[en] A team from the U.S. Department of Energy's Remote Sensing Laboratory conducted an aerial radiological survey of the area surrounding the Sandia National Laboratories/ New Mexico and Kirtland Air Force Base in Albuquerque, New Mexico, during the months of April and May 2000. The survey team measured the terrestrial gamma radiation at the site to determine the levels of natural and man-made radiation. The current survey includes the areas covered by a previous survey that was performed in 1993. The results of the aerial survey show a background exposure rate that varies between 5 and 18 microRoentgens per hour plus an appropriate 6 microRoentgens contribution from cosmic rays. The major radioactive isotopes found in this survey were potassium-40, thallium-208, bismuth-214, and actinium-228, which are all naturally occurring isotopes, and cobalt-60, cesium-137, and excess amounts of thallium-208 and actinium-228, which are due to human activity in the survey area. In regions away from the man-made activity, the exposure rates inferred from this survey agree well with the exposure rates inferred from the 1993 survey. In addition to the aerial measurements, a series of ground-based pressurized ion chamber (PIC)measurements were acquired at four sites within the survey area. These ground-based PIC measurements ranged from 5.4 to 9.5 microRoentgens and were 13 to 21 percent lower than the inferred aerial exposure-rate results

[en] Measurements of analyzing power (A), induced polarization (P) and the spin transfer coefficient (D_NN) for quasifree (rvec p,rvec n) reactions on ²⁰⁸Pb at E_lab = 495 MeV and θ_lab = 18.5 degrees were taken at the Neutron Time Of Flight facility (NTOF) at LAMPF. The data span an energy-loss range from 0-160 MeV and a momentum transfer range of q_cm = 1.7-1.9 fm^-1. These results are compared with similar measurements on ²H, ¹²C and ⁴⁰Ca previously taken at NTOF as well as with theoretical calculations

[en] Measurements of analyzing power (A) and induced polarization (P) for quasifree (rvec p,rvec n) reactions on ²⁰⁸Pb at E_lab = 494 MeV and θ_lab = 18.5 degree and ¹²C at 790 MeV and θ_lab = 13.5 degree were obtained with the Neutron Time of Flight facility (NTOF) at LAMPF

[en] Quasifree scattering on targets of CD₂ and ^natC was studied at 495 MeV using the Neutron Time of Flight facility (NTOF) at LANIPF. A complete set of (p, n) spin transfer observables was measured at an angle of 12.5 degrees, corresponding to a momentum transfer of 1.18 fm^-1 for free NN scattering. Enhancement of the ratio of the spin-longitudinal to spin-transverse response functions, not observed at a higher momentum transfer, is observed in these data at some values. of energy loss. Possible implications of this enhancement shall be discussed

[en] Purpose: To examine the effect of different scintillator surface treatments (BGO crystals) on the fraction of scintillation photons that exit the crystal and reach the photodetector (SiPM). Methods: Positron Emission Tomography is based on the detection of light that exits scintillator crystals, after annihilation photons deposit energy inside these crystals. A considerable fraction of the scintillation light gets trapped or absorbed after going through multiple internal reflections on the interfaces surrounding the crystals. BGO scintillator crystals generate considerably less scintillation light than crystals made of LSO and its variants. Therefore, it is crucial that the small amount of light produced by BGO exits towards the light detector. The surface treatment of scintillator crystals is among the factors affecting the ability of scintillation light to reach the detectors. In this study, we analyze the effect of different crystal surface treatments on the fraction of scintillation light that is detected by the solid state photodetector (SiPM), once energy is deposited inside a BGO crystal. Simulations were performed by a Monte Carlo based software named GATE, and validated by measurements from individual BGO crystals coupled to Philips digital-SiPM sensor (DPC-3200). Results: The results showed an increment in light collection of about 4 percent when only the exit face of the BGO crystal, is unpolished; compared to when all the faces are polished. However, leaving several faces unpolished caused a reduction of at least 10 percent of light output when the interaction occurs as far from the exit face of the crystal as possible compared to when it occurs very close to the exit face. Conclusion: This work demonstrates the advantages on light collection from leaving unpolished the exit face of BGO crystals. The configuration with best light output will be used to obtain flood images from BGO crystal arrays coupled to SiPM sensors

[en] The possible contribution of two-photon exchange to electron deuteron elastic scattering at relatively high momentum transfer is discussed. This study was motivated by the high precision data recently obtained at the Jefferson Laboratory. Using general arguments, based on crossing symmetry for the processes e^-+h→e^-+h and e⁺+e^-→h+bar h, we find a parametrization for the angular dependence of the interference between the one- and two-photon exchanges in the differential cross section for elastic ed scattering in terms of a new kinematical variable and compare our findings to the recent data. copyright 1999 The American Physical Society

[en] Cross sections and analyzing powers have been measured for ¹²C(p,n) at 494 MeV and 795 MeV and for Pb(p,n) at 795 MeV. The data span an energy loss range of at least 2000 MeV, which is sufficient to clearly reveal the large peak associated with quasifree neutron knockout. The kinematics, cross section, and analyzing power for this peak are compared to the corresponding observables for free nucleon-nucleon scattering and to the observables calculated with a relativistic Fermi-gas model. (orig.)

[en] We examine a new feature of the 0 degree (p,n) cross section spectra that appears at 35 MeV energy loss in Pb and Zr. To further investigate this structure we have measured a complete set of spin transfer observables for ^natPb at 0 degree using the (rvec p,rvec n) reaction at 795 MeV

[en] PETbox4 is a new, fully tomographic bench top PET scanner dedicated to high sensitivity and high resolution imaging of mice. This manuscript characterizes the performance of the prototype system using the National Electrical Manufacturers Association NU 4-2008 standards, including studies of sensitivity, spatial resolution, energy resolution, scatter fraction, count-rate performance and image quality. The PETbox4 performance is also compared with the performance of PETbox, a previous generation limited angle tomography system. PETbox4 consists of four opposing flat-panel type detectors arranged in a box-like geometry. Each panel is made by a 24 × 50 pixelated array of 1.82 × 1.82 × 7 mm bismuth germanate scintillation crystals with a crystal pitch of 1.90 mm. Each of these scintillation arrays is coupled to two Hamamatsu H8500 photomultiplier tubes via a glass light guide. Volumetric images for a 45 × 45 × 95 mm field of view (FOV) are reconstructed with a maximum likelihood expectation maximization algorithm incorporating a system model based on a parameterized detector response. With an energy window of 150–650 keV, the peak absolute sensitivity is approximately 18% at the center of FOV. The measured crystal energy resolution ranges from 13.5% to 48.3% full width at half maximum (FWHM), with a mean of 18.0%. The intrinsic detector spatial resolution is 1.5 mm FWHM in both transverse and axial directions. The reconstructed image spatial resolution for different locations in the FOV ranges from 1.32 to 1.93 mm, with an average of 1.46 mm. The peak noise equivalent count rate for the mouse-sized phantom is 35 kcps for a total activity of 1.5 MBq (40 µCi) and the scatter fraction is 28%. The standard deviation in the uniform region of the image quality phantom is 5.7%. The recovery coefficients range from 0.10 to 0.93. In comparison to the first generation two panel PETbox system, PETbox4 achieves substantial improvements on sensitivity and spatial resolution. The overall performance demonstrates that the PETbox4 scanner is suitable for producing high quality images for molecular imaging based biomedical research. (paper)

[en] Cross sections and analyzing powers have been measured for ¹²C(p,n) at 494 MeV and 795 MeV and for Pb(p,n) at 795 MeV. The data span an energy loss range of at least 200 MeV, which is sufficient to clearly reveal the large peak associated with quasifree neutron knockout. The kinematics, cross section, and analyzing power for this peak are compared to the corresponding observables for free nucleon-nucleon scattering and to the observables calculated with a relativistic Fermi-gas model. 15 refs., 3 figs