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Atom-chip Bose-Einstein condensation in a portable vacuum cell
Cold atom guiding and manipulation using lithographically patterned wires on substrates have demonstrated the possibility of making small-scale atom-chip devices for practical applications. Nevertheless, like all Bose-Einstein condensate (BEC) systems developed to date, chip-scale atomic systems require an unwieldy assembly of electronic, optical, and vacuum instrumentation. This thesis reports on the significant simplification and size reduction of the vacuum system for atom-chip-based BEC production. The atom chip itself forms one wall of the vacuum system and enables direct electrical connections outside of vacuum to the chip instead of relying on vacuum feed-throughs. We have produced a portable system that can be assembled, processed, and then inserted into an ultracold atom apparatus in much the same way that an electronic vacuum tube can be plugged into an existing receiver. Our portable atom-chip cell has a total size of less than 30 × 30 × 15 cm. The ultrahigh vacuum of 10-10 torr is maintained by a small, 8 L/s ion pump and nonevaporable getter. We have successfully achieved a 87Rb BEC in a micro Z-wire trap. The condensate has about 2,000 87Rb atoms in the F=2, MF=2 state. All cooling and trapping processes occur from 2 mm to 80 μm below the chip. This work suggests that a chip-based BEC-compatible vacuum system can occupy a volume of less than 0.5 liter.