Single-Photon Atomic Cooling - Raizen Lab - The University of ...

Nor-Cal Products Inc. (AMV-1502-CF). Attached to the metal valve via a
zero length reducer is a 1-1/3 ′′ tee. Both sides of the tee have 1/2 ′′ copper
pinch-off tubes (Huntington, CPT-133-050) attached. One of these was used
as a connection port to a turbo-pump station during the vacuum bakeout. It
was sealed when the bakeout was complete. The other pinch-off tube houses
a glass ampule containing ≈ 200 mg of Rb (ESPI, purity 3N5). The ampule
was cracked from the outside by squeezing the copper tube with pliers when
the pump down was complete but while the chamber was still attached to the
turbo-pump station.
The ≈ 200 mg piece of solid Rb contains the isotope of interest, 87 Rb,
at the natural abundance level of ≈ 28%. One may wonder what role, if any,
the more abundant isotope 85 Rb played in our experiment. The isotopic shift
is sufficiently large so that 85 Rb is not resonant with the laser beams tuned
near the D2 transition in 87 Rb. This means that 85 Rb is not captured in our
MOTs. However, the two isotopes can collide resulting in magnetic trap loss.
The combined vapor pressure of both isotopes determines the collision rate,
and hence the lifetime of atoms in the magnetic trap. In this sense the presence
of 85 Rb has a somewhat detrimental effect.
The pressure in the upper chamber is determined by the vapor pressure
of solid rubidium at room temperature which can be approximated by Eq. 2.1
log10Pv = 2.881 + 4.857 − 4215
T .
The experiment resides in a room servo-looped to maintain a temperature
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