Technical Design Report Super Fragment Separator

DRAFT
The magnets will be operated in DC mode but it must be guaranteed that all magnets in a multiplet
can be ramped up from gmin to gmax and ramped down from gmax to gmin within 12 minutes. This is
necessary in order to guarantee a frequent changing of the magnet setting due to experimental
requirements. The maximum current of one magnet must not exceed 300 ampere. All magnets are
individually powered. The breakdown voltage, Vbd, against ground of all magnets, sensors and
connections must be:
V > 2 ⋅V
+ V
bd
where Vqm is the maximum quench voltage to ground and Vsm = 500 V is a safety margin.
Magnetic design
The 2D/3D magnetic design for the quadrupoles was performed using the code Opera-2D/3D [15].
Figure 2.4.45 shows the cross section of a standard quadrupole magnet for the Super-FRS. The
pole tip radius of 250 mm was chosen in order to provide sufficient space for the beam pipe (190
mm inner diameter + 10 mm expected wall thickness), for the cryostat (expected thickness of 30
mm), and for the octupole correction coils (about 5-15 mm), which are needed to correct the
ion-optical 3 rd -order image aberrations. For simplicity of winding the main coil is designed as a
race track coil with a cross section of (55 × 50) mm 2 .
Figure 2.4.45: Cross section (1/4 part) of the standard superferric quadrupole magnet for the Super-FRS
including octupole correction coils.
Figure 2.4.46 shows the dependencies of the average field gradient along the elliptical aperture for
a quadrupole magnet. It presents the field quality distributions for the medium/high field gradients
of 5.6, 7.7 and 8.7 T/m. The field gradient deviation is well inside the specification of ±8·10 -4
relative units. For the highest field gradients of 10 T/m, however, the 6 th harmonics increases
exponentially such that field quality distribution reduces to few ‰ (see Figure 2.4.47). These errors
can be corrected by additional 12-pole correction coils also embedded into the quadrupole. The
present layout of the quadrupole magnet leaves enough space to include these correction coils if
necessary which will allow to reduce the field gradient deviation to ≈ ±4·10 -4 even for the highest
gradient of 10 T/m.
qm
sm
46