Dr. Paul DeYoung, Physics
The r-process predicts the formation of elements heavier than iron and occurs in neutron star mergers and supernovae. The β decay strength function reveals nuclear structure properties necessary to improve r-process models. Measurements of the 91Rb strength function, a nucleus involved in the r process, were made at the National Superconducting Cyclotron Laboratory (NSCL) this past July (2018). The 91Rb were made with the A1900 fragment recoil separator, then stopped in a long gas cell, and finally implanted in a mylar tape. Spectra and multiplicity of γ rays from the daughter, 91Sr, coincident with β particles from the decay of implanted 91Rb give one the information needed to determine the β decay strength function. Electrons produced by the β decay were measured in a plastic detector constructed at Hope College and γ rays were detected in the Summing NaI (SuN) detector. Coincidences between electrons and γ rays were needed to identify the energy level in the 91Sr daughter nucleus to which the parent 91Rb decayed and to quantify the probability of that decay path. β particles from the decay of 91Rb are difficult to distinguish from background events due to the buildup of long-lived daughter particles that subsequently also β decay. A tape system extending into the beam pipe through SuN is needed to move radioactive daughter particles away from the detector. Thus, a conventional Si surface barrier β detector could not be employed because of minimal space inside the beam pipe. The needed β detector was fabricated to fit inside the small beam pipe and around the tape system. The 20 cm long, barrel-shaped detector was constructed out of scintillating plastic with wave-shifting fiber optic cables on the exterior leading to photomultiplier tubes outside the SuN detector. Preliminary results are shown.
Repository citation: von Seeger, William and Gombas, Jason, "Determining the β Decay Strength Function of 91Rb" (2019). 18th Annual Celebration of Undergraduate Research and Creative Activity (2019). Paper 32.
April 12, 2019. Copyright © 2019 Hope College, Holland, Michigan.