THE MANIPULATION OF IONS USING ELECTROMAGNETIC TRAPS

Electromagnetic traps, in addition to providing very clean and gentle confinement for very precise and sensitive observation of charged particles, are very versatile devices for collecting and preparing charged particles from outside sources for observation by devices which are also outside, devices which may in themselves be other electromagnetic traps. This paper introduces the basic principles of using electromagnetic traps for collecting and cooling and presents some preliminary test results from using Paul traps for these purposes. Specifically, in relatively modest Paul traps with 28 mm between end electrodes a collection efficiency of 0.2% was achieved for a 60 keV DC beam of Xe-132 ions and small collections of K-39 ions were cooled to 0.3 eV or lower. These results indicate that, with prebunching of a DC beam to the RF of a larger Paul trap and careful design of the extraction system, practically 100% collection efficiency into very small clouds of cold ions could be achieved. Preliminary plans are presented for a system to be installed for mass measurements of short-lived radionuclides at the new ISOLDE facility at the CERN proton booster. Other possible experimental uses for the techniques arc suggested.