Accelerator Facts
First beam |
Accelerator |
Proton energy(MeV)** |
Beam Velocity*** |
1941 |
First cyclotron* |
5.5 |
11 % |
1974 |
Injector cyclotron |
17 |
19 % |
1975 |
Main stage cyclotron |
208 |
56 % |
1988 |
Cooler synchrotron |
470 |
75 % |
1997 |
Cooler injector synchrotron |
220 |
59 % |
* located in Swain Hall; usually accelerated deuterons (heavy hydrogen) or helium
** unit of energy is million electron volts
*** percent of speed of light
Cyclotrons
NOTE: The unit of energy for particle beams is MeV, or million electron volts. This is the energy that an electron would acquire if it were to be accelerated by a force equal to one million volts.
- The cyclotron system consists of an ion source that produces the beam, first acceleration in a radio-frequency quadrupole (0.025 MeV to 0.75 MeV), the injector cyclotron (0.75 MeV to 17 MeV), and the main stage cyclotron (17 MeV to 200 MeV).
- Magnetic fields confine and steer the beam; only electric fields can accelerate.
- The radio-frequency quadrupole electric field oscillates at 35.58 MHz (million cycles per second).
- A cyclotron has a fixed magnetic field. The accelerating electric field inside the machine oscillates at a fixed frequency. The accelerating protons travel in a spiral orbit. The beam leaves the injector once it reaches a radius of 2.1 m. That radius is 6.95 m in the main stage. The beam spiral makes about 350 revolutions in the main stage.
- The transit time for protons from the ion source to the patient or the test stand is about 0.0001 seconds. The distance traveled is about 6 miles.
- The maximum magnetic field is about 16.5 kGauss. The magnet pole tips where the field is large are about 1.5 inches apart. The beam travels in the gap.
- The beam is about the size of the lead in a No. 2 pencil.
- The four magnets on the main stage cyclotron weigh about 2 million pounds, roughly the same as 20 jumbo jets (747s) or 1600 large cars.
- The injector cyclotron is the world's first separated sector cyclotron with the magnet split into (four) pieces. It was built to demonstrate that this design works. It has been copied in other machines.
- The cyclotrons and their beam lines use about 1.5 Megawatts of power.
- The accelerating electrodes produce an electric field of 18,500 volts.
- The vacuum inside the cyclotrons is about 5 x 10-6 Torr, or about one part per billion of normal atmospheric pressure.
Cooler Synchrotron (now decommissioned)
- The system consisted of an ion source, radio-frequency quadrupole (0.025 MeV to 3 MeV), drift-tube linear accelerator (3 MeV to 7 MeV), accumulator synchrotron (7 MeV to 220 MeV), and the electron-cooled storage ring (220 MeV to 470 MeV).
- The Cooler made use of a co-moving electron beam to remove random motions inside the beam. This was the first such ring used for experiments in nuclear physics. The design was widely copied.
Low Energy Neutron Source
- The phase-I plan consists of an ion source, radio-frequency quadrupole (0.025 MeV to 3 MeV) and drift-tube linear accelerator (3 MeV to 7 MeV).
- The beam will hit a beryllium target, producing neutrons. The neutrons will be slowed down, or moderated, until their energy is about 1 part per billion of the original energy.
Building Size
- The total building area (all floors) is about 130,000 sq.ft. or about 3 acres.
- The lab contains 3 accelerators, about 250 power supplies, about 1000 feet of beam pipe, and about 1000 computer-interfaced devices.
Electricity Usage
- The cyclotrons and their beam lines consume about 1.5 Megawatts of power.
- The average laboratory power usage is about 2.2 Megawatts.
- The annual power bill is approximately $650,000.
- The lab's peak power usage goes up to 4.0 Megawatts, about 10% of the total campus usage.
- The lab has installed capacity for 11.8 Megawatts.
