One of the greatest wishes of nuclear physicists has finally come true. After decades of waiting, a $942 million accelerator was officially put into use in the United States on May 2, Nature reported. Experiments will depict unexplored areas of the nucleus and reveal how stellar and supernova explosions create most of the elements in the universe.

The accelerator, called the rare isotope beam facility (frib), is located at Michigan State University. Construction began in 2014 and was completed at the end of last year. Most of its budget is funded by the U.S. Department of energy. It replaces the National Science Foundation accelerator at the same location, the national superconducting cyclotron Laboratory (NSCL).

For decades, nuclear physicists have been pushing for a facility that produces rare isotopes several orders of magnitude faster than NSCL and similar accelerators around the world. In the late 1980s, scientists first proposed the accelerator and reached a consensus in the 1990s. “People in the nuclear physics community insist that we need such tools,” said Witold nazarewicz, a theoretical nuclear physicist and chief scientist of frib

All frib experiments will be conducted underground. Atoms of a particular element (usually uranium) are ionized and sent to a 450 meter long accelerator, which bends like a paper clip to accommodate a 150 meter long hall. At the end of the pipe, the ion beam will hit a graphite wheel, which rotates continuously to avoid overheating at any particular location. Most nuclei pass through graphite, but some collide with their carbon nuclei. This causes uranium nuclei to split into smaller combinations of protons and neutrons, each representing different elements and isotopes.

Then, the light beam composed of various atomic nuclei will be directed to the “debris separator” on the ground. The separator consists of a series of magnets that deflect each nucleus to the right, depending on its mass and charge. Through fine tuning, frib can generate a beam composed entirely of one isotope for each specific experiment.

Finally, the required isotopes can reach the experimental hall through the beam tube. Bradley Sherrill, scientific director and nuclear physicist of frib, said that for the rarest isotopes, the productivity may be as low as one nucleus a week, but frib will be able to produce and study almost every kind of nucleus.

A unique feature of frib is that it has a second accelerator, which can receive rare isotopes and impact them on fixed targets to simulate high-energy collisions in stars or supernovae.

It is worth mentioning that frib will explore relevant fields together with similar accelerators in Japan, Russia and Germany in the future. (Xin Yu)