investigate the effect of deformation on the compressional-mode giant resonances. The strength distributions for the isoscalar giant resonances ( L ⩽3) have been extracted for the spherical nucleus 144 Sm and the deformed nucleus 154 Sm. We have observed that the effects of deformation are different for the low- and high-excitation-energy components of the isoscalar giant dipole resonance in 154 Sm. Evidence for the theoretically predicted coupling between the isoscalar dipole resonance and the high-energy octupole resonance is reported.

A study of nucleon properties in nuclei through (p, 2p) reactions

Abstract The differential cross sections and analyzing powers have been measured for a proton knockout reaction from s 1/2 orbits of several target nuclei aiming at studying nuclear medium effects in the nucleon-nucleon interaction, and in-medium nucleon properties through it. It is confirmed from the cross section data that the reaction mechanism is simple and contribution from the multi-step processes is less than ten percent, only a few percent for a 12 C target case. The analyzing power shows a distinct reduction from the value of the free proton-proton scattering and the target dependence, which is equivalent to the density dependence, of the reduction suggests existence of a medium effect. The study has been extended to the measurement of other spin observables, polarization and spin-transfer coefficients, and a preliminary result is given.

Bi-modal isoscalar giant dipole strength in 58Ni

The strength distribution of the isoscalar giant dipole resonance (ISGDR) in Ni-58 has been obtained over the energy range 10.5-49.5 MeV via extreme forward angle scattering (including 0 degrees) of 386 MeV alpha particles. We observe a bi-modal El strength distribution for the first time in an A <90 nucleus. The observed ISGDR strength distribution is in reasonable agreement with the predictions of a recent RPA calculation. (c) 2006 Elsevier B.V. All rights reserved.

Thin ice target for 16O(p,p′) experiment

A windowless and self-supporting ice target is described. An ice sheet with a thickness of 29.7 mg/cm

Structure and decay of the s-hole state in 11B studied via the 12C(p,2p)11B∗ reaction

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New data acquisition system for the focal plane polarimeter of the Grand Raiden spectrometer

cooled by liquid nitrogen was placed at the target position of a magnetic spectrometer and worked stably in the