A radiofrequency quadrupole system for mass separation and ion bunching at SHIPTRAP

At SHIPTRAP, very proton-rich exotic nuclei are produced and separated from the primary beam in the velocity filter SHIP, stopped in a gas cell, bunched and transferred to a double Penning trap system. A radio-frequency quadrupole (RFQ) system consisting of a RFQ cooler, RFQ mass filter and RFQ buncher has been developed in order to remove contaminant ions and abundant reaction products other than nuclei of interest, which so far limits the performance of SHIPTRAP. The newly developed system will also allow for quick identification of the ions produced. Operation parameters of the system have been optimized and the performance has been investigated. The cooler mass filter combination shows full transmission up to a mass resolving power of about 200 (FWHM) and suppression of neigboring masses over at least four orders of magnitude. Studies of the RFQ buncher show that peak widths of the extracted ion bunches of about 50 ns can be reached while maintaining full energy acceptance of the Penning trap. Using the detectors installed at SHIPTRAP this would allow for broadband time-of-flight mass spectrometry with a resolution of about 300.