NuStAR

Intense beams of radioactive ions provided by the Super-FRS at GSI in Darmstadt will help provide answers to a series of fundamental questions of importance in nuclear structure, nuclear reactions, and nuclear astrophysics.

  1. What are the limits of nuclear existence? Where does the neutron-dripline lie?
  2. Do new forms of collective motion occur far from the valley of nuclear stability?
  3. Are there new forms of nuclear matter in very loosely bound nuclear systems?
  4. How does the ordering of quantum states, with all of its consequent implications
    for nuclear structure and reactions, alter in highly dilute or neutron-rich matter?
  5. Do symmetries seen in near-stable nuclei also appear far from stability
    and do we observe new symmetries?
  6. How are the elements and isotopes found in the Universe formed?
  7. Where are the sites of the r-process(es) of nucleosynthesis?
  8. What is the nuclear equation of state for neutron stars?

The UK nuclear-physics community has international leadership in many areas which address these questions.

DESPEC Fast-Timing Array

FAIR, the Facility for Antiproton and Ion Research, which is under construction at GSI in Darmstadt, will be the world’s foremost accelerator complex and experimental facility for nuclear physics. It will allow the study of the microscopic world at the level of atoms, nuclei and their component building blocks, the neutron and proton, as well as their constituent quarks and gluons. One of the principal objectives of FAIR is to provide intense secondary beams of short-lived, unstable nuclear species produced in the fragmentation and fission of relativistic beams of stable ions from two new synchrotrons, SIS100/300.

These radioactive ions will be used to probe the structure and dynamics of nuclei and nuclear matter via nuclear reactions and decays. As well as their intrinsic interest, such studies are of high importance both in the generation of energy and in the creation of the chemical elements in stellar processes. The radioactive ions are produced by passing the intense beam of heavy ions through a target, where they break up and are separated in-flight by a large magnetic separator, the Super-FRS. In this way beams of virtually every kind of isotope can be delivered, including very short-lived species, with a wide range of energies. Beams of the heaviest unstable nuclei will be produced with intensities 103 – 104 times greater than available at present.

FAIR is the highest priority project of the UK nuclear physics community. It is one of the major infrastructures required in Europe and is on the ESFRI roadmap. The Project Grant reported here involves all but one of the UK nuclear-physics research groups, requesting resources to build the equipment to exploit the radioactive beams that will become available at FAIR.

Unlike other areas of “big science” there is no single facility that can answer all of these questions; this is because a variety of approaches is needed, with different reaction mechanisms. It is only with the measurement of a range of observables that the whole picture can be constructed. NuSTAR, when completed, will be a facility where many of the necessary different approaches can be applied, using beams with the widest range of nuclear species available and with the highest intensities and energies.