Application to the SLS booster

The SLS booster differs from the boosters used in the majority of the light sources. The three peculiarities that concern us are:

• Large number of bending magnets with a relatively large bending radius.
• Two families of bending magnets with different bending radii.
• Sextupole component integrated in the bending magnet, through the pole profile, that brings the chromaticity to positive values. The sextupolar components are m_BD = 1.22 m^-3 and m_BF = 0.875 m^-3
• Two families of sextupoles (S_F and S_D) are used to make adjustments in the chromaticity. The first family (S_F) consists of 6 magnets, and the second (S_D) of 12. All sextupoles are 0.2 meters long, have an aperture radius of 18 mm and can reach a maximum field of 0.063 T at the poletip.

The consequences of these facts can be summarized as:

• The large radius of the bending magnets will make the sextupolar component induced by the eddy currents smaller than in in a `conventional' booster (the sextupolar component escalates with the inverse of $\rho$).
• There will be two different sextupolar contributions during the ramping, due to the two different bending radius.
• The changes in the strength of S_F and S_D required to compensate the effect of the eddy currents will be small, and the magnets will not be required to change polarities during the ramping, avoiding hysteresis problems.

In the following sections we will examine in more depth these facts.