The octupoles take pole position

To see its way clearly, the LHC will need whole strings of spectacles. For an accelerator, clear vision means bringing the two proton beams together with enormous precision. And to do so, it will have hosts of corrector magnets. There will be about 5000 superconducting corrector magnets coming under ten different categories: dipoles, quadrupoles, sextupoles, octupoles, decapoles, and even dodecapoles. These corrector magnets will nearly always be coupled to main magnets, either to correct their magnetic fields or to affect the particle beams in specific ways.
After the sextuples and decapole-octupoles, mounted inside the cold masses of the main dipoles and in series production since 2001, it is the octupoles' turn to take centre stage. The first preseries octupole was delivered to CERN in December 2001, inaugurating a series of 168 such magnets. This octupole is also the first preseries corrector octupole associated with the main quadrupoles. The cold masses of the quadrupole magnets, called Short Straight Sections, will not only include octupoles but also dipoles, sextupoles and corrector quadrupoles.
The octupole (MO) consists of a double aperture magnet that generates a field concentrated round eight poles for each of the two beams. It is used for Landau damping of the beams. Put simply, 'the octupoles are a sort of panacea for getting rid of instabilities that may be encountered by the packets of protons", explains Albert Ijspeert, of the ICP Group (Insertions, Correctors and Protection), in charge of corrector magnets in LHC Division.
This first octupole was manufactured by the Spanish firm Antec using a procedure developed by CERN involving technology transfer. The CERN teams have developed a semi-automatic coil winding technique allowing the production of two coil layers at a time. The approach will make for faster production and completion of the 1344 coils required for the 168 octupole magnets due to be produced between now and mid-2004.
Antec had already successfully tested the first coils at 4.2 Kelvin (-269 °C). Now, the octupole has just undergone even more advanced tests at CERN to study its behaviour at 1.9 Kelvin (-271 °C), LHC's operating temperature, and to measure its field quality. As soon as the results are analysed by the MTA (Magnet Test & Analysis) Group, the octupole will be sent to the magnet producer so that it can be fitted to the first of the approximately 400 Short Straight Sections that are coming soon.