Model for the overall phase-space acceptance in a Zeeman decelerator

Abstract

We present a new formalism to calculate phase-space acceptance in a Zeeman decelerator. Using parameters closely mimicking previous Zeeman deceleration experiments, this approach reveals a hitherto unconsidered velocity dependence of the phase stability which we ascribe to the finite rise and fall times of the current pulses that generate the magnetic fields inside the deceleration coils. It is shown that changing the current switch-off times as the sequence progresses, so as to maintain a constant mean acceleration per pulse, can lead to a constant phase stability and hence a beam with well-defined characteristics. We also find that the time overlap between fields of adjacent coils has an influence on the phase-space acceptance. Previous theoretical and experimental results suggested unfilled regions in phase space that influence particle transmission through the decelerator. Our model provides, for the first time, a means to directly identify the origin of these effects due to coupling between longitudinal and transverse dynamics. Since optimum phase stability is restricted to a rather small parameter range in terms of the reduced position of the synchronous particle, only a limited range of final velocities can be attained using a given number of coils. We evaluate phase stability for different Zeeman deceleration sequences, and, by comparison with numerical three-dimensional particle trajectory simulations, we demonstrate that our model provides a valuable tool to find optimum parameter sets for improved Zeeman deceleration schemes. An acceleration-deceleration scheme is shown to be a useful approach to generating beams with well-defined properties for variable-energy collision experiments. More generally, the model provides significant physical insights applicable to other types of particle decelerators with finite rise and fall time fields.

References in corpus (10)

• Cold and Ultracold Molecules: Science, Technology, and Applications
• Quo vadis, cold molecules? - Editorial review
• Cold Molecule Spectroscopy for Constraining the Evolution of the Fine Structure Constant
• Stopping supersonic oxygen with a series of pulsed electromagnetic coils: A molecular coilgun
• Quantum-state resolved bimolecular collisions of velocity-controlled OH with NO radicals
• Low-energy molecular collisions in a permanent magnetic trap
• Operation of a Stark decelerator with optimum acceptance
• Slow and velocity-tunable beams of metastable He${}_2$ by multistage Zeeman deceleration
• Getting a Grip on the Transverse Motion in a Zeeman Decelerator
• Multistage Zeeman deceleration of metastable neon

Cited by in corpus (5)

• Design and construction of a multistage Zeeman decelerator for crossed molecular beams scattering experiments
• A new concept multi-stage Zeeman decelerator
• Zeeman deceleration of electron-impact-excited metastable helium atoms
• A New Design for a Traveling-Wave Zeeman Decelerator: II. Experiment
• Advanced switching schemes in a Stark decelerator