Technical Design Report Super Fragment Separator

DRAFT
Crucial for the layout of the beam catcher is the spot size of the primary beam which determines the
maximum temperature. The two different extraction modes will be treated separately. At first we
concentrate on the fast extraction as in this case no thermal conduction can distribute the heat and
the danger of damaging or even melting the catcher is much higher.
The fast extracted primary beam is characterized by a much larger phase space volume (see section
2.4.1), which results in favourable large beam spots at the catcher. For the fast extraction mode
with σp/p = 0.25 % but still keeping a small spot size of (1x2) mm 2 (1-σ) on the target and the same
case as in Figure 2.4.104 the calculated projections of the beam size in horizontal (x) and vertical
direction (y) are shown in Figure 2.4.105.
Figure 2.4.105: Spot size of the uranium primary beam on the beam catcher BC3 at PF1 in horizontal (left)
and vertical (right) direction in fast extraction mode. The peaks are projections of the distributions in Figure
2.4.104.
A beam dumped at an earlier stage in the Pre-Separator has less dispersion, but this is compensated
by less focusing and thus results in a similar spot size. In general, the spot size in the fast extraction
regime can never become less than 1.0 cm 2 defined as a 1-σ level. It is even larger as the spot size at
the target must be also increased to ensure that the target survives. Starting with a spot size of (3x7)
mm 2 (1-σ) at the target the resulting spot size on all three catchers is given in Figure 2.4.106 as
function of the mean position where the primary beam may hit.
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