The cyclotron of the "Arts
et métiers" Museum
The cyclotron exposed to the
"Arts et métiers" Museum was used by Frederic
and Irene Joliot-Curie who worked on the nuclear transmutation
to the "College de France". Their research leads to
discovered of the neutron.
- the cyclotron has an energy
of 7 MeV
- the electromagnet weighs 25
tons (that exposed with the museum is factitious)
Cyclotron exposed in the
The inventor of the cyclotron
Lawrence Ernest Orlando (Nobel
Prize 1939) built the first experimental cyclotron in 1929. But
it is in fact in 1931 that the apparatus was really operational.
It accelerated protons of energy 13 keV.
Constitution of a cyclotron
- two electrodes in the shape
of D (dee).
- a generator high frequency connected to the " dees ".
- a device to make the high vacuum in the cyclotron.
- a device sending ionized particles to the center of the cyclotron.
- an electromagnet creating an intense magnetic field.
- a channel of extraction to the end of which is the target.
alternating terminals + and -
to the vacuum pomp
What for a cyclotron is
using to ?
A cyclotron is used to accelerate
particles charged and to produce isotopes.
The accelerated particles are ejected outside by a window to
be then sent on targets.
It is used in research :
- in nuclear physics in astrophysics
- in chemistry for the synthesis
of molecules labelled
- in medicine for the production
of isotopes used in tomography by emission of positon (T.E.P)
The maximum energy acquired
by the particles is about 10 MeV (1 eV = J).
Principle of a cyclotron
The ions produced by the source
are accelerated by an electric force under
the action of a electrique field (q:
charge of the particle). The particles are then deviated with
a constant speed v, by a magnetic force under
the action of a magnetic field and
have half-circles trajectories with a radius and
a angular velocity .
This angular velocity is independent of energy.
The deviated ions are again
in the area between the two " dees " and are again
accelerated under the action of the electric field which was
reversed. The kinetic energy of the particles increases with
each passage between the " dees " and the radius of
their circular trajectory increases successively. The maximum
kinetic energy reached is
with : maximum speed attack
and : useful maximum
radius of the cyclotron
Other types of cyclotrons
Cyclotrons with separate
They are made up of 4 zones with field extremely separated by
4 zones without field.
(maximal energies : 1 GeV).
Synchrocyclotrons : These apparatuses make it possible
to reach the energies raised until approximately 1 GeV. They
require electromagnets of very big sizes and high masses (7 000
Synchrotrons : They are modern giant models of
the cyclotrons which have several hundred meters of ray and which
make it possible to obtain protons of energy of several GeV.
The L.E.P (Large Electron Positron Collider) is a collider of
27 km (16,8 miles) circumference which makes it possible to study
the mutual annihilation of the electrons and the positrons. In
the L.E.P, the particles are accelerated by an electric field
and are deviated according to a circular trajectory thanks to
a magnetic induction variable field.
Air sight of the site
of the C.E.R.N on the border Free-Switzerland (picture C.E.R.N.)
Software of simulation of
a cyclotron usable with scientific students
This software under DOS (87
KB in file zip) carried out by C Rivoisy is downloadable on the
site of the academy of Nantes (France). Click on
This software makes it possible
to simulate the trajectory of a positive particle of load equal
to the elementary charge e and to modify the value of
the magnetic field B, accelerating tension U, and
its frequency f.