Identification and separation of radioactive isotope beams by the BigRIPS separator at the RIKEN RI Beam Factory

Abstract

We have developed a method for achieving excellent resolving power in in-flight particle identification of radioactive isotope (RI) beams at the BigRIPS fragment separator at the RIKEN Nishina Center RI Beam Factory (RIBF). In the BigRIPS separator, RI beams are identified by their atomic number Z and mass-to-charge ratio A/Q which are deduced from the measurements of time of flight (TOF), magnetic rigidity (B) and energy loss (E), and delivered as tagged RI beams to a variety of experiments including secondary reaction measurements. High A/Q resolution is an essential requirement for this scheme, because the charge state Q of RI beams has to be identified at RIBF energies such as 200-300 MeV/nucleon. By precisely determining the B and TOF values, we have achieved relative A/Q resolution as good as 0.034% (root-mean-square value). The achieved A/Q resolution is high enough to clearly identify the charge state Q in the Z versus A/Q particle identification plot, where fully-stripped and hydrogen-like peaks are very closely located. The precise Bdetermination is achieved by refined particle trajectory reconstruction, while a slew correction is performed to precisely determine the TOF value. Furthermore background events are thoroughly removed to improve reliability of the particle identification. In the present paper we present the details of the particle identification scheme in the BigRIPS separator. The isotope separation in the BigRIPS separator is also briefly introduced.

Triaxiality of neutron-rich Ge84,86,88 from low-energy nuclear spectra

“…The isotopes of interest were produced by in-flight fission, selected by the Bρ-E-Bρ method and identified on an event-by-event basis by the time of flight-Bρ-E method in BigRIPS [34], in two different settings. 87 As and 85 Ge were obtained with rates of 2059 and 731 s −1 , respectively, for 22 h. For 10.5 h, 89 As was provided at a rate of 140 s −1 .…”

Spallation reaction study for fission products in nuclear waste: Cross section measurements for 137Cs, 90Sr and 107Pd on proton and deuteron

“…The particle identification for the secondary beams was made event-by-event by measuring the time of flight (TOF), the magnetic rigidity (Bρ), and the energy loss ( E) as described in Refs. [8,9] with similar experimental setups. The beam energies were both 185 MeV/nucleon for 137 Cs and 90 Sr in front of the secondary targets.…”

Cross sections for nuclide production in proton- and deuteron-induced reactions on 93Nb measured using the inverse kinematics method

“…The secondary beam was separated and identified by using the BigRIPS. The particle identification was performed event-by-event using detectors installed in the BigRIPS beamline via the TOF−Bρ − E method [7,8]. The particle identification plot of the secondary beam is shown in Fig.…”