COLETTE: A linear Paul-trap beam cooler for the on-line mass spectrometer MISTRAL

A segmented, radiofrequency quadrupole mass filter COLETTE (Cooler for Emittance Elimination) was designed for cooling continuous radioactive beams for injection into the transmission spectrometer MISTRAL at CERN–ISOLDE. A description of the design of COLETTE is given, along with details of performance including measured emittances of less than 8 π mm mrad with 20 keV beams from the test bench SIDONIE in Orsay. On-line results with stable and short-lived radionuclide beams from ISOLDE are also presented.