Recent upgrades to the CRIS Decay Spectroscopy Station: Accessing $β$- and $γ$-ray spectroscopy on pure isomeric beams
The Decay Spectroscopy Station (DSS) of the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at ISOLDE-CERN has been upgraded to perform isomer-selective $β$- and $γ$-ray spectroscopy, including a new tape system to perform spectroscopy, free from residual activity. The baseplate of the detection chamber was redesigned to incorporate the tape, a MicroTOF detector for beam diagnostics, and a custom-made, high-vacuum-compatible plastic scintillator. The vacuum operation reached a stable pressure of $10^{-7}$ mbar in the detection chamber, overcoming vacuum issues from the previous design. Around the detection chamber, up to three high-purity germanium (HPGe) detectors and four LaBr detectors can be installed, giving a total photopeak efficiency of the HPGe detectors of 7% at 200 keV. The implementation of a 24-channel digital DAQ system combines the detection array with the CRIS setup to perform laser-assisted $β$- and $γ$-ray spectroscopy. A commissioning experiment with isomeric beams of $^{106g,106m}$In, purified by narrow-band laser resonance ionization, showed complete removal of activity from the $β$ detector and full separation of the ground and isomeric state of $^{106}$In. An average $β$-detection efficiency of 19(2)% was determined from the experiment.