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An apparatus for immersing trapped ions into an ultracold gas of neutral atoms
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View: Figures


Image of FIG. 1.
FIG. 1.

Layout of the vacuum apparatus in a partially exploded view: The science chamber (upper section) is connected to the BEC chamber (in the lower section) via a differential pumping stage (turquoise) along the dashed vertical axis. The MOT chamber (green) and the BEC chamber (red) which form the lower section are also connected via a differential pumping stage (turquoise). The science chamber exhibits a large DN200CF flange (blue) on top, the “science flange,” onto which the ion trap (not shown here) is mounted. A channeltron detector (brown) is connected along the axis of the linear ion trap. All three chambers are evacuated by their own pumping sections (grey). (Note: For better visibility the upper section is rotated clockwise by 90° around the dashed vertical axis.)

Image of FIG. 2.
FIG. 2.

Top view of the vacuum system: The science chamber (red), covers up the BEC chamber (not visible).

Image of FIG. 3.
FIG. 3.

Explosion view of the BEC chamber and the magnetic QUIC trap coils. The QUIC trap is generated by the two quadrupole coils and the Ioffe coil (blue). The coils are mounted outside the vacuum to the walls of the BEC chamber. The atoms enter the chamber along the magnetic transport axis and leave it along the vertical axis.

Image of FIG. 4.
FIG. 4.

BEC chamber and Ioffe coil: The BEC chamber features a small insertion slot with an end wall thickness of only 1.3 mm, so that the Ioffe coil (brown) and its holder (blue) can be mounted at a minimum distance of only 11.1 mm from the center of the chamber. The position of the atom cloud, when it is stored in the QUIC trap, is denoted by the black cross. The dimensions are given in mm.

Image of FIG. 5.
FIG. 5.

Science flange (DN200CF): The Paul trap (blue and golden) as well as the Ba oven (red) are mounted on MACOR ceramic parts (pale yellow). The imaging objective consists of four lenses, all of them held in place by a massive aluminum mount (brown) (see also Sec. III D).

Image of FIG. 6.
FIG. 6.

Ferrite-toroid transformer with a turns ratio of 2:36. By adjusting the capacity C P, the impedance of the trap (corresponding to C T) is matched and the ratio between the output and the input voltage (V O/V in) is maximized. In order to be able to monitor the output voltage, a capacitive voltage divider (C D1 and C D2) is used.

Image of FIG. 7.
FIG. 7.

Linear ion trap (Paul trap). The trap consists of four rf electrodes (blue) for confinement in the x-y plane, two endcap electrodes (golden) for confinement along the z axis, and four compensation electrodes (green) for the generation of dc electrical fields in the x-y plane. All electrodes are made of stainless steel AISI 316L. The dimensions are given in mm.

Image of FIG. 8.
FIG. 8.

Magnetic transport line: The neutral atom cloud is transported over a distance of 431.2 mm from the MOT chamber (green) to the BEC chamber (golden). Together with their respective aluminum housings (blue), the required magnetic field coils (brown) are mounted to the stainless steel chambers.

Image of FIG. 9.
FIG. 9.

A moving optical standing wave is used to transport the ultracold atoms vertically from the QUIC trap in the BEC chamber into ion trap in the science chamber. The distance between QUIC trap and Paul trap is not to scale.

Image of FIG. 10.
FIG. 10.

Optical transport of ultracold atoms. (a) A ramp of the form y(t) = D[tanh (n(2tT)/T) + tanh (n)]/2tanh (n) is chosen for the vertical position of the atoms versus time, where D = 304  mm is the transport distance, T = 0.9  s the transport time, and n = 4.5 the form parameter. (b) From the ramp y(t), we can derive the velocity v(t) of the atoms and the corresponding relative detuning (frequency shift) Δν(t) between the two lattice beams.

Image of FIG. 11.
FIG. 11.

Absorption images of the atom cloud after the interaction with a localized ion cloud. The atoms are transported to the ion trap and brought into contact with the ion cloud for 1 s. The Paul trap is loaded with a cloud of hundreds of Rb+ ions, which are responsible for the localized loss of atoms around the ion trap center. Outside of the ion trap center the atom loss is very small, as the atoms, being trapped in lattice sites, cannot get into contact with the ion cloud. The transport distance is varied between 303.90 mm and 303.925 mm. Arrows indicate where the ion cloud has depleted the neutral atomic ensemble. For a transport distance of 303.91 mm, the depletion region is located in the center of the atomic cloud, indicating a good vertical alignment. The pictures are taken after a time-of-flight of 12 ms.

Image of FIG. 12.
FIG. 12.

Probing the position of the optical dipole trap with a single ion. (a) First, the ion is moved away 300 µm from its normal position to prevent any collisions with the atoms during the final evaporation stage. This is done by changing one of the endcap voltages of the ion trap which moves the ion along the ion-trap axis (z axis). The position of the optical dipole trap is controlled by moving the laser beams with the help of AOMs. (b) By switching back to the original endcap voltages, the ion is moved back within several ms to its original position where it can now probe the local density of the atomic cloud.

Image of FIG. 13.
FIG. 13.

The number of remaining atoms after a given atom-ion interaction time of t = 1  s. When the center of the atom cloud (i.e., the dipole trap) coincides with the position of the ion, the number of remaining atoms is minimal (see also Ref. 17). The position of the dipole trap is controlled by the drive frequency of AOMs. (Here, the vertical beam of the crossed dipole trap is moved along the x′-direction.)


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Scitation: An apparatus for immersing trapped ions into an ultracold gas of neutral atoms