A NEW GIANT CYCLOTRON

At the University of California, under the direction of E. O. Lawrence, it is planned to build, within the next three years, a new cyclotron, which will be the largest in the world. The cost of this installation is estimated at 1.4 million dollars, of which 1.15 million is being allocated by the Rockefeller Foundation and 250 thousand by the University of California.

This cyclotron will have the following principal characteristics:

1. Weight of the electromagnet core about 4,500 tons.
2. Weight of the copper winding about 400 tons.
3. Diameter of the pole pieces 460 cm.
4. Height of the vacuum chamber 100 cm.

The radio-frequency power will be supplied to the dees through tuned resonant lines placed in vacuum. The diameter of the shells of these lines will be about 3.5 m, and their length about 10 m. The internal conductors, to which the dees are attached, will have a diameter of about 0.5 m. The surfaces of these conductors and the inner surfaces of the shells are to be made of copper and provided with water cooling. All this is necessary because the power supply of this cyclotron must be about 2,500 kW.

Initially it is proposed to operate at a wavelength of about 57 m, which will make it possible to obtain deuteron beams with energies of 50 MeV; later, with the wavelength reduced to 40 m, the energy will be about 100 MeV.

One of the interesting problems is the creation of a vacuum in such a large volume. It is estimated that the pumping speed required for this purpose must be from one to two hundred thousand liters per second. It is noteworthy that at such high speeds small openings in the vacuum chamber cease to play any role (as was already found with 1.5-meter cyclotrons).

The new cyclotron is to be housed in a special building with an area of about 1,500 m². The electromagnet will be located in the middle of the hall. It will rest on a concrete foundation and will be sunk about 3.3 m below floor level, so that only part of it, about 7.5 m high, will be in the hall. The control station is to be placed about 45 m from the electromagnet, outside the main room (the building will stand on the top of a hill, and the control cabin will be cut into its slope).

One of the authors of this project, D. Cooksey, believes that with a beam of deuterons of 100 MeV energy the length of the luminous beam emerging from the cyclotron will be about 42 m.

N. Khlebnikov, Moscow

LITERATURE

1. J. Appl. Physics, 11, 339, 1940.