Figure 3

Cross section through the physics package. The front panel, including handles, is shown on the left-hand side of the picture. The fiber connectors interface the physics package to the fibers coming from the laser system. The interior of the locker is not crew-accessible. An ion getter pump (IGP), a cold cathode gauge vacuum sensor and the electrical feed-throughs for the atom chip are located directly behind the front panel. Other parts of the vacuum system are encapsulated in a magnetic shield. The shield consists of two mu-metal layers and an aluminium layer in between. A custom made titanium sublimation pump is located inside the shield to be close to the science chamber. This ultra-high vacuum chamber is pumped through holes inside the copper mounting structure for the atom chip. The atom chip sits in the center of the science chamber. Three sets of coils attached to the chamber create homogeneous magnetic fields. One additional pair creates magnetic fields inside the chamber with a strength of up to 175 G. The physics package locker also contains parts of the control electronics. In particular, controllers and drivers with high current and high voltage output are placed in this locker to shorten the transmission paths. All cables and fibers are omitted for clarity