Conceptual design of a hybrid neutron-gamma detector for study of β-delayed neutrons at the RIB facility of RIKEN

Abstract

BRIKEN is a complex detection system to be installed at the RIB-facility of the RIKEN Nishina Center. It is aimed at the detection of heavy-ion implants, β-particles, γ-rays and β-delayed neutrons. The whole detection setup involves the Advanced Implantation Detection Array (AIDA), two HPGe Clover detectors and a large set of 166 counters of 3He embedded in a high-density polyethylene matrix. This article reports on a novel methodology developed for the conceptual design and optimisation of the 3He-tubes array, aiming at the best possible performance in terms of neutron detection. The algorithm is based on a geometric representation of two selected parameters of merit, namely, average neutron detection efficiency and efficiency flatness, as a function of a reduced number of geometric variables. The response of the detection system itself, for each configuration, is obtained from a systematic MC-simulation implemented realistically in Geant4. This approach has been found to be particularly useful. On the one hand, due to the different types and large number of 3He-tubes involved and, on the other hand, due to the additional constraints introduced by the ancillary detectors for charged particles and gamma-rays. Empowered by the robustness of the algorithm, we have been able to design a versatile detection system, which can be easily re-arranged into a compact mode in order to maximize the neutron detection performance, at the cost of the gamma-ray sensitivity. In summary, we have designed a system which shows, for neutron energies up to 1(5) MeV, a rather flat and high average efficiency of 68.6%(64%) and 75.7%(71%) for the hybrid and compact modes, respectively. The performance of the BRIKEN system has been also quantified realistically by means of MC-simulations made with different neutron energy distributions. *

Commissioning of the BRIKEN detector for the measurement of very exotic β-delayed neutron emitters

“…Our approach to the measurement of P xn is to use direct neutron counting to select the βxn channel in combination with β counting which provides the total number of decays. A new high efficiency neutron counter has been designed [5] and assembled for this purpose. From the different detector configurations studied in [5] we chose the one including two CLOVER-type HPGe detectors, for γ spectroscopy, that maximizes the total neutron detection efficiency ε n and at the same time minimizes the dependence of ε n on neutron energy E n in the 0-5 MeV range.…”

“…A new high efficiency neutron counter has been designed [5] and assembled for this purpose. From the different detector configurations studied in [5] we chose the one including two CLOVER-type HPGe detectors, for γ spectroscopy, that maximizes the total neutron detection efficiency ε n and at the same time minimizes the dependence of ε n on neutron energy E n in the 0-5 MeV range. The detector was combined with the Advanced Implantation and Decay Array (AIDA) [6] and installed at the RIKEN Nishina Center.…”

Evaluation of Simultaneous Fitting Method for \(\beta\)-Decay Half-Lives and \(\beta\)-Delayed Multi Neutron Emission Probabilities Developed for the Briken Experiment

“…The detection of DNs following the β decay is realized by a neutron counters array, in which neutrons were slowed down in a high-density polyethylene block (moderator) until being captured in the 3 He counters. The design of this detector array can be found in [15]. The output raw data of the implant, beta and neutron events contains both the timing and spatial position, thanks to the digital electronics and time-stamping system.…”

Strong one-neutron emission from two-neutron unbound states in β decays of the r -process nuclei Ga86,87Yokoyama1, Grzywacz2, Rasco3 et al. 2019Phys. Rev. CSelf Cite16030View full textAdd to dashboardCite

“…The active stopper array was placed in the center of the high-density polyethylene moderator of the 3 He neutron counter array, BRIKEN [25]. The BRIKEN system is composed of 140 3 He counters and two clover-type HPGe detectors [26] for high-resolution γ -ray detection.…”

“…The BRIKEN system is composed of 140 3 He counters and two clover-type HPGe detectors [26] for high-resolution γ -ray detection. In this configuration, BRIKEN has 62(2)% neutron effective efficiency ( n ) at ≈1 MeV of neutron energy [25].…”