A Measurement of the Longitudinal Spin-Dependent Total Cross Section Difference, ??L, in the n-d System
To study these disagreements, we have initiated a program of measurements of the longitudinal spin-dependent total cross section difference, ??L, using a polarized neutron beam and a polarized deuteron target for incident neutron energies of 1.18, 5.0, 6.88, and 9.0 MeV. Calculations have shown that ??L should be sensitive to the three-nucleon force.
We performed these measurements at Triangle Universities Nuclear Laboratory in Durham, NC. A polarized neutron beam was produced as a secondary beam from polarized proton or deuteron beams. The charged particle beams were created in the TUNL Atomic Beam Polarized Ion Source and were accelerated by a tandem Van de Graaff accelerator. The charged particle and neutron polarizations were determined from elastic scattering measurements.
The deuteron target was polarized via dynamic nuclear polarization. A 3He-4He dilution refrigerator cooled the target to 250 mK and a superconducting magnet produced the 2.5 T magnetic field that is necessary to polarize the target. The target was irradiated with 69 GHz microwaves to achieve 20-30% polarization. The polarization was monitored by nuclear magnetic resonance and calibrated by reference to a ??L measurement at 1.18 MeV.
The measurements of ??L show good agreement with potential models at 6.88 and 9.0 MeV neutron energy, indicating no large disagreements with theory. However, the results are not precise enough to rule out the presence or absence of three nucleon forces.
Advisor:Werner Tornow; Dean J. Lee; Christopher R. Gould; David G. Haase; Hugon Karwowski
School Location:USA - North Carolina
Source Type:Master's Thesis
Date of Publication:07/08/2004