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Technical Design Report Super Fragment Separator

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Beam from<br />

FRS<br />

-7<br />

10 mbar<br />

MUSIC<br />

Scintillator<br />

Vacuum<br />

Window<br />

Monoenergetic<br />

Degrader<br />

Homogeneous<br />

Degrader 3 x<br />

Scintillator<br />

Movable<br />

Slits<br />

DRAFT<br />

100 mbar He<br />

Helium gas filled<br />

stopping cell<br />

252<br />

Cf Source<br />

(for Offline Test)<br />

-2<br />

10 mbar<br />

Extraction-<br />

RFQ<br />

-5<br />

10 mbar<br />

RFQ-Beam<br />

Distribution<br />

System<br />

Cooler-<br />

RFQ<br />

Silicondetector<br />

Ortho-TOF-MS<br />

Figure 2.4.119: Schematic figure of the experimental setup of the Ion Catcher experiment behind the FRS.<br />

A multi-wire proportional chamber (MWPC) is used for beam tracking and ion rates are measured in a<br />

multiple sampling ionisation chamber (MUSIC). The ions are range-focused in the degrader system, consisting<br />

of a homogeneous and a monoenergetic degrader. Three scintillators in front of the gas cell are<br />

employed to measure the ratio of ions that do not enter the gas cell. Ions are stopped in the gas cell in<br />

helium at a pressure of 100 mbar and extracted, separated from the gas in an extraction RFQ, and guided in<br />

an RFQ-based beam distribution system alternatively to a silicon detector for counting radioactive ions or a<br />

time-of-flight mass spectrometer with orthogonal acceleration (Ortho-TOF-MS) for identification of the ions<br />

and extraction time measurement.<br />

2.4.11.3 Production targets<br />

Similar to the present SIS18/FRS/ESR facility, both, slow and fast extraction from SIS100/300 will<br />

be used at <strong>Super</strong>-FRS: the former (with typical extraction times of a few seconds) for counter<br />

experiments at the experimental caves, the latter for experiments with radioactive secondary beams<br />

in the storage rings (here short beam pulses with a length of typically τ ~ 50 ns will be needed). The<br />

very high instantaneous power deposited in the target by fast-extracted beams (up to ~ 200 GW)<br />

could lead to destruction of the production target [64] by a single beam pulse. It is, therefore,<br />

essential to take special care in designing a target for fast extraction.<br />

The key parameter for target technology is the specific power deposited by the primary beam and<br />

by the fragments produced in the target. Since only ions lighter than the projectile are formed in<br />

projectile fragmentation and fission, it is reasonable to consider only the parameters of the incident<br />

beams. The optimum target thickness will range from a few g/cm 2 up to about 8 g/cm 2 depending<br />

on the atomic number Z of the projectile and the selected energy. Table 2.4.28 lists typical specific<br />

energies deposited in graphite chosen as the target material by three benchmark beams, 40 Ar, 136 Xe<br />

and 238 U. All beam intensities are taken as 10 12 ions/cycle, and the beam energies are 1 A GeV. The<br />

beam spot is assumed to be a two-dimensional Gaussian distribution with σx = 1 mm and σy = 2<br />

mm.<br />

130

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