An interior view of the MSU-funded High Rigidity Spectrometer and Rare Isotope Harvesting Vault building addition at FRIB.

DOE Office of Science Funds High Rigidity Spectrometer (HRS) Instrument at FRIB

The U.S. Department of Energy Office of Science (DOE-SC) has awarded $115 million for the High Rigidity Spectrometer (HRS) project at the Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU). The HRS instrument will enable scientists to characterize the properties of isotopes that are created in rare-isotope reactions produced at about 50 percent of the speed of light. With the ability to measure properties such as the mass, charge, and velocity of rare isotopes produced in those conditions, HRS will be a centerpiece experimental instrument of FRIB’s fast-beam program that will substantially increase FRIB’s scientific reach and productivity.

Supporting a user community of over 500 scientists planning to use HRS, the new cooperative agreement provides $115,306,881 over seven years to establish and operate HRS. The 2015 Nuclear Science Advisory Committee (NSAC) Long Range Plan identified HRS as a key instrument for FRIB.

The HRS cooperative agreement is in addition to the recently awarded FRIB cooperative agreement supporting FRIB operations. The DOE-SC awarded $529 million over five years to operate FRIB as a DOE-SC user facility to enable unprecedented discovery opportunities envisioned by a user community of 1,800 scientists, supporting the mission of the DOE-SC Office of Nuclear Physics. HRS serves about one-fourth of those users.

With near 100-percent efficiency, HRS will transmit isotopes that are traveling at velocities for which the rare-isotope production rate is optimal. In addition, at the higher velocities, the foils in the rare-isotope production target—in which reactions between isotopes take place—can be much thicker, greatly increasing the chances that a desired isotope reaction will occur. The combined effects of a higher rare-isotope beam intensity and the use of thicker target foils will greatly increase the sensitivity of the scientific program at FRIB.

HRS will thus extend FRIB’s scientific reach to neutron-rich isotopes by up to a factor of more than 100. This will be beneficial in particular for experiments with the most neutron-rich isotopes that have the highest potential for discovery. The increase will enable forefront experiments not otherwise possible anywhere in the world, such as detailed studies of calcium-60. Calcium-60 has 12 more neutrons than the heaviest stable isotope of calcium found in nature. It is of particular interest to understand the forces that bind neutrons and protons into nuclei.


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