Status of the NSCL Cyclotron Gas Stopper

TL;DR

The NSCL Cyclotron Gas Stopper is a novel device designed to efficiently thermalize energetic rare isotope beams using a reverse cyclotron with buffer gas, enhancing low-energy beam production for nuclear physics experiments.

Contribution

This paper presents the design, simulations, and construction status of a new cyclotron-based gas stopper for improved ion thermalization compared to linear gas cells.

Findings

Simulations show high efficiency for light and medium mass ions.

Optimized magnetic field design enhances ion transport and stopping.

Construction is underway with promising performance expectations.

Abstract

A gas-filled reverse cyclotron for the thermalisation of energetic beams is under construction at NSCL/MSU. Rare isotopes produced via projectile fragmentation after in-flight separation will be injected into the device and converted into low-energy beams through buffer gas interactions as they spiral towards the centre of the device. The extracted thermal beams will be used for low energy experiments such as precision mass measurements with traps or laser spectroscopy, and further transport for reacceleration. Detailed calculations have been performed to optimize the magnetic field design as well as the transport and stopping of ions inside the gas. An RF carpet will be used to transport the thermal ions to the axial extraction point. The calculations indicate that the cyclotron gas stopper will be much more efficient for the thermalisation of light and medium mass ions compared to linear gas cells. In this contribution we will discuss simulations of the overall performance and acceptance of machine, the beam matching calculations to the fragment separator emittance, and the construction status.