Speaker
Description
In the Spallation Neutron Source based neutron Electric Dipole Moment (SNS nEDM)
experiment, spins of polarized ultracold neutrons and polarized 3He will be manipulated in
a 0.3 - 0.5 K superfluid 4He bath. Measurements will be made using two different modes:
free precession and critical dressed spin. In the former, both spin species undergo a π/2
flip and then precess at their Larmor frequency in a B0 ∼ 30 mG field. In the latter, after
a π/2 flip, a large off-resonance RF-field is used to make the two species have the same
effective precession frequency. The PULSTAR test apparatus will investigate the techniques
required to perform these operations experimentally using a full-sized measurement
cell without an electric field, and using neutrons from the NC State PULSTAR ultracold
neutron source. This apparatus allows significantly shorter cooling and turn-around times
than the full-size SNS nEDM experiment. Other planned investigations using this apparatus
include: the difference in motion between the 3He and neutron in superfluid helium that
can cause a false EDM signal, and the pseudo-magnetic field caused by the spin-dependent
difference of the n-3He scattering length. The apparatus is currently under construction
with commissioning beginning towards the end of this year.
