Nuclear Physics (1986) / Chapter Skim
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10 Recommended Priorities for Nuclear Physics
10 Recommended Priorities for Nuclear Physics
Pages 169-188
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From page 169... ...
In 1979 NSAC produced its first Long Range Plan for Nuclear Science; its second Long Range Plan was completed in 1983. The purpose of these studies is to review previous and ongoing programs, evaluate current requirements, and anticipate future needs; they also seek to ensure that existing facilities are maintained and 169
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From page 170... ...
Designs must be optimized to support those programs most likely to produce new results in critical research areas and to satisfy the needs of the largest number of users. An accelerator's capability for providing beams of a given particle with a specific energy can be described by three parameters: the beam intensity, or the number of particles striking the target per second, expressed as beam current; the energy resolution, or the narrowness of the energy spread of the beam, usually expressed as percent of total energy; and the duty factor, or the fraction of time that particles actually strike the target.
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From page 171... ...
Some experiments require electrons, with their particularly well-understood interactions; others require intense beams of protons or secondarily produced mesons; still others require high-energy heavy ions. The ability to bring such complementary experimental techniques to bear on a variety of research problems in nuclear structure and nuclear reactions has been a crucial element in many of the major advances in nuclear physics during the past decade.
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From page 172... ...
The Planned Continuous Electron Beam Accelerator Facility The electron accelerators designed and built in the 1960s for nuclearphysics research contributed much to our understanding of the distribution of electric charge in nuclei, the coherent collective excitations of the nucleus, and the incoherent electrodisintegration of the nucleus. These accelerators, however, had relatively low energy, poor energy resolution, and poor duty factor.
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From page 173... ...
Subsequently, in the 1983 report of the NSAC Panel on Electron Accelerator Facilities, a specific recommendation for such a machine, to be operated as a national facility, was made: a 100 percent-duty-factor, 4-GeV linear-accelerator/stretcher-ring complex now called the Continuous Electron Beam Accelerator Facility (CEBAF) , which was proposed by the Southeastern Universities Research Association.
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From page 174... ...
At such relativistic energies, the head-on collision of two heavy nuclei will create an extremely hot, dense region of nuclear matter encompassing hundreds of cubic fermis in volume. The enormous energy density achieved throughout this large volume will constitute a unique combination of conditions not available in the collisions of electrons, protons, or light nuclei-for creating the quark-gluon plasma.
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From page 175... ...
of its 1983 Long Range Plan: Our increasing understanding of the underlying structure of nuclei and of the strong interaction between hadrons has developed into a new scientific opportunity of fundamental importance-the chance to find and to explore an entirely new phase of nuclear matter. In the interaction of very energetic colliding beams of heavy atomic nuclei, extreme conditions of energy density will occur, conditions which hitherto have prevailed only in the very early instants of the creation of the universe.
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From page 176... ...
Since current funding levels are barely adequate to respond, with the present facilities, to the exciting scientific opportunities confronting the field, we recommend an increase in nuclear-physics operating funds sufficient to support the necessary accelerator research and development as well as the operations and research programs at these two new facilities as they come into being. Complementary Aspects of CEBAF and the RNC Both of the new accelerators being planned by the United States nuclear-physics community the Continuous Electron Beam Accelerator Facility (CEBAF)
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From page 177... ...
These nuclei are relatively large objects, with volumes of up to several hundred cubic fermis. When they collide head-on, all the nuclear matter can interact and be heated to such enormous temperatures and energy densities that the quarks and gluons become Reconfined from the nucleons, and large numbers of quarks, antiquarks, and gluons are created.
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From page 178... ...
electron operation below 1 GeV, substantially enhanced kaon beams, improved medium-energy neutnno capability, antiproton beams, improved proton beams of variable energy between 200 and 800 MeV, and also above 800 MeV, intense neutron sources with energies up to a few hundred MeV, capabilities for accelerating very heavy ions with easily varied energy between 3 and 20 MeV per nucleon, a high-intensity pulsed muon facility, and a number of other options. We estimate that a reasonable fraction of these opportunities can be realized within the currently envisioned base program.
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From page 179... ...
with good intensity and energy resolution at energies of up to several hundred MeV Intense secondary beams of radioactive nuclei Intense kaon beams of high purity Intense muon and neutrino beams of high quality Heavy ions through uranium, at energies between 10 and 100 MeV per nucleon Low-energy and medium-energy antinucleon beams Solar neutr~no detector sensitive to lowenergy (less than 300-keV) neutrinos a The sequence of items is not intended to suggest relative priorities.
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From page 180... ...
Given our commitment to the construction of the National Electron Accelerator Laboratory [now called the Continuous Electron Beam Accelerator Facility] and the heavy-ion collider discussed above, the financial assumptions of this report preclude a major additional facility.
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From page 181... ...
The closer the link between theory and experiment, the more effective they both become in synthesizing a coherent and elegant body of knowledge. Although the NSAC 1979 Long Range Plan stressed the need for increased support of nuclear theory, a comparison of the current FY 1984 budget for nuclear physics with the FY 1979 budget shows that during the intervening 5 years, funding for nuclear theory has remained essentially constant as a percentage of the whole (5.8 percent in FY 1984 versus 6.0 percent in FY 19794.
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From page 182... ...
It is an extremely efficient preaccelerator for a larger accelerator and is currently being developed at various laboratories in the United States and around the world. Borrowing a technique developed by elementary-particle physicists, scientists at the Indiana University Cyclotron Facility are adding a beam cooler a storage ring in which the accelerated beam will be circulated and "cooled" via interaction over part of the ring with a collinear electron beam of the same velocity to reduce greatly its energy spread.
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From page 183... ...
The electron-cyclotron-resonance ion source and the electronbeam ion source, both of which underwent their pioneering development in Europe, are currently being put to use in the United States. Along with various schemes for laser-driven ion sources and polarized ion sources, they will be important elements of future nuclear-physics research programs.
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From page 184... ...
· Instigate a program of temporary support of tenure-track faculty positions to sustain nuclear physicists during the present period of low university retirement rates. · Consider the educational aspects of new facilities where practicable; they should attract the highest-caliber graduate students and give them the best possible training.
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From page 185... ...
The network consists of 16 data centers in 11 countries; each center is responsible for the evaluation of specified information in order to avoid costly duplication of effort. All evaluated data are published in Nuclear Data Sheets or Nuclear Physics and are entered into the computerized Evaluated Nuclear Structure Data File maintained by the National Nuclear Data Center at Brookhaven National Laboratory.
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From page 187... ...
Appendixes
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Key Terms
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