We report the first observation of a double isovector giant dipole state in nuclei (i.e., an isovector giant dipole resonance built on another giant dipole). Two new resonances were observed in (/r + \K~) double charge exchange (at 7^-292 MeV) on nat S at excitation energies of 24.7 and 28.7 MeV. The energy centroid is very close to the energy at which the double dipole C/*= 5 0" , ",2 + ; T-2) state is expected to appear. The angular distributions for the resonances have a clear quadrupole shape. The measured cross sections and the angular distribution agree well with a simple sequential two-step calculation in which single charge exchange through the giant dipole resonance to the double dipole is evaluated.

We present the first measurements of the survival time of ultracold neutrons (UCNs) in solid deuterium (SD2). This critical parameter provides a fundamental limitation to the effectiveness of superthermal UCN sources that utilize solid ortho-deuterium as the source material. Superthermal UCN sources offer orders of magnitude improvement in the available densities of UCNs, and are of great importance to fundamental particle-physics experiments such as searches for a static electric dipole moment and lifetime measurements of the free neutron. These measurements are performed utilizing a SD2 source coupled to a spallation source of neutrons, providing a demonstration of UCN production in this geometry and permitting systematic studies of the influence of thermal up-scatter and contamination with para-deuterium on the UCN survival time.PACS numbers: 29.25. Dz, 28.20.Gd, 32.80.Pj Neutrons with kinetic energies less than 340 neV (corresponding to a temperature T< 5mK) can be trapped in material bottles and are referred to as ultracold neutrons (UCNs) [1,2,3]. UCN densities at reactor sources have gradually increased with reactor power and improved techniques for extracting the UCN flux. The highest bottled densities reported in the literature, 41/cm 3 , have been obtained at the Institut Laue-Langevin (ILL) reactor in Grenoble [4].Measurements of the neutron electric dipole moment [5,6] and the neutron lifetime [7,8,9] attest to the utility of bottled UCNs for fundamental experiments with neutrons. UCNs may prove useful in improved measurements of angular correlations in neutron beta-decay [10,11], although experiments of this kind utilizing UCNs have not yet been performed. All of these experimental programs have been limited by the available densities of UCNs.Superthermal UCN production, where the production rate of UCNs due to down-scattering in energy is larger than the combined up-scatter and nuclear-absorption rates in the material, was first proposed in 1975 by Golub and Pendlebury [12] in superfluid 4 He and experimentally investigated shortly thereafter [13,14]. In this process phonon creation in the liquid is used to down-scatter cold neutrons to the UCN regime, while up-scattering is suppressed by maintaining the superfluid at sufficiently low temperature. Because 4 He has no nuclear absorption, the only limitations to the density of UCNs accumulated are wall losses and neutron beta decay. The production of UCNs by this process has been observed and agrees with theoretical expectations [14,15,16,17,18].While superfluid 4 He is an excellent superthermal converter, a few other materials, such as solid deuterium (SD 2 ), satisfy the criteria for superthermal production. The limiting UCN density, ρ UCN , one can obtain using a SD 2 source is given by the product of the rate of UCNs production in the solid, R, and the lifetime of UCNs in the solid, τ SD : ρ UCN = Rτ SD . A storage bottle opened to such a source will come into density equilibrium with the density in the solid. This led to the proposal of a thi...

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Non-charge-exchange inclusive cross sections have been measured at 500 MeV incident pion energy at quasifree scattering kinematics for both positive and negative pion charges. Peaks identified with quasifree knockout are seen at momentum transfers from 314 to 724 MeV/c. The widths and sizes of the peaks seen are consistent with the knockout of single nucleons from the nuclear surface. The data are consistent with no softening of the pion quasifree response at high momentum transfer, in contrast to the result seen in 500-MeV pion charge exchange data. PACS number(s): 25.80.Ls