Design and Development of a Trochoidal Mass Analyzer for the Berkeley Gas-filled Separator, J. M. Gates, N. E. Esker, K. E. Gregorich, G. K. Pang, H. Nitsche, Lawrence Berkeley National Laboratory, Berkeley, California, USA − Several upgrades to the Berkeley Gas-filled Separator (BGS) at the Lawrence Berkeley National Laboratory (LBNL) are currently underway.  These upgrades will include a new mass analyzer coupled to the BGS to i) provide a M/ΔM separation of ~500 and ii) transport nuclear reaction products to a shielded detector station on the tens of milliseconds timescale.  These upgrades will allow for direct A and Z identification of ii) new actinide and transactinide isotopes with ambiguous decay signatures such as electron capture or spontaneous fission decay and i) superheavy nuclei such as those produced in the 48Ca + actinide reactions.


In the proposed setup, nuclear reaction products recoil from the target and are separated from the beam and unwanted reaction products in the BGS.  There they pass through a window and into a radio-frequency gas catcher where they are thermalized and extracted into a radio-frequency quadrupole (RFQ) trap.  The nuclear reaction products are cooled and bunched in the RFQ trap, where they maintain a +1 or +2 charge, and are injected into the mass analyzer.  The proposed mass analyzer consists of crossed electric and magnetic fields such that the ions take trochoidal trajectories.  Simulations predict that high mass dispersion and M/ΔM separation of >500 is possible with a 50‑cm long, ≤1.5 T magnetic field and electric field of <500 V/cm.  Here we will present the design of and future plans for the mass analyzer.


Financial Support was provided by the Office of High Energy and Nuclear Physics, Nuclear Physics Division, and by the Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231.