(see Figure 4). The ring will receive bunches of 1-TeV protons from the injector; the protons will be distributed around the ring and accelerated until they reach an energy of 20 TeV. When the protons are at the desired energy level, it will be possible to deflect the two beams so that they collide head-on with one another in the center of the particle detectors that surround the beams at the interaction points. After acceleration to full energy, the beams will continue to circulate for many hours while the experimental detectors record collision events. When the beam intensity falls, a new batch of protons will be introduced into the SSC and accelerated.

The main-ring bending and focusing magnets will use superconducting wire to carry the electric current that sets up the magnetic field. The costly and sophisticated superconducting cable as well as the great precision and quality control required in assembly will

make the magnets expensive to build, although they will be relatively inexpensive to operate, because the superconducting coils have essentially no electrical resistance. In principle, a 20-TeV accelerator (of considerably larger circumference) could be built with conventional copper conductor electromagnets, but, because of the resistance of the wire, it would consume at least 4000 MW of power (as opposed to a total of 100 MW to be consumed by the entire SSC complex, much of which is necessary to cool the superconducting magnets to their required operating temperature) and lead to impractically high operating costs. Using superconducting magnets will reduce the total power consumption of the magnetic confinement system and permit the creation of magnetic fields several times stronger than any that could be achieved with conventional electromagnets. A stronger magnetic field will make it possible to confine protons of a given energy (say, 20 TeV) to an orbit of smaller radius and thus reduce the required length of the accelerator tunnel. The design circumference of the SSC-53 miles-is determined by the maximum intensity of its magnetic field-6.6 tesla-and the maximum energy of the protons-20 TeV.

The accelerator will also require hundreds of miles of cryogenic

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plumbing (at the boiling point of liquid helium, 4 K) to establish superconductivity. Such systems (though with a lower magnetic field) have been successfully constructed and used on a large scale in the Tevatron ring of the Fermi National Accelerator Laboratory, but the SSC cryogenic system will be some 13 times larger in scale than anything ever attempted.

THE SSC AS A CIVIL WORKS PROJECT

The proposed SSC will be the largest scientific instrument ever made. The tunnel, which will be the largest component of the facility, will be out of sight and covered by at least 35 feet of earth to ensure that no significant radiation ever reaches the surface. Approximately every 5 miles along the 53-mile tunnel, a cluster of surface buildingshousing cryogenic refrigerators, helium compressors, power supplies, and support facilities, and providing points of access-will be visible. Additional shafts allowing access to the collider tunnel will be located midway between adjacent service areas.

The campus-a focal point of the site will be a science research center large enough to accommodate a staff of 3000, with a central office building, an auditorium, and various laboratory, support, and industrial buildings.

The SSC will consist of five major components: (1) an underground injector complex of cascaded accelerators to accelerate protons from rest to 1 TeV; (2) a main collider ring to accelerate, focus, and guide two beams of protons in opposite directions around the tunnel until they each reach an energy of 20 TeV, and then to "store" them in the ring until they are depleted through collisions; (3) collision/experimental areas containing the particle detectors; (4) campus/laboratory areas; and (5) a site infrastructure of roads and

utilities.

The experimental areas containing the massive particle detectors will be located in two regions clustered diametrically opposite each other on the circumference of the collider ring. Each experimental area will have surface structures and underground collision and access halls. The dimensions of the collision halls will vary to allow a spectrum of possible experimental apparatus. The largest collision halls could be up to 160 feet long, 120 feet wide, and 130 feet high. Because the outside parts of the detectors are very likely to include large assemblies of thick steel plates-making the individual detector components enormously heavy-a thick concrete floor with

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steel plate capable of supporting loads of up to 9 tons/ft2 will be used in the halls.

The campus area may have 15 or more buildings clustered in four major groups—a central laboratory building and auditorium, industrial buildings, warehouses, and auxiliary support buildings. The central laboratory building will provide office and laboratory space for administrative and technical personnel. One building might contain all the major offices of the facility and light laboratories for the development and testing of electronic components. Industrial buildings will house limited component assembly activities, various workshops, and associated offices. Warehouses will serve as receiving and storage facilities. The auxiliary support buildings-fire, rescue, site patrol, visitor services, waste management, and vehicle storage buildings-will provide services to the entire complex. The central laboratory facilities with their associated office and shop buildings, and assembly and staging areas, will be arranged like a small college

campus.

Roads and utilities, adjacent to the campus, will include a main electrical substation consisting of incoming high-voltage electrical service, transformers, switch gear, and distribution systems. A second substation will be located on the far side of the ring. Water treatment facilities will process the cooling water used for the SSC. A road network will be needed in the campus, injector, and experimental areas, to connect the cluster regions, and to provide access to the service areas and access points located around the ring.

A significant part of the project's capital cost will go toward the 9500 superconducting magnets, whose design, construction, and testing will require advanced technologies and precision engineering of the highest order. In addition to the magnets, other advanced systems for the SSC will include the radiofrequency acceleration cavities, cryogenic facilities, particle detectors, supercomputers, and laboratory equipment.

The construction of conventional facilities, by contrast, will not require significant innovation as much as a scaling-up of existing methods. Construction of the tunnel and experimental halls, as well as the requisite infrastructure of utilities, transportation, housing, laboratories, offices, shops, maintenance, and so on, will be large in scope but straightforward in principle. It will be possible to excavate the 10-foot-diameter tunnel by cut-and-fill methods or tunnel-boring machines, or by a combination of both. The area enclosed by the ring will be left, for the most part, completely untouched.