Technical Design Report Super Fragment Separator

DRAFT
With the cooling capacity specification of the FAIR refrigerator CRYO1, numerical simulation has
been performed for one multiplet cooldown. Figure 2.4.132 shows the schematic model of the cold
mass, mainly iron, and the surrounding helium flow for cooldown. The discrete spaces of the cold
mass and helium flow for discrete derivative equations are shown as well. To simulate the practical
cooldown process, two limitations have been set up. The first one is that the temperature difference
along the cold mass should not be larger than 50 K at any cooldown time. The second one is that the
inlet temperature of helium gas is regulated by using one or two linear ramps at the starting phase
until the maximum cooling capacity of the FAIR refrigerator CRYO1 is reached. The simulation
results of the temperature profile in the cold mass over its length at different cooldown time can be
seen in Figure 2.4.133. It is anticipated that two multiplets in one group as shown in Figure 2.4.130
could be cooled down to liquid helium temperature in parallel within about 5 days under the
specified full cooling capacity of the FAIR refrigerator CRYO1.
Temperature [K]
300
280
260
240
220
200
180
160
140
120
100
80
60
40
20
Temperature profile in cold mass over one multiplet length during its cooldown by using half of the
cooling power (117.5 g/s, one half of the full capacity 235 g/s ) of CRYO1 (3.5 kW at 4.5 K)
0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5
Section [m]
0.5 day
1.0 day
1.5 days
2.0 days
3.0 days
4.0 days
5.0 days
Figure 2.4.133: Temperature profile in cold mass of one multiplet for different cooldown times.
In order to know if the overall cooldown time of the whole Super-FRS SC magnets is influenced by
the different ways of the multiplets' grouping, three grouping ways, i.e., a) 2 multiplets cooldown
in parallel in one group (as shown in the Figure 2.4.130), b) 3 multiplets cooldown in parallel in
one group, and c) 3 multiplets cooldown in series in one group, have been checked under different
cooling powers of refrigerator CRYO1. Table 2.4.31 contains the results in terms of anticipated
minimal cooldown time of the Super-FRS. For comparison, the predicted cooldown time of the
standard cell and the one sector of LHC have also been listed in the table. One can see that the
cooldown for 3 multiplets in parallel (14.5 days) takes about 10% more time than the cooldown in
series (13 days) under the same cooling power conditions. The cooldown time for the individual
components is highly dependent on the cooling power provided by the refrigerator, and the allowed
temperature gradient over cold mass length, rather than the grouping and individuality. The overall
cooldown time (about 60 to 70 days) of the whole Super-FRS is more or less determined by the
specified cooling capacity of the FAIR refrigerator CRYO1.
149