# A new concept multi-stage Zeeman decelerator

## TL;DR

This paper introduces a novel multi-stage Zeeman decelerator optimized for molecular beam scattering, featuring alternating hexapoles and solenoids for effective transverse and longitudinal control, demonstrated with metastable helium atoms.

## Contribution

The paper presents a new decelerator design with separated focusing and deceleration elements, allowing large longitudinal acceptance and narrow transverse distribution, suitable for scattering experiments.

## Key findings

- Achieved up to 60% kinetic energy removal from helium atoms.
- Successfully demonstrated acceleration, deceleration, and guiding modes.
- Decelerator is cost-effective, easy to build, and operates at 10 Hz.

## Abstract

We present a new concept for a multi-stage Zeeman decelerator that is optimized particularly for applications in molecular beam scattering experiments. The decelerator consists of a series of alternating hexapoles and solenoids, that effectively decouple the transverse focusing and longitudinal deceleration properties of the decelerator. It can be operated in a deceleration and acceleration mode, as well as in a hybrid mode that makes it possible to guide a particle beam through the decelerator at constant speed. The deceleration features phase stability, with a relatively large six-dimensional phase-space acceptance. The separated focusing and deceleration elements result in an unequal partitioning of this acceptance between the longitudinal and transverse directions. This is ideal in scattering experiments, which typically benefit from a large longitudinal acceptance combined with narrow transverse distributions. We demonstrate the successful experimental implementation of this concept using a Zeeman decelerator consisting of an array of 25 hexapoles and 24 solenoids. The performance of the decelerator in acceleration, deceleration and guiding modes is characterized using beams of metastable Helium ($^3S$) atoms. Up to 60 % of the kinetic energy was removed for He atoms that have an initial velocity of 520 m/s. The hexapoles consist of permanent magnets, whereas the solenoids are produced from a single hollow copper capillary through which cooling liquid is passed. The solenoid design allows for excellent thermal properties, and enables the use of readily available and cheap electronics components to pulse high currents through the solenoids. The Zeeman decelerator demonstrated here is mechanically easy to build, can be operated with cost-effective electronics, and can run at repetition rates up to 10 Hz