31 research outputs found
Interaction of Cooled Ion Beams with Internal Fiber Targets
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
The cross section minima in elastic Nd scattering: a ``smoking gun'' for three nucleon force effects
Neutron-deuteron elastic scattering cross sections are calculated at
different energies using modern nucleon-nucleon interactions and the
Tucson-Melbourne three-nucleon force adjusted to the triton binding energy.
Predictions based on NN forces only underestimate nucleon-deuteron data in the
minima at higher energies starting around 60 MeV. Adding the three-nucleon
forces fills up those minima and reduces the discrepancies significantly.Comment: 11 pages, 6 figure
Study of the production mechanism of the eta meson by means of analysing power measurements
Information about the production mechanism of the eta meson in proton-proton
collisions can be inferred by confronting the experimental studies on the
analysing power for the p(pol)p --> pp eta reaction with the theoretical
predictions of this observable. Results show that the predictions of pure
pseudoscalar- or vector meson exchange model are insufficient to describe the
analysing powers.Comment: 4 pages, 4 figures, Presented at MESON 2006: 9th International
Workshop on Meson Production, Properties and Interactions, Cracow, Poland,
9-13 Jun 200
A Precision Measurement of pp Elastic Scattering Cross Sections at Intermediate Energies
We have measured differential cross sections for \pp elastic scattering with
internal fiber targets in the recirculating beam of the proton synchrotron
COSY. Measurements were made continuously during acceleration for projectile
kinetic energies between 0.23 and 2.59 GeV in the angular range deg. Details of the apparatus and the data analysis are
given and the resulting excitation functions and angular distributions
presented. The precision of each data point is typically better than 4%, and a
relative normalization uncertainty of only 2.5% within an excitation function
has been reached. The impact on phase shift analysis as well as upper bounds on
possible resonant contributions in lower partial waves are discussed.Comment: 23 pages 29 figure
Spin‐Flipping Polarized Deuterons At COSY
We recently stored a 1.85 GeV/c vertically polarized deuteron beam in the COSY Ring in Jülich; we then spin‐flipped it by ramping a new air‐core rf dipole’s frequency through an rf‐induced spin resonance to manipulate the polarization direction of the deuteron beam. We first experimentally determined the resonance’s frequency and set the dipole’s rf voltage to its maximum; then we varied its frequency ramp time and frequency range. We used the EDDA detector to measure the vector and tensor polarization asymmetries. We have not yet extracted the deuteron’s tensor polarization spin‐flip parameters from the measured data, since our short run did not provide adequate tensor analyzing‐power data at 1.85 GeV/c. However, with a 100 Hz frequency ramp and our longest ramp time of 400 s, the deuterons’ vector polarization spin‐flip efficiency was 48±1%. © 2004 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87592/2/763_1.pd
Cooler Target Development
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
A new form of three-body Faddeev equations in the continuum
We propose a novel approach to solve the three-nucleon (3N) Faddeev equation
which avoids the complicated singularity pattern going with the moving
logarithmic singularities of the standard approach. In this new approach the
treatment of the 3N Faddeev equation becomes essentially as simple as the
treatment of the two-body Lippmann-Schwinger equation. Very good agreement of
the new and old approaches in the application to nucleon-deuteron elastic
scattering and the breakup reaction is found.Comment: 20 pages, 3 eps figure
Cooler Experiment Preparation
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Magnetic modeling of actively shielded rotating MRI magnets in the presence of environmental steel.
Rotating MRI systems could enable novel integrated medical devices such as MRI-Linacs, MRI-xray-angiography systems, and MRI-proton therapy systems. This work aimed to investigate the feasibility of rotating actively shielded superconducting MRI magnets in the presence of environmental steel-in particular, construction steel in the floor of the installation site. Two magnets were investigated: a 1.0 T split bore magnet, and a 1.5 T closed bore magnet. Each magnet was scaled to emulate field strengths of 0.5, 1.0, and 1.5 T. Finite Element Modeling was used to simulate these magnets in the presence of a 3 × 4 m steel plate located 1250 mm or 1400 mm below the isocenter. There are two possible rotation directions: around the longitudinal (z) axis or around the transverse (x) axis. Each model was solved for rotation angles between 0 and 360° in 30° intervals around each of these axes. For each simulation, a 300 mm DSV was extracted and decomposed into spherical harmonics. For the closed-bore magnet, total induced perturbation for the zero degree rotation angle was 223, 432, and 562 μT peak-to-peak (pk-pk) for the 0.5, 1.0, and 1.5 T models respectively (steel at 1250 mm). For the split-bore magnet, the same numbers were 1477, 16747, and 1766 μT. The substantially higher perturbation for the split-bore magnet can be traced to its larger fringe field. For rotation around the z-axis, total perturbation does not change as a function of angle but is exchanged between different harmonics. For rotation around the x-axis, total perturbation is different at each rotation angle. For the closed bore magnet, maximum perturbations occurred for a 90° rotation around the transverse axis. For the split-bore magnet, the opposite was observed, with the same 90° rotation yielding total perturbation lower than the conventional position. In all cases, at least 95% of the total perturbation was composed of 1st and 2nd order harmonics. The presence of environmental steel poses a major challenge to the realization of an actively shielded rotating superconducting MRI system, requiring some novel form of shimming. Possible shimming strategies are discussed at length