Ion surfing: a new mode for cryogenic gas catchers, experimental results

A new mode of ion-transport and collection for low-energy precision experiments at projectile fragmentation facilities was recently proposed by Bollen [1]. Present beam thermalization methods use gas-filled linear chambers equipped with sets of electrodes that provide an electrostatic gradient and/or alternating electric fields to transport the ions towards an extraction orifice. A new cryogenic linear gas cell of the National Superconducting Cyclotron Laboratory at Michigan State University will transport ions using only electrodynamic RF fields imposed on a series of linear conductive stripes. Traditionally, the ions migrate along a descending electrostatic potential gradient applied on the individual stripes, called the drag field, which requires a large potential difference to be applied in the gas for transport over long distances. The new method to transport the ions, called ``ion surfing,'' replaces the drag field with a traveling wave. The new method can transport ions at greater speed while simplifying the overall system. We will present the results of recent measurements for the transport of 85-Rb ions over distances up to 40 cm with various gas pressures at room temperature. \\[4pt] [1] G. Bollen, Int. J. Mass Spect.\textbf{ 299} (2011) 13