Session LH: Instrumentation IV

Directly Measuring SHE Mass Numbers with FIONA

Super Heavy Elements (SHEs), which occur at the extreme limits of proton (Z) and neutron (N) numbers, are ideal testing grounds for investigations of exotic atomic and nuclear properties. Unfortunately, these elements are extremely difficult to study as they are short-lived and have alpha-decay chains that end in the spontaneous fission of nuclei with poorly-established Z and  N. Presently, relative mass number (A) assignments for observed SHE isotopes are mostly well understood, but their placement on the nuclidic chart is heavily dependent on the extrapolated accuracy of the current nuclear mass models. It is extremely important to make a direct-experimental measurement of a SHE A so that we can anchor all of the relative A assignments, thus confirming the A of all observed SHEs. Lawrence Berkeley National Laboratory (LBNL) has a long history of studying SHEs with the Berkeley Gas-Filled Separator (BGS), which has recently been coupled to the newly-constructed apparatus For the Investigation of Nuclide A (FIONA). FIONA was designed to cool and bunch ions selected by the BGS before transporting them into a low-background area where they are separated and identified by their mass-to-charge ratio (A/q) on a tens-of-milliseconds timescale. Recent results will be presented.   

Development of α-ToF detector for correlation measurement of atomic masses and decay properties

The atomic mass is a unique quantity for each nucleus. Precise mass measurement allows us to identify the atomic number as well as the mass number. Recently, we measured the masses of fusion evaporation products provided from GARIS-II + MRTOF system. Next plan is the measurement the masses of superheavy nuclei (SHN) to identify the nuclides, the expected event rate is less than one event per day due to small cross section.

Follow-Ups on Great Achievements: New MRTOF-MS Projects at RIKEN-RIBF

The exotic isotopes of 249-253Md [1] and many other rare species like 210-214Ac/Ra [2] and intermediate-mass nuclei [3] and about 70 other isotopes have successfully been measured using a multi-reflection time-of-flight spectrograph (MRTOF-MS) at the super-heavy element (SHE)-mass facility of RIKEN-KEK [4]. After successful completion of the first SHE-Mass campaign, the setup has been redesigned for higher efficiencies. It has been relocated (with GARIS-II) to be behind the RRC accelerator with the new aim to measure the masses of 284Nh and 288Mc. Further MRTOF-MS devices are being developed to perform mass measurements of the most exotic species produced at RIKEN and will be placed in various locations as behind RIKEN's zero-degree spectrometer for symbiotic operation with other experiments. In this contribution, an overview of the future plans for low-energy precision mass measurements will be provided.

Installation of an Enge Split-Pole Spectrograph at Notre Dame

The structure of neutron-deficient exotic nuclei determines the proton-capture rates in a variety of explosive astrophysical events.  Such nuclei can be studied using light-ion transfer reactions at the Notre Dame Nuclear Science Lab (NSL).  To facilitate these studies, an Enge Split-Pole spectrograph is being transferred to the NSL from Oak Ridge National Laboratory.  The progress of the installation and plans for its use will be detailed in this presentation.   

New Developments with the Enge Split-Pole Spectrograph at Florida State University

The large acceptance Enge Split-Pole Spectrograph (SPS), formerly at Yale University, has recently been installed at Florida State University with a complement of new and upgraded auxiliary detectors and data acquisition systems. This setup can be used to measure nuclear structure information such as excitation energies, branching ratios, and angular distributions of states populated via transfer reactions. The auxiliary detector systems in conjunction with the SPS will be used for a variety of nuclear structure and astrophysics applications, including indirect measurements of reaction rates involving proton-rich nuclei, spectroscopic factors for exploring complete proton shell closures, unbound single proton states in the $\it{fp}$-shell, super-radiance in the $\it{sd}$-shell, and the measurement of ($\alpha$, p) reactions important in X-ray burst nucleosynthesis. The commissioning and first scientific runs with the SPS will be discussed.   

Detector System for the Enge Split-Pole Spectrograph at Florida State University

As a collaborative project between Louisiana State University (LSU) and Florida State University (FSU), a large-acceptance Enge Split-Pole Spectrograph (SPS) was recently installed at FSU. The SPS is used to conduct charged-particle spectroscopy experiments using stable beams to study transfer reactions of interest to nuclear structure and astrophysics. Along with the SPS's installation, auxiliary detector systems have been refurbished and developed. These include the Silicon Array for Branching Ratio Experiments (SABRE) and the Focal Plane Detector (FPD). SABRE is an array of silicon detectors that is used to detect charged-particle decays to determine the angular momentum distributions of decay particles and branching ratios. The FPD is a proportional counter positioned at the focal plane of the SPS, where it measures the energy loss and two different positions along the path of the reaction products dispersed by the SPS to determine particle identification and magnetic rigidity. The design, development, and commissioning of these detectors will be discussed.
  

Establishing a model for the number of generated neutron using irradiated protons to a target in an accelerator-based neutron source for boron neutron capture therapy.

An accelerator-based neutron source for boron neutron capture therapy (BNCT) is installing into National Cancer Center Hospital. In clinical situations, controlling the number of generated neutron is important for BNCT in order to provide an adequate radiotherapy. The purpose of this study is to establish a model for the number of generated neutron using irradiated protons to a target in the neutron source. Experiments were performed with an accelerator-based neutron source with a solid-state Li target (Cancer Care Intelligence systems, Inc.). A maximum thermal load to the target reaches 50 kW to acquire sufficient neutrons for BNCT. According to previous studies, the thermal load induces decrement of the Li target thickness, and its decrement induces reduction of the number of generated neutron per unit of proton current. Thus, the model was established by considering the thermal loads in this study. The calculated neutron flux using the model was compared with the measured one. Mean difference and standard deviation between the calculated and the measured neutron flux was (0.0±1.0)%. The model might be able to reflect interactions between the target and protons adequately. Therefore, the accelerator-based neutron source has a potential to perform BNCT using the model.