EBIS/T charge breeding for intense rare isotope beams at MSU

Abstract

Experiments with reaccelerated beams are an essential component of the science program of existing and future rare isotope beam facilities. NSCL is currently constructing ReA3, a reaccelerator for rare isotopes that have been produced by projectile fragmentation and in-flight fission and that have been thermalized in a gas stopper. The resulting low-energy beam will be brought to an Electron Beam Ion Source/Trap (EBIS/T) in order to obtain highly charged ions at an energy of 12 keV/u. This charge breeder is followed by a compact linear accelerator with a maximum beam energy of 3 MeV/u for 238 U and higher energies for lighter isotopes. Next-generation rare isotope beam facilities like the Facility for Rare Isotope Beams FRIB, but also existing Isotope Separator On-line (ISOL) facilities are expected to provide rare-isotope beam rates in the order of 10 11 particles per second for reacceleration. At present the most promising scheme to efficiently start the reacceleration of these intense beams is the use of a next-generation highcurrent charge-breeder based on an EBIS/T. MSU has formed a collaboration to develop an EBIT for this purpose. A new high-current EBIS/T breeder will be developed and constructed at MSU, where also first tests on achievable beam rate capability will be performed. The EBIT is planned to be installed at the Isotope Separator and Accelerator facility ISAC at TRIUMF laboratory for on-line tests with rare isotope beams and to provide intense energetic reaccelerated radioactive beams. The status of the ReA3-EBIS/T in the NSCL reaccelerator project is given with a brief summary of results, followed by a discussion of plans for the future high-intensity EBIS/T charge breeder.

Charge breeding of radioactive ions with EBIS and EBIT

“…An example of an RIB facility using an EBIT as breeder is the ReA3 at NSCL/MSU, which is a 3 MeV/A re-accelerator of thermalized projectile fragmentation and fission beams [35]. Its layout is presented in Fig.…”

“…This method has previously been used at ISOLTRAP with great success [55]. Pure radioactive manganese nuclei, 61 Mn t 1/2 =670 ms and later also 62 Mn t 1/2 =880 ms, copiously produced by RILIS, were injected into REX in an explorative experiment [56]. The ions were trapped inside REXTRAP for various times ranging from 300 ms to 1100 ms, before being transferred to REXEBIS, charge bred for 28 ms to 15+, and thereafter accelerated to Miniball.…”

“…In contrast to REX-ISOLDE a bunching Penning trap is not situated in front of the breeder but continuous injection of 60 keV singly charged ions decelerated to a few hundred eV is employed. The MSU EBIT [61,62] has been designed in collaboration with MPIK in Heidelberg and ISAC/TRIUMF and is based on the TITAN EBIT (see below), although changes have been implemented in order to adapt it to breeding for re-acceleration. The main changes compared to the TITAN EBIT are an improved electron gun design and a different magnetic field configuration.…”

“…Thereafter, an exceptionally performing EBIT breeder, presently in the early planning stage, will be discussed. The latter, endorsed by the Department of Energy, US, is a high-current breeder to be developed and constructed at MSU in collaboration with a number of other institutes [62].…”