Technical Design Report Super Fragment Separator

2.4.8 Particles Sources
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2.4.9 Electron Cooling
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2.4.10 Stochastic Cooling
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2.4.11 Experimental Devices
2.4.11.1 Beam catcher
DRAFT
The beam catcher serves two purposes, firstly to absorb the main part of the primary beam energy
and secondly to shield the subsequent parts of the separator from a high level of secondary radiation.
The challenge is to solve the technical problems due to the specific energy deposition of the
heavy ions up to uranium for fast and slow extraction modes as it is outlined in section 2.4.11.3.
Most of the kinetic energy of the heavy ions has to be absorbed by the beam catcher system,
whereas in the production target only about 10 % is lost. The beam energy of up to 58 kJ is deposited
in one pulse of 50 ns for fast extracted uranium ions at 1.5 GeV/u.
The layout of the beam catcher system is determined by the goals to provide save and efficient
operating conditions including possible maintenance. Furthermore, it requires a well defined operating
range and interlock system. The choice of the relevant parameters is given below.
The maximum beam energy is limited to 1500 MeV/u for the heaviest ions at maximum intensity,
whereas for light ions one can safely go up to 2700 MeV/u.
For the minimum operating energy one has to consider to stay in the favourable ratio of the atomic
and nuclear interaction length, which considerably reduces the effective Bragg peak in the stopping
power. This condition is relatively easy to achieve for the critical case of fast extraction due to the
fixed operating domain of the collector ring CR, i.e. the stochastic cooling requires 740 MeV/u and
the operation in the isochronous mode at about 780 MeV/u.
For the allowed energy range of slowly extracted beams one has only the restriction that the energy
loss of the primary beam in the target may be sufficiently large that the beam is stopped in front of
the first beam catcher.
The calculated energy deposition is presented in Figure 2.4.102 for different projectiles at 1 GeV/u.
The reduction of the energy deposition due to the formation of lighter-Z fragments is clearly
demonstrated. The Bragg peak of uranium ions still represents the maximum of the curve, whereas
the Bragg peak of xenon is still visible but it is not the maximum of the curve any more. For the
case of argon ions the Bragg peak is reduced even more by nuclear interaction. At the entrance of
the beam catcher the energy deposition of uranium ions exceeds the one of lighter ions by far, but at
larger penetration depth the situation is reversed due to the faster stopping of the higher charged
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