The High Rigidity Spectrometer for FRIB

A new High Rigidity Spectrometer (HRS) has been proposed as the first major addition to the Facility of Rare Isotope Beams (FRIB) experimental facilities. Its high magnetic rigidity (8 Tm maximum) matches the rigidities at which production rates of rare-isotope beams (RIBs) via projectile fragmentation or in-flight fission are optimized across the entire nuclear chart, and hence maximizes the potentiality of the fast-beam experimental program. In combination with the ability to use thicker reaction targets at the higher rigidities, luminosity gain will be by a factor of 2 to 100 for over 90% of experiments with neutron-rich RIBs (with the largest gains for the most neutron-rich isotopes), compared to what is possible with the existing spectrometers at NSCL (4 Tm maximum). This enhancement will offer unprecedented discovery potential by providing access to critical isotopes that are not available otherwise. The HRS consists of the High-Transmission Beam Line, through which RIBs that are produced and separated in the Fragment Separator are transported to the reaction target with minimal losses, and the Spectrometer Section, which analyzes the reaction product with large angular and momentum acceptances and high resolution that are achieved simultaneously. The HRS can accommodate different ion-optical modes, and run experiments in conjunction with major auxiliary detectors such as the Gamma Ray Energy Tracking Array (GRETA) and the Modular Neutron Array (MoNA-LISA). In this presentation, an overview of the scientific opportunities with the HRS and the present layout of the HRS will be given.