The inner layer of the EDDA Detector consists of 640 scintillating fibres (Kuraray SCSF-81, 'new cladding' (NOT multi cladding)) having a diameter of 2.5 mm. The fibers are arranged in 4 layers of 160 fibres each. Layer 1 and 3 are wound clockwise (looking downstream the COSY beamtube), Layer 2 and 4 are wound counter-clockwise. The fibres of layer 3 and 4 cover the inefficient regions between the fibres of layers 1 and 3.
Each layer is supported by a special carbon-fiber tube having 160 grooves mill-cut in its surface. These grooves guide the fibres with a precision of +/- 0.05mm.
The fibers are fixed using two sorts of glue:
During assembly the fibers were fixed with few drops of cyane acrylate
glue; after a whole layer was assembled the fibers were stabilized using
a special diluant-free glue (Ciba-Geigy XW339).
The amount of applied cyane acrylate glue is neclegible; XW339 fills about
50% of the volume between the fibers plus a film of 0.1 mm on the fiber´s
surface.
The carbon fiber tube of layer (n+1) fits onto layer n with a tolerance
of less than 0.2 mm; the original plan to cover each layer with a capton
foil was not realized.
The 4th layer is covered with one layer (0.1 mm) of capton and two layers
(0.05 mm each) of tedlar.
The fibers are numbered as follows:
So fiber n covers the gap between fiber (n-1) and (n+1).
Put into the form z=b*(phi+n*delta+phi0) with
the parameters for the 4 layers are:
Additionally, there is more information available: