Extrapolation of neutron-rich isotope cross-sections from projectile fragmentation

Using the measured fragmentation cross sections produced from the 48Ca and 64Ni beams at 140 MeV per nucleon on 9Be and 181Ta targets, we find that the cross sections of unmeasured neutron rich nuclei can be extrapolated using a systematic trend involving the average binding energy. The extrapolated cross-sections will be very useful in planning experiments with neutron rich isotopes produced from projectile fragmentation. The proposed method is general and could be applied to other fragmentation systems including those used in other radioactive ion beam facilities.Comment: accepted for publication in Europhysics Letter

Comparison between experimental data and Monte-Carlo simulations of neutron production in spallation reactions of 0.7-1.5 GeV protons on a thick, lead target

Abstract. Relativistic protons with energies 0.7-1.5 GeV interacting with a thick, cylindrical, lead target, surrounded by a uranium blanket and a polyethylene moderator, produced spallation neutrons. The spatial and energetic distributions of the produced neutron field were measured by the Activation Analysis Method using Al, Au, Bi, and Co radio-chemical sensors. The experimental yields of isotopes induced in the sensors were compared with Monte-Carlo calculations performed with the MCNPX 2.4.0 code

Neutron production in Pb/U assembly irradiated by protons and deuterons at 0.7-2.52 GeV

Relativistic protons or deuterons hit the thick, lead target. Emitted neutrons were multiplied by fission inside the uranium blanket. The high energy neutron field produced in the setup was measured by the means of threshold reactions in activation foils. The comparison with MCNPX 2.6.C simulations was done

A non-contact laser-based alignment system (LBAS) for nuclear-physics experiments

High-resolution reconstruction of reaction dynamics in nuclear-physics experiments with radioactive beams requires accurate knowledge of the beam-particle trajectories and the precise alignment of detectors with respect to the reaction target. In many cases, sub-millimeter position measurements of fragile beam-tracking and particle-detector systems are essential. We have constructed a laser-based alignment system (LBAS) which is a non-contact, high-precision alignment tool designed for applications where excellent spatial positioning must be achieved. The working principles and performance of the laser-based alignment system are presented.link_to_subscribed_fulltex

Neutron-hole states in 45Ar from 1H(46Ar, d) 45Ar reactions

To improve the effective interactions in the pf shell, it is important to measure the single-particle and single-hole states near the N = 28 shell gap. In this paper, the neutron spectroscopic factors of hole states from the unstable neutron-rich 45Ar (Z = 18,N = 27) nucleus have been studied using the 1H(46Ar,d) 45Ar transfer reaction in inverse kinematics. Comparison of our results with the particle states of 45Ar produced in 2H(44Ar, p) 45Ar reaction shows that the two reactions populate states with different angular momenta. Using the angular distributions, we are able to confirm the spin assignments of four low-lying states of 45Ar. These are the ground state (f7/2), the first-excited state (p3/2), and the s1/2 and d3/2 states. While large basis shell-model predictions describe spectroscopic properties of the ground and p3/2 states very well, they fail to describe the s1/2 and d3/2 hole states. © 2013 American Physical Society.link_to_subscribed_fulltex

Neutron spectroscopic factors of Ar34 and Ar46 from (p,d) transfer reactions

Single-neutron-transfer measurements using (p,d) reactions have been performed at 33 MeV per nucleon with proton-rich Ar34 and neutron-rich Ar46 beams in inverse kinematics. The extracted spectroscopic factors are compared to the large-basis shell-model calculations. Relatively weak quenching of the spectroscopic factors is observed between Ar34 and Ar46. The experimental results suggest that neutron correlations have a weak dependence on the asymmetry of the nucleus over this isotopic region. The present results are consistent with the systematics established from extensive studies of spectroscopic factors and dispersive optical-model analyses of Ca40-49 isotopes. They are, however, inconsistent with the trends obtained in knockout-reaction measurements. © 2011 The American Physical Society.link_to_subscribed_fulltex

Isospin effects in 40,48Ca+40,48Ca collisions

The isospin dependence of two proton correlations is studied in 40Ca+40Ca and 48Ca+48Ca collisions at E / A = 80 MeV. Measurements were performed with the HiRA detector array complemented by the 4π Ball at NSCL. We observe a strong isospin dependence of the pp-correlation functions; however the emitting source radius extracted using the imaging technique yields no sensitivity to the isospin of the reaction system. We interpret this result as a consequence of smaller fraction of fast proton emission in the neutron rich 48Ca system. © 2010 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Mechanisms in knockout reactions

We report the first detailed study of the relative importance of the stripping and diffraction mechanisms involved in nucleon knockout reactions, by the use of a coincidence measurement of the residue and fast proton following one-proton knockout reactions. The measurements used the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results for the reactions Be9(C9,B8+X)Y and Be9(B8,Be7+X)Y are presented and compared with theoretical predictions for the two reaction mechanisms calculated using the eikonal model. The data show a clear distinction between the stripping and diffraction mechanisms and the measured relative proportions are very well reproduced by the reaction theory. This agreement adds support to the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes. © 2009 The American Physical Society.link_to_subscribed_fulltex