High-accuracy global time and frequency transfer with a space-borne hydrogen maser clock

A proposed system for high-accuracy global time and frequency transfer using a hydrogen maser clock in a space vehicle is discussed. Direct frequency transfer with a accuracy of 10 to the minus 14th power and time transfer with an estimated accuracy of 1 nsec are provided by a 3-link microwave system. A short pulse laser system is included for subnanosecond time transfer and system calibration. The results of studies including operational aspects, error sources, data flow, system configuration, and implementation requirements for an initial demonstration experiment using the Space Shuttle are discussed

The retarding ion mass spectrometer on dynamics Explorer-A

An instrument designed to measure the details of the thermal plasma distribution combines the ion temperature-determining capability of the retarding potential analyzer with the compositional capabilities of the mass spectrometer and adds multiple sensor heads to sample all directions relative to the spacecraft ram directions. The retarding ion mass spectrometer, its operational modes and calibration are described as well as the data reduction plan, and the anticipated results

Inverse-kinematics one-neutron pickup with fast rare-isotope beams

New measurements and reaction model calculations are reported for single neutron pickup reactions onto a fast \nuc{22}{Mg} secondary beam at 84 MeV per nucleon. Measurements were made on both carbon and beryllium targets, having very different structures, allowing a first investigation of the likely nature of the pickup reaction mechanism. The measurements involve thick reaction targets and $\gamma$-ray spectroscopy of the projectile-like reaction residue for final-state resolution, that permit experiments with low incident beam rates compared to traditional low-energy transfer reactions. From measured longitudinal momentum distributions we show that the \nuc{12}{C} (\nuc{22}{Mg},\nuc{23}{Mg}+\gamma)X reaction largely proceeds as a direct two-body reaction, the neutron transfer producing bound \nuc{11}{C} target residues. The corresponding reaction on the \nuc{9}{Be} target seems to largely leave the \nuc{8}{Be} residual nucleus unbound at excitation energies high in the continuum. We discuss the possible use of such fast-beam one-neutron pickup reactions to track single-particle strength in exotic nuclei, and also their expected sensitivity to neutron high-$\ell$ (intruder) states which are often direct indicators of shell evolution and the disappearance of magic numbers in the exotic regime.Comment: 8 pages, 5 figure

Octupole strength in the neutron-rich calcium isotopes

Low-lying excited states of the neutron-rich calcium isotopes $^{48-52}$Ca have been studied via $\gamma$-ray spectroscopy following inverse-kinematics proton scattering on a liquid hydrogen target using the GRETINA $\gamma$-ray tracking array. The energies and strengths of the octupole states in these isotopes are remarkably constant, indicating that these states are dominated by proton excitations.Comment: 15 pages, 3 figure

Post-bloom mechanical thinning for can peaches using a hand-held electrical device

[EN] Hand thinning is a necessary but costly practice in peach (Prunus persica L. Batsch) production. A hand-held mechanical device has been tested to thin peach trees, trained in " free Italian vase" , 50-62days after full bloom. Hand thinning (HT); mechanical thinning (MT); mechanical and hand thinning (MHT); and un-thinned (UT) were tested from 2008 to 2011 in Murcia, south-eastern Spain. After thinning, the distance between the remaining fruits was measured: the shortest distance was 5.2cm for MT, with no significant differences between MHT and HT at 8.6 and 8.8cm, respectively. The differences in distances did not affect the yield and size of the fruit at harvesting in any of the cases. There were no significant differences between HT, MT and MHT treatments in fruit per tree, mean fruit weight and yield efficiency in the 4years the test lasted. Farmers considered the hand-held mechanical device positively because it increased field efficiency. Moreover, with HT the operating time was 291hha -1, with MHT it was 87hha -1 and with MT, 27hha -1. The most expensive system was HT (2442€ha -1) as opposed to 824€ha -1 for MHT. The lowest cost was for MT with 296€ha -1. The net value of fruit (€ha -1) showed no significant differences between HT, MT, and MHT. Based on our study, MT appears to be a promising technique for thinning peach trees for the canning industry, because although the reduction of production costs is not high in comparison with the total cost of the crop, the increase in work speed is of great interest to thin the trees on the most appropriate dates. © 2012 Elsevier B.V.This research was funded by the Consejeria de Agricultura de la Region de Murcia, Spain. The authors thank Eng. Regino Aragon (IMIDA) and Marin Gimenez Hermanos S.A. (Caravaca, Spain) for their support.Martín Gorriz, B.; Torregrosa, A.; García Brunton, J. (2012). Post-bloom mechanical thinning for can peaches using a hand-held electrical device. Scientia Horticulturae. 144:179-186. doi:10.101016/j.scienta.2012.07.003S17918614

Correlations in intermediate-energy two-proton removal reactions

We report final-state-exclusive measurements of the light charged fragments in coincidence with 26Ne residual nuclei following the direct two-proton removal from a neutron-rich 28Mg secondary beam. A Dalitz-plot analysis and comparisons with simulations show that a majority of the triple- coincidence events with two protons display phase-space correlations consistent with the (two-body) kinematics of a spatially-correlated pair-removal mechanism. The fraction of such correlated events, 56(12) %, is consistent with the fraction of the calculated cross section, 64 %, arising from spin S = 0 two-proton configurations in the entrance-channel (shell-model) 28Mg ground state wave function. This result promises access to an additional and more specific probe of the spin and spatial correlations of valence nucleon pairs in exotic nuclei produced as fast secondary beams.Comment: accepted for publication in Physical Review Letter

Probing elastic and inelastic breakup contributions to intermediate-energy two-proton removal reactions

The two-proton removal reaction from 28Mg projectiles has been studied at 93 MeV/u at the NSCL. First coincidence measurements of the heavy 26Ne projectile residues, the removed protons and other light charged particles enabled the relative cross sections from each of the three possible elastic and inelastic proton removal mechanisms to be determined. These more final-state-exclusive measurements are key for further interrogation of these reaction mechanisms and use of the reaction channel for quantitative spectroscopy of very neutron-rich nuclei. The relative and absolute yields of the three contributing mechanisms are compared to reaction model expectations - based on the use of eikonal dynamics and sd-shell-model structure amplitudes.Comment: Accepted for publication in Physical Review C (Rapid Communication