Electron cooling

The electron cooling is a method to cool a beam in a particle using an electron beam, i.e., the size of the bunches in the phase-space emittance or smaller. The mass of the particles of the cooled beam must be greater than the electron mass.

History

In 1966, the electron cooling has been proposed as a method for damping oscillations of a proton beam in a storage ring of Gersch Izkowitsch Budker. Electron cooling " NAP -M" storage ring at the Budker Institute was first demonstrated in 1974 at the Nuclear Physics ( BINP ) in Akademgorodok. At CERN, a first plant was built in 1977. Nowadays, the electron cooling is used in many synchrotron particle accelerators and storage rings are used.

Operation

With an electron source, an electron beam is generated. This jet is accelerated by a static electric field. The potential of the accelerating electric field, all electrons are accelerated independently of their precise way of providing the same amount. This means that the velocity distribution of the electrons is very narrow. The electron beam is accelerated so far that the speed of its electrons with the average velocity of the particles in the particle beam corresponds.

By the acceleration of the electron beam by means of magnetic fields is superimposed on the particle. In a straight flight path frequently encounter such particles to the electrons that do not swim with the flow of electrons. Through these shocks it comes to momentum transfer to the electrons and thus to cool the beam. After a few meters common route, the electrons are decoupled and collected.

The particle beam to be cooled can only be cooled down until it is in thermal equilibrium with the electron beam by electron cooling.

The energy is to accelerate electrons of mass to the same speed as the particle mass and energy.

Use

The electron cooling is an important tool in the production of anti-matter, so has the Antiproton Decelerator at CERN electron cooling, a higher cooling rate than the stochastic cooling.

The use in pre-accelerators is also widely used, for example, be in the Low Energy Ion Ring ( Leir ) lead ions for the Large Hadron_Collider (LHC ) provided.

Another use of electron cooling in the improvement of beam quality, such as the radiator synchrotron COSY.

The use of the electron cooling is limited by the energy required to accelerate the electrons, the electrons in the previous cooling systems electron energies of up to a maximum of 300 keV were common, corresponding to a proton energy of 550 MeV. At high speeds, therefore, the stochastic cooling was used.

The largest plant is located at the Fermi National Accelerator Laboratory. There antiprotons are cooled with an energy of up to 8 GeV electron with a maximum electron energy of 4.3 MeV since mid-July 2005 on a 20 m long cooling section. In operation, a current flows of up to 0.5 A.

See also

• Beam temperature