High-precision mass measurements for the rp-process at JYFLTRAP

Abstract

Abstract. The double Penning trap JYFLTRAP at the University of Jyväskylä has been successfully used to achieve high-precision mass measurements of nuclei involved in the rapid proton-capture (rp) process. A precise mass measurement of 31 Cl is essential to estimate the waiting point condition of 30 S in the rp-process occurring in type I x-ray bursts (XRBs). The mass-excess of 31 Cl measured at JYFLTRAP, -7034.7(3.4) keV, is 15 more precise than the value given in the Atomic Mass Evaluation 2012. The proton separation energy S p determined from the new mass-excess value confirmed that 30 S is a waiting point, with a lowertemperature limit of 0.44 GK. JYFLTRAP: a double Penning trap for mass measurementsExotic nuclei are produced at the University of Jyväskylä by using a stable ion beam delivered by the K130 cyclotron to the Ion Guide Isotope Separator On-Line (IGISOL) facility. The produced ions created either by fission or fusion reactions on a thin target are extracted out from the ion guide gas cell and accelerated to 30 keV. They are then mass separated with a 55° dipole magnet and cooled in a radiofrequency cooler and buncher (RFQ). The RFQ periodically releases a bunch of ions to the double Penning trap setup JYFLTRAP [1] where a static quadrupolar electric field and an homogenous magnetic field is applied.In a Penning trap, an ion has three eigenmotions: the axial (νz), the magnetron (ν-) and the reduced cyclotron motion (ν+). The cyclotron frequency is connected to the mass of the ion and the magnetic field of the trap by:(1)