Focal Plane Detection System of Gas-filled Recoil Separator in Lanzhou

Key words: 
• focal plane detection system /
• time-of-flight /
• position sensitive silicon detector /
• side silicon detector /
• gasfilled recoil separator /
• Si-box detector array

Abstract: A new designed focal plane detection system was mounted at the gas-filled recoil separator at Institute of Modern Physics, Chinese Academy of Sciences, which consisted of a time-of-flight (TOF) detector, a silicon-box (Sibox) detector array and a silicon veto detector. Three position sensitive silicon detectors (PSSD) were surrounded by eight side silicon detectors (SSD) without position sensitive, forming a box of the detector open from the front side. The detection efficiency for -decays of implanted nuclei was about 80%. The anticoincidence condition for the signals from the TOF detector and Si-box detector array was used to distinguish between the pulses originating from the implanted nuclei and their -decays. The veto detector information was used to discriminate events due to high-energy charged particles．External energy calibration and position calibration of PSSD are described concisely in this work. This system
has been used in experiments of ⁴⁰Ca+¹⁷⁵Lu and ⁴⁰Ca+¹⁶⁹Tm. Clean a-decay spectra obtained in these reactions indicated the detection system has a good performance in background suppression. Evaporation residues can be identified by the energy-time-position correlation method. On the whole, the new designed focal plane detection system has achieved thedesign requirements.