Cartridge Fiber Reach Limits
Sloan Digital Sky Survey Telescope Technical Note 20020212
Larry Carey
Each spectrographic cartridge consists of 32 fiber bundles, with
20 fibers per bundle. Each bundle of fibers is clamped below the
plate (in sky orientation) by an aluminum anchor block. The fiber
emerges from this anchor block with heavy jacketing and is terminated
with a precision ferrule which is plugged into a hole on the plate.
The reach of a fiber is determined by the point at which it emerges
from the anchor block.
In the fall of 2001 the fiber reach of the science and guide
fibers in a typical spectrographic cartridge was measured by Russell
Owen and Larry Carey. The measurement method consisted of the
following steps:
1: Fix the test cartridge in the plugging station in preperation
for plugging.
2: Place a sheet of paper directly on the surface of the plate to
be plugged.
3: Select a representative fiber and hold it with thumb and index
finger, approximately 1" above the ferrule.
4: Mark the paper to document the limits of free (ie.
non-stressed) motion of the fiber in all directions with the ferrule
oriented vertically, and held as described above.
5: Using a plumb-bob, mark the paper directly below the location
where the fiber emerges from its clamp.
Using this technique to measure several fibers, we deteremined
that each fiber can reliably reach holes within a circle of radius 7"
centered at a point 1.5" beyond where the jacketed fiber emerges from
the anchor block.
For a plate to be pluggable, each fiber must have a free hole
available within its unique 7" radius circle.
Date Created: 02/12/2002