Oak Ridge 60 Inch Vertical Heavy-ion Cyclotron Dees
date: label: Date made
content: May 20, 1952
name: label: maker
content: Oak Ridge National Laboratory
notes: label: Description
content: Dee assembly from the Oak Ridge 63-inch cyclotron, as adapted for the Atom Smashers exhibition at the National Museum of American History.
label: Description
content: Here, hollow D-shaped copper electrodes (dees) are mounted on heavy stems placed through a steel plate. This dee assembly is positioned vertically, rather than horizontally as in most cyclotrons. When the assembly was received at NMAH, the metal casing enclosing the dee stems was removed, and the stems were truncated by about two feet.
label: Description
content: In 1951 the Atomic Energy Commission gave the Oak Ridge National Laboratory authorization to construct a heavy-particle cyclotron. This led to the OREL 63-Inch Heavy-Particle Cyclotron designed and built by the Electronuclear Research Division of the Laboratory. The first beam was obtained on May 20, 1952 and a productive research program was initiated shortly afterwards.
label: Description
content: This cyclotron was the first built expressly to accelerate ions heavier than hydrogen and helium. Designed by Alexander Zucker, it helped open an active field of atomic and nuclear research pursued with much larger and costlier accelerators. It was constructed to determine whether the explosion of a powerful thermonuclear bomb might trigger a chain reaction of nitrogen nuclei, igniting the earth’s atmosphere. Experiments with this cyclotron, colliding nitrogen ions with nitrogen ions, established that this fear was unwarranted.
label: Description
content: The basic design of the 63-inch is that of a conventional, fixed-frequency cyclotron. In operation, triply charged nitrogen were produced by the ion source were accelerated in a magnetic field of 15,500 gauss. These ions were then electrostatically deflected at the radius of 25.6 inches yielding an external beam of nitrogen ions with a mean energy of about 28 MeV. The accelerating system operated at a frequency of 5.1 MHz/sec and employed dee-to-earth voltages between 35 and 50 kV.
label: Description
content: The vertical position of the dees is characteristic of cyclotrons designed at Oak Ridge. This departure from common practice at the time arose from parasitical use of the Calutrons, the large, ganged electromagnetic mass separators built during the Second World War to produce uranium-235 for the first atomic bombs. This and earlier Oak Ridge cyclotrons were “plugged into” Calutron magnets, in place of one of the scores of uranium isotope separation units.
label: Description
content: Basic principles of the cyclotron
label: Description
content: The cyclotron is the simplest of circular particle accelerators. (See https://www.physics.rutgers.edu/cyclotron/theory_of_oper.shtml to see a diagram of a typical cyclotron.) At its center is a vacuum chamber which is placed between the pole pieces of a large electromagnet. Within the chamber is a pair “dees” - two flat D-shaped hollow metallic shells - positioned back-to-back forming a cylindrical space, with a uniform gap between the straight sides of the two dees. The plane of the dees is parallel to the faces of the magnet pole pieces. An alternating voltage is applied across the gap between the dees, creating an associated time-varying electric field in that space.
label: Description
content: Electrically charged particles, such as protons, alpha particles or heavier ions, are introduced into the chamber from an ion source at the center. The charged particles are constrained to travel in a circular path inside the dees in a plane perpendicular to the direction of the static uniform magnetic field produced by the electromagnet. The electric field accelerates the particles across the gap between the dees. The electric field is made to alternate with the “cyclotron period” of the particle (determined by magnetic field strength and the particle’s mass and charge). Thus, when the particles complete a semi-circle and arrive at the gap again, the electric field has reversed, so that the particles are again accelerated across the gap. Due to their increased speed in the constant magnetic field, the particles now move in a larger circle.
label: Description
content: The increasing speed of the particles causes them to move in a larger radius with each half-rotation, resulting in a spiral path outward from the center to the outer rim of the dees. When they reach the rim the particles are pulled out by a deflecting electrode, and hit a target located at the exit point at the rim of the chamber, or leave the cyclotron through an evacuated beam tube to hit a remote target. Nuclear reactions due to the collisions of the particle beam and the target atoms will create secondary particles which may be guided outside of the cyclotron and into instruments for analysis.
label: Location
content: Currently not on view
place: label: place made
content: United States: Tennessee, Oak Ridge
topic: label: general subject association
content: Science & Scientific Instruments
setName: label: See more items in
content: Medicine and Science: Modern Physics
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content: Energy & Power
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content: Science & Mathematics
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content: Modern Physics
creditLine: label: Credit Line
content: Oak Ridge National Laboratory
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1977.0359.41.1
label: accession number
content: 1977.0359
objectType: label: Object Name
content: Cyclotron, 63 Inch, dees
physicalDescription: label: Physical Description
content: copper; steel (overall material)
label: Measurements
content: overall (approx.): 172 cm x 329 cm x 58 cm; 67 23/32 in x 129 17/32 in x 22 27/32 in
label: Measurements
content: base: 44 cm; 17 5/16 in
label: Measurements
content: dee stems (diam.): 10 cm; 3 15/16 in
label: Measurements
content: dee stems (ctr. to ctr.): 46 cm; 18 1/8 in
label: Measurements
content: steel plate thickness: 3.7 cm; 1 15/32 in