The Intra-Pulse Multi-Energy (IPME) method of material discrimination mitigates main disadvantages of the traditional “interlaced” approach: ambiguity caused by sampling different regions of cargo and reduction of effective scanning speed. A novel concept of creating multi-energy probing pulses using a standing-wave structure allows maintaining a constant energy spectrum while changing the time duration of each sub-pulse and thus enables adaptive cargo inspection. Depending on the cargo density, the dose delivered to the inspected object is optimized for best material discrimination, maximum material penetration, or lowest dose to cargo. A model based on Monte-Carlo simulation and experimental reference points were developed for the optimization of inspection conditions.

In the US, inbound international general aviation flights need to be inspected daily. The objects of interest include explosives, weapons, currency, and contraband. An imaging system capable of seeing through the skin of the aircraft to identify suspicious items would considerably speed up the inspection process. For inspection of shipping containers, cars, trucks, and other vehicles, AS&E has fielded many hundreds of X-ray backscatter systems composed mostly of the Z Backscatter® Van and the Z Portal® system. Due to their complicated shapes, large variation in profiles and sizes, and particular operational settings, aircraft require a specialized type of scanner which has been developed by AS&E. Initial feasibility experiments have demonstrated that the X-ray backscatter method is very effective for detecting objects of interest inside aircraft of different types and sizes. Analysis of images illustrating the imaging tradeoffs is presented. In designing a product for this task the challenges are not limited to X-ray imaging. Due to operational issues, special considerations are needed for collision avoidance, zero-turn-radius, shape-following scanning, adaptive detection area, and video overlay. This paper details the requirements and tradeoffs involved in the system design, along with an overview of the prototype and its performance.

The neutron-rich nucleus 74Ni was studied with inverse-kinematics inelastic proton scattering using a 74Ni radioactive beam incident on a liquid hydrogen targetat a center-of-mass energy of 80 MeV. From the measured de-excitation gamma-rays, the population of the first 2+ state was quantified. The angle-integrated excitation cross section was determined to be 14(4) mb. A deformation length of delta = 1.04(16) fm was extracted in comparison with distorted wave theory, which suggests that the enhancement of collectivity established for 70Ni continues up to 74Ni. A comparison with results of shell model and quasi-particle random phase approximation calculations indicates that the magic character of Z = 28 or N = 50 is weakened in 74Ni.

The one-proton knockout reaction Be-9(Ti-54, Sc-53 + gamma) X at 72 MeV/nucleon has been measured. The location of the first 3/2(-) state at 2110(3) keV was confirmed, and new gamma-ray transitions were observed at 1111(2), 1273(2), 1539(4), and 2495(5) keV. Large spectroscopic strength to excited states in 53Sc was found and attributed to the knockout of sd-shell protons.

γ-ray decays from excited states in 30 Ne and inclusive and exclusive cross sections were measured in the 9 Be( 32 Mg, 30 Ne + γ)X two-proton knockout reaction at incident beam energies of 99.7 and 86.7 MeV/nucleon. The measured cross section is suppressed compared to calculations and is indicative of a reduced overlap of initial and final state wave functions in 32 Mg and 30 Ne. We interpret this reduction as due to large 4p4h amplitudes present in the 30 Ne ground state wave function, but not 32 Mg. Such large intruder components are predicted to help stabilize the heavier fluorine isotopes against neutron emission.

S. Ettenauer,1,* H. Zwahlen,1,2 P. Adrich,1 D. Bazin,1 C. M. Campbell,1 J. M. Cook,1,2 A. D. Davies,1,2 D.-C. Dinca,1,2 A. Gade,1,2 T. Glasmacher,1,2 J.-L. Lecouey,1 W. F. Mueller,1 T. Otsuka,3,4 R. R. Reynolds,5 L. A. Riley,6 J. R. Terry,1,2 Y. Utsuno,7 and K. Yoneda1 1National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA 2Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA 3Department of Physics and Center for Nuclear Study, University of Tokyo, Hongo, Tokyo 113-0033, Japan 4RIKEN, Hirosawa, Wako-shi, Saitama 351-0198, Japan 5Department of Physics, Florida State University, Tallahassee, Florida 32306, USA 6Department of Physics and Astronomy, Ursinus College, Collegeville, Pennsylvania 19426, USA 7Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan (Received 2 April 2008; published 15 July 2008)

In contrast to transmission X-ray imaging systems where inspected objects must pass between source and detector, Compton backscatter imaging allows both the illuminating source as well as the X-ray detector to be on the same side of the target object, enabling the inspection to occur rapidly and in a wide variety of space-constrained situations. A Compton backscatter image is similar to a photograph of the contents of a closed container, taken through the container walls, and highlights low atomic number materials such as explosives, drugs, and alcohol, which appear as especially bright objects by virtue of their scattering characteristics. Techniques for producing X-ray images based on Compton scattering will be discussed, along with examples of how these systems are used for both novel security applications and for the detection of contraband materials at ports and borders. Differences between transmission and backscatter images will also be highlighted. In addition, tradeoffs between Compton backscatter image quality and scan speed, effective penetration, and X-ray source specifications will be discussed.

K. Yoneda, ∗ A. Obertelli, A. Gade, 2 D. Bazin, B. A. Brown, 2 C. M. Campbell, 2 J.M. Cook, 2 P. D. Cottle, A. D. Davies, 2 D.-C. Dinca, 2, † T. Glasmacher, 2 P.G. Hansen, 2 T. Hoagland, K. W. Kemper, J.-L. Lecouey, ‡ W. F. Mueller, R. R. Reynolds, B. T. Roeder, J.R. Terry, 2 J. A. Tostevin, and H. Zwahlen 2 National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 Department of Physics, Florida State University, Tallahassee, FL 32306 Department of Physics, School of Electronics and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom (Dated: February 8, 2008)

The neutron-rich nucleus 30 Na in the vicinity of the "Island of Inversion" was investigated using intermediate-energy Coulomb excitation. A single γ-ray transition was observed and attributed to the 3 + 1 → 2 + gs decay. A transition probability of B(E2; 2 + gs → 3 + 1 ) =147(21)e 2 fm 4 was determined and found in agreement with a previous experiment and with large-scale shell-model calculations. Evidence for the strong excitation of the 4 + 1 state predicted by the shell-model calculations was not observed.

The breakdown of the N=20 magic number in the so-called island of inversion around Mg-32 is well established. Recently developed large-scale shell-model calculations suggest a transitional region between normal- and intruder-dominated nuclear ground states, thus modifying the boundary of the island of inversion. In particular, a dramatic change in single-particle structure is predicted between the ground states of Mg-30 and Mg-32, with the latter consisting nearly purely of 2p-2h N=20 cross-shell configurations. Single-neutron knockout experiments on Mg-30,Mg-32 projectiles have been performed. We report on a first direct observation of intruder configurations in the ground states of these very neutron-rich nuclei. Spectroscopic factors to low-lying negative-parity states in the knockout residues are deduced and compare well with shell-model predictions.

Rare isotope beams of neutron-deficient 106,108,110Sn from the fragmentation of 124Xe were employed in an intermediate-energy Coulomb excitation experiment. The measured B(E2,0(1)(+)-->2(1)(+)) values for 108Sn and 110Sn and the results obtained for the 106Sn show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the Z = 50 shell to the structure of low-energy excited states in this region.

Quadrupole deformation parameters, |β2,(p,p′)|, have been deduced for 36,38,40Si from measured inelastic proton-scattering cross sections. Due to the strong Z=14 subshell gap, low-lying quadrupole collectivity in these nuclei is attributed to the excitation of valence neutrons. Enhanced collectivity at N=26 indicates a reduced N=28 shell gap at large neutron excess in this chain of isotopes. Data are compared to large-scale shell-model calculations and prior Coulomb excitation measurements on 36,38Si.