The Bevatron was a particle
accelerator — specifically, a weak-focusing synchrotron — at Lawrence
Berkeley National Laboratory which began operating in 1954. The antiproton was discovered there in 1955, resulting in the 1959 Nobel
Prize in physics for Emilio
Segrč and Owen
Chamberlain. It accelerated protons into a fixed target, and was named for its ability to impart energies of billions of eV. (This is the reason why it was named Bevatron: Billions of eV Synchrotron.)
It was finally decommissioned in 1993, although the building is still present and visible in satellite images at least as late as 2006.
The Bevatron was largely designed to be energetic enough to create antiprotons,
and thus test the hypothesis that every particle has a corresponding anti-particle. At the time it was built, there was no
known way to confine a particle beam to a narrow aperture, so the beam space was about four square feet in cross section.
In order to create antiprotons (mass 938 MeV) in collisions with nucleons in a stationary target while conserving both energy and momentum,
a proton beam energy of slightly over 5 GeV is required. The combination of beam aperture and energy required a huge, 10,000
ton iron magnet. The next generation of accelerators used "strong focusing", and required much smaller apertures, and
thus much cheaper magnets. The AGS (Alternating
Gradient Synchrotron) at Brookhaven was the first next-generation machine, with an aperture roughly
an order of magnitude less in both transverse directions, and reaching 30 GeV proton energy, yet with a less massive magnet
ring.
In the years following the antiproton discovery, much pioneering work was done here using beams
of protons extracted from the accelerator proper, to hit targets and generate secondary beams of elementary particles, not
only protons but also neutrons, pions, "strange particles", and many others. These could in turn be passed for
further study through various targets and specialized detectors, notably the liquid
hydrogen bubble
chamber, for which Luis
Alvarez received the Nobel Prize in 1968.
http://en.wikipedia.org/wiki/Bevatron
TSL Technical Information - cyclotron hall
See the other
side of the Cyclotron
1. External
ion injection: The external ion source can be used with axial injection into the cyclotron. An ECR source is used for a wide variety of ions (from alfa particles to Xenon).
2. The
Cyclotron: Isochronous cyclotron for all particles except protons above 100 MeV. For protons in the range
100-180 MeV the cyclotron works as a synchrocyclotron. Particles
and energies available.
3. Radiofrequency
system: (System1 in figure) Two accelerating electrodes each covering an angle from 72 degrees at centre
to 42 degrees at max. radius. Possible to use between 12.25 and 24.5 MHz (on the orbit frequency of the ions and on harmonics
2, 3 and 4). Two modes of operation: Fixed frequency (isochronous cyclotron) and Frequency Modulation (synchrocyclotron) Max.
accelerating voltage 50 kV in fixed frequency mode and 16 kV when used in FM mode over a frequency band approx. 24-22 MHz.
Max. power per system is 140 kW.
4. Vacuum
system: Two large diffusion pumps with cryogenic baffles (and one smaller) combined with two cryopanels
in the cyclotron chamber, giving a vacuum of approx. 10-7 mbar without gas load from internal
ion source and 10-6 mbar with internal ion source.
5. QA1
and QA2 (Quadrupole magnets for focussing of the beam)
6. Internal
Ion Source: Internal Penning Ionization sources are used for protons and some light ions (deuterons, alfa
particles).
7. Sond 1: Measure the beam current.
8. Collimator: Used to reduce the beam size and the beam current.
9. BMA1 This bending magnet can switch the beam between the a-line and the b-line.
Main data of the Gustaf Werner Cyclotron
Single pole with three sectors for vertical focussing
Pole
base diameter 2.8 m
Pole gap hill-hill 0.2 m, valley-valley 0.362 m
Magnet yoke (iron) weight 600 tons
Copper
coil weight 50 tons, power consumption max. 300 kW
13 sets of radial gradient field correction coils and two sets of harmonic
correction coils
Max. average field 1.75 T at a max. useful radius of 1.2 m
Bending limit K= 192 Q2/A
MeV
Focussing limit (protons) 100 MeV, avoided by using frequency modulation up to 180 MeV
Beamline drawing
http://www.tsl.uu.se/technical/tt_cychall.html
