The NSCL cyclotron gas stopper – Under construction

Rare isotopes are produced at the NSCL by projectile fragmentation at energies on the order of 100MeV/u for a wide range of research. In order to provide these exotic ions to low-energy high precision experiments such as the Penning-trap mass spectrometer LEBIT and the collinear laser spectroscopy setup, or to the NSCL’s re-accelerator (ReA), the beam must be slowed down into the eV range by solid degraders and interaction with buffer gas. A novel gas-filled reverse cyclotron is currently under construction by the NSCL and will complement a recently installed linear gas-filled cell. The new device is based on a 2.6T maximum-field cyclotron-type three-sectored magnet to confine the injected beam while it is slowed down in ≈100mbar of high-purity helium gas, cooled to liquid-nitrogen temperature. Once thermalized, the beam is transported to the center of the device by a novel RF-carpet system, extracted along the symmetry axis and accelerated to a few tens of keV of energy for delivery to the users.