A Simulation Framework for Ramsey Interferometry

Abstract

The sensitivity of Ramsey interferometry experiments is governed by the interplay between the beam phase-space distribution and the magnetic field environment through which the spins propagate. Quantitative optimisation thus requires a consistent treatment of optics, magnetics and spin dynamics. We present a simulation framework that enables such an analysis by combining neutron optics simulations in McStas, magnetic field modelling in COMSOL and spin-dynamics simulation in the new RamseyProp program. We describe how important experimental parameters such as adiabaticity, flip angle distributions and Ramsey fringe contrast can be studied. The code is being applied to design an experiment to search for axion-like particles at the European Spallation Source (ESS). We examine how the pulsed time structure of the ESS can be exploited to perform Ramsey interferometry on a broad neutron velocity spectrum. In the absence of velocity or timing restrictions, the standard deviation of the spin flip angle at zero detuning can be reduced from 0.67 to 0.17 radians using time-dependent amplitude modulation. Similarly, the phase sensitivity can be improved by a factor of 4 for a 10 m long setup starting 15 m from the ESS moderator.

14 pages, 7 figures; version accepted for publication in the Journal of Instrumentation (JINST)

References in corpus (8)

• Optical Magnetometry
• Electric Dipole Moments of the Atoms, Molecules, Nuclei and Particles
• New Observables for Direct Detection of Axion Dark Matter
• Recent Progress in the Physics of Axions and Axion-Like Particles
• Axion-induced effects in atoms, molecules and nuclei: Parity nonconservation, anapole moments, electric dipole moments, and spin-gravity and spin-axion momentum couplings
• Monte Carlo Particle Lists: MCPL
• The HIBEAM Instrument at the European Spallation Source
• A Ramsey Neutron-Beam Experiment to Search for Ultralight Axion Dark Matter at the ESS