Historical Content Note: The following material is reprinted from publications from throughout Fermilab's history. It should be read in its original historical context.

The Main Ring Falls into Place

The Main Accelerator is the largest single component in the NAL accelerator system. Protons will be injected into the Main Accelerator from the Booster at Eight Billion Electron Volts. The Booster is a rapid-cycling synchrotron, approximately 500 feet in diameter. The Main Accelerator is a synchrotron of 6,562 feet in diameter -- or 1.24 miles. Its circumference is approximately four miles. In the Main Accelerator, the protons will be accelerated to full energy. Initially, this energy will be 200 BeV, but more power supplies could be added later to increase the accelerator's peak energy to 400, or possibly even 500, BeV. This additional acceleration still would take place in the Main Accelerator. After reaching maximum energy, the protons are extracted and transported to experimental areas.

For months, members of the Main Accelerator system have been working with DUSAF engineers on the plans for the design and fabrication of the Main Accelerator sections. Each Main Ring section is nine feet in height, 10 feet wide and 10 feet in length.

Made of concrete, 10 inches thick, the sections are pre-cast in three sizes and assembled like a giant jig-saw. There will be about 2,000 sections in the completed ring. (A "protomain" -- a prototype of the Main Accelerator -- is located in the NAL Village as a model of a typical installation.) Work on the construction and installation of the Main Ring sections is being conducted by two contracting firms -- Schless-Madden, a joint venture, and Corbetta Construction Company of Illinois.

Here is a photographic layout showing the tunnel sections in various phases of construction and installation. Phase One of the Main Accelerator, the first super-period, is about 30 per cent complete. Work is beginning on Phase Two, the remaining five-sixths of the structure. The photos, by Tony Frelo and Mrs. Joan Maute, provide a spring time view of construction progress at NAL.

The gradual curve of the giant Ring begins to take shape. (1 of 5)
An aerial view of one of the two casting yards on the NAL construction site. Main Ring sections are pre-cast in the cubicles at the left. They are stored in the field and transported by truck to the nearby Main Ring excavation as they are needed. (2 of 5)
Tunnel sections being placed into the Main Ring enclosure at the National Accelerator Laboratory. When completed, the enclosure will be made up of about 2,000 of the 10 foot sections and will have a circumference of about 4 miles. March '70. NAL Photo. (3 of 5)
Section C-5 takes its place in the biggest NAL circle. When complete, the Main Ring will contain about 2,000 sections. (4 of 5)
One section being lowered to the continuous cast-in-place concrete foundation at the bottom of the excavation. (5 of 5)