Development and operation of gas catchers to thermalize fusion–evaporation and fragmentation products

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 204; pp. 582 - 586
• Main Authors: Savard, G., Clark, J., Boudreau, C., Buchinger, F., Crawford, J.E., Geissel, H., Greene, J.P., Gulick, S., Heinz, A., Lee, J.K.P., Levand, A., Maier, M., Münzenberg, G., Scheidenberger, C., Seweryniak, D., Sharma, K.S., Sprouse, G., Vaz, J., Wang, J.C., Zabransky, B.J., Zhou, Z.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2003
• Subjects: 29.25.Rm; 29.27.Eg
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(02)02134-1

A new approach to the production of low energy radioactive beams involves the stopping of fast beams produced by fragmentation, in-flight fission or fusion–evaporation reaction into a large gas catcher where the reaction products are thermalized in high-purity helium and extracted as singly charged ions for post-acceleration. This removes the limitation present in standard ISOL technique for species that are difficult to extract from the target/ion source assembly. This approach has been implemented at Argonne since 1998 to inject fusion–evaporation products in an ion trap system. Via a series of improvements since then, we now reach efficiencies for these devices of close to 50% with delay times below 10 ms. In preparation for the RIA project, a larger device for stopping fragmentation products is in preparation. The basic principles behind these devices together with results obtained and experience gained operating these devices will be presented. Preparation for a test of the large gas cell at the full RIA energy at GSI will also be presented.