Commissioning the A1900 projectile fragment separator

An important part of the recent upgrade of the NSCL facility is the replacement of the A1200 fragment separator with a new high acceptance device called the A1900. The design of the A1900 device represents a third generation projectile fragment separator (relative to the early work at LBL) as it is situated immediately after the primary accelerator, has a very large acceptance, a bending power significantly larger than that of the cyclotron and is constructed from large superconducting magnets (quadrupoles with 20 and 40 cm diameter warm bores). The A1900 can accept over 90% of a large range of projectile fragmentation products produced at the NSCL, leading-to large gains in the intensity of the secondary beams. The results of initial tests of the system with a restricted momentum acceptance (+/-0.5%) indicate that the A1900 is performing up to specifications. Further large gains in the intensities of primary beams, typically two or three orders of magnitude, will be possible as the many facets of high current extraction from the ion sources, acceleration of intense, low charge-state ions in the K500 cyclotron, transfer and stripping injection in K1200 cyclotron are optimized. A liquid-lithium cooled beryllium target system is being constructed to use with the high power beams (up to approximate to5 kW) that will be available from the coupled-cyclotron facility. An overview of the design, construction and commissioning studies of the A1900 device will be presented along with some of the results from the initial exotic isotope production studies. (C) 2002 Elsevier Science B.V. All rights reserved.