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

and has walls 5 mm thick. The glass disc has a diameter of 75 mm, a thickness
of 17 mm and a hole through its center with a diameter of 20 mm which allows
passage between it and the middle chamber. The piece was prepared and
assembled by Hellma Cells Inc. using a remarkable technique. Each of the
glass plates used in constructing the cell was polished and optically contacted.
The cell was then heated to just below the material melting point, fusing the
pieces together without the use of any cement or adhesive. This technique
produces very high optical quality cells which are free of any material (i.e.
adhesive) which could potentially be UHV incompatible.
The all glass lower cell is connected to the middle chamber through the
use of spring energized seals manufactured by Garlock Helicoflex (H-307330).
These seals work via the elastic deformation of a metal jacket surrounding
a close-wound helical spring. The metal jacket is chosen to have a greater
ductility than both the glass cell and steel chamber it connects. The seals
we used have two small ridges on the top and bottom which concentrate the
compression load in small region (see Fig. 3.5).
The seals are available with jackets made from a variety of materials.
The jacket used in the experimental apparatus was made from silver. While a
good seal was formed, this product was found to damage the glass cell. The
damage is visible in Fig. 3.4 as a white ring on the disc shaped section of
the cell. After the damage was discovered we experimented with aluminum
jacketed seals (H-307592) and found that they seal equally well and do not
damage the glass substrate.
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