6288
.pdf
Nuclear Physics: The Core of Matter, The Fuel of Stars
http://www.nap.edu/catalog/6288.html
204 |
APPENDIX |
|
FIGUREA.2 AerialviewoftheRelativisticHeavyIonCollider(RHIC)acceleratorcomplexatBrookhavenNationalLaboratoryonLong Island. Thefacilitywillgeneratetwocounter-circulating,high-energybeamsofheavy(forexample,gold)nuclei;thesebeamswillintersect andcollideinsixinteractionregionslocateduniformlyaroundtherings. Theinsertshowsarecentphotoofthetunnelthathousesthe accelerator,withanarrayofpowerfulsuperconductingmagnetsneededtobendthehigh-energybeams. (CourtesyRHIC.) |
Copyright © National Academy of Sciences. All rights reserved.
Nuclear Physics: The Core of Matter, The Fuel of Stars
http://www.nap.edu/catalog/6288.html
ACCELERATOR FACILITIES FOR NUCLEAR PHYSICS IN THE UNITED STATES |
205 |
into operation at Oak Ridge National Laboratory to permit research with precisely controlled beams of radioactive nuclei generated by the ISOL (isotope separator online) technique. Light ions (protons, deuterons, and others) accelerated by the Oak Ridge Isochronous Cyclotron strike an isotope-production target. Radioactive atoms produced in the target are extracted, ionized, mass selected, charge exchanged, preaccelerated, and injected into a 25-MV electrostatic tandem for acceleration to final energies.
The 88” Cyclotron at Lawrence Berkeley National Laboratory is a variableenergy isochronous cyclotron with spiral-sector focusing. A new ECR source, operating at 14 GHz, and producing high intensities of highly charged ions has revolutionized the acceleration of heavy nuclei. The 88” Cyclotron now provides ion beams of energies up to and above the Coulomb barrier for medium-mass nuclei, as well as lighter ion beams with energies up to 35 MeV/nucleon.
On a considerably smaller scale, university accelerators serve the important function of providing specialized capabilities that cannot be met by the national user facilities. Examples of problems requiring lower beam energies and thus smaller accelerators are studies of fundamental symmetries in light nuclei, nuclear structure far from stability, reactions near the Coulomb barrier, or the study of nuclear reactions that are relevant to astrophysics.
At present, eight small accelerators (also shown in Figure A.1) are supported by NSF and DOE. These are situated on university campuses and serve local faculty and students, but they also are often used by visitors who take advantage of their unique capabilities. In most cases, the capabilities of these machines result from intensive, sometimes even speculative, development work on new instrumentation, such as novel detectors or ion sources. The modest cost of accelerator operation and the availability of the accelerator over long periods of time permit developments that could not be carried out in a cost-effective way on large machines.
The accelerators at Florida State University, the State University of New York at Stony Brook, and the University of Washington consist of tandem electrostatic accelerators coupled to superconducting linear accelerators to augment their energy. At Florida State University, polarized Li ions are produced by laser pumping and are used to study spin effects in elastic and inelastic processes. New capabilities at Stony Brook include the development of a magneto-optical trap for production and trapping of short-lived radioactive nuclei. The accelerator at the University of Washington is equipped with a new ion source in the tandem terminal to provide the intense beams of alpha particles required for weak interaction studies.
The early work on production of radioactive beams at the University of Notre Dame led to systematic studies with 8Li of importance to cosmology. At Texas A&M University, a new beam-analysis system and spectrometer coupled to the K500 Superconducting Cyclotron provides radioactive-beam capabilities for studies of exotic nuclei and astrophysics. The availability of polarized beams
Copyright © National Academy of Sciences. All rights reserved.
Nuclear Physics: The Core of Matter, The Fuel of Stars
http://www.nap.edu/catalog/6288.html
206 |
APPENDIX |
of protons and deuterons at the Triangle Universities Nuclear Laboratory (TUNL) in North Carolina and at the University of Wisconsin is of importance to studies of few-body systems. The technical developments for polarized beams and targets are applied at the larger facilities in a symbiotic relationship between small university accelerators and the large national and international facilities. The large ESTU tandem accelerator at Yale University, which has been used to accelerate heavy ions of mass up to gold, is being augmented with a mass-separator facility in the terminal of the machine for use primarily in the nuclear-structure and nuclear-astrophysics programs.
Copyright © National Academy of Sciences. All rights reserved.