Gravitational Wave Group
The cooling test of a Multi-Stage Suspension System (2-stages)
2 Stage suspension system
2-stage is the minimum layer for the cryogenic laser interferometer
suspension system. In order to obtain some elemantal data for thermal
conductivity and isolation in multi-stage suspension system, we constructed
a simple 2-stage suspension using pure aluminum wires or sapphire fibers.
In the first experiment, we use aluminum (AL 1050) test mass as a mirror mass.
Cooling using 99.999% pure aluminum wires
The cooling speed including the suspension system is 7.5 days due to
the increase of heat capacity inside the cryostat. The used aluminum wire
diameter is 0.5 mm. The suspension point
and the coil holder are cooled together with the radiation shields. On the
other hand, the upper and mirror mass takes 15 days to be cooled at 9 and
10 K. This process can be simulated by even a simple model, assuming some
thermal conductivity for the pure aluminum which is reasonable compared with
previous data.
Cooling using sapphire fibers
The used sapphire fiber diameter is 0.25 mm.
The suspension point and the coil holder are cooled together with the radiation shields.
On the other hand, the upper and mirror mass takes 35 days !! to be cooled at 20 K.
The less cross section of the saphire fibers seem to enhance the equilibrium temperature
of the upper and the mirror mass.