Experiments to Control Atom Number and Phase-Space Density in ...

and thus to coat the viewports.
Figure 7.29: Spectroscopy cell.
lithium reservoir
The spectroscopy cell is heated near the lithium reservoir with high-temperature
heater tape. It is insulated using fiber glass. To avoid frequency shifts due to the presence
of magnetic fields, the heater tape is wound around the cell in such a way as to minimize
the resulting magnetic fields due to currents flowing through the tape. Except near the
lithium reservoir the spectroscopy cell is kept near room temperature. Lithium atoms
therefore stick to the walls of the cell, which reduces the risk of coating the viewports
with lithium. The first time the lithium reservoir is heated to a temperature of about
450 ◦ C. This breaks any oxide layer that might have been formed on the surface of the
lithium metal during the preparation and loading into the cell.
7.3.1.3 Frequency-Offset Lock Setups
Frequency-offset locking has many applications in atomic physics experiments.
Most importantly for the lithium setup, it is an easy method to lock the imaging diode
laser and the master laser, used to seed the tapered amplifier, relative to the spectroscopy
laser with a frequency offset ∆f. Using a tunable scheme, it is possible to dynamically
change the laser frequency during the course of the experimental sequence. This is
important especially for the master laser, where the frequency offset ∆f controls the
MOT detuning. ∆f can then be changed to compress the MOT prior to loading atoms
121