A new detector system for radioactive ion beam experiments at the focal plane of the recoil mass spectrometer HIRA at NSC

Abstract

7Be radioactive ion beam (RIB) has been produced by an in-flight separation technique using the recoil mass spectrometer Heavy Ion Reaction Analyzer (HIRA) at NSC. To carry out nuclear reaction studies using the low-intensity RIB, a compact geometry detector system has been installed at the HIRA focal plane. The new detector setup consists of a Multi-Wire Proportional Counter (MWPC) followed by a DE-E detector telescope. The MWPC is used for obtaining the RIB profile and normalization. Fast timing signal of the MWPC is also used for the time-of-flight measurements for correction of energy spread of the RIBs in event mode. The detector telescope consists of a gas ionization chamber which gives energy loss (DE), followed by a two-dimensional position-sensitive silicon detector which gives residual energy and position. The telescope provides particle identification, energy and reaction angle information. The measured position resolution of the MWPC is about 0.9 mm (FWHM). The detector setup has also been used in stable beam experiments as well where the MWPC provides mass spectrum of the recoils at the RMS focal plane according to their position.