## 3 Mechanical Design of BPL
While aramid cord suspension has been used in some cryogenic applications--SAFIRE, CUORE, MINERvA [4; 5], there are still very limited data about the long-term use of aramid fibers in cryogenic applications. In [6], a single Kevlar-braided loop was considered to be a good candidate for internal cryostat suspension. In [7], the long-term mechanical creep of Kevlar 49 fiber at a temperature of 4.2 K was investigated. The fiber (0.5 mm in diameter) was loaded with a mass of 2.7 kg for a period of 8 months. A 0.004% creep strain was reported. The creep was very limited, but this was measured in a period that was much shorter than the 30 years of planned operation of the SIS100 accelerator and at a temperature of 4.2 K instead of the 80 K of the BPL thermal shield. The aramid braided-rope designed for the suspension of the SIS100 BPL would have to remain functional for the 30 years of SIS100 operation, with no possibility of exchanging damaged elements of the suspension system. Because of the lack of experimental data for the long-term creep behavior of aramid cords, the second option of steel rod suspension is used. The process pipes are supported inside the thermal shield by G11 support plates. All the plates are clamped onto return pipe B (outer diameter 108 mm). The first plate on the upstream end of the module is a fixed support plate; the other plates are sliding ones. It allows the relative axial movements of the process pipes. At the downstream end of the module, there are axial bellows to compensate for the thermal contraction of the process pipes. The G11 support plates are supported inside the TS on G11 roller arms equipped with four G11 wheels. The wheels provide sliding support for the G11 plates (Figure 12). Figure 11: Thermal conductivity of various materials used for cryogenic support and range on thermal shield (TS) support temperatures. Red line shows the operational temperature range. Busbar pairs are clamped to carry the significant Lorenz forces due to the high electrical current transferred by each busbar pair. These forces act in a repelling manner. The equidistant and short clamping avoids plastic deformation of the superconducting cable. In order to achieve a high-quality magnetic field, the electromagnetic cross-talk between the four busbar pairs has to be minimized [12; 17] by a stable relative position and, especially, the orientation of the busbar pairs. The clamped busbar pair is slid into a stainless steel support pipe, providing a stiffness sufficient to keep the BB pair in the correct position with respect to the process pipes and the thermal shield (Figure 13). The support pipes are supported in the G11 support plates. During the thermal shrink of the busbars, the clamps slide inside to avoid the axial stresses of the busbars. The support pipes are electrically connected by grounding cables. At the downstream end of the module, the thermal compensation loops are placed on the busbar pairs. The loop compensates for up to 40 mm of the thermal contraction of the busbars (Figure 14). Figure 12: PP The sliding support of process pipes, G11 roller arm, and G11 wheels. Figure 4:0 Segments of the busbar (BB) support system.