Technical Design Report Super Fragment Separator

DRAFT
Table 2.4.5: Transmission T of different fragments through the Super-FRS, into the CR, and the emittances
and momentum spread at the exit of the Super-FRS (MF7).
fragment
primary beam
132 Sn
238 U
232 Fr
238 U
104 Sn
124 Xe
22 O
40 Ar
T to MF7 [%] 24 46 79 52
T into CR [%] 14 46 76 33
ratio MF7 / CR 0.59 0.99 0.96 0.63
εx [mm mrad] 169 82 90 115
εy [mm mrad] 151 38 64 140
2 σp/p [%] 3.05 1.21 1.47 3.03
At the highest projectile intensities fast extraction represents the most extreme conditions for the
production target, see section 2.4.11.3. Easing of stress can be achieved if the stringent conditions
for the size of the beam spot are mitigated. However, an increased size of the beam spot in the
dispersive direction means that the fragment separation power is decreased as demonstrated with
the detailed simulations in Figure 2.4.13. For many in-ring experiments this is no severe restriction.
Figure 2.4.13: Calculated separation power as a function of the spot size σx (dispersive coordinate) at the
production target. The selected example represents the separation of 132 Sn produced in projectile fission of
238 U. Both degraders at PF2 and MF2 had a thickness of half of the 132 Sn ion range.
Main-Separator to the low-energy experimental area
The Low-Energy Branch, which delivers secondary beams with typical magnetic rigidities up to 10
Tm, includes a high-resolution dispersive separator stage behind the achromatic Pre- and Main-
Separator. In combination with a set of profiled energy degraders, including a monoenergetic
degrader [7], this setup has been designed to drastically reduce the energy spread and thus the range
straggling of the hot fragments. Hence, there are two operating modes for this branch. After the
energy-spread reduction and absorbers to reduce the mean fragment energies, high-resolution
gamma- and particle-spectroscopy research can be done. Alternatively, the exotic beams can be
stopped and cooled in a gas and quickly transferred to ion or atom traps. The system will be fast and
universal for all elements and be independent of the chemical properties. With the energy-buncher
stage the separated fragment beams can be slowed down and their large momentum spread of up to
5 % can be reduced to a range straggling close to an ideal monoenergetic beam.
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