Part 2

For techniques of radiochemistry to be employed successfully, high interaction rates (and therefore high beam intensities) are needed. For this reason, chemistry targets are usually inserted right into the cyclotron so that they can be bombarded directly by the circulating beam. After the bombardment is completed the target is removed from the cyclotron. It is then taken to a chemistry laboratory and subjected to detailed chemical procedures. Individual elements are removed, and the radioactive isotopes of each element are identified by quantitative counting techniques. In some cases a mass spectrometer is used to analyze the products. Many deductions about the nature of the breakup of the target nucleus can be drawn from the pattern of the observed radioactive products. Sometimes the nucleus splits almost in half. This is called fission. More frequently smaller parts of the nucleus are split off. Two general types of reactions, known as spallation and fragmentation, are distinguished. One of the goals of this research is to learn more about the constitution of the nucleus and of the forces which bind the particles in the interior of the nucleus.

FOOTNOTES:

[7] Mesons are elementary particles intermediate in mass between the electron and proton.

[8] It may be interesting to note that the [pi]^0 meson was discovered with this cyclotron in 1950. This was the first particle to be discovered with an accelerator. All particles that had been previously discovered were observed first in cosmic rays or some other form of natural radiation.

BIBLIOGRAPHY

1. Gerald A. Behman, Particle Accelerators: I. Bibliography, II. List of Accelerator Installations, UCRL-8050, January 1, 1958.

2. Samuel Glasstone, The Acceleration of Charged Particles, in _Sourcebook on Atomic Energy_, Second Edition (Van Nostrand, Princeton, 1958), Ch. IX.

3. M. S. Livingston, _High-Energy Accelerators_ (Interscience Publishers, New York, 1954).

4. M. Stanley Livingston and Edwin M. McMillan, History of the Cyclotron, Physics Today _12_, 18-34 (October 1959).

5. E. M. McMillan, Particle Accelerators, in _Experimental Nuclear Physics_, Emilio Segre, Editor, Vol. III (Wiley, New York, 1959), Part XIII.

6. Bob H. Smith _et al._, The Electrical Aspects of the UCRL 740-Mev Synchrocyclotron, UCRL-3779 Rev., October 2, 1957.

7. Robert L. Thornton, Frequency-Modulation and Radiofrequency System for the Modified Berkeley Cyclotron, UCRL-3362, April 3, 1956.

8. Robert R. Wilson, Particle Accelerators, Scientific American _198_, 64-76 (March 1958).

APPENDIX

SUMMARY OF SPECIFICATIONS

Present fields of research % of time -------------------------- --------- Nuclear physics 86 Nuclear chemistry 2 Biophysics 12

_Scheduled operation_ 156 hours/week

_Performance_

_Internal Beams_

Alpha Helium-3 Protons Deuterons particles ions ------- --------- --------- -------- Maximum energy (Mev) 730 460 910 1140 Energy spread (Mev) 55 Beam intensity Average current ([mu]a) 0.75 0.75 0.25 Peak current ([mu]a) 120 120 40 Beam radius, maximum (in.) 82 82 82 82 Time required for acceleration (msec) 6 4.5 4.5 Number of revolutions during acceleration 75,000 60,000 60,000 Distance traveled during acceleration (miles) 450 360 360 Velocity at maximum energy (% of speed of light) 82 60 60 69 Mass increase at maximum energy (% of rest mass) 75 25 25 40 Range of full-energy particles (in. of aluminum) 37 12 7

_External Beams_

Physics cave Meson cave ----------------------- ------------------- Protons Neutrons [pi]^+ [pi]^+ [pi]^- ------- -------- ------ -------- --------- Energy (Mev) 730 310 100|250 100| 300 Energy spread (Mev) 14 10| 20 10| 30 Beam area (cm^2) 25 40 100|100 100| 100 Flux (particles/cm^2-sec) 2x10^10 5x10^5 5x10^4 1000|100 1500|1000

_Acceleration chamber (vacuum tank)_

Size length (ft) 25 width (ft) 20 height (ft) 4

Material: mild steel

Operating pressure (mm Hg) 10^-5

Vacuum pumps: six 20-in. oil-diffusion pumps with 8-in. boosters: one Beach-Russ 750-cfm; one Kinney 300-cfm; two Kinney 105-cfm.

Pumping speed of oil-diffusion pumps (liters/sec) 20,000

_Magnet_

Core diameter (in.) 184 Pole-tip diameter (in.) 188.75 Pole gap at center (in.) 14 Magnetic field strength (gauss) at center 23,400 at radius of 82.2 in., where n = 0.2 22,275 Weight of steel (tons) 4,000 Magnet coils Main coils Auxiliary coils ---------- --------------- material solid copper hollow copper (1/4 x 4 in.) (1-3/16 x 1-1/16 in.) weight of copper (tons) 300 40 number of turns (total) 2,600 425 ampere turns 1.9 x 10^6 1.1 x 10^6 current (amp) 1600 2800 voltage (v) 550 560 power (kw) 900 1600 coolant oil water

_Radiofrequency system_

Dee system number of dees 1 size length (in.) 126 width (in.) 180 height (in.) 48 material: 1/64-in.-thick copper, stretched over a stainless steel frame dee aperture (in.) 4-3/16

Oscillator type: self-excited grounded-grid 10 tube: one Machlett ML5681 dc input, operating condition (kw) 10 dee bias, maximum dc (v) 2000

Protons Deuterons Alpha particles ------- --------- --------------- rf duty cycle (%) 38 28 28 dee-to-ground voltage, peak (kv) 9 6 6

Frequency-modulation system type: vibrating-reed (tuning-fork) capacitor number of units: two (two blades each) blades size width (in.) 45 length (in.) 32 thickness: tapered from 1.4 to 0.06 in. weight (lb) 500 vibrational frequency (cps) 64 electrical capacitance ([mu][mu]f) 300 to 6,500 peak-to-peak excursion (in.) 1 minimum separation of blade and stator (mils) 50

Protons Deuterons Alpha particles ------- --------- --------------- frequency sweep (Mc) 36-18 18-13.5 18-13.5

Ion source: conventional open-arc type

_Beam extractor_

LeCouteur-type regenerator combined with magnetic channel

_Building and facilities_

Room dimensions diameter (ft) 160 height (ft) 90

Crane type: radial capacity (tons) 30 overhead span (ft) 77

Concrete shielding: 15 ft thick on sides, 4 ft on top

_History_

Design started: January 1940. Construction started: August 1940. First operation for deuterons and alpha particles: November 1946. for protons: December 1948. Rebuilt: 1955-1957.

[Transcriber's Note: The following changes have been made to the printed text: Page 15, added closing quote (are called "caves" because) Page 19, "iostopes" corrected to "isotopes" ]

End of Project Gutenberg's LRL Accelerators, by Lawrence Radiation Laboratory