Thesis Committee: Haiyan Gao, Glenn Edwards, Kate Scholberg , and Seog Oh (exofficio non-voting member)
ABSTRACT:
In this experiment, we aim to measure the neutron electric dipole moment
with unprecedented sensitivity. Polarized Ultra Cold Neutrons are submerged
in a superfuid 4He and polarized 3He mixture at 300 to 500 mK. A uniform
magnetic field and electric field are applied parallel to the polarizations of
both the neutrons and the 3He. The precession frequency of the neutrons
is measured relative to that of the 3He nuclei, which is determined through
SQUID, by way of the scintillation light signal produced by the 3He + n -> p
+ t + 734 keV spin-dependent reaction. The electric field is reversed and the
neutron precession frequency is measured again. The difference between the
two precession frequency measurements is proportional to the neutron electric
dipole moment.
The 3He polarization plays a crucial role in the sensitivity of the experiment,
as it determines the strength of the scintillation signal and the strength of the
SQUID signal. 3He is also used as an in situ co-magnetometer in the analysis
of systematic errors. The 3He must change polarization direction by coupling
to a magnetic field as it is being injected in the 4He superfluid. In the reference
frame of the dipoles, the dipoles experience a time-varying magnetic field which
induces polarization loss. After the injection the polarization is measured using
NMR. This paper concerns the design of magnetic fields to minimize the polarization
loss of 3He during its transport into the 4He superfluid and to minimize
the effect of nuclear relaxation during the polarization measurement.
Here is the thesis in PDF: Mestler_thesis.pdf