On-line installation of the Superallowed Transition Beta-Neutrino Decay Ion Coincidence Trap

¹ Department of Physics, University of Notre Dame, Notre Dame, IN, USA
² Physics Divison, Argonne National Laboratory, Argonne, IL, USA
³ Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA, USA
⁴ École normale supérieure Paris-Saclay, France

^* e-mail: mbrodeur@nd.edu

Published online: 7 August 2024

Abstract

The Cabibbo-Kobayashi-Maskawa quark mixing matrix currently does not satisfy unitarity at the 2σ-level. This could be the result of an inaccurate value of one or both of its largest matrix elements V_us and V_ud. In the case of V_ud, the most precise measurement is obtained from the f t-value measurements of superallowed beta-transitions between 0⁺ states. The accuracy of this determination can, in turn, be tested by extracting V_ud in other transitions including superallowed transitions between mirror nuclei. The Superallowed Transition Beta-Neutrino Decay Ion Coincidence Trap (St. Benedict) is currently under construction at the Nuclear Science Laboratory of the University of Notre Dame to perform such a determination, with the goal of shedding more light on this tension with unitarity. St. Benedict will take a radioactive ion beam produced by TwinSol, thermalize it in a large volume gas catcher, then transport it in two separate differentially-pumped volumes using a radio-frequency (RF) carpet and a radio-frequency quadrupole (RFQ) ion guide before injecting it in an RFQ trap to create cool ion bunches for injection in the measurement Paul trap. In this paper, we detail the installation of the beam preparation components of St. Benedict, and present the results of the first RIBs successfully stopped and extracted from its gas catcher.