Using Tracy2, we have used the two sextupoles families to
keep the chromaticity during the ramping cycle fixed at a value of
(1,1). Figure 7 shows the required integrated
sextupole strength (the sextupoles are simulated as thin lenses). The
figure 8 shows the magnetic field at the pole tip for
the sextupoles, assuming a length of the sextupoles of 20 cm and a
half-aperture of 18 mm. As can be seen, the required sextupole
strength in the SF magnet is almost constant and the magnetic field
follows a curve equivalent to the energy (given by F(t),
equation 12) . The curve for SD is more complex with a
maximum at energy of 
1.5 GeV, not at the extraction. The
strengths required can be easily provided by the current design of the
SLS booster sextupoles.
